Quantitation of propofol metabolites by LC-MS/MS demonstrating long detection window for urine drug monitoring

Introduction

Chromatographic methods for analysis of propofol and its metabolites have been widely used in pharmacokinetic studies of propofol distribution, metabolism, and clearance. Application of chromatographic methods is also needed in clinical and forensic laboratories for detecting and monitoring propofol misuse.

Objective

We report a method for sensitive analysis of propofol, propofol 1-glucuronide (PG), 4-hydroxypropofol 1-glucuronide (1-QG), 4-hydroxypropofol 4-glucuronide (4-QG) and 4-hydroxypropofol 4-sulfate (4-QS) in urine by LC-MS/MS analysis. The method employs a simple dilute-and-analyze sample preparation with stable isotope internal standardization.

Results

Validation studies demonstrate a linear calibration model (100-10,000 ng/mL), with dilution integrity verified for the extended range of concentrations experienced in propofol use. Criteria-based validation was achieved, including an average coefficient of variation of 6.5 % and a percent bias of -4.2 ng/mL. The method was evaluated in 12 surgical patients, with monitoring periods lasting up to 30 days following intravenous propofol administrations of 100-3000 mg on the day of surgery. While the concentration ratio of PG to 4-hydroxy propofol metabolite decreased significantly in the days following surgery, PG maintained the highest concentration in all specimens. Both PG and 1-QG were detectable throughout the monitoring periods, including in a patient monitored for 30 days. Lower concentrations were determined for 4-QG and 4-QS, with evidence of detection up to 20 days. Propofol was not detectable in any urine specimens, thereby proving ineffective for identifying drug use.

Conclusion

The validated method for quantifying propofol metabolites demonstrates its applicability for the sensitive detection of propofol misuse over a long window of drug-use detection.

Evolution of LC-MS/MS in clinical laboratories

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has attracted significant attention in clinical practice owing to its numerous advantages. However, the widespread adoption of this technique is hindered by certain limitations, such as inappropriate analyte selection, low levels of automation, and a lack of specific reference intervals and quality control programs. This review comprehensively summarizes the current challenges associated with LC-MS/MS and proposes potential resolutions. The principle of utility should guide the selection of biomarkers, prioritizing their practical value over sheer quantity. To achieve full-process automation, methodological innovation is crucial for developing high-throughput equipment. Establishing reference intervals for mass spectrometry-based assays across multiple centers and diverse populations is essential for accurate result interpretation. Additionally, the development of commercial quality control materials assumes pivotal importance in ensuring assay reliability and reproducibility. Harmonization and standardization efforts should focus on the development of reference methods and materials for the clinical use of LC-MS/MS. In the future, commercial assay kits and laboratory-developed tests (LDTs) are expected to coexist in clinical laboratories, each offering distinct advantages. The collaborative efforts of diverse professionals is vital for addressing the challenges associated with the clinical application of LC-MS/MS. The anticipated advancements include simplification, increased automation, intelligence, and the standardization of LC-MS/MS, ultimately facilitating its seamless integration into clinical routines for both technicians and clinicians.

Determination of intracellular tenofovir-diphosphate and emtricitabine-triphosphate concentrations in dried blood spots for pre-exposure prophylaxis adherence

OBJECTIVES

We measured the intracellular concentrations of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP) in dried blood spots (DBS) for pre-exposure prophylaxis (PrEP) adherence using sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS).

METHODS

A total of 191 DBS were obtained from 85 participants who were receiving tenofovir disoproxil fumarate (TDF; 300 mg) and emtricitabine (FTC; 200 mg) as PrEP at the Sexual Health Clinic, National Center for Global Health and Medicine, Tokyo, Japan. DBS punch (3 mm) added to 25 μL of 50% methanol and 400 μL of internal standard solution was used for solid phase extraction. Chromatographic separation was achieved on an Atlantis Premier BEH C18 AX Column (50 mm × 2.1 mm i.d.; particle size 1.7 μm) using gradient elution (flow rate: 0.6 mL/min); injection volume: 7 μL and run time: 5.5 min. Calibration curves for the two drugs were linear in the range 0.05-12.5 ng/punch.

RESULTS

We determined the intracellular TFV-DP and FTC-TP concentrations in 191 DBS obtained from 85 patients administered with TDF and FTC as PrEP. The analytical performance data (calibration curve and QC samples) for all the analytical runs met the acceptance criteria. Intracellular concentrations of TFV-DP and FTC-TP in the DBS remained stable for at least 24 h after oral administration.

CONCLUSIONS

A multiplex LC-MS/MS method was successfully developed for DBS, which can be useful for monitoring the levels of TFV-DP and FTC-TP in individuals receiving PrEP.

Baicalin inhibited PANX-1/P2Y6 signaling pathway activation in porcine aortic vascular endothelial cells infected by Glaesserella parasuis

Glaesserella parasuis can induce endothelial barrier damage in piglets, although the mechanism by which this pathogen triggers inflammatory damage remains unclear. Baicalin possesses anti-inflammatory and anti-oxidant activities. However, whether baicalin can relieve endothelial barrier damage caused by Glaesserella parasuis infection has not yet been studied. Hence, we evaluated the ability of baicalin to counteract the changes induced by Glaesserella parasuis in porcine aortic vascular endothelial cells. The results showed that Glaesserella parasuis could upregulate the expression of pannexin 1 channel protein and promote the release of adenosine triphosphate, adenosine diphosphate, adenosine 3'-monophosphate, uridine triphosphate, uridine diphosphate, and uridine monophosphate in porcine aortic vascular endothelial cells. The expression level of purinergic receptor P2Y6 was upregulated in porcine aortic vascular endothelial cells triggered by Glaesserella parasuis. In addition, Glaesserella parasuis could activate phospholipase C-protein kinase C and myosin light chain kinase-myosin light chain signaling pathways in porcine aortic vascular endothelial cells. Baicalin could inhibit pannexin 1 channel protein expression, reduce adenosine triphosphate, adenosine diphosphate, adenosine 3'-monophosphate, uridine triphosphate, uridine diphosphate, and uridine monophosphate release, and attenuate the expression level of P2Y6 in porcine aortic vascular endothelial cells induced by Glaesserella parasuis. Baicalin could also reduce the activation of phospholipase C-protein kinase C and myosin light chain kinase-myosin light chain signaling pathways in porcine aortic vascular endothelial cells triggered by Glaesserella parasuis. Our study report that Glaesserella parasuis could promote pannexin 1 channel protein expression, induce nucleosides substance release, and P2Y6 expression in porcine aortic vascular endothelial cells and baicalin could inhibit the expression levels of pannexin 1, nucleosides substance, and P2Y6 in the porcine aortic vascular endothelial cells induced by Glaesserella parasuis, which might be served as some targets for treatment of inflammation disease caused by Glaesserella parasuis.

Simultaneous determination of colistin sulfate and tigecycline in human plasma by liquid chromatography-tandem mass spectrometry method

OBJECTIVE

To establish a high-performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS) to simultaneously determine colistin sulfate and tigecycline in human plasma.

METHODS

Polymyxin B1 internal standard (20 µL) was added into 200 µL of plasma sample. The samples were treated with methanol-5% trichloroacetic acid (50:50, V/V) solution, and the protein precipitation method was adopted for post-injection analysis. The chromatographic column was a Dikma C18 (4.6 mm × 150 mm, 5 μm). For the mobile phase, 0.1% formic acid in aqueous solution was used for phase A, 0.1% formic acid in acetonitrile solution for phase B, and gradient elution was also applied. The flow rate was 0.8 mL/min, the column temperature was 40 °C, and the injection volume was 10 µL; Electrospray ionization and multiple reaction ion monitoring were adopted and scanned by the HPLC-MS/MS positive ion mode.

RESULTS

The endogenous impurities in the plasma had no interference in the determination of the analytes. There existed a good linear relationship of colistin sulfate within the range of 0.1-10 µg/mL (R2 = 0.9986), with the lower limit of quantification (LLOQ) of 0.1 µg/mL. There existed a good linear relationship of tigecycline within the range of 0.05-5 µg/ mL (R2 = 0.9987), with the LLOQ of 0.05 µg/mL. The intra- and inter-day relative standard deviations of colistin sulfate and tigecycline were both less than 15%, and the accuracy was between 88.21% and 108.24%. The extraction had good stability, the extraction recovery rate was 87.75-91.22%, and the matrix effect was 99.40-105.26%.

CONCLUSION

This study successfully established a method for simultaneously detecting colistin sulfate and tigecycline plasma concentrations. The method was simple, rapid, and highly sensitive and could be applied for therapeutic medication monitoring.

