Favorable effects of weak acids on negative-ion electrospray ionization mass spectrometry

Effect of sodium formate and lactic acid bacteria treated rye silage on methane yield and energy balance in Hanwoo steers

This study was performed to evaluate the effects of rye silage treated with sodium formate (Na-Fa) and lactic acid bacteria (LAB) inoculants on the ruminal fermentation characteristics, methane yield and energy balance in Hanwoo steers. Forage rye was harvested in May 2019 and ensiled without additives (control) or with either a LAB inoculant or Na-Fa. The LAB (Lactobacillus plantarum) were inoculated at 1.5 × 1010 CFU/g fresh matter, and the inoculant was sprayed onto the forage rye during wrapping at a rate of 4 L/ton of fresh rye forage. Sixteen percent of the Na-Fa solution was sprayed at a rate of approximately 6.6 L/ton. Hanwoo steers (body weight 275 ± 8.4 kg (n = 3, group 1); average body weight 360 ± 32.1 kg (n = 3, group 2)) were allocated into two pens equipped with individual feeding gates and used in duplicated 3 × 3 Latin square design. The experimental diet was fed twice daily (09:00 and 18:00) during the experimental period. Each period comprised 10 days for adaptation to the pen and 9 days for measurements in a direct respiratory chamber. The body weights of the steers were measured at the beginning and at the end of the experiment. Feces and urine were collected for 5 days after 1 day of adaptation to the chamber, methane production was measured for 2 days, and ruminal fluid was collected on the final day. In the LAB group, the ratio of acetic acid in the rumen fluid was significantly lower (p = 0.044) and the ratio of propionic acid in the rumen fluid was significantly higher (p = 0.017). Methane production per DDMI of the Na-FA treatment group was lower than that of the other groups (p = 0.052), and methane production per DNDFI of the LAB treatment group was higher than that of the other groups (p = 0.056). The use of an acid-based additive in silage production has a positive effect on net energy and has the potential to reduce enteric methane emissions in ruminants.

A new derivatizing reagent for the determination of 5-nitro-2-furaldehyde in trout muscle by liquid chromatography-tandem mass spectrometry

The 5-nitro-2-furaldehyde (5-NF) is an aldehyde aromatic organic compound that has been envisaged as an alternative marker for detecting nitrofurazone treatment abuse and to avoid the false positive results induced by the semicarbazide. Analyzing 5-NF presents challenges, and its derivatization reaction with hydrazine reagents is required to enhance the capability of its detection and its identification. This study aims at developping an analytical method for 5-NF determination in trout muscle samples based on chemical derivatization prior to analysis by liquid chromatography-tandem mass spectrometry. Four commercially available hydrazine reagents, namely: N,N-Dimethylhydrazine (DMH), 4-Hydrazinobenzoic acid (HBA), 2,4-Dichlorophenylhydrazine (2,4-DCPH) and 2,6-Dichlorophenylhydrazine (2,6-DCPH) were proposed for the first time as derivatizing reagents in the analysis of 5-NF. The derivatization reaction was simultaneously performed along with the extraction method in acidic condition using ultrasonic assistance and followed by liquid extraction using acetonitrile. The efficiency of the chemical reaction with 5-NF was examined and the reaction conditions including the concentration of hydrochloric acid, pH, temperature, reaction time and the concentration of the derivatizing reagents were optimized. Experiments with fortified samples demonstrated that 2,4-DCPH derivatizing reagent at 20 mM for 20 min of ultrasonic treatment under acidic condition (pH 4) gave an effective sample derivatization method for 5-NF analysis. Under the optimized conditions, the calibration curves were linear from 0.25 to 2 μg kg-1 with coefficient of determination >0.99. The recoveries ranged from 89 % to 116 % and precision was less than 13 %. The limit of detection and quantification were 0.1 and 0.2 μg kg-1, respectively.

The effects of modifiers on electrospray ionization for small-to-medium-sized molecules in comparison with solution-phase ionization

Modifiers are essential additives in electrospray ionization (ESI) mass spectrometric analysis to enhance the production of ionic species in the gas phase for the detection of small-to-medium-sized molecules in biological and aqueous samples. Therefore, an appropriate modifier, in conjunction with the right ionization polarity, is crucial for sensitive ESI mass spectrometric analysis. However, the charge carried by basic and acidic functional groups in solution is neither quantitatively nor qualitatively reflected in the MS spectrum. For example, adding an acidic modifier will cause sufficient protonation of a basic functional group in solution; however, this may result in inferior positive ESI compared to using a basic modifier. Another example is when the MS spectrum does not reflect the charge distribution of multiply charged molecules in solution. Therefore, this review will summarize and discuss the proposed mechanisms by which modifiers induce and influence ESI. It will also cover molecular characteristics that affect ESI, such as charge state and polarity, which result in a difference between solution-phase ionization and ESI.

Bioassay-Guided Fractionation of Acetone and Methanol Extracts of Quercus infectoria Galls with Antimalarial Properties

The antimalarial properties of crude extracts from Quercus infectoria galls were investigated through bioassay-guided fractionation. Acetone (QIA) and methanol (QIM) crude extracts have been reported to have promising antimalarial activity against Plasmodium falciparum (3D7 strain). These extracts were subjected to fractionation using automated preparative high-performance liquid chromatography (prep-HPLC) to identify the most active fractions. Nine fractions were isolated from each extract, of which the fractions QIA11 and QIM16 showed antimalarial activity, with IC50 values of 17.65 ± 1.82 μg/mL and 24.21 ± 1.88 μg/mL, respectively. In comparison, the standard antimalarial drug artemisinin has an IC50 value of 0.004 ± 0.001 μg/mL). Through high-resolution liquid chromatography coupled with mass spectrometry (HR-LCMS) analysis of the fractions, four known compounds were successfully identified: gallic acid, ellagic acid, 1,3,6-tris-o-(3,4,5-trihydroxybenzoyl)-beta-d-glucose and 1-O,6-O-digalloyl-beta-D-glucose.

Assessment of Untargeted Metabolomics by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry to Define Breast Cancer Liquid Biopsy-Based Biomarkers in Plasma Samples

An early diagnosis of cancer is fundamental not only in regard to reducing its mortality rate but also in terms of counteracting the progression of the tumor in the initial stages. Breast cancer (BC) is the most common tumor pathology in women and the second deathliest cancer worldwide, although its survival rate is increasing thanks to improvements in screening programs. However, the most common techniques to detect a breast tumor tend to be time-consuming, unspecific or invasive. Herein, the use of untargeted hydrophilic interaction liquid chromatography-mass spectrometry analysis appears as an analytical technique with potential use for the early detection of biomarkers in liquid biopsies from BC patients. In this research, plasma samples from 134 BC patients were compared with 136 from healthy controls (HC), and multivariate statistical analyses showed a clear separation between four BC phenotypes (LA, LB, HER2, and TN) and the HC group. As a result, we identified two candidate biomarkers that discriminated between the groups under study with a VIP > 1 and an AUC of 0.958. Thus, targeting the specific aberrant metabolic pathways in future studies may allow for better molecular stratification or early detection of the disease.

