Optimization of a ultra-high-pressure liquid chromatography-tandem multiple reaction monitoring mass spectrometry method for monitoring haloacetic acids as chlorinated disinfection by-products in the fresh-cut industry

Haloacetic acids (HAAs) are one of the most important chlorinated disinfection by-products generated during water disinfection in the fresh-cut industry, and they can remain in the product, resulting in a consumer health risk. In this study, ultra-high-pressure liquid chromatography-tandem multiple reaction monitoring mass spectrometry (UHPLC-MRM) analysis used for drinking water was optimized and applied for the quantification of nine HAAs (HAA9) in fresh-cut lettuce and process water samples, with the complex matrix interferences for separation, and quantification problems. The method showed good selectivity, specificity and linearity, satisfactory values for trueness (recoveries of 80-116 %), precision (<22 %), and uncertainty (<55 %). Quantification limits varied from 1 to 5 µg L-1 or µg kg-1. The matrix effect for tribromoacetic, bromochloroacetic and chlorodibromoacetic acid was corrected by matrix-matched calibration and standard addition. After storage at -20 °C, only monobromoacetic acid was the HAA which loss happened after 7 days. The application of the methodology in lettuce and process water samples from the industry was successfully implemented. Therefore, this method could be employed for the quality control and regulatory analysis of HAAs in fresh products and process water from the fruit and vegetable industry.

How does the order of sample analysis influence the matrix effect during LC-MS bioanalysis?

Mass spectrometry coupled with liquid chromatography is a valuable tool for drug development and personalised drug therapy. The matrix effect is caused by enhancing or suppressing the analyte signal intensity by the interfering compounds of biological fluids. The matrix effect may influence the reliability of the quantitative results. Thus, its evaluation is a critical part of bioanalytical method validation. Identified factors affecting the matrix effect are the physicochemical properties of the analyte, type of biological material, analytical conditions, the ion source construction and calculation method. The order of analysis of test samples (pure solutions and post-extraction spiked samples) is another factor possibly affecting quantifying the matrix effect variability between sources. Our primary goal was to find which experimental design - interleaved or set of blocks - is more sensitive to detect matrix effect variability. Additionally, to better understand the reason of variability, we evaluated the influence of chromatographic elution and the type of plasma (normal, lipemic or hemolyzed), co-elution, and carry-over of phospholipids. We used chemometric methods: Principal Component Analysis and Partial Least-Squares Discriminant Analysis. Although a comparable (but statistically different) matrix effect (%RSDMF) is observed using the interleaved and block schemes, for some compounds, the order of the samples strongly influences the results. The interleaved scheme was generally more sensitive in detecting the matrix effect than the block scheme. Thus, reporting the order of samples is needed to ensure the repeatability of experiments. Chemometrics suggests that lipemic samples analyzed in isocratic conditions are most prone to the matrix effect. Different compositions of matrix lots of the same type - especially lipemic - may influence method reliability. Thus, evaluating more than one source of lipemic and hemolyzed plasma is recommended.

Immuno-Mass Spectrometry Workflow for Quantification of Serum α-Fetoprotein Using Antibody-Immobilized Magnetic Beads and Modified Eluents

Immuno-mass spectrometry (MS) is a powerful method for the quantitative analysis of low-abundance proteins in biological specimens. In these procedures, collecting specifically and efficiently the target protein antigens from the antigen-antibody complex generated on the surface of nanocarrier beads is crucial and can be performed by hydrolyzing the proteins directly on the beads or after elution. Herein, we optimized the conditions of the immunoaffinity purification via elution using serum α-fetoprotein (AFP) as a model and its specific antibody immobilized covalently on magnetic beads. Antibody-coated beads were incubated with human serum spiked with standard AFP for antigen-antibody reaction. AFP was then eluted from the beads using various eluents, including organic solvents, to optimize the elution conditions. After proteolytically hydrolyzing the eluted protein, stable isotope-labeled standard peptides were added to the hydrolysate to quantify the eluted AFP via liquid chromatography-tandem MS. Using an optimized workflow for quantitative analysis afforded a correlation between the amount of spiked AFP and heavy to light ratios calculated based on peptide ion peak areas, from which an endogenous AFP concentration of 2.3±0.6 ng/mL was determined in normal serum; this is consistent with previous reports using radioimmunoassay methods. The present immuno-MS workflow could apply to the detection and quantitation of other low-abundance biofluid biomarkers.