Establishment of a modified QuEChERS extraction and liquid chromatography-tandem mass spectrometry method for multiple pesticide residues followed by determination of the residue levels and exposure assessment in livestock urine

The establishment of an analytical method for pesticide residues in livestock urine can realize the real-time monitoring of pesticide pollution in livestock breeding. In this study, a novel method was developed for the determination of 106 pesticide residues in livestock urine based on a modified QuEChERS extraction and liquid chromatography-tandem mass spectrometry. Acetonitrile was used to extract target analytes through acidic and alkaline switching of the sample environment. The purification effect of captiva EMR-Lipid on samples was investigated. Three kinds of materials, C18, polar enhanced polymer (PEP), N-propylethylenediamine (PSA), were selected from 20 kinds of materials as adsorbents for QuEChERS. A mass analysis was carried out using simultaneous scanning in both positive and negative ion mode and multiple reaction monitoring mode. All analytes showed good linearity, with correlation coefficients (R2) greater than 0.9923; their limits of quantification were 0.02-1.95 ng/mL. The average recoveries at low, medium, and high spiked levels were in the range of 70.1 %-117.3 %, with intra-day precision ranging from 3.4 % to 16.9 % and inter-day precision ranging from 4.0 % to 19.3 %. The established analytical method was used to analyze the pesticide residue in swine urine and bovine urine collected from farms in Yining, Xinjiang, China. A total of 8 pesticides were detected, and the residue ranged from less than the limit of quantitation to 22.4 ng/mL. The top three pesticides with the highest detection frequency were clothianidin, thiamethoxam, and dinotefuran. The exposure assessment based on the monitored pesticide residue concentration levels showed that the detected pesticides could pose little risk to cattle and pigs.

Simultaneous analysis of carcinogenic N-nitrosamine impurities in metformin tablets using on-line in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

Contamination of active pharmaceutical ingredients (APIs) and pharmaceutical preparations with carcinogenic N-nitrosamines has led to recalls of these products and supply shortages to patients. The present study describes the development of a highly sensitive method for simultaneous analysis of seven N-nitrosamines using on-line in-tube solid-phase microextraction (IT-SPME) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine their actual contamination in metformin tablets. Using a Carboxen 1006 PLOT capillary as the extraction device for IT-SPME, these compounds were efficiently extracted and concentrated 6‒24-fold by subjecting 40 µL of sample to 25 repeated draw/eject cycles at a rate of 0.2 mL/min. The seven N-nitrosamines were separated within 11 min by gradient elution with 0.1 % formic acid solution and acetonitrile as the mobile phase using a CAPCELL PAK C18 MGII column and detected by multiple reaction monitoring in positive ion mode. The calibration curve showed linearity in the range 0.2‒50 ng/mL and detection limits (S/N = 3) in the range 3‒112 pg/mL. The intra-day and inter-day precisions were less than 5.5 % and 7.0 % (n = 6), respectively, with accuracies ranging from 93‒117 %. Following ultrasonic extraction with water, centrifugation and filtration of the supernatant liquid through a membrane filter, the N-nitrosamine impurities in metformin tablets could be analyzed by IT-SPME/LC‒MS/MS. Their limits of quantification (S/N = 10) were 0.1‒5.1 pg/mg API and recoveries ranged from 87‒102 %. Analysis of eight metformin tablets from eight manufacturers showed that 5.8‒7.5 pg/mg N-nitrosodimethylamine were present in three tablets, with no other N-nitrosamines detected in any of the eight tablets. This method may be useful in testing for N-nitrosamine impurities in pharmaceutical preparations.

Quantification of risperidone and paliperidone by liquid chromatography-tandem mass spectrometry in biological fluids and solid tissues obtained from two deceased using the standard addition method

Risperidone (RIS) is an atypical antipsychotic agent and its 9-hydroxylated metabolite named paliperidone (PAL) also has pharmacological properties similar to that of RIS. Quantifications of RIS and PAL in authentic human biological fluids and solid tissues by liquid chromatography (LC)-tandem mass spectrometry (MS/MS) have not been reported yet although those in plasma (and blood) were reported abundantly. In the present work, a quantification method for RIS and PAL based on the standard addition method was devised and validated for the human fluid and solid tissue specimens. RIS and PAL in biological fluids were quantified only after their dilution and deproteinization. The concentrations of RIS and PAL in the heart whole blood, pericardial fluid, stomach contents, bile, urine, liver, kidney and cerebrum were determined for a deceased who had been treated with RIS therapeutically, and also a deceased who had ingested RIS with other drugs intentionally. To our knowledge, this is the first report on the quantification of RIS and PAL by LC-MS/MS in the authentic human tissues and biological fluids.

Proteomic identification and quantification of Clostridium perfringens enterotoxin using a stable isotope-labelled peptide via liquid chromatography-tandem mass spectrometry

PURPOSE

Detection of Clostridium perfringens enterotoxin (CPE) in human stool is critical evidence of food poisoning. However, processing patient-derived samples is difficult and very few methods exist to confirm the presence of CPE. In this study, a technique was developed using proteomic analysis to identify and quantify CPE in artificial gut fluid as an alternative.

METHODS

The standard CPE was spiked into artificial gut fluids, and effective methods were developed by employing both a stable isotope-labelled internal standard peptide and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Proteotypic peptide EILDLAAATER formed by tryptic digestion was selected for quantitation of CPE. The peptide was identified using product ion spectra. Although the nontoxic peptides originating from CPE showed very low detectability in extraction and tryptic digestion, they could be detected with sufficient sensitivity using the method we developed. Based on a spiked recovery test at two concentrations (50 and 200 µg/kg), the recovery values were 85 and 78%, respectively. The relative standard deviations of repeatability and within-laboratory reproducibility were less than 8 and 11%, respectively. These standard deviations satisfied the criteria of the Japanese validation guidelines for residues (MHLW 2010, Director Notice, Syoku-An No. 1224-1). The limit of quantification (LOQ) was estimated to be 50 µg/kg. The combination of the product ion spectra and relative ion ratio supported CPE identification at the LOQ level.

CONCLUSIONS

To the best of our knowledge, this is the first report of proteomic analysis of CPE using LC-MS/MS. The method would greatly help in assessing CPE reliably.

Determination of synthetic hallucinogens in oral fluids by microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry

A fast and simple procedure based on microextraction by packed sorbent (MEPS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the simultaneous quantification of 28 synthetic hallucinogens in oral fluids, including lysergic acid diethylamide and substances from NBOMe, NBOH, NBF, 2C, and substituted amphetamine categories. Extraction conditions such as type of sorbent, sample pH, number of charge/discharge cycles, and elution volume were studied. Hallucinogenic compounds were extracted from oral fluid samples using C18 MEPS, loading with 100 μL sample (adjusted to pH 7) in 3 cycles, washing with 100 μL deionized water, and eluting with 50 μL methanol in 1 cycle, giving quantitative recoveries and no significant matrix effects. Limits of detection from 0.09 to 1.22 μg L^-1; recoveries from 80 to 129% performed in spiked oral fluid samples at 20, 50, and 100 μg L^-1; and high precision with relative standard deviations lower than 9% were obtained. The proposed methodology was demonstrated to be appropriate for the simple and sensitive determination of NBOMe derivates and other synthetic hallucinogenic substances in oral fluid samples.

Analysis of vaporized caffeine in smoke from e-cigarettes using liquid chromatography-tandem mass spectrometry and clarification of minor components

PURPOSE

Electronic cigarettes (e-cigarettes) are used widely, and e-cigarettes containing caffeine (Caf) have recently become commercially available. However, no risk evaluation of these Caf-containing products has been performed to date. Such an evaluation requires a sensitive analytical method for quantifying Caf in smoke from e-cigarettes. The aim of this study was to establish a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying vaporized Caf from commercially available e-cigarettes, and to determine minor components related to Caf in cigarette smoke extract (CSE).

METHODS

A sampling system for Caf using a suction pump was designed and sampling conditions were optimized.

RESULTS

The optimized LC-MS/MS conditions allowed the sensitive determination of Caf in smoke with a limit of detection of 0.03 ng/mL at a signal-to-noise ratio of 3. The method was applied to CSEs from five e-cigarette products and the concentration of Caf ranged from 0.894 ± 0.090 to 3.32 ± 0.14 μg/mL smoke (n = 3). Additionally, minor components related to Caf, such as theobromine, theophylline, and paraxanthine, were detected in CSE and in e-liquid at very low concentrations, indicating that they were impurities in e-liquid and vaporized along with Caf.

CONCLUSION

This is the first report to determine the concentration of vaporized Caf using an LC-MS/MS method and to clarify several minor components in smoke from e-cigarettes.