Derivatization of carboxylic groups prior to their LC analysis - A review

Carboxylic acids (CAs) represent a large group of important molecules participating in various biologically significant processes. Analytical study of these compounds is typically performed by liquid chromatography (LC) combined with various types of detection. However, their analysis is often accompanied by a wide variety of problems depending on used separation system or detection method. The dominant ones are: i) poor chromatographic behavior of the CAs in reversed-phase LC; ii) absence of a chromophore (or fluorophore); iii) weak ionization in mass spectrometry (MS). To overcome these problems, targeted chemical modification, and derivatization, come into play. Therefore, derivatization still plays an important and, in many cases, irreplaceable role in sample preparation, and new derivatization methods of CAs are constantly being developed. The most commonly used type of reaction for CAs derivatization is amidation. In recent years, an increased interest in the isotopic labeling derivatization method has been observed. In this review, we comprehensively summarize the possibilities and actual trends in the derivatization of CAs that have been published over the past decade.

Occurrence, biomagnification, and risk assessment of parabens and their metabolites in marine fish: The case study of Vietnam

Parabens have emerged as the primary preservative of choice in numerous consumer goods, prompting growing apprehension regarding their potential for human exposure. The study employed the optimized QuEChERs sample extraction method and the UHPLC-Q-Orbitrap HRMS system to generate the initial contamination profiles of seven parabens and their four metabolites in a total of 114 fish samples found along the coastline of Vietnam. The findings of the study indicated that methylparaben was the predominant substance detected, exhibiting the highest concentration in the largehead hairtail (Trichiurus lepturus) species at 32.8 ng g-1 dry weight (dw). Additionally, the metabolites with the highest detectable concentrations in the largehead hairtail were found to be 4-HB and 3,4-DHB, with levels of 8822.0 ng g-1 dw and 3490.8 ng g-1 dw, respectively. Besides, the study reveals notable variations in paraben concentrations across three distinct regions in Vietnam, namely the Central, North, and South (Mann-Whitney U test, p < 0.05). The trophic magnification factors (TMF) for methylparaben, ethylparaben, ethyl protocatechuate, and 4-hydroxybenzoic acid exhibited values exceeding 1, indicating substantial biomagnification of these substances within the marine food web of Vietnam. Additionally, noteworthy positive associations have been observed between methylparaben and ethylparaben, as well as their respective metabolites. Based on the findings of the study, it can be concluded that there is no direct impact of seafood consumption on human health in Vietnam.

Hands-Free Analytical Urine Testing Technology Validated for Drug-Facilitated Crime Investigations

Forensic laboratories need quick and simple technology to improve turnaround times, while delivering reliable results. The goal of this study is first to create a simplified workflow to meet new Academy Standards Board requirements for urine testing in drug-facilitated crime investigations and, second, to create "ready-to-go", "hands-free" testing technology to further streamline analytical procedures. A first of its kind, the ToxBox forensic test kit is used to validate a single analytical procedure for opioids, benzodiazepines, cannabinoids, antidepressants, and several other drug classes. Method performance indicators follow accreditation requirements and include accuracy, precision, measurement uncertainty, calibration models, reportable range, sensitivity, specificity, carryover, interference, ion suppression/enhancement, and analyte stability. "Hands-free" testing platforms require the use of new suspended-state technology to stabilize NIST-traceable standards premanufactured at precise concentrations in the presence of sample preparation reagents. By suspending all reaction components in the solid state, with air gaps between the phases, reference standards and process controls are built in a "ready-to-go" format and stabilized for long-term storage in the presence of a sample matrix, β-d-glucuronidase, and enzymatic buffers. "Hands-free" test kits are removed from storage, incubated at either ambient temperature or 60 °C, and assayed using validated methods. This is the first example of how complex forensic testing workflows can be streamlined with new "hands-free" testing strategies to meet analytical challenges associated with quantitative and confirmatory analyses.

4-Aminobenzoic acid, 2-phenoxyethanol and iodine used as tracers in a short-term in vivo-kinetics study for tattoo ink ingredients: Mass spectrometry method development and validation

Tattoos have been gaining popularity in recent years, leading to a growing interest in researching tattoo inks and the tattooing process itself. Since the exposure to soluble tattoo ink ingredients has not yet been investigated, we here present the method validation for a short-term biokinetics study on soluble tattoo ink ingredients. The three tracers 4-aminobenzoic acid (PABA), 2-phenoxyethanol (PEtOH) and iodine will be added to commercially available tattoo inks, which will subsequently be used on healthy study participants. Following the tattooing process, blood and urine will be sampled at specific time points and analysed for these tracers. For this purpose, a method using liquid chromatography separation coupled to a quadrupole time-of-flight mass spectrometer (LC-QTOF-MS) in positive and negative ESI mode for the quantification of PABA, PEtOH and selected metabolites and an inductively-coupled plasma (ICP)-MS method for the determination of iodine were developed and validated. For LC-QTOF-MS analysis, the most applicable additives for LC eluents (0.01 % formic acid for positive and 0.005 % acetic acid for negative mode) were identified. Protein precipitation with acetonitrile was chosen for sample preparation. The methods were validated for selectivity, specificity, carryover, linearity, limit of detection (LOD) and quantification (LOQ), matrix effects, accuracy and precision, stability under different conditions and dilution integrity according to national and international guidelines with an allowed maximum variation of ±15 %. The LC-QTOF-MS method met the imposed guideline criteria for most parameters, however, some metabolites showed strong matrix effects. Validation of the ICP-MS method revealed that the KED-H2 collision mode is superior to the standard analysis mode due to enhanced method accuracy. The methods were validated for the relevant matrices plasma, urine, tattoo ink and tattoo consumables and proved to be applicable for the main target substances in the short-term biokinetics study. A proof-of-concept study showed successful quantification of iodine and PABA metabolites. The PEtOH metabolite was also quantified, but showed strong matrix effects in urine. Therefore standard addition was selected as an alternative quantification method.

Investigation of the adsorption/desorption mechanism of perfluoroalkyl substances on HLB-WAX extraction phases for microextraction

The C-F alkyl structural backbone of per- and polyfluoroalkyl substances makes this class of molecules resistant to heat and degradation, leading to their high persistence and mobility in the environment and bioaccumulation in the tissues of living organisms. In this study, 15 PFAS with an alkyl chain length from C₄ to C₁₄, currently monitored by the U.S. Environmental Protection Agency (EPA), were preconcentrated by solid-phase microextraction (SPME) and analyzed by liquid chromatography-tandem mass spectrometry. The adsorption and desorption mechanisms of PFAS onto ion-exchange extraction phases was evaluated to understand the extraction process of PFAS from various environmental matrices under different conditions. This was achieved using two SPME geometries, namely fibers and thin films. The use of thin films resulted in a twofold improvement in extraction efficiency compared to fibers, especially for the short-chain PFAS. Methanol:water (80:20, v/v) was chosen as the optimized desorption solution, with ammonium formate added to minimize carryover. Extraction time profiles for both SPME geometries showed faster equilibration with thin films (30 min) compared to fibers (90-120 min). The linear dynamic range obtained with this method using fibers and thin films ranged from 10 to 5000 ng L^-1 and 2.5-5000 ng L^-1, respectively, with acceptable accuracy (70-130%) and precision (<15%). LOD ranged within 2.5-10 ng L^-1 for fibers and 0.01-0.25 ng L^-1 for thin films. Investigating the factors affecting PFAS recovery in complex samples enabled the quantitative assessment of PFAS contamination in various environmental water samples such as seawater, melted snow and biospecimens like human plasma. A 96-SPME holder was used for validation, which is compatible with sampling in 96-well plates and ensures high throughput in the analysis of real samples. The total concentration of PFAS detected in seawater and snow was 51.3 ng L^-1 and 16.4 ng L^-1, respectively.