Liquid chromatographic methods in the determination of inosine monophosphate dehydrogenase enzyme activity: a review

Inosine monophosphate dehydrogenase (IMPDH) is a crucial enzyme involved in the de novo synthesis of purine nucleotides. IMPDH activity is used to evaluate the pharmacodynamics/pharmacokinetics of immunosuppressant drugs such as mycophenolic acid and thiopurines. These drugs are often used to prevent organ transplant rejection and as steroid-sparing agents in autoinflammatory diseases such as inflammatory bowel disease and rheumatoid arthritis. Numerous analytical techniques have been employed to evaluate IMPDH activity in biological matrices. However, hyphenated LC techniques were most widely used in the literature. This review focuses on hyphenated LC methods used to measure IMPDH activity and provides detailed insight into the sample preparation techniques, chromatographic conditions, enzymatic assay conditions, detectors and normalization factors employed in those methods.

Biocompatible magnetite nanoparticles coated with ionic liquid-based surfactantas a hydrophilic sorbent for dispersive solid phase microextraction of cephalosporins prior to their quantitation by HPTLC

Extraction of highly hydrophilic compounds from biological fluids including urine or plasma samples is a dilemma due to high hydrophilicity of the matrix itself. The main aim of the current work is to explore the competence of ionic liquid (IL)-based surfactant-coated mineral oxide nanoparticles (NPs) in dispersive solid-phase microextraction (d-SPME) of highly hydrophilic analytes taking cefoperazone (CPZ) as a model analyte for the study. The IL-based surfactant coated Fe₃O₄ NPs is utilized as an innovative adsorbent for the separation and pre-concentration of CPZ after intramuscular injection (I.M) in rabbits. The utilized magnetite NPs were synthesized via simple and reliable co-precipitation procedure, which doesn't require any air-free environment and depends on a single iron (III) salt. Characterization of the as-synthesized NPs was achieved by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX). Surface area measurements show that Fe₃O₄ NPs have large surface area of 75 m² g^-1. The developed approach utilizes the unique properties of the IL-based surfactant including multiple polar interaction types provided by the polar head in addition to merits of Fe₃O₄ nanoparticles, which include large adsorptive capacity and magnetic properties, to improve separation, save time, and achieve satisfactory recovery. Comprehensive study was developed for the factors, that affect the adsorption capacity such as pH, NPs amount, IL-based surfactant concentration, ionic strength, adsorption time, and desorption conditions. Moreover, the adsorption data was fitted to Langmuir and second-order kinetic models as reflected by the reasonable determination coefficients of 0.9319 and 0.9726, respectively. Under the optimized conditions, the developed approach achieves good correlation coefficient of 0.9975, and 0.9981 over linearity range of 0.7-12.0 and 4.0-50.0 µg mL^-1 for both CPZ standard solutions and spiked rabbit plasma, respectively. It also provides good sensitivity expressed by the low values of limit of detection (LOD) of 0.2 and 1.2 µg mL^-1 and limit of quantitation (LOQ) of 0.7 and 4.0 µg mL^-1 for both the standard solutions and spiked plasma, respectively. The developed approach was also applied successfully for monitoring CPZ in rabbit plasma samples with satisfactory recovery % (83-110). In addition, a detailed pharmacokinetic study is performed where pharmacokinetic parameters of CPZ in rabbit plasma samples were calculated.

Effects of Broad Spectrum Antibiotics on Measurement of Immunosuppressant Drugs

BACKGROUND

Antibiotics used parenterally can affect blood drug level measurements, as measured in diagnostic tests.

OBJECTIVE

To investigate the effect of six different antibiotics commonly used in intensive care units on tacrolimus, sirolimus, everolimus and cyclosporin A levels measured by mass spectrometry.

METHODS

Ampicillin + sulbactam (AB1, IV, 1 g), imipenem + cilastatin sodium (AB2, IV, 500 mg), piperacillin + tazobactam (AB3, 4.5 g, IV), ertapenem (AB4, IV, 1 g), meropenem trihydrate (AB5, 500 mg, IV) and ceftriaxone (AB6, 1 g, IV) antibiotics were used for the interference assay. Measurements were performed on the Shimadzu 8045 (Japan) LC-MS/MS instrument. Bias values were calculated.

