Matrix effect in quantitative LC/MS/MS analyses of biological fluids: a method for determination of finasteride in human plasma at picogram per milliliter concentrations

Evaluation of Matrix Effects and Extraction Efficiencies of LC-MS/MS Methods as the Essential Part for Proper Validation of Multiclass Contaminants in Complex Feed

This work provides a proposal for proper determination of matrix effects and extraction efficiencies as an integral part of full validation of liquid chromatography coupled to tandem mass spectrometry-based multiclass methods for complex feedstuff. Analytical performance data have been determined for 100 selected analytes in three compound feed matrices and twelve single feed ingredients using seven individual samples per matrix type. Apparent recoveries ranged from 60-140% for 52-89% of all compounds in single feed materials and 51-72% in complex compound feed. Regarding extraction efficiencies, 84-97% of all analytes ranged within 70-120% in all tested feed materials, implying that signal suppression due to matrix effects is the main source for the deviation from 100% of the expected target deriving from external calibration. However, the comparison between compound feed and single feed materials shows great variances regarding the apparent recoveries and matrix effects. Therefore, model compound feed formulas for cattle, pig, and chicken were prepared in-house in order to circumvent the issue of the lack of a true blank sample material and to simulate compositional uncertainties. The results of this work highlight that compound feed modeling enables a more realistic estimation of the method performance and therefore should be implemented in future validation guidelines.

Oral Cannabidiol Does Not Convert to Δ8-THC or Δ9-THC in Humans: A Pharmacokinetic Study in Healthy Subjects

Introduction: Recent studies have suggested that cannabidiol (CBD) could interconvert into Delta-8- and Delta-9- tetrahydrocannabinol. Materials and Methods: Thus, we tested the plasma samples of 120 healthy human subjects (60 male and 60 female), 60 in fasting and the other 60 under normal feeding conditions after acute administration of an oral solution containing CBD 300 mg. To do this, we developed a bioanalytical method to determine CBD and the presence of THC in plasma samples by Ultra-High Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry. Results: The results showed that THC was not detected in plasma after the administration of CBD, and those study participants did not present psychotomimetic effects. Conclusions: The findings presented here are consistent with previous evidence suggesting that the oral administration of CBD in a corn oil formulation is a safe route for the administration of the active substance without bioconversion to THC in humans.

Development and validation of a UPLC-MS/MS method for simultaneous determination of LBPT and its metabolites in human plasma

Aim: A UPLC-MS/MS method was developed to determine LBPT as well as its four metabolites in human plasma to support the clinical study aiming to evaluate the efficacy of LBPT tablet in patients undergoing hip/knee replacement. Methodology: Plasma samples were prepared by protein precipitation and then separated on a C₁₈ analytical column using (A) acetonitrile (B) 0.1% formic acid and 10 mM ammonium formate in water. The detection was performed on a triple quadrupole tandem mass spectrometer in positive electrospray ionization using multiple reactions monitoring mode. Results & conclusion: The method has been validated in accordance with the US FDA guidelines and was applied to the measurement of five analytes in human plasma samples from a Phase II clinical trial.

Quantification of aminobutyric acids and their clinical applications as biomarkers for osteoporosis

Osteoporosis is a highly prevalent chronic aging-related disease that frequently is only detected after fracture. We hypothesized that aminobutyric acids could serve as biomarkers for osteoporosis. We developed a quick, accurate, and sensitive screening method for aminobutyric acid isomers and enantiomers yielding correlations with bone mineral density (BMD) and osteoporotic fracture. In serum, γ-aminobutyric acid (GABA) and (R)-3-aminoisobutyric acid (D-BAIBA) have positive associations with physical activity in young lean women. D-BAIBA positively associated with hip BMD in older individuals without osteoporosis/osteopenia. Lower levels of GABA were observed in 60–80 year old women with osteoporotic fractures. Single nucleotide polymorphisms in seven genes related to these metabolites associated with BMD and osteoporosis. In peripheral blood monocytes, dihydropyrimidine dehydrogenase, an enzyme essential to D-BAIBA generation, exhibited positive association with physical activity and hip BMD. Along with their signaling roles, BAIBA and GABA might serve as biomarkers for diagnosis and treatments of osteoporosis.

Wang et al. develop an LC/MS based screening method to separate and quantify aminobutyric acids isoforms. Applying it to osteoporosis clinical studies, their method yields important correlations with bone mineral density and osteoporotic fracture and highlight the role of γ-aminobutyric acid and β-aminoisobutyric acid as biomarkers for osteoporosis.

Validation and implementation of an ultrasensitive liquid chromatographic-tandem mass spectrometric (LC-MS/MS) assay for dapivirine quantitation in breast milk

BACKGROUND

The non-nucleoside reverse transcriptase inhibitor dapivirine has been evaluated as a topical microbicidal agent to prevent HIV-1 acquisition. Several clinical trials have evaluated the pharmacokinetics of dapivirine when administered as a 25-mg intravaginal ring. Recent studies have focused on the distribution of dapivirine into breast milk. Drug distribution during lactation and breastfeeding can have implications in terms of infant drug exposure. Thus, sensitive bioanalytical tools are required to characterize the pharmacokinetics of dapivirine in breast milk.

METHODS

Whole breast milk was spiked with dapivirine and internal standard. Lipid content was disrupted via pre-treatment with n-hexane, and supernatants were subjected to solid phase extraction. Extracted materials were subjected to liquid chromatographic-tandem mass spectrometric (LC-MS/MS) analysis. Separation occurred using a Waters BEH C8, 50 × 2.1 mm UPLC column with a 1.7 µm particle size and dapivirine was detected on an API 5000 mass analyzer. Methods were validated in accordance with FDA Bioanalytical Method Validation recommendations.

RESULTS

The analytical method was optimized for dapivirine extraction from breast milk. The analytical measuring range of the assay was 10-1000 pg/mL. Calibration curves were generated via weighted linear regression of standards. Intra- and inter-assay precision and accuracy studies demonstrated %CVs ≤ 14.6% and %DEVs ≤ ±12.7%. Stability and matrix effects studies were also conducted and deemed acceptable. The method was applied to a previously reported phase 1 clinical trial and demonstrated appropriate performance in the quantitation of dapivirine in breast milk samples from lactating women.

CONCLUSIONS

An ultrasensitive LC-MS/MS assay has been developed and validated for the quantitation of dapivirine in breast milk. The described method meets validation acceptance criteria and has been applied to a phase 1 clinical trial.