Molecular characteristics of ambient organic aerosols in Shanghai winter before and after the COVID-19 outbreak

During the global pandemic of COVID-19, the world adopted different strategies to avoid the human and economic loss, and so does China. The reduction of human activities during this time period caused reduction in PM emissions. This study adopted a HPLC-Q-TOF-MS to compare the chemical compositions of ambient aerosol samples collected in Shanghai winter before (2018, 2019) and after (2021) the COVID-19 outbreak. The identified compositions were classified into subgroups of CHO, CHN, CHON, CHONS, CHOS and CHN compounds. Results showed that CHO compounds and CHON compounds were dominating the organic compounds in ESI- and ESI+, respectively. The average percentages of CHO- compounds were 57.97 % in 2018, 58.98 % in 2019, and 43.93 % in 2021, respectively. The average percentages of CHON+ compounds were 52.74 % in 2018, 50.34 % in 2019, and 52.02 % in 2021, respectively. The proportion of aliphatic compounds increased gradually during the three years, especially in 2021, indicating that CHO compounds were less affected by aromatic precursors after the COVID-19 outbreak. The contribution of anthropogenic emissions in Shanghai was weakened compared with the previous years. In addition, there was an enhanced emission source containing hydroxyl for CHOS compound formation in 2021. The variations of atmospheric oxidation degree among the three years were not significant.

Influence of mobile phase composition on the analytical sensitivity of LC-ESI-MS/MS for the concurrent analysis of bisphenols, parabens, chlorophenols, benzophenones, and alkylphenols

Phenols are significant environmental endocrine disruptors that can have adverse health effects on exposed individuals. Correlating phenol exposure to potential health implications requires the development of a comprehensive and sensitive analytical method capable of analyzing multiple phenols in a single sample preparation and analytical run. Currently, no such method is available for multiple classes of phenols due to electrospray ionization (ESI) limitations in concurrent ionization and lack of sensitivity to certain phenols, particularly alkylphenols. In this study, we investigated the influence of mobile phase compositions in ESI on concurrent ionization and analytical sensitivity of liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) during the analysis of multiple classes of phenols, and we propose a comprehensive and sensitive analytical method for various classes of phenols (i.e., bisphenols, parabens, benzophenones, chlorophenols, and alkylphenols). The proposed method was affected by 0.5 mM ammonium fluoride under methanol conditions. It enabled the concurrent ionization of all the phenols and significantly improved the analytical sensitivity for bisphenols and alkylphenols, which typically have poor ionization efficiency. This method, combined with a "dilute and shoot" approach, allowed us to simultaneously quantify 38 phenols with good chromatographic behavior and sensitivity. Furthermore, the method was successfully applied to the analysis of 61 urine samples collected from aquatic (swimming) and land (indoor volleyball and outdoor football) athletes.

Analysis of 2′-hydroxyflavanone (2HF) in mouse whole blood by HPLC–MS/MS for the determination of pharmacokinetic parameters

Given the lack of investments, structure, and difficulty of metabolite isolation, promising natural product studies do not progress to preclinical studies, such as pharmacokinetics. 2′-Hydroxyflavanone (2HF) is a flavonoid that has shown promising results in different types of cancer and leishmaniasis. For accurate quantification of 2HF in BALB/c mouse blood, a validated HPLC-MS/MS method was developed. Chromatographic analysis was performed using C18 (5μm, 150 mm × 4.6 mm). The mobile phase consisted of water containing 0.1% formic acid, acetonitrile, and methanol (35/52/13 v/v/v) at a flow rate and total running time of 0.8 mL/min and 5.50 min, respectively, with an injection volume of 20 µL. 2HF was detected by electrospray ionization in negative mode (ESI-) using multiple reaction monitoring (MRM). The validated bioanalytical method showed satisfactory selectivity without significant interference for the 2HF and IS. In addition, the concentration range between 1 and 250 ng/mL showed good linearity (r = 0.9969). The method showed satisfactory results for the matrix effect. Precision and accuracy intervals varied between 1.89% and 6.76% and 95.27% and 100.77%, respectively, fitting the criteria. No degradation of 2HF in the biological matrix was observed since stability under freezing and thawing conditions, short duration, postprocessing, and long duration showed deviations less than 15%. Once validated, the method was successfully applied in a 2HF oral pharmacokinetic study with mouse blood, and the pharmacokinetic parameters were determined. 2HF demonstrated a Cmax of 185.86 ng/mL, a Tmax of 5 min, and a half-life (T1/2) of 97.52 min.

Evaluating the "wrong-way-round" electrospray ionization of antiretroviral drugs for improved detection sensitivity

The presence of antiretroviral drugs (ARVDs) in the aquatic environment poses a significant health risk to the ecosystem. The dilution of these compounds during wastewater treatment processes, followed by discharge into the environment, results in extremely low concentrations in the range of ng/L. Therefore, to enable detection of these low concentrations, it is important to determine the most efficient electrospray ionization (ESI) mode using the right mobile phase modifier and to establish a selective extraction procedure. In this study, we compared the ESI intensity in the positive and negative mode using both formic acid (FA) and ammonium hydroxide (NH₄OH) as mobile phase modifiers. The results revealed a phenomenon known as the "wrong-way-round" (WWR) ESI in which high intensity [M + H]⁺ ions were detected under basic conditions using NH₄OH as modifier and, similarly, high intensity [M-H]^- ions were detected under acidic conditions using FA as modifier. Furthermore, mixed-mode strong cation (MCX) and mixed-mode strong anion (MAX) exchange sorbents were evaluated for extraction recoveries, which yielded extraction recoveries between 60 and 100%. Finally, the recoveries obtained using mixed-mode ion exchange sorbents compared to ion production during the ESI process provide evidence that ions produced in solution do not necessarily reflect the ions that are produced during the ESI process. Based on the results of this study, it is recommended to evaluate the optimal ionization mode under basic and acidic conditions, instead of defaulting to the use of acidic modifiers with positive ion detection.

Quantification of Gut Microbiota Dysbiosis-Related Organic Acids in Human Urine Using LC-MS/MS

Urine organic acid contains water-soluble metabolites and/or metabolites—derived from sugars, amino acids, lipids, vitamins, and drugs—which can reveal a human’s physiological condition. These urine organic acids—hippuric acid, benzoic acid, phenylacetic acid, phenylpropionic acid, 4-hydroxybenzoic acid, 4-hydroxyphenyl acetic acid, 3-hydroxyphenylpropionic acid, 3,4-dihydroxyphenyl propionic acid, and 3-indoleacetic acid—were the eligible candidates for the dysbiosis of gut microbiota. The aim of this proposal was to develop and to validate a liquid chromatography−tandem mass spectrometry (LC-MS/MS) bioanalysis method for the nine organic acids in human urine. Stable-labeled isotope standard (creatinine-d3) and acetonitrile were added to the urine sample. The supernatant was diluted with deionized water and injected into LC-MS/MS. This method was validated with high selectivity for the urine sample, a low limit of quantification (10−40 ng/mL), good linearity (r > 0.995), high accuracy (85.8−109.7%), and high precision (1.4−13.3%). This method simultaneously analyzed creatinine in urine, which calibrates metabolic rate between different individuals. Validation has been completed for this method; as such, it could possibly be applied to the study of gut microbiota clinically.