Assessment of the migration of perfluorinated compounds and primary aromatic amines from PTFE-coated non-stick cookware marketed in Turkey

Two perfluorinated compounds (PFCs) and 17 different primary aromatic amines (PAAs) were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in migrants from 35 cookware samples marketed in Turkey. Among PFCs, only PFOA was identified in 6 samples. Only two components among PAAs, namely aniline (ANL) and 4,4'-methylenedianiline (4,4'-MDA), were detected in analyzed samples. Although aniline was detected in all samples, 4,4'-MDA was detected in only 4 samples. The effects of simulant volume, temperature, and repeated use on the release of these migrants from non-stick cookware were investigated. Three simulant volumes (200, 500, and 1000 mL) were used in migration tests. PFCs and PAAs were identified in simulants at 200 and 500 mL. The increase in the amount of simulant caused a decrease in the concentration of these migrants. The lowest migration values were observed in the samples at consecutive usage cycles. PFCs and PAAs exhibited the highest migration ability with increasing temperature.

Proteomic signature of tubulointerstitial tissue predicts prognosis in IgAN

BACKGROUND

IgA nephropathy (IgAN) is associated with a significant risk of progression to kidney failure. Tubular atrophy is an established important risk factor for progressive disease, but few studies have investigated tubulointerstitial molecular markers and mechanisms of progression in IgAN.

METHODS

Based on data from the Norwegian Renal Registry, two groups were included: IgAN patients with (n = 9) or without (n = 18) progression to kidney failure during 10 years of follow-up. Tubulointerstitial tissue without discernible interstitial expansion or pronounced tubular alterations was microdissected, proteome was analysed using tandem mass spectrometry and relative protein abundances were compared between groups.

RESULTS

Proteome analyses quantified 2562 proteins with at least 2 unique peptides. Of these, 150 proteins had significantly different abundance between progressive and non-progressive IgAN patients, 67 were more abundant and 83 less abundant. Periostin was the protein with the highest fold change between progressive and non-progressive IgAN (fold change 8.75, p < 0.05) and periostin staining was also stronger in patients with progressive vs non-progressive IgAN. Reactome pathway analyses showed that proteins related to inflammation were more abundant and proteins involved in mitochondrial translation were significantly less abundant in progressive vs non-progressive patients.

CONCLUSIONS

Microdissection of tubulointerstitial tissue with only mild damage allowed for identification of proteome markers of early progressive IgAN. Periostin abundance showed promise as a novel and important risk marker of progression.

Investigation of Pesticide Residues in Fragaria and Myrica rubra Sold in Hangzhou

ABSTRACT

This study investigated the concentration of the pesticide residues found in Fragaria and Myrica rubra sold in the city of Hangzhou, People's Republic of China. From an analysis of 151 (77 Fragaria and 74 M. rubra) samples using gas chromatography-tandem mass spectrometry (GC-MS/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), 41 pesticide residues were found to be present. Of the 41 residues, 14 were found using GC-MS/MS and 27 were found using LC-MS/MS. Of the 151 samples, 10 (13.0%) of the 77 Fragaria samples and 5 (6.8%) of the 74 M. rubra samples were found to contain a specific pesticide residue, and only 4 Fragaria samples and 2 M. rubra samples were found to be without pesticide residue. In addition, 18 of the 41 pesticides were not detected in either Fragaria or M. rubra samples. Of the 41 residues, 10 were detected in Fragaria samples and 20 were detected in M. rubra samples. In Fragaria, procymidone was the most commonly detected residue, with a detection rate of 88.3%, followed by prochloraz, with a detection rate of 53.2%. In M. rubra, prochloraz was the most commonly detected residue, with a detection rate of 71.6%, followed by carbendazim, with a detection rate of 68.9%. The pesticide residues in some samples exceeded the maximum residue limit set in China. The limit of dimethomorph was exceeded in three of the Fragaria samples, and that of dichlorvos was exceeded in two of the M. rubra samples.

HIGHLIGHTS

Changes in S-(2-succinyl)cysteine and advanced glycation end-products levels in mouse tissues associated with aging

Cysteine is non-enzymatically modified by fumarate, which is an intermediate of the tricarboxylic acid cycle, leading to the formation of S-(2-succinyl)cysteine (2SC). Post-translational modification of physiological proteins by fumarate causes enzyme dysfunction. The aim of the study was to evaluate the changes in 2SC accumulation in physiological tissues associated with aging. Brain, liver, kidney, and serum samples were collected from 4-, 12-, and 96-week-old male C57BL/6J mice, and the level of 2SC was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after pretreatment, including delipidation, protein precipitation, and hydrolysis using hydrochloric acid. The 2SC level in the brain was higher than that in other tissues, and its accumulation significantly increased with age. Similarly, N^ε-(carboxymethyl)lysine levels, an advanced glycation end-products (AGEs) that accumulates in tissues in an age-dependent manner, was found to be increased in the brain and kidneys of elderly mice. Accumulation of N^δ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine increased significantly with age, but only in the kidneys. The fumarate content in the brain was similar to that in the liver and kidney at 4 and 12 weeks of age. Furthermore, fumarate contents increased in the liver and kidney at 96 weeks of age, whereas its level did not change in the brain. Our results demonstrated that the changes in 2SC and AGEs levels in tissues reflected differing metabolism and enhanced oxidative stress in each organ; in particular, the metabolism in the brain and kidneys is highly affected by aging.

Maximizing Depth of PTM Coverage: Generating Robust MS Datasets for Computational Prediction Modeling

Post-translational modifications (PTMs) regulate complex biological processes through the modulation of protein activity, stability, and localization. Insights into the specific modification type and localization within a protein sequence can help ascertain functional significance. Computational models are increasingly demonstrated to offer a low-cost, high-throughput method for comprehensive PTM predictions. Algorithms are optimized using existing experimental PTM data, thus accurate prediction performance relies on the creation of robust datasets. Herein, advancements in mass spectrometry-based proteomics technologies to maximize PTM coverage are reviewed. Further, requisite experimental validation approaches for PTM predictions are explored to ensure that follow-up mechanistic studies are focused on accurate modification sites.

Identification and characterization of proteins, lipids, and metabolites in two organic fertilizer products derived from different nutrient sources

The biochemical composition of organic fertilizers largely determines their nutrient supply characteristics following soil application as well as their potential impact on soil microbial communities. Yet, limited information is available regarding the biochemical composition of organic fertilizers derived from different nutrient sources. Here, we qualitatively analyzed the presence and abundance of proteins, lipids, and metabolites in a liquid fish fertilizer (LFF) product and a type of granular organic fertilizer (GOF) commonly used in organic vegetable production, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Our results suggest that the presence and abundance of proteins, lipids, and metabolites differ greatly between GOF and LFF. The qualitative analysis shows LFF as a rich source of metabolites, while complex proteins and long-chain saturated fatty acids are dominant in GOF. The degree of biochemical composition complexity may help explain the varying impacts of different types of organic fertilizers on nutrient availability, soil health, and environmental quality.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s13765-021-00625-2.

Simultaneous trace analysis of 10 benzophenone-type ultraviolet filters in fish through liquid chromatography-tandem mass spectrometry

We developed and validated a trace analytical method for the simultaneous determination of 10 benzophenone (BP)-type ultraviolet filters (BPs; BP, BP-1, BP-2, BP-3, BP-8, 2-hydroxybenzophenone [2-OHBP], 4-hydroxybenzophenone [4-OHBP], 4-methylbenzophenone [4-MBP], methyl-2-benzoylbenzoate [M2BB], and 4-benzoylbiphenyl [PBZ]) to analyze BPs in 110 commercial fish samples. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was employed. The developed method exhibited satisfactory linearity (R² > 0.993), favorable precision with intraday and interday relative standard deviation ranges of 1.0%-26.6% and 2.3%-29.3%, respectively, and a limit of detection ranging from 0.001 to 0.1 ng/g. BP and 2-OHBP were detected in 100% of the samples; BP-3, 4-OHBP, PBZ, and 4-MBP were detected in >70% of the samples; M2BB was detected in 33% of the samples, and BP-2 and BP-8 were not detected. Higher mean (minimum-maximum) levels of 2-OHBP and BP were found in fish samples with low lipid content, ranging from 18 (1.1-218.3) to 10 (0.5-45.4) ng/g, and those with high lipid content, ranging from 22 (1.5-76.4) to 9.6 (5.2-18.5) ng/g; low levels of the remaining six BPs were found, ranging from 0.01 to 0.9 ng/g. The mean 2-OHBP levels were 21.3, 14.4, and 30.2 ng/g for fish samples obtained from aquaculture in Taiwan, the wild in Taiwan, and different countries, respectively, with levels up to 218.3 ng/g (field eel) for a sample from Indonesia. BPs may not pose a health risk to Taiwanese adults through the consumption of fish; however, additional studies are needed to examine the risk that these contaminants may pose to ecosystems and human health.