An LC-MS/MS method for creatine and creatinine analysis in paraquat-intoxicated patients

A sudden increase in serum creatinine after paraquat intoxication has been reported in several clinical studies. However, this dramatic change of creatinine may be possibly due to an interconversion of creatine-creatinine in relation to paraquat toxicity. In order to investigate the creatine-creatinine relationship, a liquid chromatography tandem mass spectrometry in combination with electrospray ionization was developed and validated for simultaneous determination of creatine and creatinine in the serum. The chromatographic separation was achieved on a Gemini® C₆-Phenyl column with a gradient elution consisting of 0.1% formic acid in ultrapure water and methanol as the mobile phase. The method yielded suitable levels of specificity and selectivity, and calibration curves of creatine and creatinine in serum were linear over the concentration range of 0.5-200 µg mL^-1. The limit of quantification of both compounds was 0.5 µg mL^-1, and the method was accurate within the recovery range of 96.23-102.75%, indicating the robustness of the method. The method was successfully applied to toxicological samples from paraquat-intoxicated patients, and the concentrations of creatine and creatinine were quantified. High creatine concentrations in serum samples were observed which may lead to high serum creatinine despite normal kidney function as creatine is converted to creatinine in proportion to its concentration.

Comparing Data-Independent Acquisition and Parallel Reaction Monitoring in Their Abilities To Differentiate High-Density Lipoprotein Subclasses

High-density lipoprotein (HDL) is a diverse group of particles with multiple cardioprotective functions. HDL proteome follows HDL particle complexity. Many proteins were described in HDL, but consistent quantification of HDL protein cargo is still a challenge. To address this issue, the aim of this work was to compare data-independent acquisition (DIA) and parallel reaction monitoring (PRM) methodologies in their abilities to differentiate HDL subclasses through their proteomes. To this end, we first evaluated the analytical performances of DIA and PRM using labeled peptides in pooled digested HDL as a biological matrix. Next, we compared the quantification capabilities of the two methodologies for 24 proteins found in HDL₂ and HDL₃ from 19 apparently healthy subjects. DIA and PRM exhibited comparable linearity, accuracy, and precision. Moreover, both methodologies worked equally well, differentiating HDL subclasses' proteomes with high precision. Our findings may help to understand HDL functional diversity.

A Rapid Dilute-and-Shoot UPLC-MS/MS Assay to Simultaneously Measure 37 Drugs and Related Metabolites in Human Urine for Use in Clinical Pain Management

Background

Monitoring of medication compliance and drug abuse is used by clinicians to increase patient prescription drug compliance and reduce illicit drug abuse and diversion. Despite available immunoassays, chromatography-mass spectrometry–based methods are considered the gold standard for urine drug monitoring owing to higher sensitivities and specificities. Herein, we report a fast, convenient ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) assay to detect or quantify 37 clinically relevant prescription drugs, drugs of abuse, and related glucuronides and other metabolites in human urine by single diluted sample injection.

Methods

Analytes consisted of prescription and illicit opioids, benzodiazepines, and drugs of abuse, including parent compounds and glucuronidated and nonglucuronidated metabolites. Urine samples were diluted with water and supplemented with deuterated internal standards without enzymatic hydrolysis, analyte extraction, or sample purification. Analytes were separated by reversed-phase UPLC and quantified by positive-mode electrospray ionization and collision-induced dissociation MS. Assay validation followed Food and Drug Administration bioanalytical guidelines.

Results

Total analytical run time was 5.5 min. All analytes demonstrated acceptable inter- and intraassay accuracy, imprecision, and linearity throughout clinically relevant analytical ranges (1–2000 ng/mL, depending on analyte). All analytes demonstrated acceptable selectivity, stability, matrix effects, carryover, and performance compared to national reference laboratory or previously validated in-house methods. A total of 23 and 14 analytes were validated for quantitative and qualitative testing, respectively.

Conclusions

A convenient UPLC-MS/MS assay for simultaneously monitoring 37 analytes in human urine was validated for use in pain management testing. Advantages of this multiplex assay include facile sample preparation and higher-throughput definitive detection including glucuronide metabolite quantification.

Impact of matrix effects and ionization efficiency in non-quantitative untargeted metabolomics

INTRODUCTION

LC-MS-based untargeted metabolomics has become increasingly popular due to the vast amount of information gained in a single analysis. Many studies utilize metabolomics to profile metabolic changes in various representative biofluids, tissues, or other sample types. Most analyses are performed measuring changes in the metabolic pool of a single biological matrix due to an altered phenotype, such as disease versus normal. Measurements in such experiments are typically highly reproducible with little variation due to analytical and technological advancements in mass spectrometry. With the expanded application of metabolomics into various non-analytical scientific disciplines, the emergence of studies comparing the signal intensities of specific analytes across different biological matrices (e.g. plasma vs. urine) is becoming more common, but the matrix effect between sample types is often neglected. Additionally, the practice of comparing the signal intensities of different analytes and correlating to relative abundance is also increasingly prevalent, but the response ratio between analytes due to differences in ionization efficiency is not always accounted for in data analysis. This report serves to communicate and raise awareness of these two well-recognized issues to prevent improper data interpretation in the field of metabolomics.

OBJECTIVES

We demonstrate the impact of matrix effects and ionization efficiency with labeled analytical standards in human plasma, serum, and urine and describe how the direct comparison of non-quantitative signal intensities between biofluids, as well as between different analytes in the same biofluid, in untargeted metabolomics is inaccurate without proper response corrections.

METHODS

Human plasma, serum, and urine (n = 4 technical replicates per biofluid) were spiked with a panel of labeled internal standards all at identical concentrations, simultaneously extracted, and analyzed by UHPLC-HRMS. Signal intensities were compared for demonstration of the impact of matrix effects in untargeted metabolomics. A neat mixture of two co-eluting, structurally-similar labeled standards at the same concentration was also analyzed to demonstrate the effect of ionization efficiency on signal intensity.

RESULTS

Despite being spiked at identical concentrations, labeled standards we examined in this study showed significant differences in their signal intensities between biofluids, as well as from each other in the same biofluid, due to matrix effects. Co-eluting standards were also found to yield significantly different signal intensities at identical concentrations due to differences in ionization efficiency.

CONCLUSIONS

Due to the presence of matrix effects in untargeted, non-quantitative metabolomics, the signal intensity of any single analyte cannot be directly compared to the signal intensity of that same analyte (or any other analyte) between any two different matrices. Due to differences in ionization efficiency, the signal intensity of any single analyte cannot be directly compared to the signal intensity of any other analyte, even in the same matrix.