Rapid determination of key impurities in high purity bisphenol A with reversed phase separation and triple quadrupole mass spectrometry

Liquid chromatography with diode array detection (DAD) or ultraviolet spectroscopic (UV) detection as the most important analytical technique for the accurate quantification of impurities in bisphenol compounds normally requires long analysis time for baseline separation of all components as well as highly concentrated sample solutions for the detection of trace levels. To expand the application possibilities to all stages of polymerisation processes, an easy and robust reversed phase separation for 7 known impurities of bisphenol-A (BPA) including 4-isopropenylphenol and its dimeric isomers, o, p-bisphenol-A and trisphenol was established in this work. The method has been validated for the detection with triple quadrupole mass spectrometry (qqqMS) and DAD. In the investigated concentration range 0.5 - 100 mg/kg, the linearity is verified for both detection techniques. The limit of quantification (LOQ) for each impurity is with 0.5 - 1.5 mg/kg for qqqMS and 15 mg/kg for DAD sufficient for the evaluation of BPA as a raw material for polymerisation processes. The separation time for all impurities is 10 min whereas earlier reported methods need a minimum of 25 to 40 min. In addition the necessary sample concentration of BPA could be reduced to 5 mg/mL compared to existing methods where the sample concentration typically is > 50 mg/mL. For all those reasons the validated method can be efficiently applied for frequent process monitoring. Furthermore, 4 additional impurities were detected and identified. Mainly these are reaction products from the isopropenylphenol structure in combination with confirmed impurities as trisphenol or chroman. The quantification of these structures was established with trisphenol as reference and two structures were detected in all BPA qualities of this study in a concentration range from 20 - 400 mg/kg.

Simple and sensitive determination of sulfites in Chinese herbal teas by ultrahigh-performance liquid chromatography tandem mass spectrometry

Sulfites are used widely in food and beverage production to prevent browning or oxidation. However, the overingestion of sulfites is harmful to human health and may cause medical complications. Chinese herbal teas have been widely consumed for centuries. However, sulfite levels in Chinese herbal teas are rarely investigated and reported. Here, we present a simple, sensitive, and quantitative method to determine sulfites in Chinese herbal teas using ultrahigh-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) coupled with dispersive solid phase extraction. The method utilized a SeQuant ZIC-HILIC column for separation, and the optimal gradient eluents consisted of acetonitrile and aqueous solution with 0.1% acetic acid and 10 mM ammonium acetate. Porous chitosan/partially reduced graphene oxide/diatomite (CS/prGO/DM) composites were used as efficient dispersive solid phase extraction adsorbents for sample preparation. Several parameters were investigated during the extraction process, including sample-to-extraction solvent volume ratios, the extraction procedure and dosage of the adsorbent. Under the optimum conditions, the developed method gave a good determination coefficient (r² > 0.99), low detection limits (0.51-12.1 μg kg^-1) and high recoveries in the range of 83.8-102.7% at different spiked levels. The method has the great advantages of being time saving, good reproducibility and much lower detection limits when compared to titration methods. The method was further applied to analyze real herbal tea samples collected from the local market, demonstrating that our developed method is robust and useful for determining sulfites in practical application.

Metabolite Profiling of Soy By-Products: A Comprehensive Approach

Soy is the major oilseed crop as soybeans are widely used to produce biofuel, food, and feed. Other parts of the plant are left on the ground after harvest. The accumulation of such by-products on the soil can cause environmental problems. This work presents for the first time a comprehensive metabolite profiling of soy by-products collected directly from the ground just after mechanical harvesting. A two-liquid-phase extraction using n-heptane and EtOH-H2O 7:3 (v/v) provided extracts with complete characterization by gas chromatography and ultra-high-performance liquid chromatography both coupled to time-of-flight mass spectrometry. A total of 146 metabolites, including flavones, flavonols, isoflavonoids, fatty acids, steroids, mono-, sesqui-, di-, and triterpenoids, were tentatively identified in soy by-products and soybeans. These proved to be sources of a wide range of bioactive metabolites, thus suggesting that they could be valorized while reducing potential environmental damage in line with a circular economy model.

Diving into the Structural Details of In Vitro Transcribed mRNA Using Liquid Chromatography–Mass Spectrometry-Based Oligonucleotide Profiling

The production process of in vitro transcribed messenger RNA (IVT-mRNA)-based vaccines has matured in recent years, partly due to the fight against infectious diseases such as COVID-19. One key to success has been the use of modified, next to canonical, nucleotides and the efficient addition of a Cap-structure and poly A tail to the 5’ and 3’ end, respectively, of this massive biomolecule. These important features affect mRNA stability and impact translation efficiency, consequently boosting the optimization and implementation of liquid chromatography–mass spectrometry (LC–MS)-based oligonucleotide profiling methods for their characterization. This article will provide an overview of these LC–MS methods at a fundamental and application level. It will be shown how LC–MS is implemented in mRNA-based vaccine analysis to determine the capping efficiency and the poly A tail length, and how it allows, via RNA mapping, (i) to determine the mRNA sequence, (ii) to screen the fidelity of the manufactured modifications, and (iii) to identify and quantify unwanted modifications resulting from manufacturing or storage, and sequence variants resulting from mutation or transcription errors.

Standard-Free Quantification of Dicarboxylic Acids: Case Studies with Salt-Rich Effluents and Serum

The present study evaluates the ionization efficiency (IE) of linear and branched C₂-C₁₄ dicarboxylic acids (DCAs) by electrospray ionization (ESI) under different conditions. The influence of the concentration of organic modifier (MeOH); mobile phase additive; and its concentration, pH, and DCA structure on IE values is studied using flow injection analysis. The IE values of DCAs increase with the increase of MeOH concentration but also decrease with an increase of pH. The former is due to the increase in solvent evaporation rates; the latter is caused by an ion-pairing between the diacid and the cation (ammonium), which is confirmed by the study with different amines. The investigation of DCA ionization in the presence of different acidic mobile phase additives showed that a significant improvement in the (-)ESI responses of analytes was achieved in the presence of weak hydrophobic carboxylic acids, such as butyric or propanoic acid. Conversely, the use of strong carboxylic acids, such as trichloroacetic acid, was found to cause signal suppression. The results of the IE studies were used to develop the liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method that provided instrumental limits of detection in the range from 6 to 180 pg. Furthermore, upon applying the nonparametric Gaussian process, a model for the prediction of IE values was developed, which contains the number of carbons in the molecule and MeOH concentration as model parameters. As a case study, dicarboxylic acids are quantified in salt-rich effluent and blood serum samples using the developed LC-HRMS method.

Direct determination of nosiheptide residue in animal tissues by liquid chromatography-tandem mass spectrometry

Because only very weak signals of fragment ions of nosiheptide can be obtained, nosiheptide is usually detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) via the determination of its hydrolyzed degradation product named HMIA in previous studies. The indirect method suffers from several problems, such as complicated samplepreparation, unavailable commercial HMIA, and the risk of the false-positive result by HMIA. However, we found that nosiheptide could produce several significant fragment ions under high collision energy (CE). Therefore, we developed a method for the direct determination of nosiheptide by LC-MS/MS in animal tissues. The sample was extracted with ACN, then degreased with n-hexane, and purified by an HLB solid-phase extraction (SPE) cartridge. After being filtered through the PTFE filter, it was analyzed by LC-MS/MS in selected reaction monitoring (SRM) mode. The influencing factors, such as mobile phase, SPE cartridge, filter material, and matrix effect, were investigated. Nosiheptide showed a good linear relationship (R2 ≥ 0.999) within the concentration range from 0.3 μg/L to 20 μg/L under optimized conditions. The limit of detection (LOD) was 0.3 μg/kg, while the limit of quantification (LOQ) was 1.0 μg/kg in chicken, bovine muscle, swine muscle, and swine liver. The average recoveries at spiked levels of 1.0, 2.0, and 10 μg/kg ranged from 83% to 101%, with the relative standard deviations (RSDs) <12%. Compared with the methods previously reported, our newly developed method was more simple, convenient, and sensitive. Moreover, it was successfully applied for the determination of nosiheptide residue in medicated chicken samples.