Low-temperature partitioning extraction followed by liquid chromatography tandem mass spectrometry determination of multiclass antibiotics in solid and soluble wastewater fractions

An analytical method based on low-temperature partitioning extraction (LTPE) followed by high performance liquid chromatography coupled to triple quadrupole mass spectrometry analysis was developed and validated for the determination of eight multiclass antibiotics in wastewater. The analyzed target antibiotics included one β-lactam, two sulfonamides, three fluoroquinolones, one macrolide and one diaminopyrimidine. LTPE parameters such as sample pH, volume ratio between sample and extractor solvent, ultra-sonic extraction time, extraction tube material, solvent and volume to reconstitute the sample extracts, were optimized. Additionally, the influence of solids on extraction efficiency was evaluated. Quantification of the target antibiotics was performed by double consecutive injection method, without the use of a labeled compound, in order to correct matrix effects. The whole samples were analyzed, including, liquid and solid fractions of wastewater. The results revealed that the filtration step can underestimate the total antibiotics concentration, particularly to the hydrophobic compounds that have higher affinity for solids, indicating that the suspended wastewater particulate should not be neglected. The method detection limit ranged from 18.54 ng L^-1 (trimethoprim) to 78.49 ng L^-1 (ciprofloxacin). Intra-day precision of less than 12.3% was achieved. The recoveries values ranged from 13.9% (sulfadiazine) to 48.9% (erythromycin) in influent samples and from 19.1% (sulfadiazine) to 57.2% (ciprofloxacin) in effluent samples. The method was applied to the measurement of antibiotic residues in influent and effluent from wastewater treatment plants. The majority target antibiotics were detected in wastewater samples. Their concentrations ranged from 237 to 9553 ng L^-1 in influent and from 212 to 1660 ng L^-1 in effluent. This work provides new insights on the applicability of LTPE for antibiotic residues extraction from wastewater. In addition, the performed analysis highlights the importance of measuring total concentrations of analytes in whole sample.

Comparison of four different multiclass, multiresidue sample preparation methods in the analysis of veterinary drugs in fish and other food matrices

In 2018, AOAC International issued Standard Method Performance Requirements (SPMR) 2018.010 - Screening and Identification Method for Regulated Veterinary Drug Residues in Food. In response, we compared 4 different multiresidue methods of sample preparation using the same analytical method entailing ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Tilapia was chosen for testing, and the analytes and monitoring levels were from SPMR 2018.010. The methods consist of efficient procedures with published validation results from the US Department of Agriculture (USDA), Food and Drug Administration (FDA), and Canadian Food Inspection Agency (CFIA), and an enhanced-matrix removal (EMR)-Lipid protocol from China. Each method was used to prepare 102 final extracts of tilapia spiked or not at different levels with the 78 targeted analytes plus metabolites. The same FDA/USDA rules of mass spectral identification were employed in all analyses to assess rates of false positives and negatives. Quantitative accuracy of the methods was also compared in terms of recoveries and reproducibility of spiked tilapia, incurred catfish, and spiked and certified reference material of bovine muscle. Each method yielded generally acceptable results for the targeted veterinary drugs, but the USDA "extract & inject" method was the fastest, simplest, and cheapest to achieve equally or more acceptable results for the widest scope of analytes for the tested food matrices.

A proteome signature of umbilical cord serum associated with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a congenital anomaly characterized by a defect in the diaphragm. Despite the recent improvements in its treatment, CDH is associated with a high rate of neonatal mortality, which is often related to pulmonary hypoplasia (PH) as well as pulmonary hypertension. A better understanding of the underlying pathological mechanisms of PH in CDH could help establish a new treatment to improve its prognosis. In this study, we investigated serum biological profiles in neonates with CDH. For comprehensive investigation, umbilical cord serum samples were collected from isolated CDH cases (n = 4) and matched healthy controls (n = 4). Samples were analyzed using liquid chromatography–tandem mass spectrometry. A total of 697 proteins were detected; of them, 98 were identified as differentially expressed proteins. Among these differentially expressed proteins, complement C1q subcomponent showed the largest fold change, followed by complement C5. In the pathway enrichment analysis, the complement and coagulation cascades expressed the most significant enrichment (p = 2.4 × 10⁻²⁶). Thus, the complement pathway might play some role in the pathophysiology of CDH.

Collaborative compounding of metal-organic frameworks for dispersive solid-phase extraction HPLC-MS/MS determination of tetracyclines in honey

Metal-organic frameworks (MOFs), a sort of dispersive solid-phase extraction (d-SPE) material, has shown considerable prospects in the pretreatment of food, biological and other complex samples. Herein, we developed a method for compounding MOFs for d-SPE and trace determination of tetracyclines (TCs) in honey. When the compounding ratio of MIL-101 (Cr), MIL-100 (Fe) and MIL-53 (Al) was 7:1:2, adsorption-extraction was effective. Followed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), the limits of detection were 0.073-0.435 ng/g and the limits of quantitation ranged from 0.239 to 1.449 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline. The method was applied to four kinds of honey samples with recoveries from 88.1% to 126.2%. The compounding of MOFs provides a strategy for purification and multi-target extraction from complex food matrices by d-SPE.

A case of fatal intoxication by ingestion of an herbicide formulation containing fluroxypyr-meptyl and triclopyr

Fluroxypyr-meptyl and triclopyr are synthetic auxin-like herbicides that are used to control woody and broadleaf weeds. Herein, we report a case of fatal intoxication involving fluroxypyr-meptyl and triclopyr. A 61-year-old man was found dead at his farm with several suicide notes, and a white plastic bottle and a plastic cup with traces of white emulsion were found next to him. The plastic bottle was labeled as an herbicide formulation containing fluroxypyr-meptyl and triclopyr. Forensic toxicological screening of the stomach contents revealed the presence of fluroxypyr-meptyl, fluroxypyr and triclopyr. However, no fluroxypyr-meptyl was detected in blood owing to its rapid hydrolysis to fluroxypyr. In this study, fluroxypyr and triclopyr in blood were extracted using solid-phase extraction, and analyzed by liquid chromatography-tandem mass spectrometry. The analytical method was validated in terms of linearity, precision, accuracy, recovery and matrix effect, and the acceptable criteria were satisfied. Toxicological analysis showed that fluroxypyr and triclopyr concentrations were 19.7 μg/mL and 137.4 μg/mL in peripheral blood and 16.5 μg/mL and 147.8 μg/mL in heart blood, respectively. Based on these toxicological results and autopsy findings, the cause of death was determined to be acute fatal intoxication by ingestion of the pesticide containing fluroxypyr-meptyl and triclopyr. This is the first report of the determination of fluroxypyr and triclopyr in a fatal intoxication case.

Multiplex LC-MS/MS for simultaneous determination of 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D3, albumin, and vitamin D-binding protein with its isoforms: One-step estimation of bioavailable vitamin D and vitamin D metabolite ratio

Bioavailable vitamin D and vitamin D metabolite ratio (VMR) have emerged as potential novel vitamin D markers. We developed a multiplex liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine all elements necessary for the calculation of bioavailable vitamin D and VMR, including 25-hydroxyvitamin D [25-(OH)D] and 24,25-dihydroxyvitamin D₃ [24,25-(OH)₂D₃], VDBP and its isoforms, and albumin. Following separate reactions of hexane extraction and trypsin digestion, serum samples were analyzed using LC-MS/MS to measure 25-(OH)D₃, 25-(OH)D₂, 24,25-(OH)₂D₃, VDBP and its isoforms, and albumin. Analytical performances were assessed. Korean (n = 229), Arab (n = 98), White (n = 99) and Black American (n = 99) samples were analyzed. Bioavailable vitamin D and VMR were calculated. All target molecules were clearly separated and accurately quantified by LC-MS/MS. Analytical performances, including imprecision, accuracy, ion suppression, limit of quantification, linearity, and comparison with existing methods were within acceptable levels. The allele frequencies of VDBP isoforms in various races resulted similar to previously known values. The levels of bioavailable vitamin D were highest in White Americans and lowest in Black Americans. We have successfully developed a multiplex LC-MS/MS-based assay method that can simultaneously perform the measurement of all parameters needed to calculate bioavailable vitamin D and VMR. Our devised method was robust and reliable in terms of analytical performances and could be applied to routine clinical samples in the future to more accurately assess vitamin D status.

Circulating steroids and mood disorders in patients with polycystic ovary syndrome

Aberrant androgen metabolism is a characteristic feature of polycystic ovary syndrome (PCOS). Various androgens as well as their precursors and metabolites can accumulate in the blood of PCOS patients. Although these steroids include neuroactive steroids, such as allopregnanolone and androstenedione (Δ4A), it remains unknown whether altered blood steroid levels contribute to the high risk of mood disorders in PCOS. In this study, we measured blood levels of 11 steroids in 25 PCOS patients using liquid chromatography-tandem mass spectrometry and chemiluminescent enzyme immunoassay, and assessed the psychological status of these patients using the Hospital Anxiety and Depression Scale (HADS) questionnaire. We also examined age and the degree of metabolic abnormalities of each patient. Steroid values of the patients were compared to our previous data from 31 eumenorrheic women. As a result, 20 patients exhibited aberrant blood levels of one or more of the 11 tested steroids. In most cases, Δ4A and allopregnanolone levels were within or close to the reference ranges. Levels of four steroids were negatively correlated with patients' age, while no correlation was observed between steroid values and metabolic conditions. Seven patients showed high HADS scores. HADS scores were correlated with blood Δ4A levels even after stratifying by body mass indexes, but not with the levels of other steroids or clinical data. These results indicate that the high frequency of anxiety and depression in PCOS patients cannot be ascribed to altered blood levels of a specific steroid, although there may be a weak association between circulating Δ4A levels and psychological conditions of the patients.