Development and validation of a multiplex UHPLC-MS/MS method for the determination of the investigational antibiotic against multi-resistant tuberculosis macozinone (PBTZ169) and five active metabolites in human plasma

The emergence of Mycobacterium tuberculosis strains resistant to current first-line antibiotic regimens constitutes a major global health threat. New treatments against multidrug-resistant tuberculosis (MDR-TB) are thus eagerly needed in particular in countries with a high MDR-TB prevalence. In this context, macozinone (PBTZ169), a promising drug candidate with an unique mode of action and highly potent in vitro tuberculocidal properties against MDR Mycobacterium strains, has now reached the clinical phase and has been notably tested in healthy male volunteers in Switzerland. To that endeavor, a multiplex UHPLC-MS/MS method has been developed for the sensitive and accurate human plasma levels determination of PBTZ169 along with five metabolites retaining in vitro anti-TB activity. Plasma protein precipitation with methanol was carried out as a simplified sample clean-up procedure followed by direct injection of the undiluted supernatant for the bioanalysis of the six analytes within 5 min, using 1.8 μm reversed-phase chromatography coupled to triple quadrupole mass spectrometry employing electrospray ionization in the positive mode. Stable isotopically-labelled PBTZ169 was used as internal standard (ISTD), while metabolites could be reliably quantified using two unlabeled chemical analogues selected as ISTD from a large in-house analogous compounds library. The overall methodology was fully validated according to current recommendations (FDA, EMEA) for bioanalytical methods, which include selectivity, carryover, qualitative and quantitative matrix effect, extraction recovery, process efficiency, trueness, precision, accuracy profiles, method and instrument detection limits, integrity to dilution, anticoagulant comparison and short- and long-term stabilities. Stability studies on the reduced metabolite H₂-PBTZ169 have shown no significant impact on the actual PBTZ169 concentrations determined with the proposed assay. This simplified, rapid, sensitive and robust methodology has been applied to the bioanalysis of human plasma samples collected within the frame of a phase I clinical study in healthy volunteers receiving PBTZ169.

False Immunosuppressant Measurement by LC-MS/MS Method Due to Radiopaque Agents

BACKGROUND

Although liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is preferred as a reliable method, some molecules in the blood matrix may lead to false positive or false negative results. False positive or negative results show the direction of the deviation rate from the target value.

AIM

The aim of this study was to investigate the effect of seven different radiopaque agents on four immunosuppressant drugs.

METHODS

Every agent coded with RM1 to RM7 was added to control materials containing tacrolimus, everolimus, sirolimus, and cyclosporine A drugs. Measurements were performed using an LC-MS/MS instrument. Bias values were calculated to detect the deviation rates.

RESULTS

All RMs led to false negative results in the tacrolimus and cyclosporine A levels at a rate of -19.77% (95% CI, -27.16 to 12.52) to -44.45% (95% CI, -49.20 to -39.69). The smallest deviations were seen in the everolimus levels with the administration of RM6 (gadodiamide) and in the sirolimus levels with RM1 (gadobutrol) at the rates of 4.04% (95% CI, -11.36 to -3.17) and 2.11% (95% CI, -7.18 to 7.11), respectively. The most affected drug by RM4 (gadopentetate dimeglumine salt) was sirolimus at the rate of 114.01% (95% CI, 97.31 - 130.76). RM5 (gadodiamide) interfered cyclosporine A at the most. The highest deviations were observed with the administration of RM3 (iohexol) in the everolimus and sirolimus levels at the rates of 153.72% (95% CI, 142.44 to 164.78) and 171.41% (95% CI, 157.91 to 184.97), respectively.

CONCLUSION

Radiopaque agents interfered the measurement of immunosuppressant drugs. Especially, everolimus and sirolimus levels were affected due to using iohexol. The choice of gadodiamide or ioversol is important to reduce the risk of interference for everolimus measurement. The blood samples should be obtained for measurement of drug levels before contrast-enhanced imaging.

Significant role of supercritical fluid chromatography - mass spectrometry in improving the matrix effect and analytical efficiency during multi-pesticides residue analysis of complex chrysanthemum samples

As an important "food and drug dual-use" product, chrysanthemums are widely used in both botanical medicine and food applications. However, the misuse of pesticides during chrysanthemum cultivation makes pesticide residue monitoring crucial. The aim of the present work was to address this practical demand for the simultaneous determination of multiple pesticide residues in various species of chrysanthemums. Both the sample pre-treatment and instrumental methods were systematically investigated. Seven chrysanthemum samples were extracted using acetonitrile and purified by dispersive solid-phase extraction with amino-modified multi-walled carbon nanotubes (MWCNTs-NH₂) and C18 as the cleanup co-adsorbents. After optimizing the amounts of MWCNTs-NH₂ and C18, matrix effects could not be avoided during LC-MS/MS analysis of 112 pesticides, although satisfactory recoveries were obtained. The use of SFC-MS/MS was evaluated, which demonstrated the significant positive role of SFC-MS/MS in reducing the matrix effects during pesticide residue analysis. In addition, the use of SFC-MS/MS permitted a shorter run time and afforded greater analytical efficiency. Method validation was further performed to evaluate the linearity, sensitivity, recovery, and precision of the developed method. Good linearity was observed for 92% of the analytes in the concentration range of 2-250 μg L^-1 for all seven of the chrysanthemum samples. The LODs of the 112 pesticides ranged from 0.01 to 31.41 μg L^-1, depending on the sample, while the mean recoveries of all of the spiked pesticides ranged from 81.8% to 102% for concentrations of 20, 50, and 200 μg kg^-1. These results clearly demonstrate the applicability of the developed method for the simultaneous determination of multi-pesticides in various chrysanthemum samples.

Determination of BPI15086 and its metabolite in human plasma by ultra-high performance liquid chromatography-MS/MS and its application to a pharmacokinetic study

Aim: BPI15086 is a potent, irreversible mutant-selective inhibitor of both EGFR (EGFR tyrosine kinase inhibitor) and the T790M resistance mutations tyrosine kinase. A simultaneous quantification method of BPI15086 and its main metabolite in human plasma using LC-MS/MS is documented and fully validated in this study. Methodology & results: Plasma samples were extracted and chromatographed on an Acquity ultra-high performance liquid chromatography BEH C18 column with a gradient elution. Detection was performed on a Sciex 5500 QTRAP^® mass spectrometer using positive electrospray ionization. The results indicated that the method had excellent sensitivity and specificity. Conclusion: For the first time a sensitive and robust ultra-high performance liquid chromatography-MS/MS method was established and validated of BPI15086 in human plasma, this method was successfully applied in a first-in-human Phase I clinical trial studying the pharmacokinetics of the BPI15086 tablet in Chinese non-small-cell lung cancer patients.

Development and Validation of an Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry Method for the Concurrent Measurement of Gabapentin, Lamotrigine, Levetiracetam, Monohydroxy Derivative of Oxcarbazepine, and Zonisamide Concentrations in Serum in a Clinical Setting

BACKGROUND

Therapeutic drug monitoring of antiepileptic drugs (AEDs) is often necessary to prevent associated destructive toxicities. Tandem mass spectrometry (MS/MS) with stable-isotope-labeled internal standards is considered the gold standard for the measurement of AEDs. This study presents the development and validation of a clinical ultra-performance liquid chromatography-MS/MS method for the concurrent measurement of gabapentin, lamotrigine, levetiracetam, monohydroxy derivative of oxcarbazepine, and zonisamide in human serum.