Dried blood spots analysis of 6β-hydroxycortisol and cortisol using liquid chromatography/tandem mass spectrometry for calculating 6β-hydroxycortisol to cortisol ratio

Dried blood spot (DBS) sampling is a minimally invasive method used to collect blood samples of any population for personalized medicine. We aimed to develop a sensitive and reliable analytical method for measuring 6β-hydroxycortisol (6β-OHF) and cortisol concentrations in DBS by liquid chromatography/tandem mass spectrometry so as to utilize DBS as a less invasive blood sampling method for calculating the ratio of 6β-OHF/cortisol. The lower limits of quantification obtained using four DBS were 1.08 pg/50 μl for 6β-OHF and 1.01 pg/50 μl for cortisol. The 6β-OHF and cortisol in DBS were stable for 28 days at room temperature. The intraday and interday accuracy and precision of the method was <12%. Additionally, the 6β-OHF and cortisol in DBS were measured before, during, and after 3 days of clarithromycin administration to two of the subjects. Then, their concentration was compared in the plasma and whole blood collected simultaneously. The concentrations of 6β-OHF and cortisol in four DBS ranged from 0.007 to 0.079 ng/50 μl and from 1.15 to 6.66 ng/50 μl, respectively. The 6β-OHF/cortisol ratio in DBS decreased by approximately 50% on administering clarithromycin compared with that before the administration of clarithromycin. The 6β-OHF/cortisol ratio in DBS also showed a strong correlation with that in whole blood (r = 0.9694) and plasma (r = 0.9383). This method provides high accuracy and precision for measuring 6β-OHF and cortisol in DBS. It also allows the use of DBS instead of plasma for calculating the 6β-OHF/cortisol ratio. The 6β-OHF/cortisol ratio could be an index of CYP3A activity in clinical setting.

An improved method for galactosyl oligosaccharide characterization

Due to beneficial effects of galactosyl oligosaccharides (GOS) on digestive and immune health, their characterization has become increasingly important. This is especially so as GOS are synthesized enzymatically and contain oligosaccharides of different sizes and linkages. High performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) is widely used for GOS characterization. With its high resolving power, it can separate structural isomers. Here we present a significant improvement to currently used methods. Our approach combines high resolution HPAE separation on a CarboPac PA300 column with 4 µm particle size with PAD and Orbitrap mass spectrometry (MS) detections to provide in-depth information on GOS composition. Oligosaccharide resolution, especially in the disaccharide region, is significantly improved and can be routinely achieved. Improvement in technology to remove sodium before MS results in minimal peak dispersion, allowing GOS degrees of polymerization 2 to 6 to be identified based on mass spectra obtained from intact oligosaccharides and confirmed using fragmentation patterns observed in MS/MS data. Combining HPAE with MS led to identification of 28 oligosaccharides in a commercial GOS sample. We attempted to correlate oligosaccharide structure with observed elution behavior. To our knowledge this is first such attempt and can form a basis for a comprehensive structure vs HPAE elution behavior database.

Cutting-edge approach using dual-channel chromatography to overcome the sensitivity issues associated with polarity switching in pesticide residues analysis

A fast and sensitive method was validated for the analysis of pesticide residues in baby food. After an QuEChERS-based extraction, the samples were analysed with a dual-channel liquid chromatography instrument coupled to a triple quadrupole mass spectrometer. The method consisted of two independent injections per sample. In the first injection the sample was analysed with a mobile phase optimal for the positive polarity ionisation (water, methanol, formic acid, and ammonium formate), whereas in the second injection the mobile phase was optimised for the negative polarity ionisation (water, acetonitrile, acetic acid). The total number of pesticides was 264, out of which 238 were analysed with the methanol gradient and 26 with the acetonitrile gradient. The dual-channel instrument allowed for sample multiplexing. Thus, sample throughput was equivalent to that of a single-channel system. The limit of quantitation, determined according to the DG SANTE guidance document, was 0.003 mg/kg for 97% of the evaluated compounds. The validation study was followed by a real sample survey. In 42 samples, 16 positives were found.

Mass Spectrometry of Nucleic Acid Noncovalent Complexes

Nucleic acids have been among the first targets for antitumor drugs and antibiotics. With the unveiling of new biological roles in regulation of gene expression, specific DNA and RNA structures have become very attractive targets, especially when the corresponding proteins are undruggable. Biophysical assays to assess target structure as well as ligand binding stoichiometry, affinity, specificity, and binding modes are part of the drug development process. Mass spectrometry offers unique advantages as a biophysical method owing to its ability to distinguish each stoichiometry present in a mixture. In addition, advanced mass spectrometry approaches (reactive probing, fragmentation techniques, ion mobility spectrometry, ion spectroscopy) provide more detailed information on the complexes. Here, we review the fundamentals of mass spectrometry and all its particularities when studying noncovalent nucleic acid structures, and then review what has been learned thanks to mass spectrometry on nucleic acid structures, self-assemblies (e.g., duplexes or G-quadruplexes), and their complexes with ligands.

Cross platform solutions to improve the zebrafish polar metabolome coverage using LC-QTOF MS: Optimization of separation mechanisms, solvent additives, and resuspension solvents

Untargeted metabolomics has been widely used for studies with zebrafish embryos. Until now, the number of analytical approaches to determine metabolites in zebrafish is limited, and there is a lack of consensus on the best platforms for comprehensive metabolomics analysis of zebrafish embryos. In addition, the capacity of these methods to detect metabolites is unsatisfactory and the confidence level for identifying compounds is relatively low. To improve the metabolome coverage, we mainly focused on the optimization of separation mechanisms, mobile phase additives, and resuspension solvents based on liquid chromatography (LC) coupling to high-resolution mass spectrometry (HRMS) techniques. Moreover, the procedures for optimizing methods were assessed when taking metabolite profiles in both positive and negative ionization modes into account. Four LC columns were studied: C18, T3, PFP, and HILIC. In positive ionization mode, it was strongly recommended to employ the HILIC approach operated at the neutral condition, which led to the presence of more than 4700 features and the annotation of 151 metabolites, mainly zwitterionic and basic compounds, in comparison to reverse phase (RP)-based methods with less than 1000 features. In negative ionization mode, the PFP column operated at 0.02% acetic acid showed the best performance in terms of metabolite coverage: 3100 metabolic features were detected and 218 metabolites were annotated in zebrafish embryos. Metabolite profiles mainly contained acidic and zwitterionic compounds. HILIC-based platforms were complementary to RP columns when analyzing highly polar metabolites. Additionally, it was preferable to reconstitute zebrafish extracts in 100% water for analysis of metabolites on RP columns, with a 20-30% increase in the number of identified metabolites compared to a 50% water in methanol solution. However, water/methanol (1:9, v/v), as resuspension solution, was advantageous over water/methanol (1:1, v/v) for HILIC analysis showing an 8-15% increase in detected metabolites. In total 336 polar metabolites were annotated by the combination of the optimized HILIC (positive) and PFP (negative) approaches. The largest metabolome coverage of polar metabolites in zebrafish embryos was obtained when three approaches were combined (negative PFP and HILIC, and HILIC positive) resulting in more than 420 annotated compounds.