RESULTS

The least affected immunosuppressant was cyclosporine A (between -6.88% and 3.40%). The most affected were everolimus and sirolimus. Ertapenem caused negative interference on the level of everolimus at the rate of -27.34% and sirolimus at the rate of -26.79%. Piperacillin + tazobactam and imipenem + cilastatin sodium caused positive interferences on sirolimus at the rate of 24.24% and 22.73%, respectively. Ampicillin + sulbactam, meropenem trihydrate and ceftriaxone affected the sirolimus levels at lower rates (-4.49%, 5.93% and 9.86%). Everolimus levels deviated at the rate of -11.21% to -16.99% due to imipenem + cilastatin sodium, meropenem trihydrate and ceftriaxone.

CONCLUSION

This study demonstrated the potential of antibiotic use affecting immunosuppressant levels. Antibiotic interference, especially in transplant patients, may cause erroneous immunosuppression, increasing the likelihood of rejection.

Validation of a simple liquid chromatography coupled to tandem mass spectrometry method for the simultaneous determination of tacrolimus, sirolimus, everolimus and cyclosporin A in dried matrix on paper discs

INTRODUCTION

Due to its high specificity and sensitivity, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is the gold standard method for immunosuppressant quantification in therapeutic drug monitoring. In this context, dried blood spots (DBS) have become a promising strategy as a sample collection procedure. Although the advantages of DBS over venipuncture are well known, this approach has limitations that strongly influence the acceptance of analytical results. Among them, the most important is hematocrit (Ht). The easiest way of overcoming this problem is by analyzing complete spots. In this strategy, called dried matrix on paper discs (DMPD), blood is volumetrically applied on pre-punched discs.

OBJECTIVES

To validate an LC-MS/MS method for the quantification of tacrolimus, sirolimus, everolimus and cyclosporin A using DMPD.

METHODS

The procedure was validated according to international guidelines using a commercial kit. The following performance parameters were evaluated: selectivity, carryover, linearity, accuracy, precision, lower limit of quantitation, relative recovery, commutability and stability. In addition, a method comparison study was performed to evaluate the clinical influence of Ht on the results.

RESULTS

All performance parameters were within acceptance criteria and, hence, it was determined that the validated method is fit for the intended purpose. Likewise, calculated bias values on medical decision levels showed that there was no clinical influence of Ht on the results.

CONCLUSION

Unlike other similar methodologies that have been published, here, a simple method has been fully validated. This is the first LC-MS/MS methodology adapting a commercial kit to use DMPD as a sampling strategy.

Determination of Tryptophan and Kynurenine by LC-MS/MS by Using Amlodipine as an Internal Standard

Tryptophan is an essential amino acid that plays an important role in cell metabolism, and kynurenine is its main metabolic pathway. By using ultra-high-performance liquid chromatography coupled to electrospray ionization triple-quadrupole mass spectrometry, tryptophan and kynurenine were determined using amlodipine as an internal standard. The analysis was carried out on an ACE-C18 (4.6 mm × 50 mm, 5 μm) reversed-phase analytical column using the gradient elution mode. For quantitative determination, amlodipine was used as an internal standard. Detection was performed using multiple reaction monitoring in electrospray ionization mode at m/z 205.1 → 117.7 and 187.9 for tryptophan, m/z 209.1 → 146 and 93.9 for kynurenine, and m/z 409.2 → 294.1 for the internal standard. Good linearity of the analyte to internal standard peak area ratios was seen in the concentration range 1.25-4000 ng/mL for tryptophan and 0.5-1600 ng/mL for kynurenine. The method showed excellent linearity with regression coefficients of 0.99 for kynurenine and 0.996 for tryptophan. The limits of quantification were 0.55 ng/mL for tryptophan and 0.47 ng/mL for kynurenine. The % RSD for all analytes ranged from 0.3 to 3.4% for intraday and 0.4 to 8.9% for interday experiments. A simple LC-MS/MS method has been developed and validated for measuring Kyn and Trp by using an affordable and more easily available internal standard, which is amlodipine.

Determination of non-cholesterol sterols in serum and HDL fraction by LC/MS-MS: Significance of matrix-related interferences

Background

Non-cholesterol sterols (NCS) are promising biomarkers for estimation of cholesterol homeostasis properties. In addition, determination of NCS in high-density lipoprotein (HDL) fraction (HDL-NCS) could provide information on cholesterol efflux. However, matrix effects interfere in liquid chromatography-mass spectrometry (LC-MS) analysis of NCS, thereby impairing the method sensitivity. The aims of this study were development, optimization and validation of LC-MS method for quantification of NCS in serum and HDL-NCS. Additionally, matrix effect interferences and methods application in individual serum samples were examined.