Tandem mass spectrometry of small-molecule signal transduction inhibitors: Accurate-m/z data to adapt structure proposals of product ions

Protein kinases inhibitors or, more generally, signal transduction inhibitors (STIs) can be used to treat diseases in which deregulation of the protein kinase activity plays a role, such as in cancer. A wide variety of drugs has been developed and/or is under investigation to act as protein kinase inhibitors, especially in tyrosine kinase inhibition. The bioanalysis of STIs has received considerable attention in the past 20 years. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) in selected-reaction monitoring (SRM) mode is the method-of-choice in such studies. In several of these studies from us and others, structures are proposed for the product ions applied in SRM. A critical review of these proposed structures is presented using accurate-m/z data, which we have now generated with a linear-ion-trap-Orbitrap hybrid mass spectrometer. This led to adaptation and new structural proposals of 18 product ions for 13 STIs. Our investigation endorses the power of accurate-m/z analysis in structure elucidation of product ions in bioanalytical LC-MS-MS studies and for which the SRM mode in tandem-quadrupole instruments is apparently less suitable.

Isolation of proteins from spent coffee grounds. Polyphenol removal and peptide identification in the protein hydrolysates by RP-HPLC-ESI-Q-TOF

Several works have been focused on the extraction of polysaccharides, polyphenols and caffeine from spent coffee grounds (SCG) and their application in food formulations, but the peptide bioactivity from SCG protein hydrolysates has never been addressed. In the present work and for the first time, two different methods to isolate proteins from SCG have been compared, demonstrating that a urea-based extraction buffer provides a higher yield. This extraction method was then applied to compare the protein content in SCG from different coffee-brewing preparations, showing a higher protein content in SCG from espresso coffee machines. In addition, a polyphenol extraction step to remove interferences has been evaluated and the hydrolysis of the extracted proteins using alcalase and thermolysin enzymes has been compared. The effect of roasting degree on the antioxidant and in vitro angiotensin-converting enzyme (ACE)-inhibitory activity has been evaluated. The results show that the ACE-inhibitory activity is higher when SCG proteins are obtained from medium and dark roasted coffees and then hydrolyzed with thermolysin. Finally, the peptides contained in these hydrolysates have been identified by reversed-phase high-performance liquid chromatography coupled via electrospray ionization to a quadrupole time-of-flight mass spectrometer (RP-HPLC-ESI-Q-TOF).

Testosterone serum levels are not predictive of maternal virilization in hyperreactio luteinalis

Background

Elevated concentrations of circulating testosterone are present in hyperreactio luteinalis (HL), a pregnancy-specific, self-limited condition. HL is associated with maternal virilization in about 30% of cases. The correlation between testosterone levels and maternal virilization has not yet been quantified. Our aim was to identify a testosterone cut-off level which may allow to predict maternal virilization.

Methods

A literature research was performed. Publications were chosen if serum testosterone concentrations and presence or absence of maternal virilization was mentioned. Additionally, we report serial levels of steroids analyzed by Liquid chromatography–tandem mass spectrometry (LC–MS/MS) in one case of HL managed at our institution.

Results

In all, 31 cases fulfilled the search criteria. We found significant overlap between testosterone levels in asymptomatic women and women with signs of virilization (range 6.2–37.3 nmol/l and 13.7–197.5 nmol/l, respectively). The method applied for testosterone analysis was mentioned in three reports only. Peak serum testosterone concentration in our case was 120.3 nmol/l.

Conclusion

From the available data, maternal virilization in HL cannot be predicted by the level of circulating testosterone. However, comparability of results is hampered by the analytical methods applied. LC–MS/MS should preferably be used for reporting concentrations of circulating testosterone.

Dexamethasone measurement during low-dose suppression test for suspected hypercortisolism: threshold development with and validation

BACKGROUND AND AIM

Dexamethasone Suppression Test (DST), recommended for Cushing's Syndrome (CS) diagnosis, explores the pituitary feedback to glucocorticoids. Its diagnostic accuracy could be affected by dexamethasone bioavailability, and therefore, we have developed and validated a dexamethasone threshold after 1-mg DST.

MATERIALS AND METHODS

We studied 200 subjects: 125 patients were considered retrospectively and 75 were enrolled prospectively as the validation cohort. Serum dexamethasone, Late Night Salivary Cortisol (LNSC), and Urinary Free Cortisol (UFC) were measured with LC-MS/MS. Normal LNSC and UFC levels were used to exclude CS. The lower 2.5th percentile of dexamethasone distribution in non-CS patients with cortisol ≤ 50 nmol/L after 1-mg DST was used as threshold.

RESULTS

16 patients were CS and 184 non-CS (108 adrenal incidentaloma and 76 excluded CS); 4.5 nmol/L resulted the calculated threshold. Cortisol after 1-mg DST confirmed high sensitivity (100% at 50 nmol/L cut-off) and moderate-low specificity (63%, increased to 91% at 138 nmol/L) to diagnose CS in the whole cohort of patients. We could reduce the number of false-positive results (from 10 to 6 and from 7 to 4 in AI and excluded CS) considering adequate dexamethasone levels. Dexamethasone levels were not affected by hypercortisolism, age, gender, smoke, weight, and creatinine. 6% of non-CS patients did not achieve adequate dexamethasone levels (40% of tests with serum cortisol > 138 nmol/L after 1-mg DST).

CONCLUSIONS

We developed and validated the routine dexamethasone measurement during 1-mg DST: it is independent from patient's clinical presentation, and it should be used to increase the specificity of serum cortisol levels.

Determination of methylmalonic acid, 2-methylcitric acid, and total homocysteine in dried blood spots by liquid chromatography-tandem mass spectrometry: A reliable follow-up method for propionylcarnitine-related disorders in newborn screening

OBJECTIVES

Determination of methylmalonic acid, 2-methylcitric acid, and total homocysteine in dried blood spots by liquid chromatography-tandem mass spectrometry has usually been used as a second-tier test to improve performance of newborn screening for propionylcarnitine-related disorders. However, factors that potentially affect its detection results have not been investigated, and we aimed to evaluate these influencing factors and explore their potential utility in newborn screening and initial follow-up for propionylcarnitine-related disorders.

METHODS

This study comprised a prospective group (1998 healthy infants, to establish cutoff values and investigate the influencing factors) and a retrospective group (804 suspected positive cases screened from 381, 399 newborns for propionylcarnitine-related disorders by tandem mass spectrometry, to evaluate the performance of newborn screening and initial follow-up).

RESULTS

Cutoff values for methylmalonic acid, 2-methylcitric acid, and total homocysteine were 2.12, 0.70, and 10.05 µmol/l, respectively. Concentration of methylmalonic acid, 2-methylcitric acid, and total homocysteine in dried blood spots is not impacted by sex, age, birth weight, gestational age, or dried blood spot storage time. A total of 75 of 804 cases were screened positive by combined tandem mass spectrometry and liquid chromatography-tandem mass spectrometry, thus eliminating 90% of the false positives without compromising sensitivity. Eighteen propionylcarnitine-related disorders were successfully identified, including one CblX case missed in the initial follow-up by tandem mass spectrometry.

CONCLUSIONS

Methylmalonic acid, 2-methylcitric acid, and total homocysteine detected in dried blood spots by liquid chromatography-tandem mass spectrometry is a reliable, specific, and sensitive approach for identifying propionylcarnitine-related disorders. We recommend this assay should be performed rather than tandem mass spectrometry in follow-up for propionylcarnitine-related disorders besides second-tier tests in newborn screening.