Fluoride-assisted liquid chromatography-tandem mass spectrometry method for simultaneous analysis of propofol and its metabolites without derivatization in urine

The misuse of propofol for recreational purposes has become a serious social issue. Accordingly, practical and sensitive analytical methods to investigate the chronic abuse and toxicity of propofol are required. However, current propofol determination methods using liquid chromatography-mass spectrometry (LC-MS/MS) suffer from problems associated with loss in sample preparation due to its volatility and its poor ionization efficiency and collision-induced dissociation in mass spectrometry. Herein, we have developed a sensitive and accurate fluoride-assisted LC-MS/MS method combined with direct-injection for propofol determination. Ionization via fluoride-ion attachment/induced deprotonation, effected by ammonium fluoride in the mobile phase, was found to dramatically improve the sensitivity of propofol without derivatization. Furthermore, direct injection without derivatization enables the simultaneous analysis of propofol and its phase II metabolites without analyte loss. The optimal concentration of ammonium fluoride in the mobile phase was found to be 1 mM under methanol conditions. The linearity is good (R² ≥ 0.999) and the intra- and inter-day precisions for propofol determination are between 1.9 and 8.7%. The accuracies range from 87.5% to 105.4% and the limits of detection and quantitation for propofol in urine are 0.15 and 0.44 ng mL^-1, respectively. The present method was successfully applied to human urine and showed a sufficient sensitivity to determine propofol and five phase II metabolites over 48 h in human urine after administration. Consequently, the fluoride-assisted LC-MS/MS method was demonstrated to be sensitive, accurate, and practical for the determination of propofol and its metabolites.

Quantitative Determination of Methohexital in Human Whole Blood by Liquid Chromatography Tandem Mass Spectrometry

A rapid, simple and sensitive liquid chromatography tandem mass spectrometry method for the determination of methohexital in human whole blood was developed and validated. Ethyl acetate/n-hexane (9:1) was used as extraction solvent while aprobarbital was used as internal standard. Methohexital was recovered by liquid-liquid extraction from 100 μL of human whole blood. The mobile phase was water-acetonitrile, and an ACQUITY BEH C18 (2.1 × 100 mm, 1.7 μm) column was adopted. Negative electrospray ionization source and multiply reaction monitoring mode were applied. The transitions of m/z were 261.2/42.2 and 261.2/119.0 for methohexital. The limit of detection was 0.5 ng/mL, which was lower than the previous methods. Wide linear range (2-2,000 ng/mL) with a good correlation coefficient (r > 0.99) was also obtained. The intra- and inter- day precisions represented by relative standard deviation were <11.5%, and the recoveries were >79.67%. This analytical method involved small sample volume and had been proven to be rapid, easy, sensitive and specific. Therefore, it could be used for the clinical analysis of methohexital.

Trihydroxycholanoyl-taurine in brains of rodents with hepatic encephalopathy

Hepatic encephalopathy (HE), a neurological disease resulting from liver failure, is difficult to manage and its causes are unclear. Bile acids have been postulated to be involved in the provenance and progression of various diseases including HE. Hence, the characterization of bile acid profiles in the brains of subjects with and without liver failure can provide important clues for the potential treatment of HE. Nanoflow ultra-performance liquid chromatography electrospray ionization ion mobility mass spectrometry (UPLC-ESI-IM-MS) is a highly sensitive method for detection of specific molecules, such as bile acids in brain samples, at biologically relevant concentrations. We used UPLC-ESI-IM-MS to characterize bile acid profiles in brain samples from seven "healthy" control rodents and 22 "diseased" rodents with liver failure (i.e., induced HE). An isomer of trihydroxycholanoyl-taurine was detected in brain tissue samples from both rats and mice with induced HE; however, this isomer was not detected in the brains of healthy rats and mice. Our findings were confirmed by comparing IM arrival times (AT), exact mass measurements (m/z), and mass spectral fragmentation patterns of the experimentally observed suspected species to standards of trihydroxycholanoyl-taurine isomers. Moreover, In Silico Fractionation was employed to provide an additional analytical dimension to verify bile acid identifications.

Pinus pinaster Early Hormonal Defence Responses to Pinewood Nematode (Bursaphelenchus xylophilus) Infection

The pinewood nematode (PWN) is the causal agent of pine wilt disease, a pathology that affects conifer forests, mainly Pinus spp. PWN infection can induce the expression of phytohormone-related genes; however, changes at the early phytohormone level have not yet been explored. Phytohormones are low-abundance metabolites, and thus, difficult to quantify. Moreover, most methodologies focus mainly on Arabidopsis or crop species. This work aimed to validate a fast (run time 6.6 min) liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS/MS) analytical method to quantify 14 phytohormones in Pinus pinaster stem tissues. This method was further applied to evaluate, for the first time, early phytohormone changes in susceptible and resistant phenotypes of P. pinaster 24, 48 and 72 h after inoculation (HAI) with PWN. A significant increase in salicylic acid (SA, 48 and 72 HAI) and jasmonic acid methyl ester (JA-ME, 72 HAI) was observed in susceptible phenotypes. Results indicate that the higher susceptibility of P. pinaster to PWN infection might result from an inefficient trigger of hypersensitive responses, with the involvement of JA and SA pathways. This work provides an important update in forest research, and adds to the current knowledge of Pinus spp. defence responses to PWN infection.

Analysis of Nucleosides and Nucleotides in Plants: An Update on Sample Preparation and LC-MS Techniques

Nucleotides fulfill many essential functions in plants. Compared to non-plant systems, these hydrophilic metabolites have not been adequately investigated in plants, especially the less abundant nucleotide species such as deoxyribonucleotides and modified or damaged nucleotides. Until recently, this was mainly due to a lack of adequate methods for in-depth analysis of nucleotides and nucleosides in plants. In this review, we focus on the current state-of-the-art of nucleotide analysis in plants with liquid chromatography coupled to mass spectrometry and describe recent major advances. Tissue disruption, quenching, liquid-liquid and solid-phase extraction, chromatographic strategies, and peculiarities of nucleotides and nucleosides in mass spectrometry are covered. We describe how the different steps of the analytical workflow influence each other, highlight the specific challenges of nucleotide analysis, and outline promising future developments. The metabolite matrix of plants is particularly complex. Therefore, it is likely that nucleotide analysis methods that work for plants can be applied to other organisms as well. Although this review focuses on plants, we also discuss advances in nucleotide analysis from non-plant systems to provide an overview of the analytical techniques available for this challenging class of metabolites.

Isomer separation and analysis of amphiphilic polysialogangliosides using reversed-phase liquid chromatography-mass spectrometry

Gangliosides are amphiphilic, acidic glycosphingolipids possessing one or more sialic acid residues and several isobaric structural isomers with different abundances and bioactivities. Therefore, the distinction between these isomers is crucial for their proper profiling. Although liquid chromatography-mass spectrometry has been successfully employed for this purpose, the distinction process can still be improved, particularly regarding liquid chromatography. Recently, a reversed-phase liquid chromatography method that could separate disialoganglioside isomers was reported; however, the distinction of trisialoganglioside isomers using reversed-phase liquid chromatography has not been demonstrated. Here, we investigated the practicality of a reversed-phase liquid chromatography with an octadecylsilane column for separating polysialoganglioside isomers and successfully achieved the isomer separation of disialogangliosides and trisialogangliosides for the first time. We also confirmed several crucial factors in the mobile-phase composition, which affect the differential retention and mass spectral response of the isomers. First, an organic modifier, acetonitrile, exhibited superior selectivity against polysialogangliosides over methanol. Second, ammonium bicarbonate was the best ammonium salt additive among those tested, in terms of the separation efficiency and mass spectral response. Third, as the ammonium salt concentration increased, the negative electrospray ionization response was extensively suppressed, and the retention of gangliosides increased.