METHODS

To determine the optimal assay analyte range, one year of AED therapeutic drug monitoring results (n = 1825) were evaluated. Simple protein precipitation with acetonitrile containing isotopically labeled internal standards was used. Reverse-phase ultra-performance liquid chromatography chromatographic separation was used, having a total run time of 3 minutes. Quantification of analytes was accomplished using electrospray ionization in positive ion mode and collision-induced dissociation MS. Assay parameters were evaluated per Food and Drug Administration bioanalytical guidelines.

RESULTS

After evaluating internal patient data, the analytical measuring range (AMR) of the assay was established as 0.1-100 mcg/mL. All AEDs were linear across the AMR, with R values ranging from 0.9988 to 0.9999. Imprecision (% coefficient of variation) and inaccuracy (% difference) were calculated to be <20% for the lower limit of quantitation and <15% for the low, mid, and high levels of quality controls across the AMR. All AEDs demonstrated acceptable assay parameters for carryover, stability under relevant storage conditions, matrix effects, recovery, and extraction and processing efficiency. In addition, the assay displayed acceptable concordance to results obtained from a national reference laboratory, with Deming regression R of 0.99 and slope values ranging from 0.89 to 1.17.

CONCLUSIONS

A simple, cost-effective, and robust ultra-performance liquid chromatography-tandem mass spectrometry method for monitoring multiple AEDs was developed and validated to address the clinical needs of patients at our institution.

Simultaneous Quantitation of Isoprenoid Pyrophosphates in Plasma and Cancer Cells Using LC-MS/MS

Isoprenoids (IsoP) are an important class of molecules involved in many different cellular processes including cholesterol synthesis. We have developed a sensitive and specific LC-MS/MS method for the quantitation of three key IsoPs in bio-matrices, geranyl pyrophosphate (GPP), farnesyl pyrophosphate (FPP), and geranylgeranyl pyrophosphate (GGPP). LC-MS/MS analysis was performed using a Nexera UPLC System connected to a LCMS-8060 (Shimadzu Scientific Instruments, Columbia, MD) with a dual ion source. The electrospray ionization source was operated in the negative MRM mode. The chromatographic separation and detection of analytes was achieved on a reversed phase ACCQ-TAG Ultra C18 (1.7 µm, 100 mm × 2.1 mm I.D.) column. The mobile phase consisted of (1) a 10 mM ammonium carbonate with 0.1% ammonium hydroxide in water, and (2) a 0.1% ammonium hydroxide in acetonitrile/methanol (75/25). The flow rate was set to 0.25 mL/min in a gradient condition. The limit of quantification was 0.04 ng/mL for all analytes with a correlation coefficient (r2) of 0.998 or better and a total run time of 12 min. The inter- and intra-day accuracy (85–115%) precision (<15%), and recovery (40–90%) values met the acceptance criteria. The validated method was successfully applied to quantitate basal concentrations of GPP, FPP and GGPP in human plasma and in cultured cancer cell lines. Our LC-MS/MS method may be used for IsoP quantification in different bio-fluids and to further investigate the role of these compounds in various physiological processes.

Separation and identification of the epimeric doping agents - Dexamethasone and betamethasone in equine urine and plasma: A reversed phase chiral chromatographic approach

Chirality is one of the most important considerations when controlling doping. The epimeric corticosteroids dexamethasone and betamethasone are significantly potent and long-acting, and they are highly abused in equestrian sports. The scope of this study was to develop a simple and reliable analytical method for simultaneously identifying and separating regularly abused co-eluting corticosteroids in equine urine and plasma. In this paper, we present a simple and rapid method for the chiral separation and identification of epimeric mixtures of dexamethasone and betamethasone using a Thermo Q Exactive high resolution accurate mass spectrometer. The high resolution accurate mass spectrometer system provided extremely high sensitivity, enabling detection of each isomer at a very low concentration from complex biological matrices. Chromatographic separation was performed using amylose and cellulose chiral columns. Reversed phase media showed very good potential for providing a successful chiral resolution in LC-MS analysis. This study also focused on optimizing the mobile phase for elution strength, nature of the organic modifier, additives, and column temperature.

Mass spectrometric method for distinguishing isomers of dexamethasone via fragment mass ratio: An HRMS approach

The major challenge in identifying dexamethasone, betamethasone, and paramethasone from a mixture of these corticosteroids is difficulty in achieving an efficient separation. In this study, we aimed to develop an efficient technique to identify these co-eluting isomers based on the mass spectral patterns of them and their corresponding phase II metabolites after electrospray ionization. Fragmentation pathways in tandem mass spectrometry revealed acceptable specificity within the groups of conjugates. The method was validated using individual isomers and mixtures at various compositions. The effects of concentration and collision energies on fragmentation patterns were also studied extensively. Matrix-fortified equine urine and plasma samples were also included so that matrix effects and interferences on fragmentation ratios could be elucidated. Preliminary results using biological samples demonstrated the suitability of this analytical strategy for direct measurement from their fragmentation patterns. Possible fragmentation pathways for each isomer were proposed.

Simultaneous ultraperformance liquid chromatography/tandem mass spectrometry determination of four antihypertensive drugs in human plasma using hydrophilic-lipophilic balanced reversed-phase sorbents sample preparation protocol

Therapeutic drug monitoring of angiotensin-converting enzyme inhibitors has a great impact on blood pressure control in patients with heart failure and hepatic and renal impairment. To provide an efficient tool for drug assessment in plasma, a UPLC-MS/MS method was developed for simultaneous determination of benazepril hydrochloride, fosinopril sodium, captopril and hydrochlorothiazide in human plasma samples. Solid phase extraction was applied for sample preparation using OASIS^® hydrophilic-lipophilic balanced reversed-phase sorbents cartridges. Chromatographic separation was performed using an Agilent SB-C₁₈ column and methanol-0.1% formic acid in water (95:5, v/v) as mobile phase, at flow rate 0.3 mL/min. Detection was accomplished using a tandem mass spectrometer. The method was validated according to US Food and Drug Administration guidelines. It showed good linearity over concentration ranges 5-400 ng/mL for benazepril hydrochloride, fosinopril sodium and hydrochlorothiazide and 100-3500 ng/mL for captopril. CV% values were <13.92% whereas the mean accuracy ranged from 94.50 to 113.82% for quality control samples and their extraction recoveries ranged from 90.60 to 99.38%. In conclusion, the present study revealed method selectivity and sensitivity; it can be applied for estimation of angiotensin converting enzyme inhibitors and hydrochlorothiazide in human plasma for dose adjustment and therapeutic drug monitoring.