Exposure Assessment of Multiple Mycotoxins in Black and White Sesame Seeds Consumed in Thailand

ABSTRACT

This study was conducted to determine the occurrence of 16 well-recognized and emerging mycotoxins in black and white sesame seed samples sold in Thailand and to evaluate possible health risks to consumers. Samples were extracted and cleaned with a modified QuEChERS procedure. Multiple mycotoxins in sesame seed samples were analyzed with a validated liquid chromatography-tandem mass spectrometry method. The risk of mycotoxin exposure via dietary intake of sesame seeds was evaluated based on the hazard quotient, margin of exposure (MOE), and quantitative liver cancer risk established by European Food Safety Authority, the Food and Agriculture Organization of the United Nations, and the World Health Organization. Of the 200 samples, 21.5% were contaminated with mycotoxins, 19.5% were contaminated with a single mycotoxin, and 2% were contaminated with multiple mycotoxins. Although 9% of total samples were contaminated with aflatoxins (AFs), only one black sesame seed sample and one white sesame seed sample were above the regulatory limits for the European Union (2 μg/kg). The MOE values derived from consumption of black and white sesame seeds were generally <10,000, especially in the group consuming the most. The number of liver cancer cases over a lifetime associated with AFB1 exposure based on the upper bound values for the group consuming high level of black and white sesame seeds (97.5 percentile) was estimated at more than 1 case per one million persons. Therefore, a potential risk to consumer health exists through the consumption of black and white sesame seeds and subsequent exposure to AFB1. However, further evaluation with larger sample sizes is necessary for more accurate calculations. Continuous monitoring of mycotoxin contamination in sesame seeds with risk assessments is recommended.

HIGHLIGHTS

Vibrational extraction QuEChERS for analysis of antiparasitic agents in fish by liquid chromatography coupled with tandem mass spectrometry

A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea, organophosphate, pyrimidinamine, pyrethrin and pyrethroid classes in salmon by liquid chromatography coupled with tandem mass spectrometry. Samples were extracted with acetonitrile-water as the extraction solvent with use of a vibrational shaking apparatus with a ceramic homogenizer. After extraction, the acetonitrile extracts were cleaned up by incubation at low temperature (-20 °C, 1 h) to remove fat, followed by dispersive solid-phase extraction using Z-Sep+ and primary-secondary amine as sorbents. Validation was performed following the 2002/657/EC and SANTE/11813/2017 guidelines. The trueness of the method ranged from 87% to 121% and precision ranged from 4.1% to 23.7%, with the exception of cyphenothrin, dicyclanil and azamethiphos. The method developed is particularly advantageous because the use of a vibrational shaker allows unattended extraction of samples and eliminates a laborious tissue disruption step, which increases sample throughput in the laboratory. The sample preparation and chromatographic separations can be performed in 5 and 4 h, respectively, for 36 samples. Graphical abstract.

Stabilities of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and their derivatives under controlled conditions analyzed using liquid chromatography coupled with tandem mass spectrometry

Bisphenol A diglycidyl ether (BADGE), bisphenol F diglycydyl ether (BFDGE), and their related compounds are widely used as precursors in production of epoxy resins. The high reactivity of these compounds makes the development of analytical methodologies that ensure appropriate metrological accuracy crucial. Consequently, we aimed to determine whether and to what extent the composition of the solution and storage conditions affect the stability of selected BADGE and BFDGE derivatives. The stabilities of these compounds were studied using liquid chromatography–tandem mass spectrometry with electrospray ionization (HPLC-ESI–MS/MS). The chromatographic method elaborated here has allowed for separation of the analytes in time shorter than 6 min, for both methanol and acetonitrile-based mobile phases. The obtained calibration curves for all analytes were linear in the range tested. The values of limit of detection (LODs) were in the range of 0.91–2.7 ng/mL, while values of limit of quantitation (LOQs) were in the range of 2.7–5.7 ng/mL. The chosen experimental conditions were compared in terms of the content of organic solvent in solution, storage temperature, and time. Our results show that the content of BADGE, BADGE·HCl, BFDGE, three-ring NOGE decreased with increasing water content (> 40% v/v). For BADGE and three-ring NOGE, significant changes in concentration were noted as early as 24 h after the test solutions had been prepared. In addition, a reduction in the storage temperature (4 to − 20 °C) reduced the rate of transformation of the monitored analytes. Our study will increase quality control in future research and may increase the reliability of the obtained results.

Development of an underivatized LC-MS/MS method for quantitation of 14 neurotransmitters in rat hippocampus, plasma and urine: Application to CUMS induced depression rats

Sensitive and comprehensive measurement of systemic metabolites of tryptophan, phenylalanine and glutamate metabolism in biological samples is effective for understanding the pathogenesis of depression and other neurological diseases. Therefore, this study developed an underivatized liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous monitoring the 3 components of glutamate metabolism in rat hippocampus and 11 components of tryptophan and phenylalanine metabolism in rat hippocampus, plasma and urine, and applied it to investigate their changes in rats induced by chronic unpredictable mild stress (CUMS). The investigated analytes are as follows: tryptophan, serotonin, 5-hydroxyindoleacetic acid, kynurenine, kynurenic acid, xanthurenic acid, 3-hydroxyanthranilic acid, quinolinic acid, phenylalanine, tyrosine, tyramine, glutamate, glutamine and gamma-aminobutyric acid. The method was verified to be sensitive and effective with satisfactory linearity, accuracies in the range of 78.2%-120.4%, and precisions less than 17.8% for all identified analytes. A series of significant changes in CUMS-induced rats can be detected: tryptophan, serotonin and tyrosine levels decreased and quinolinic acid increased in both hippocampus and plasma. In addition, the kynurenine/tryptophan ratios increased in hippocampus and plasma, the kynurenic acid/quinolinic acid ratios of plasma and urine were significantly reduced. These findings demonstrated that the CUMS procedure could lead to the central and peripheral imbalances of tryptophan and phenylalanine metabolism. In conclusion, a LC-MS/MS method for simultaneous measurement of several neurotransmitters in rat hippocampus, plasma and urine was developed and successfully applied to investigation of the central and peripheral changes in CUMS-induced rats. The method would be expected to provide applicability to the study of the mechanisms of depression and other related diseases associated with these neurotransmitters.

Occurrence of Multiple Mycotoxins in Various Types of Rice and Barley Samples in Thailand

HIGHLIGHTS

Contamination with multiple mycotoxins was found in rice and barley. BEA, DAS, ZEA, and aflatoxins were the mycotoxins most frequently found in samples. The assessed mycotoxin exposure does not represent a health risk for consumers.

The diagnostic accuracy of increased late night salivary cortisol for Cushing's syndrome: a real-life prospective study

INTRODUCTION AND AIM

A prompt diagnosis of Cushing's Syndrome (CS) in high-risk populations is mandatory: 1-mg dexamethasone suppression test (1-mg DST), late night salivary cortisol (LNSC), and urinary-free cortisol (UFC) are recommended, despite thresholds calculated in retrospective studies. Our aim was to study the diagnostic accuracy of LNSC measured with chemiluminescence assay in a prospective study, confirming discrepancies with mass spectrometry (MS).

MATERIALS AND METHODS

We enrolled 117 controls and 164 suspected CS (CS = 47, non-CS = 117). In case of increased LNSC, high clinical suspicion of CS or adrenal incidentaloma, patients were hospitalized to exclude/confirm CS.

RESULTS

LNSC levels were higher in patients with suspected CS, CS, and non-CS than controls. Considering 16 nmol/L as threshold for CS, overall LNSC revealed SE 97% and SP 84% in the whole group of subjects considered, achieving positive/negative likelihood ratio of 5.56/0.045, respectively. 35 out of 81 subjects with increased LNSC were non-CS (15 diabetic and 20 obese): considering only those patients with increased likelihood to have a CS (the non-CS patients) SP decreased to 70%, and further reduced to 60% if we discharged subjects with adrenal incidentaloma. MS analyses reduced partially the number of false-positive LNSC.

CONCLUSIONS

LNSC measured in automated chemiluminescence is reliable in clinical practice: it present a high diagnostic accuracy to exclude hypercortisolism in patients with normal cortisol levels. MS could be used to reduce the number of false-positive results; nevertheless, some non-CS subjects with functional hypercortisolism could have a mild impairment of cortisol rhythm.

Targeted metabolomics for the quantitative measurement of 9 gut microbiota-host co-metabolites in rat serum, urine and feces by liquid chromatography-tandem mass spectrometry

Gut microbiota-host co-metabolites play an essential role in maintaining homeostasis, and their concentration changes are closely related to a variety of diseases. Developing a targeted metabolomics analytical platform for these co-metabolites will help to elucidate the relationship between intestinal flora and host. Here we present a simple and sensitive liquid chromatography-tandem mass spectrometry method for the analysis of nine gut microbiota-host co-metabolites in rat serum, urine and feces. The compounds were separated on a reversed-phase C₁₈ column using gradient elution with a solvent system consisting of methanol and water (containing 0.05% formic acid) and a 7-min run time. All of the calibration curves exhibited good linear relationships (R² ≥ 0.9984, Percent Residual Accuracy ≥93.27%). The intra- and interday precision, expressed as relative standard deviation (RSD), was ≤ 14.84%. The accuracy was within 100 ± 13.16% for all analytes. The recovery of the nine compounds in biological samples was ≥ 85.80% with an appropriate RSD (≤12.04%). The validated method was successfully applied to monitor the global changes of these metabolites in obesity. Taken together, these results demonstrate that the method can simultaneously determine the nine co-metabolites in multiple biological matrices and is an essential part of the targeted metabolomics analytical platform, which may become an approach to evaluate the occurrence, development and therapeutic effects of metabolic diseases.