Surface acoustic wave nebulization improves compound selectivity of low-temperature plasma ionization for mass spectrometry

Mass spectrometry coupled to low-temperature plasma ionization (LTPI) allows for immediate and easy analysis of compounds from the surface of a sample at ambient conditions. The efficiency of this process, however, strongly depends on the successful desorption of the analyte from the surface to the gas phase. Whilst conventional sample heating can improve analyte desorption, heating is not desirable with respect to the stability of thermally labile analytes. In this study using aromatic amines as model compounds, we demonstrate that (1) surface acoustic wave nebulization (SAWN) can significantly improve compound desorption for LTPI without heating the sample. Furthermore, (2) SAWN-assisted LTPI shows a response enhancement up to a factor of 8 for polar compounds such as aminophenols and phenylenediamines suggesting a paradigm shift in the ionization mechanism. Additional assets of the new technique demonstrated here are (3) a reduced analyte selectivity (the interquartile range of the response decreased by a factor of 7)—a significant benefit in non-targeted analysis of complex samples—and (4) the possibility for automated online monitoring using an autosampler. Finally, (5) the small size of the microfluidic SAWN-chip enables the implementation of the method into miniaturized, mobile LTPI probes.

A novel isotope dilution UHPLC-ESI-MS/MS method for the quantification of 3-monochloropropane-1,2-diol in Caco-2 cell transport and receiving buffers

A routine, selective and sensitive ultra-high performance liquid chromatography-electrospray ionisation tandem triple quadrupole mass spectrometry (UHPLC-ESI-MS/MS) method was developed and validated for the quantification of 3-monochloropropane-1,2-diol (3-MCPD) in Caco-2 cell transport buffer (FaSSIF-V2, the second version of a fasted state simulated intestinal fluid) and receiving buffer (HBSS, Hank's balanced salt solution). The method involves measuring deuterated 3-MCPD (3-MCPD-d5) as internal standard (IS) during the entire analytical procedure to obtain precise and accurate results. The separation was performed on a Poroshell 120 HILIC column (2.7 µm, 3.0 × 50 mm) at a flow rate of 0.3 mL/min using water (containing 0.025% acetic acid) and acetonitrile (containing 0.025% acetic acid) as the mobile phases. Mass spectrometric detection was operated in dynamic multiple reaction monitoring (dMRM) in negative ion mode. The method exhibited high sensitivity. The limits of detection (LOD) for 3-MCPD in FaSSIF-V2 and HBSS were 0.012 and 0.014 µmol/L, and the limits of quantification (LOQ) were 0.039 and 0.045 µmol/L, respectively. Satisfactory results were observed for linearity (R² > 0.999), intra-day precision (RSD% <7.7% in FaSSIF-V2 and <6.6% in HBSS), inter-day precision (RSD% <5.9% in FaSSIF-V2 and <5.6% in HBSS), accuracy (% error within ± 10%), and sample stability (RSD% <7.7% and % error within ± 10%). The method has been successfully applied to quantify 3-MCPD in Caco-2 cell transport and receiving buffers. The results were in good agreement with those obtained with gas chromatography-tandem mass spectrometry (GC-MS).

Analytical Methods for Quantification and Identification of Intact Glucosinolates in Arabidopsis Roots Using LC-QqQ(LIT)-MS/MS

Glucosinolates are biologically active secondary metabolites in Brassicaceae plants that play a critical role in positive and negative interactions between plants and root-associated microbial communities. The aim of this study was to develop a reversed-phase liquid chromatography method to quantify and identify intact glucosinolates in the root of Arabidopsis thaliana (Arabidopsis) grown in non-sterile natural soil by using liquid chromatography-hybrid triple quadruple-linear ion trap (LC-QqQ(LIT)) mass spectrometry. The Synergi Fusion C18-based column was found to be effective for sufficient retention and separation of nine intact glucosinolates without the need for time-consuming desulfation or ion-pairing steps. Method validation results showed satisfactory inter-day and intra-day precision for all glucosinolates except for 4-hydroxyglucobrassicin. Good inter-day and intra-day accuracy and recovery results were observed for glucoiberin, gluconapin, glucobrassicin, 4-methoxyglucobrassicin and neoglucobrassicin. However, for 4-hydroxyglucobrassicin, glucoraphanin and glucoerucin corrections to quantification results might be necessary since the recovery and accuracy results were not optimal. Matrix effects were shown to have a negligible effect on the ionization of all target analytes. The established liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was applied to quantify target intact glucosinolates in Arabidopsis root crude extract of four different wild-type accessions where differences in terms of concentration and composition of intact glucosinolates were observed. Employment of sensitive and selective precursor ion survey scan of m/z 97 in combination with the information-dependent acquisition (IDA) of the enhanced product ion (EPI) dependent scan (Prec97-IDA-EPI) using LC-QqQ(LIT) provided high confidence in structural characterization of diverse intact glucosinolate profiles in complex Arabidopsis root crude extract.

Reviewing the metabolome coverage provided by LC-MS: Focus on sample preparation and chromatography-A tutorial

Metabolomics has become an invaluable tool for both studying metabolism and biomarker discovery. The great technical advances in analytical chemistry and bioinformatics have considerably increased the number of measurable metabolites, yet an important part of the human metabolome remains uncovered. Among the various MS hyphenated techniques available, LC-MS stands out as the most used. Here, we aimed to show the capabilities of LC-MS to uncover part of the metabolome and how to best proceed with sample preparation and LC to maximise metabolite detection. The analyses of various open metabolite databases served us to estimate the size of the already detected human metabolome, the expected metabolite composition of most used human biospecimens and which part of the metabolome can be detected when LC-MS is used. Based on an extensive review and on our experience, we have outlined standard procedures for LC-MS analysis of urine, cells, serum/plasma, tissues and faeces, to guide in the selection of the sample preparation method that best matches with one or more LC techniques in order to get the widest metabolome coverage. These standard procedures may be a useful tool to explore, at a glance, the wide spectrum of possibilities available, which can be a good starting point for most of the LC-MS metabolomic studies.

Simultaneous Determination of Eight Urinary Metabolites by HPLC-MS/MS for Noninvasive Assessment of Traumatic Brain Injury

Traumatic brain injury (TBI) is a serious public health concern for which sensitive and objective diagnostic methods remain lacking. While advances in neuroimaging have improved diagnostic capabilities, the complementary use of molecular biomarkers can provide clinicians with additional insight into the nature and severity of TBI. In this study, a panel of eight metabolites involved in distinct pathophysiological processes related to concussion was quantified using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Specifically, the newly developed method can simultaneously determine urinary concentrations of glutamic acid, homovanillic acid, 5-hydroxyindoleacetic acid, methionine sulfoxide, lactic acid, pyruvic acid, N-acetylaspartic acid, and F_2α-isoprostane without intensive sample preparation or preconcentration. The method was systematically validated to assess sensitivity (method detection limits: 1-20 μg/L), accuracy (81-124% spike recoveries in urine), and reproducibility (relative standard deviation: 4-12%). The method was ultimately applied to a small cohort of urine specimens obtained from healthy college student volunteers. The method presented here provides a new technique to facilitate future work aiming to assess the clinical efficacy of these putative biomarkers for noninvasive assessment of TBI.