A Sensitive Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Nimbolide in Mouse Serum: Application to a Preclinical Pharmacokinetics Study

A sensitive and robust liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of nimbolide in mouse serum. Exemestane was used as the internal standard (IS). Here, we employed acetonitrile-based protein precipitation (PPT) for serum sample preparation, and performed chromatographic separation using an ODS Hypersil C18 column (100 mm × 2.1 mm, 5 µm) with gradient elution (0.1% formic acid in water vs 100% acetonitrile). The run time was 6 min. Instrumental analysis was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the multiple-reaction monitoring (MRM) under positive mode. A good linear calibration was achieved in the 5–1000 ng/mL range. The intra- and inter-day precisions for nimbolide were ≤12.6% and ≤13.9% respectively. Intra-day accuracy ranged from 96.9–109.3%, while inter-day accuracy ranged from 94.3–110.2%. The matrix effect of nimbolide, detected but consistent at low and high concentrations, do not affect linearity of standard curve. In conclusion, we have developed and validated a sensitive analytical method for determination of a novel natural compound nimbolide in mouse serum, and it has been successfully applied to our preclinical study in investigating the pharmacokinetic properties of nimbolide, which could greatly facilitate the preclinical development of the promising lead compound for anticancer therapy.

Simultaneous Determination of Ten Illegal Azo Dyes in Feed by Ultra-high Performance Liquid Chromatography Tandem Mass Spectrometry

Introduction

The paper presents the method of simultaneous determination of 10 illegal azo dyes in feed by ultra-high performance liquid chromatography coupled with tandem mass spectrometry technique.

Material and Methods

The dyes were extracted with hexane, evaporated to dryness, and analysed. Separation was achieved in 7 min in a gradient elution using acetonitrile (A) and 0.1% formic acid (B) as a mobile phase.

Results

The validation results showed the repeatability of the method, which was evaluated at three levels (50, 500, and 5,000 µg/kg). All the matrix calibration curves for the working ranges were linear (R² 0.9904 to 1.0), the repeatability was between 2.1% and 24%, and recoveries ranged from 77.9% to 120%. The LOD and LOQ were at 1–2 and 5–10 µg/kg for different dyes, respectively. Furthermore, the method was applied in the homogeneity tests of the in-house prepared feed containing Sudan I at the levels of 0.5, 5, and 50 mg/kg.

Conclusions

A sensitive, selective, and fast multiresidue method was successfully developed and validated. Its robustness was confirmed by the analysis of an experimental feed containing Sudan I.

High-performance liquid chromatography quantification of enantiomers of a Dihydroxylated tetrahydrofuran natural product

Both enantiomers of petromyroxol are putative pheromones in sea lamprey (Petromyzon marinus). Here, we describe the separation and quantification of the petromyroxol enantiomers using high-performance liquid chromatography tandem mass spectrometry. The separation was tested on a wide range of chiral columns with normal phases, and effects of the chromatographic parameters such as mobile phase and temperature on the separation were optimized. The AD-H column showed the best separation of enantiomers with n-hexane and ethanol as the mobile phase. The enantiomers were detected by multiple reaction monitoring with a positive atmospheric-pressure chemical ionization on triple quadrupole mass spectrometer. Validation revealed that the method was specific, accurate, and precise. The validated method was applied to measure the amount of petromyroxol enantiomers in water conditioned with sea lamprey larvae, the source of the putative pheromone. This method will be applied in quantifying the natural scalemic petromyroxol mixture, enabling further investigations of a rare non-racemic enantiomeric pheromone mixture in a vertebrate species.

Magnetic molecularly imprinted polymer nanoparticles for simultaneous extraction and determination of 6-mercaptopurine and its active metabolite thioguanine in human plasma

Cytotoxic drugs used in cancer chemotherapy require the continuous monitoring of their plasma concentration levels for dose adjustment purposes. Such condition necessitates the presence of a sensitive technique for accurate extraction and determination of these drugs together with their active metabolites. In this study a novel solid phase extraction technique using magnetic molecularly imprinted nanoparticles (MMI-SPE) is combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) to extract and determine the anti-leukemic agent; 6-mercaptopurine (6-MP) and its active metabolite thioguanine (TG) in human plasma. The magnetic molecularly imprinted nanoparticles (Fe₃O₄@MIP NPs) were synthesized via precipitation polymerization technique and were characterized using different characterization methods A computational approach was adopted to help in the choice of the monomer used in the fabrication process. The Fe₃O₄@MIPs NPs possessed a highly improved imprinting efficiency, fast adsorption kinetics following 2nd order kinetics and good adsorption capacity of 1.0 mg/g. The presented MMI-SPE provided the optimum approach in comparison to other reported ones to achieve good extraction recovery and matrix effect of trace levels of 6-MP and TG from plasma. Chromatographic separation was carried out using a validated LC-MS/MS assay and recovery, matrix effect and process efficiency were evaluated. Recovery of 6-MP and TG was in the range of 85.94-103.03%, while, matrix effect showed a mean percentage recovery of 85.94-97.62% and process efficiency of 85.54-96.18%. The proposed extraction technique is simple, effective and can be applicable to the extraction and analysis of other pharmaceutical compounds in complex matrices for therapeutic drug monitoring applications.

The determination of capreomycin in human plasma by LC-MS/MS using ion-pairing chromatography and solid-phase extraction

A bioanalytical method was developed and validated for the quantification of capreomycin (Cm) analogs, Cm IA and Cm IB, in human plasma. This implemented ion-pairing solid phase extraction, followed by ion-pairing high-performance liquid chromatography, with tandem mass spectrometry detection. Chromatographic separation was achieved using a Discovery C18 , 5 μm, 4.6 × 50 mm analytical column. An isocratic mobile phase consisting of water and acetonitrile with 0.1% formic acid and 4mm heptafluorobutyric acid (80:20; v/v) was used at a flow-rate of 500 μL/min. An AB Sciex API 3000 mass spectrometer at unit resolution, in multiple reaction monitoring mode, was used for detection. Electrospray ionization was used for ion production. The method was successfully validated for the range 469-30,000 ng/mL for Cm IA and for Cm IB, with cefotaxime as the internal standard. The within- and between-day precision determinations for Cm IA and IB, expressed as the percentage coefficient of variation, were < 20.0% at the lower limit of quantification (LLOQ) and < 8.2% at all other test concentrations. Recovery of both analogs was > 72.3% and reproducible at the low, medium and high end of the calibration range. No significant matrix effects were observed for the analyte. The assay performed well when applied to clinical samples generated from children in a clinical multidrug resistant tuberculosis research study in South Africa.

Development, validation and utilization of a highly sensitive LC-MS/MS method for quantification of levonorgestrel released from a subdermal implant in human plasma

Levonorgestrel (LNG) is a synthetic progestin that is available in oral contraceptive tablets, a subdermal implant, and an intrauterine system for contraception. LNG pharmacokinetics are a pivotal determinant of contraceptive efficacy and essential in assessing drug-drug interactions influencing LNG exposure following different routes of LNG administration. A highly sensitive LC-MS/MS method was developed and validated to quantify levonorgestrel in human plasma. Liquid-liquid extraction was utilized with a sample volume of 500 μL to extract levonorgestrel from plasma. Chromatographic separation of LNG was achieved with a Fortis™ C18 (3 μm: 100 mm × 2.1 mm) reverse phase analytical column. The mobile phases consisted of de-ionized water plus 0.1% NH4OH (100:0.1%, v/v) (A), and methanol plus 0.1% NH4OH (100:0.1%, v/v) (B) delivered as a gradient at a flow rate of 400 μL/min. Detection of LNG and internal standard (D-(-)-norgestrel-d7) was achieved using positive polarity mode monitoring at 313.2-245.2 amu and 320.1-251.2 amu, respectively. The assay was linear over the calibration range of 49.6 to 1500 pg/mL. This method was used to quantify plasma LNG released by subdermal implant in support of a drug interaction study among women with HIV receiving efavirenz- or nevirapine-based antiretroviral therapy.