Nine phthalate metabolites in human urine for the comparison of health risk between population groups with different water consumptions

Phthalates are a group of high production volume chemicals widely detected in environment matrix and human specimens. Potential health risks due to the prevalence of their exposure through water consumption and the endocrine-disrupting activities have become an important issue. This work aims to compare the distributions of phthalate levels and potential health risks caused by phthalate exposure among three groups of participants ingesting different types of water. Here, a method with good performance was applied for the analysis of nine common phthalate metabolites in 125 human urine samples collected from Wuhan women. Seven analytes (mono‑ethyl, mono‑benzyl, mono‑n‑butyl, mono‑(2‑ethylhexyl), mono‑(2‑ethyl‑5‑oxohexyl), mono‑(2‑ethyl‑5‑hydroxyhexyl), and mono‑(2‑ethyl‑5‑carboxypentyl) phthalate) were detected in over 80% of the samples. By measuring urinary concentrations of phthalate monoesters, the exposure levels of respective parent phthalates, exposure patterns, the estimated daily intakes and accumulative risk assessments were investigated in three groups of participants consuming water from different sources (bottled water, filtered water and boiled tap water). The results showed that the exposure patterns of phthalates varied among the population groups with different water intakes, and the health risk was higher for people ingesting the boiled tap water than that of the groups consuming bottled water (purified water) and filtered water with filter cartridge containing activated carbon.

Metabolomic approaches to polyamines including acetylated derivatives in lung tissue of mice with asthma

INTRODUCTION

Recently, the relationship between polyamine (PA) metabolism and asthma has been studied in severe asthmatic therapy, but systematic PA metabolism including their acetylated derivatives was not fully understood.

OBJECTIVES

Profiling analysis of polyamines (PAs) was performed to understand the biochemical events and monitor altered PA metabolism in lung tissue of mice with asthma.

METHODS

Polyamine profiling of lung tissue of mice with asthma was performed without derivatization by liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with star pattern recognition analysis. The PA levels between control and asthma groups were evaluated by multivariate analysis.

RESULTS

In mouse lung tissue, seven PAs were determined by LC-MS/MS in multiple reaction monitoring (MRM) mode. Their levels were normalized to the corresponding mean levels of the control group for star pattern analysis, which showed distorted heptagonal shapes with characteristic and readily distinguishable patterns for each group. Levels of putrescine (p < 0.0034), N¹-acetylputrescine (p < 0.0652), and N⁸-acetylspermidine (p < 0.0827) were significantly increased in asthmatic lung tissue. The separation of the two groups was evaluated using multivariate analysis. In unsupervised learning, acetylated PAs including N¹-acetylspermine were the main metabolites for discrimination. In supervised learning, putrescine and N¹-acetylputrescine were evaluated as important metabolites.

CONCLUSIONS

The present results provide basic data for understanding polyamine metabolism in asthma and may help to improve the therapy for severe asthma patients.

Metyrapone treatment in Cushing's syndrome: a real-life study

INTRODUCTION AND AIM

Medical treatment is increasingly used in patients with Cushing's syndrome (CS). Metyrapone (MET) is an inhibitor of 11β-hydroxylase: retrospective studies reported a decrease of cortisol secretion in 50% of cases. We evaluated the effectiveness of MET in an observational study, considering the normalization of urinary-free cortisol (UFC) and late-night salivary cortisol (LNSC) levels.

MATERIALS AND METHODS

We enrolled 31 patients with CS, treated with MET for at least 1 month (16 for primary treatment and 15 after surgical failure). A planned dose-titration regimen considering baseline UFC levels was adopted; MET dose was uptitrated until UFC normalization, surgery, or side effect occurrence. UFC and LNSC levels were routinely measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Patients were treated with a median dose of 1000 mg for 9 months. UFC and LNSC decreased quickly after the first month of treatment (-67 and -57% from baseline), with sustained UFC normalization up to 12 and 24 months (in 13 and 6 patients, respectively). UFC and LNSC normalized later (after 3-6 months) in patients with severe hypercortisolism (>5-fold baseline UFC). Regarding the last visit, 70 and 37% of patients normalized UFC and LNSC, respectively. Body weight reduction (-4 kg) was observed after UFC normalization. Severe side effects were not reported, half of the female patients complained of hirsutism, and blood pressure was not increased.

CONCLUSIONS

MET therapy is a rapid-onset, long-term effective, and safe medical treatment in CS patients, achieving UFC normalization (in 70% of patients) more than cortisol rhythm recovery (in 37% of subjects).

Simultaneous determination of nine neonicotinoids in human urine using isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry

Neonicotinoids (neonics), a class of systemic insecticides, have been frequently detected in pollen, vegetables, and fruits. Recently, an increasing concern has been aroused for human exposure to neonics. However, biological monitoring for quantifying body burden of neonics has rarely been reported. In this study, we developed an isotope-dilution ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method to simultaneously quantify nine neonics, including acetamiprid (ACE), thiamethoxam (THIAM), imidacloprid (IMIP), clothianidin (CLO), flonicamid (FLO), thiacloprid (THIAC), dinotefuran (DIN), nitenpyram (NIT), and imidaclothiz (IMIT) in urine. The limits of quantification were 0.1 μg/L for ACE, FLO, DIN, NIT and IMIT, and 0.2 μg/L for THIAM, IMIP, CLO, and THIAC. The overall recoveries were 80.8-103%, 81.5-91.7% and 83.0-92.3% for QA/QC samples fortifying at 1, 25, and 100 μg/L levels, respectively. UPLC/MS/MS method was used to analyze urine samples obtained from 10 children in Hangzhou, China. The detection frequencies were 80% for ACE and IMIP, 70% for THIAM and CLO, 20% for DIN and IMIT and 10% for THIAC. FLO and NIT were not detected in those urine samples. The data provided here will be helpful for conducting biological monitoring of neonics exposure in the future.

Development of a liquid chromatography-tandem mass spectrometry method with modified QuEChERS extraction for the quantification of mebendazole and its metabolites, albendazole and its metabolites, and levamisole in edible tissues of aquatic animals

A liquid chromatography-tandem mass spectrometry quantitative method was developed for determining mebendazole and its metabolites, albendazole and its metabolites, and levamisole in muscles of bluntnose black bream, shrimp, eel and turtle based on modified QuEChERS methodology. The method included 2 g of the muscle matrix with 10 mL acetonitrile, and 0.8 g of magnesium sulphate and 0.2 g of sodium chloride for liquid-liquid partitioning. After vortex and centrifugation, the resulting liquid (5.5 mL) was purified by C₁₈ (50 mg) and Al-N (50 mg). The limits of detection were lower than 0.3 μg kg^-1 and the limits of quantitation were no more than 1 μg kg^-1 for all analytes. The recoveries of the analytes ranged from 80.0% to 113.7% with the relative standard derivation less than 10.0%. The preparation procedure provided efficient extraction and purification that enabled a sensitive and rugged determination of target compounds.

Dispersive liquid-liquid microextraction as a new clean-up procedure for the determination of parabens, perfluorinated compounds, UV filters, biocides, surfactants, and plasticizers in root vegetables

An analytical method based on ultrasound-assisted extraction and dispersive liquid-liquid microextraction (DLLME) clean-up has been developed and validated for the determination of 31 emerging pollutants in root vegetables. The target compounds were four preservatives, six perfluoroalkyl compounds, six UV filters, two biocides, eight anionic surfactants, three nonionic surfactants, and two plasticizers. The type and volume of the extraction solvent, those of the disperser solvent, the pH and NaCl content of the DLLME aqueous phase, the amount of sample, and the sonication time were optimized. Box-Behnken experimental design was applied to select the best extraction conditions. Matrix-matched calibration curves were used for quantification. Four internal standards were used to compensate for residual matrix effects. Good linearity (R² > 0.990), accuracies (expressed as the relative recovery) of >82%, and precisions (expressed as the relative standard deviation) of <18% were achieved. Method quantification limits (MQLs), calculated from spiked samples as the concentrations corresponding to signal-to-noise ratios of 10, were in the range 0.1-25 ng g^-1 dry weight (d.w.). MQL values for 26 of the 31 target compounds were lower than 5 ng g^-1 d.w. The method was successfully applied to determine the target pollutants in carrots, potatoes, and turnips from a local market. To the best of our knowledge, the proposed method constitutes the first application of DLLME as a clean-up procedure for the multiresidue determination of emerging pollutants in vegetables. The method affords similar recoveries and method detection limits to previously reported methods but requires smaller solvent volumes and sample amounts and is less expensive.