Ionisable substances chromatography: A new approach for the determination of Ketoprofen, Etoricoxib, and Diclofenac sodium in pharmaceuticals using ion - pair HPLC

An ion-pair HPLC method was developed and validated to analyze three of non-steroidal anti-inflammatory drugs (Ketoprofen, Etoricoxib, and Diclofenac sodium) in their pure and pharmaceuticals based on their ionisable characteristics. Cetyltrimethylammonium bromide (Cetrimide) was used as an ion pair reagent since it had not been used before for this purpose. Chromatographic analysis was accomplished using the C18 (250 × 4.6 mm, 5μm) column. Mobile phase consisted of a mixture of 50% Cetrimide 10 - 3 M and 50% acetonitrile to analyze Ketoprofen and Etoricoxib, whereas for Diclofenac sodium, mobile phase was a mixture of 30% Cetrimide 10 - 3 M and 70% acetonitrile. pH value was adjusted if necessary to 10 with ammonium hydroxide. The flow rate was 1mL/min and detection wavelengths were at 254 nm, 234 nm, and 254 nm for Ketoprofen, Etoricoxib, and Diclofenac sodium; respectively under ambient temperature. Retention times ( R t ) were 9.41, 7.34, and 6.66 for Ketoprofen, Etoricoxib, and Diclofenac sodium; respectively. The proposed method was evaluated for linearity, accuracy, precision, and specificity according to ICH guidelines. Ketoprofen, Etoricoxib, and Diclofenac sodium were detected in the following linear ranges: (0.031-0.500mg/mL), (0.007-0.110g/mL), and (0.016-0.250mg/mL); respectively with excellent mean recovery values (98.0-102.0%). RSD% was in an acceptable range (less than 2), proving the precision of the developed method. Specificity was proved in the presence of degradation products. Furthermore, a comparison between the results of this study and the reported HPLC methods indicated that this developed method was better in terms of simplicity, analysis time, and no use of buffers in the mobile phase. In conclusion, the developed method can successfully detect Ketoprofen, Etoricoxib, and Diclofenac sodium quantitatively and qualitatively in their dosage forms without any interference with excipients, making this method valuable, reliable, and practical to be applied in quality control laboratories.

Polyphenol profile comparisons of seed coats of five pulse crops using a semi-quantitative liquid chromatography-mass spectrometric method

INTRODUCTION

Pulse crops are nutritious and therefore widely grown. Pulse seed coats are typically discarded, despite their high content of polyphenols that are known for their antioxidant properties and health benefits. A better understanding of polyphenol diversity and biochemical pathways will ultimately provide insight into how polyphenols are linked to health benefits, which will help to better utilise these seed coats.

OBJECTIVES

To explore polyphenol profiles among seed coats of diverse genotypes of five pulse crops using a targeted liquid chromatography mass spectrometry (LC-MS) method.

METHODS

Four genotypes of each of common bean, chickpea, pea, lentil and faba bean seed coats were selected for analysis. Following extraction, polyphenols were quantified using LC-MS.

RESULTS

An LC-MS method was developed to quantify 98 polyphenols from 13 different classes in 30 min. The low-tannin seed coats had the lowest concentrations of all polyphenols. Chickpea and pea seed coats had the most similar polyphenolic profiles. The black common bean showed the most diverse seed coat polyphenol profile, including several anthocyanins not detected in any of the other seed coats.

CONCLUSION

The LC-MS method reported herein was used to show polyphenol diversity within several polyphenol classes among the pulse crop seed coats. Detected in all seed coats, flavonols and hydroxybenzoic acids appear well-conserved in the edible Fabaceae. The presence of anthocyanins, flavan-3-ols and proanthocyanins in the coloured seed coats suggests that unique divergent branches were introduced in the flavonoid biosynthetic pathway, possibly in response to environmental stressors.

Rapid Simultaneous Determination of Cascade Metabolites of Acrylamide in Urine for Toxicokinetics Profiles and Short-Term Dietary Internal Exposure

The current study developed an ultrahigh-performance liquid chromatography tandem mass spectrometry method to simultaneously analyze cascade metabolites of acrylamide in urine of rats and humans, including acrylamide, glycidamide, N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA), N-acetyl-S-(2-carbamoylethyl)-l-cysteine-sulfoxide, N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-l-cysteine, and N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-l-cysteine. A tandem solid-phase extraction procedure was novelly used to purify all metabolites at once from human urine. The rapid analysis showed high sensitivity with LOD and LOQ ranges of 0.1-0.8 and 0.4-5.8 ng/mL, respectively, and achieved acceptable within-laboratory reproducibility (RSD < 12.0%) and spiking recovery (92.2%-117.3%) within 8 min per sample. Approximately 70.7 and 63.0% of ingested acrylamide were recovered during the toxicokinetics analysis from urine of male and female rats, respectively. For nonsmoking participants, the urinary levels of acrylamide and glycidamide were higher in men than women, whereas the urinary concentration of AAMA showed the opposite behavior. The current analysis provides methodological support of cascade metabolites of acrylamide for the dietary short-term internal exposure assessment of acrylamide.

Determination of parecoxib and valdecoxib in rat plasma by UPLC-MS/MS and its application to pharmacokinetics studies

Background

The present study aimed to develop and validate a rapid, selective, and reproducible ultra-performance liquid chromatography-tandem mass spectrometry separation method for the simultaneous determination of the levels of parecoxib and its main metabolite valdecoxib in rat plasma. Moreover, this method was applied to investigate the pharmacokinetics of parecoxib and valdecoxib in rats.

Methods

Following the addition of celecoxib as an internal standard, one-step protein precipitation by acetonitrile was used for sample preparation. The effective chromatographic separation was carried out using an ACQUITY UPLC®BEH C18 reversed phase column (2.1 mm × 50 mm, 1.7 μm particle size) with acetonitrile and water (containing 0.1% formic acid) as the mobile phase. The procedure was performed in less than 3 min with a gradient elution pumped at a flow rate of 0.4 ml/min. The electrospray ionization source was applied and operated in the positive ion mode and multiple reaction monitoring mode was used for quantification using the following: target fragment ions: m/z 371 → 234 for parecoxib, m/z 315 → 132 for valdecoxib and m/z 382 → 362 for celecoxib.

Results

The method validation demonstrated optimal linearity over the range of 50–10,000 ng/ml (r² ≥ 0.9996) and 2.5–500 ng/ml (r² ≥ 0.9991) for parecoxib and valdecoxib in rat plasma, respectively.

Conclusions

The present study demonstrated a simple, sensitive and applicable method for the quantification of parecoxib and its main pharmacologically active metabolite valdecoxib following sublingual vein administration of 5 mg/kg parecoxib in rats.

n-Butylamine for Improving the Efficiency of Untargeted Mass Spectrometry Analysis of Plasma Metabolite Composition

A comparative study of the impact of n-butylamine and traditionally used additives (ammonium hydroxide and formic acid) on the efficiency of the electrospray ionization (ESI) process for the enhancement of metabolite coverage was performed by direct injection mass spectrometry (MS) analysis in negative mode. Evaluation of obtained MS data showed that n-butylamine is one of the most effective additives for the analysis of metabolite composition in ESI in negative ion mode (ESI(-)) The limitations of the use of n-butylamine and other alkylamines in the analysis of metabolic composition and a decontamination procedure that can reduce MS device contamination after their application are discussed. The proposed procedure allows the performance of high-sensitivity analysis of low-molecular-weight compounds on the same MS device in both polarities.