Evaluation of 1,5-anhydro-d-glucitol in clinical and forensic urine samples

Because of the lack of characteristic morphological findings post mortem diagnosis of diabetes mellitus and identification of diabetic coma can be complicated. 1,5-Anhydroglucitol (1,5-AG), the 1-deoxy form of glucose, competes with glucose for renal reabsorption. Therefore low serum concentrations of 1,5-AG, reflect hyperglycemic excursions over the prior 1-2 weeks in diabetic patients. Next to clinical applications determination of 1,5-AG can also be used in forensic analysis. To investigate the elimination of 1,5-AG, a liquid chromatographic-mass spectrometric method for the determination of 1,5-AG and creatinine in urine was developed and validated according to international guidelines. To evaluate ante mortem concentrations of 1,5-AG spot urine samples of 30 healthy subjects, 46 type 1 and 46 type 2 diabetic patients were analyzed. 1,5-AG urine concentrations of diabetic patients were significantly (p<0.001) lower (mean: 1.54μg/ml, n=92) compared to concentrations of healthy subjects (mean: 4.76μg/ml, n=30) which led to the idea that 1,5-AG urine concentrations post mortem might help in the interpretation of a diabetic coma post mortem. Urine of 47 deceased non-diabetics, 37 deceased diabetic and 9 cases of diabetic coma were measured. Comparison of blood and urine 1,5-AG concentrations in clinic samples (linear, R²=0.13) and forensic samples (linear, R²=0.02) showed no correlation. Urinary levels of 1,5-AG in deceased diabetic (mean 6.9μg/ml) and in non-diabetic patients (mean 6.3μg/ml) did not show a significant difference (p=0.752). However, urinary 1,5-AG concentrations in deceased due to diabetic coma (mean: 1.7μg/ml) were significantly lower than in non-diabetic (mean: 6.3μg/ml, p=0.039) and lower than in diabetic cases (mean: 4.7μg/ml, p=0.058). The determination of a reliable cut-off for the differentiation of diabetic to diabetic coma cases was not possible. Normalization of urinary 1,5-AG concentrations with the respective creatinine concentrations did not show any gain of information. In clinical (serum) and forensic blood samples a significant difference between all groups could be detected (p<0.05). Comparison of blood and urine 1,5-AG concentrations in clinical samples (linear, R²=0.13) and forensic samples (linear, R²=0.02) showed no correlation.

Development and validation of an LC-ESI-MS/MS method for the quantification of D-84, reboxetine and citalopram for their use in MS Binding Assays addressing the monoamine transporters hDAT, hSERT and hNET

MS Binding Assays represent a label-free alternative to radioligand binding assays. In this study, we present an LC-ESI-MS/MS method for the quantification of (R,R)-4-(2-benzhydryloxyethyl)-1-(4-fluorobenzyl)piperidin-3-ol [(R,R)-D-84, (R,R)-1], (S,S)-reboxetine [(S,S)-2], and (S)-citalopram [(S)-3] employed as highly selective nonlabeled reporter ligands in MS Binding Assays addressing the dopamine [DAT, (R,R)-D-84], norepinephrine [NET, (S,S)-reboxetine] and serotonin transporter [SERT, (S)-citalopram], respectively. The developed LC-ESI-MS/MS method uses a pentafluorphenyl stationary phase in combination with a mobile phase composed of acetonitrile and ammonium formate buffer for chromatography and a triple quadrupole mass spectrometer in the multiple reaction monitoring mode for mass spectrometric detection. Quantification is based on deuterated derivatives of all three analytes serving as internal standards. The established LC-ESI-MS/MS method enables fast, robust, selective and highly sensitive quantification of all three reporter ligands in a single chromatographic run. The method was validated according to the Center for Drug Evaluation and Research (CDER) guideline for bioanalytical method validation regarding selectivity, accuracy, precision, calibration curve and sensitivity. Finally, filtration-based MS Binding Assays were performed for all three monoamine transporters based on this LC-ESI-MS/MS quantification method as read out. The affinities determined in saturation experiments for (R,R)-D-84 toward hDAT, for (S,S)-reboxetine toward hNET, and for (S)-citalopram toward hSERT, respectively, were in good accordance with results from literature, clearly demonstrating that the established MS Binding Assays have the potential to be an efficient alternative to radioligand binding assays widely used for this purpose so far.

Targeting human urinary metabolome by LC-MS/MS: a review

Urine is a biological matrix that contains hundreds of metabolic end products which constitute the urinary metabolome. The development and advances on LC-MS/MS have revolutionized the analytical study of biomolecules by enabling their accurate identification and quantification in an unprecedented manner. Nowadays, LC-MS/MS is helping to unveil the complexity of urine metabolome, and the results obtained have multiple biomedical applications. This review focuses on the targeted LC-MS/MS analysis of the urine metabolome. In the first part, we describe general considerations (from sample collection to quantitation) required for a proper targeted metabolic analysis. In the second part, we address the urinary analysis and recent applications of four relevant families: amino acids, catecholamines, lipids and steroids.

Single-platform ‘multi-omic’ profiling: unified mass spectrometry and computational workflows for integrative proteomics–metabolomics analysis

Advances in instrumentation and analysis tools are permitting evermore comprehensive interrogation of diverse biomolecules and allowing investigators to move from linear signaling cascades to network models, which more accurately reflect the molecular basis of biological systems and processes.

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.

LC-MS/MS method for simultaneous determination of diethylcarbamazine, albendazole and albendazole metabolites in human plasma: Application to a clinical pharmacokinetic study

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The first LC–MS/MS method of diethylcarbamazine and albendazole along with its active metabolites.

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The method was successfully applied to analyze clinical samples.

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The highly sensitive and selective LC–MS/MS method for routine pharmacokinetic application.

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This method is useful for drug–drug interaction or TDM studies of diethylcarbamazine and albendazole in Lymphatic filariasis therapy.