Concentrations of Bisphenols in Canned Foods and Their Risk Assessment in Korea

The purpose of this study was to survey concentrations of bisphenols in canned foods using liquid chromatography-tandem mass spectrometry, to estimate the dietary exposure to bisphenols, and to assess the related risk for the Korean population from the intake of canned foods. The linearity of bisphenols in the range of 2.5 to 725 μg/L was satisfactory with correlation coefficients ( r²) of 0.999. The limit of detection was 0.14 to 5.85 μg/L, and the limit of quantitation was 0.44 to 17.73 μg/L. Sample recoveries were 70.56 to 113.6%, with relative standard deviations below 10% for spiking levels of 50 and 250 μg/kg (15 and 75 μg/kg for BPS). The bisphenol concentrations in 104 canned foods ranged from undetectable to 1,525 μg/kg. The estimated mean daily intake of bisphenols was 0.54 to 78.69 ng/kg of body weight per day, and the 95th percentile daily intake was 1.92 to 134 ng/kg of body weight per day. Therefore, the intake of bisphenols from canned foods for the population in Korea is unlikely to cause human health problems. The analytical methods used are suitable for regular monitoring and assessment of human exposure to bisphenols from foods.

Development and application of a UHPLC-MS/MS metabolomics based comprehensive systemic and tissue-specific screening method for inflammatory, oxidative and nitrosative stress

Oxidative stress and inflammation are underlying pathogenic mechanisms associated with the progression of several pathological conditions and immunological responses. Elucidating the role of signalling lipid classes, which include, among others, the isoprostanes, nitro fatty acids, prostanoids, sphingoid bases and lysophosphatidic acids, will create a snapshot of the cause and effect of inflammation and oxidative stress at the metabolic level. Here we describe a fast, sensitive, and targeted ultra-high-performance liquid chromatography-tandem mass spectrometry metabolomics method that allows the quantitative measurement and biological elucidation of 17 isoprostanes as well as their respective isomeric prostanoid mediators, three nitro fatty acids, four sphingoid mediators, and 24 lysophosphatidic acid species from serum as well as organ tissues, including liver, lung, heart, spleen, kidney and brain. Application of this method to paired mouse serum and tissue samples revealed tissue- and serum-specific stress and inflammatory readouts. Little correlation was found between localized (tissue) metabolite levels compared with the systemic (serum) circulation in a homeostatic model. The application of this method in future studies will enable us to explore the role of signalling lipids in the metabolic pathogenicity of stress and inflammation during health and disease.

Development and validation of a rapid, selective, and sensitive LC-MS/MS method for simultaneous determination of D- and L-amino acids in human serum: application to the study of hepatocellular carcinoma

A validated liquid chromatography-tandem mass spectrometry method was developed for the simultaneous determination of D- and L-amino acids in human serum. Under the optimum conditions, except for DL-proline, L-glutamine, and D-lysine, the enantioseparation of the other 19 enantiomeric pairs of proteinogenic amino acids and nonchiral glycine was achieved with a CROWNPAK CR-I(+) chiral column within 13 min. The lower limits of quantitation for L-amino acids (including glycine) and D-amino acids were 5-56.25 μM and 0.625-500 nM, respectively, in human serum. The intraday precision and interday precision for all the analytes were less than 15%, and the accuracy ranged from -12.84% to 12.37% at three quality control levels. The proposed method, exhibiting high rapidity, enantioresolution, and sensitivity, was successfully applied to the quantification of D- and L-amino acid levels in serum from hepatocellular carcinoma patients and healthy individuals. The serum concentrations of L-arginine, L-isoleucine, L-aspartate, L-tryptophan, L-alanine, L-methionine, L-serine, glycine, L-valine, L-leucine, L-phenylalanine, L-threonine, D-isoleucine, D-alanine, D-glutamate, D-glutamine, D-methionine, and D-threonine were significantly reduced in the hepatocellular carcinoma patients compared with the healthy individuals (P < 0.01). D-Glutamate and D-glutamine were identified as the most downregulated serum markers (fold change greater than 1.5), which deserves further attention in hepatocellular carcinoma research. Graphical abstract Simultaneous determination of D- and L-amino acids in human serum from hepatocellular carcinoma patients and healthy individuals. AA amino acid, HCC hepatocellular carcinoma, LC liquid chromatography, MS/MS tandem mass spectrometry, NC normal control, TIC total ion chromatogram.

Selective and rapid determination of tadalafil and finasteride using solid phase extraction by high performance liquid chromatography and tandem mass spectrometry

Highly selective and fast liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for simultaneous determination of tadalafil (TDL) and finasteride (FNS) in human plasma. The method was successfully applied for analysis of TDL and FNS samples in clinical study. The method was validated as per USFDA (United States Food and Drug Administration), EMA (European Medicines Agency), and ANVISA (Agência Nacional de Vigilância Sanitária-Brazil) bio analytical method validation guidelines. Glyburide (GLB) was used as common internal standard (ISTD) for both analytes. The selected multiple reaction monitoring (MRM) transitions for mass spectrometric analysis were m/z 390.2/268.2, m/z 373.3/305.4 and m/z 494.2/369.1 for TDL, FNS and ISTD respectively. The extraction of analytes and ISTD was accomplished by a simple solid phase extraction (SPE) procedure. Rapid analysis time was achieved on Zorbax Eclipse C18 column (50 × 4.6 mm, 5 μm). The calibration ranges for TDL and FNS were 5-800 ng/ml and 0.2-30 ng/ml respectively. The results of precision and accuracy, linearity, recovery and matrix effect of the method are acceptable. The accuracy was in the range of 92.9%-106.4% and method precision was also good; %CV was less than 8.1%.

Antigen 85B peptidomic analysis allows species-specific mycobacterial identification

BACKGROUND

Nontuberculous mycobacteria (NTM)-mediated infections are a growing cause of worldwide morbidity, but lack of rapid diagnostics for specific NTM species can delay the initiation of appropriate treatment regimens. We thus examined whether mass spectrometry analysis of an abundantly secreted mycobacterial antigen could identify specific NTM species.

METHODS

We analyzed predicted tryptic peptides of the major mycobacterial antigen Ag85B for their capacity to distinguish Mycobacterium tuberculosis and three NTM species responsible for the majority of pulmonary infections caused by slow-growing mycobacterial species. Next, we analyzed trypsin-digested culture supernatants of these four mycobacterial species by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect candidate species-specific Ag85B peptides, the identity of which were validated by LC-MS/MS performed in parallel reaction monitoring mode.

RESULTS

Theoretical tryptic digests of the Ag85B proteins of four common mycobacterial species produced peptides with distinct sequences, including two peptides that could each identify the species origin of each Ag85B protein. LC-MS/MS analysis of trypsinized culture supernatants of these four species detected one of these species-specific signature peptides in each sample. Subsequent LC-MS/MS analyses confirmed these results by targeting these species-specific Ag85B peptides.

CONCLUSIONS

LC-MS/MS analysis of Ag85B peptides from trypsin-digested mycobacterial culture supernatants can rapidly detect and identify common mycobacteria responsible for most pulmonary infections caused by slow-growing mycobacteria, and has the potential to rapidly diagnose pulmonary infections caused by these mycobacteria through direct analysis of clinical specimens.

Advanced LC-MS-based methods to study the co-occurrence and metabolization of multiple mycotoxins in cereals and cereal-based food

Liquid chromatography (LC) coupled with mass spectrometry (MS) is widely used for the determination of mycotoxins in cereals and cereal-based products. In addition to the regulated mycotoxins, for which official control is required, LC-MS is often used for the screening of a large range of mycotoxins and/or for the identification and characterization of novel metabolites. This review provides insight into the LC-MS methods used for the determination of co-occurring mycotoxins with special emphasis on multiple-analyte applications. The first part of the review is focused on targeted LC-MS approaches using cleanup methods such as solid-phase extraction and immunoaffinity chromatography, as well as on methods based on minimum cleanup (quick, easy, cheap, effective, rugged, and safe; QuEChERS) and dilute and shoot. The second part of the review deals with the untargeted determination of mycotoxins by LC coupled with high-resolution MS, which includes also metabolomics techniques to study the fate of mycotoxins in plants.

Targeted LC-MS Analysis for Plant Secondary Metabolites

Recent technological developments and methodological advances of both liquid chromatography (LC) and mass spectrometry (MS) have allowed LC-MS-based plant metabolomics to become a common tool for investigating quantity, quality, and chemical diversity of plant metabolites. Targeted LC-MS metabolite analysis focuses on the detection and quantitation of the researcher's target metabolites. Whilst the word "target analysis" has been used for the analytical measurement to obtain the absolute concentrations evaluated by authentic and/or stable-isotope-labeled standards, over time the phrase came to be also used in a broad sense for the measurement of annotatable metabolites by structural information obtained from the combination of different strategies such as MS/MS analysis, reference extracts, mutant analysis and database search. Here, we describe a general protocol for targeted LC-MS metabolite profiling of plant secondary metabolites. Additionally, we introduce some examples of peak annotation using the combination approach.