Combination therapy with anti-filarial drugs is now widely used for treatment of lymphatic filariasis. A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous quantitation of diethylcarbamazine (DEC), albendazole (ABZ) and albendazole metabolites in human plasma. Separation and detection of analytes were achieved on a reversed phase column (Acquity UPLC^®BEH C18 column (100 × 2.1 mm, 1.7 μm) with gradient elution using 0.05% formic acid in methanol and 0.05% formic acid as mobile phase. Solid phase extraction was utilized for elution of analytes from the matrix. Thereafter, analytes were monitored by using MS/MS with electrospray ionization source in positive multiple reaction monitoring mode. The MS/MS response was linear over the concentration range from 0.1–200 ng/mL for ABZ and ABZ-ON, 0.5–1000 ng/mL for ABZ-OX and 1–2000 ng/mL for DEC with a correlation coefficient (r²) of 0.998 or better. The within- and between-batch precisions (relative standard deviation, % RSD) and the accuracy (% bias) were within the acceptable limits as per FDA guideline. The validated method was successfully applied to the clinical pharmacokinetic study. Due to high sensitivity and low requirement of sample volume, the method will be applicable for therapeutic drug monitoring of this regimen.

Considerations regarding the validation of chromatographic mass spectrometric methods for the quantification of endogenous substances in forensics

The requirement for correct evaluation of forensic toxicological results in daily routine work and scientific studies is reliable analytical data based on validated methods. Validation of a method gives the analyst tools to estimate the efficacy and reliability of the analytical method. Without validation, data might be contested in court and lead to unjustified legal consequences for a defendant. Therefore, new analytical methods to be used in forensic toxicology require careful method development and validation of the final method. Until now, there are no publications on the validation of chromatographic mass spectrometric methods for the detection of endogenous substances although endogenous analytes can be important in Forensic Toxicology (alcohol consumption marker, congener alcohols, gamma hydroxy butyric acid, human insulin and C-peptide, creatinine, postmortal clinical parameters). For these analytes, conventional validation instructions cannot be followed completely. In this paper, important practical considerations in analytical method validation for endogenous substances will be discussed which may be used as guidance for scientists wishing to develop and validate analytical methods for analytes produced naturally in the human body. Especially the validation parameters calibration model, analytical limits, accuracy (bias and precision) and matrix effects and recovery have to be approached differently. Highest attention should be paid to selectivity experiments.

Dried Blood Spot Methodology in Combination With Liquid Chromatography/Tandem Mass Spectrometry Facilitates the Monitoring of Teriflunomide

Background:

Teriflunomide, a once-daily oral immunomodulator approved for treatment of relapsing-remitting multiple sclerosis, is eliminated slowly from plasma. If necessary to rapidly lower plasma concentrations of teriflunomide, an accelerated elimination procedure using cholestyramine or activated charcoal may be used. The current bioanalytical assay for determination of plasma teriflunomide concentration requires laboratory facilities for blood centrifugation and plasma storage. An alternative method, with potential for greater convenience, is dried blood spot (DBS) methodology. Analytical and clinical validations are required to switch from plasma to DBS (finger-prick sampling) methodology.

Methods:

Using blood samples from healthy subjects, an LC-MS/MS assay method for quantification of teriflunomide in DBS over a range of 0.01–10 mcg/mL was developed and validated for specificity, selectivity, accuracy, precision, reproducibility, and stability. Results were compared with those from the current plasma assay for determination of plasma teriflunomide concentration.

Results:

Method was specific and selective relative to endogenous compounds, with process efficiency ∼88%, and no matrix effect. Inaccuracy and imprecision for intraday and interday analyses were <15% at all concentrations tested. Quantification of teriflunomide in DBS assay was not affected by blood deposit volume and punch position within spot, and hematocrit level had a limited but acceptable effect on measurement accuracy. Teriflunomide was stable for at least 4 months at room temperature, and for at least 24 hours at 37°C with and without 95% relative humidity, to cover sampling, drying, and shipment conditions in the field. The correlation between DBS and plasma concentrations (R² = 0.97), with an average blood to plasma ratio of 0.59, was concentration independent and constant over time.

Conclusions:

DBS sampling is a simple and practical method for monitoring teriflunomide concentrations.

Cellular and mitochondrial determination of low molecular mass organic acids by LC-MS/MS

A selective and sensitive method for the determination of low molecular mass organic acids (LMMOAs) in cell and mitochondrial extracts is presented. The analytical method consists in the separation by reversed phase liquid chromatography and detection with tandem mass spectrometry (LC-MS/MS) of the LMMOAs like malic, succinic, formic and citric acids. These acids are among the cellular intermediates of the tricarboxylic acid cycle (TCA), thus their quantitation can provide essential information about the catabolic and anabolic processes occurring in cells under physiological and pathological conditions. The analytical method was fully validated in terms of linearity, detection and quantification limits, recovery and precision. Detection limits (LOD) for malic, succinic and fumaric acids were in the range of 1-10nM, while 20nM was obtained for citric acid. Analytical recovery in cell and mitochondrial extracts was found between 88 and 105% (CV% ≤7.1) and matrix effect was estimated to be less than 108%. The LC-MS/MS method applied to the quantification of TCA cycle metabolites revealed a different distribution of the four acids in cells and mitochondria, and it could be used to monitoring metabolic alterations associated with TCA cycle and oxidative phosphorylation dysfunctions.

Development of a quantitative approach in blood plasma for low-dosed hallucinogens and opioids using LC-high resolution mass spectrometry

The WHO annually reports an increasing abuse of new psychoactive substances (NPS), which are a heterogeneous group of synthetic drugs and are consumed as substitute for controlled drugs of abuse. In this work, we focused on highly potent derivatives such those of phenethylamine (2C), N-2-methoxybenzyl phenethylamine (NBOMes), lysergic acid diethylamide (LSD), and fentanyl. Severe to fatal intoxications were described due to their high potency. Therefore, they have to be taken at very low doses resulting in low blood concentration in the low ng/mL range, which is a challenge for reliable analytical detection and quantification. The aim of this work was therefore to design a simple, robust, and fast method for simultaneous detection and quantification of multiple substances of the different classes in human blood plasma using liquid chromatography (LC) high resolution (HR) mass spectrometry (MS) with alternating HR full-scan (HRFS) MS and "All-ions fragmentation" (AIF) MS. The paper contains results of the method validation according to the EMA guideline, including intra-/interday accuracy and precision, matrix effects, storage and benchtop analyte stability as well as selectivity and carryover. All validation criteria were fulfilled for most tested compounds except for the NBOMe derivatives, one out of ten 2C-derivatives and butyryl fentanyl, which failed at accuracy and/or precision or at the acceptance criteria for matrix effect. Reasons for this are discussed and solutions presented. Despite some limitations, the HRFS + AIFMS analysis allowed detection of most of the analytes down to 0.1ng/mL, seamless integration of new or unexpected analytes, identification and quantification with no limitations on the number of monitored compounds, and reevaluation of the acquired data also concerning metabolism studies using group-indicating fragment ions.

Matrix effect management in liquid chromatography mass spectrometry: the internal standard normalized matrix effect

LC-MS is becoming a standard for many applications, thanks to high sensitivity and selectivity; nevertheless, some issues are still present, particularly due to matrix effect (ME). Considering this, the use of optimal internal standards (ISs, usually stable-isotope labeled) is important, but not always possible because of cost or availability. Therefore, a deep investigation of the inter-lot variability of the ME and of the correcting power of the chosen IS (isotope-labeled or not) is mandatory. While the adoption of isotopically labeled ISs considered as a 'gold standard' to mitigate ME impact on analytical results, there is not consensus about the standard technique to evaluate it during method validation. In this paper, currently available techniques to evaluate, reduce or counterbalance ME are presented and discussed. Finally, these techniques were summarized in a flowchart for a robust management of ME, particularly considering the concept of 'internal standard normalized ME'.

Targeted quantification of lipid mediators in skeletal muscles using restricted access media-based trap-and-elute liquid chromatography-mass spectrometry

Lipid mediators (LMs) are a class of bioactive metabolites of the essential polyunsaturated fatty acids (PUFA), which are involved in many physiological processes. Their quantification in biological samples is critical for understanding their functions in lifestyle and chronic diseases, such as diabetes, as well allergies, cancers, and in aging processes. We developed a rapid, and sensitive LC-MS/MS method to quantify the concentrations of 14 lipid mediators of interest in mouse skeletal muscle tissue without time-consuming liquid-liquid or solid-phase extractions. A restricted-access media (RAM) based trap was used prior to LC-MS as cleanup process to prevent the analytical column from clogging and deterioration. The system enabled automatic removal of residual proteins and other biological interferences presented in the tissue extracts; the target analytes were retained in the trap and then eluted to an analytical column for separation. Matrix evaluation tests demonstrated that the use of the combined RAM trap and chromatographic separation efficiently eliminated the biological or chemical matrix interferences typically encountered in bioanalytical analysis. Using 14 LM standards and 12 corresponding deuterated compounds as internal standards, the five-point calibration curves, established over the concentration range of 0.031-320 ng mL^-1, demonstrated good linearity of r² > 0.9903 (0.9903-0.9983). The lower detection limits obtained were 0.016, 0.031, 0.062, and 0.31 ng mL^-1 (0.5, 1, 2, and 10 pg on column), respectively, depending on the specific compounds. Good accuracy (87.1-114.5%) and precision (<13.4%) of the method were observed for low, medium, and high concentration quality control samples. The method was applied to measure the amount of 14 target LMs in mouse skeletal muscle tissues. All 14 analytes in this study were successfully detected and quantified in the gastrocnemius muscle samples, which provided crucial information for both age and gender-related aspects of LMs signaling in skeletal muscles previously unknown. This method could be applied to advance the understanding of skeletal muscle pathophysiology to study the role of LMs in health and disease. Furthermore, we will expand the application of this methodology to humans and other tissues/matrices in the near future.

Metabolite Profiling, Pharmacokinetics, and In Vitro Glucuronidation of Icaritin in Rats by Ultra-Performance Liquid Chromatography Coupled with Mass Spectrometry

Icaritin is a naturally bioactive flavonoid with several significant effects. This study aimed to clarify the metabolite profiling, pharmacokinetics, and glucuronidation of icaritin in rats. An ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) assay was developed and validated for qualitative and quantitative analysis of icaritin. Glucuronidation rates were determined by incubating icaritin with uridine diphosphate glucuronic acid- (UDPGA-) supplemented microsomes. Kinetic parameters were derived by appropriate model fitting. A total of 30 metabolites were identified or tentatively characterized in rat biosamples based on retention times and characteristic fragmentations, following proposed metabolic pathway which was summarized. Additionally, the pharmacokinetics parameters were investigated after oral administration of icaritin. Moreover, icaritin glucuronidation in rat liver microsomes was efficient with CL_int (the intrinsic clearance) values of 1.12 and 1.56 mL/min/mg for icaritin-3-O-glucuronide and icaritin-7-O-glucuronide, respectively. Similarly, the CL_int values of icaritin-3-O-glucuronide and icaritin-7-O-glucuronide in rat intestine microsomes (RIM) were 1.45 and 0.86 mL/min/mg, respectively. Taken altogether, dehydrogenation at isopentenyl group and glycosylation and glucuronidation at the aglycone were main biotransformation process in vivo. The general tendency was that icaritin was transformed to glucuronide conjugates to be excreted from rat organism. In conclusion, these results would improve our understanding of metabolic fate of icaritin in vivo.

A rapid UPLC-MS/MS assay for the simultaneous measurement of fluconazole, voriconazole, posaconazole, itraconazole, and hydroxyitraconazole concentrations in serum

BACKGROUND

Triazole antifungals are essential to the treatment and prophylaxis of fungal infections. Significant pharmacokinetic variability combined with a clinical need for faster turnaround times has increased demand for in-house therapeutic drug monitoring of these drugs, which is best performed using mass spectrometry-based platforms. However, technical and logistical obstacles to implementing these platforms in hospital laboratories have limited their widespread utilization. Here, we present the development and validation of a fast and simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to measure fluconazole, voriconazole, posaconazole, itraconazole, and hydroxyitraconazole in human serum suitable for incorporation into a hospital clinical laboratory.

METHODS

Serum samples (20 µL) were prepared using protein precipitation in the presence of deuterated internal standards. Chromatographic separation was accomplished using reversed phase UPLC and analysis was performed using positive-mode electrospray ionization and collision-induced dissociation MS.

RESULTS

Total analytical run time was 3 min. All analytes demonstrated linearity (r2>0.998) from 0.1 to 10 µg/mL (1-100 µg/mL for fluconazole), acceptable accuracy and precision (%DEV<15% and %CV<15% at all levels tested), suitable stability under relevant storage conditions, and correlated well with reference laboratory results.

CONCLUSIONS

A simple and rapid UPLC-MS/MS method for monitoring multiple triazole antifungals was developed with a focus on the needs of hospital laboratories. The assay is suitable for clinical utilization and management of patients on these medications.

Rapid quantification of free and glucuronidated THCCOOH in urine using coated well plates and LC–MS/MS analysis

Aim: Generally, urine drug testing for cannabis abuse involves measuring total concentrations of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) obtained by enzymatic and/or alkaline hydrolysis of THCCOOH-glucuronide. As hydrolysis can be inconsistent and incomplete, direct measurement of the two metabolites is preferable. Methodology & results: We developed a high-throughput LC–MS/MS method for simultaneous quantification of free and glucuronidated THCCOOH in urine using coated 96-well plates for analyte extraction and column-switching chromatography. Excellent separation of the two analytes was achieved within 2.5 min, with linear ranges from 5 to 2000 μg/l for THCCOOH and from 10 to 4000 μg/l for THCCOOH-glucuronide. Conclusion: The method was successfully validated and applied to authentic urine samples from cannabis consumers, demonstrating its applicability for routine cannabinoid testing.