Methods

HDL precipitating reagent was used for HDL isolation. Matrix effect was examined by comparing different surrogates by simple regression analysis. Validation was conducted according to the FDA-ICH guideline. 20 healthy volunteers were recruited for testing of method application.

Results

The observed matrix effect was 30%, and matrix comparison showed that cholesterol was the dominant contributor to the matrix effect. Cholesterol concentration was adjusted by construction of the calibration curve for serum and HDL fraction (5 mmol/L and 2.5 mmol/L, respectively). The intraand interrun variabilities for NCSs were 4.7-10.3% for serum NCS and 3.6-13.6% for HDLNCS and 4.6-9.5% for serum NCSs and 2.5-9.8% for HDL-NCS, respectively. Recovery studies showed satisfactory results for NCSs: 89.8-113.1% for serum NCS and 85.3-95.8% for HDL-NCS.

Conclusions

The method was successfully developed and optimized. The matrix interference was solved by customising calibration curves for each method and sample type. The measurement of NCS in HDL fraction was proposed for the first time as potentially useful procedure in biomedical researches.

Simultaneous determination of 19 mycotoxins in lotus seed using a multimycotoxin UFLC-MS/MS method

Objectives

In relevance to the internal components and improper environmental conditions, lotus seeds are susceptible to fungal contamination and mycotoxins residue, leading to harmful impacts on the quality and safety, as well as their pharmaceutical efficacy and clinical use. It is necessary and urgent to assess various mycotoxins residue in lotus seeds. This study aimed to develop a sensitive method for accurate assessment of multimycotoxin residues in lotus seeds.

Methods

A simple and reliable modified ultrasonication-assisted extraction, QuEChERS purification based ultrafast liquid chromatography tandem mass spectrometry (UFLC-MS/MS) method was successfully developed for ultrasensitive determination of 19 multiclass mycotoxins in starch-rich lotus seeds. Four extraction modes and three clean-up sorbents for improving the recoveries of mycotoxins were optimized. Limits of detection (LODs) and quantification, linearity, precision, accuracy, and matrix effect were studied for method validation. For simultaneous qualitation and quantification, the 19 chemically diversified mycotoxins were well separated on a CAPCELL CORE C18 column (100 mm × 2.1 mm, 2.7 μm) and detected in positive/negative electrospray ionization mode within 7 min.

Key findings

The validated method exhibited satisfactory linearity (r &gt; 0.995), ultragood selectivity (LODs of 0.1–15.0 μg/kg), excellent precision (RSDs &lt;13.0%) and convincing accuracy (recoveries between 79.4% and 131.6% with RSDs &lt;14.4%). Matrix effect, between 54.5% and 113.6%, appeared especially for aflatoxins B1 and B2, deoxynivalenol and T-2 toxins. Matrix-matched curve-based quantification showed that 26 (57.8%) out of 45 lotus seed samples were contaminated with one or more mycotoxins, and ochratoxin A, aflatoxin B2, aflatoxin B1 and citrinin were the most prevalent mycotoxins.

Conclusions

This study reports for the first time the incidence of a wide range of 19 mycotoxins in lotus seeds and the proposed method will get broad application for more trace components in other complex matrices.

Bioanalytical method validation: new FDA guidance vs. EMA guideline. Better or worse?

Bioanalysis concerns the identification and quantification of analytes in various biological matrices. Validation of any analytical method helps to achieve reliable results that are necessary for proper decisions on drug dosing and patient safety. In the case of bioanalytical methods, validation additionally covers steps of pharmacokinetic and toxicological studies - such as sample collection, handling, shipment, storage, and preparation. We drew our attention to the difference of both the newest FDA Guidance and the EMA Guideline on bioanalytical method validation. We aimed to point out advantages of both documents from the laboratory perspective. The FDA and the EMA documents are similar, but not identical. The EMA describes the practical conduct of experiments more precisely, while the FDA presents reporting recommendations more comprehensively. There are also differences in recommended validation parameters. We hope that the International Council for Harmonisation will combine advantages of both documents to avoid confusing differences in terminology as well as the unnecessary effort of being compliant with two or more guidelines.

Forensic analysis using ultra-high-performance liquid chromatography-tandem mass spectrometry with solid-phase extraction of α-solanine and α-chaconine in whole blood

Purpose

The potato glycoalkaloids (PGAs), α-solanine and α-chaconine can exert adverse effects on human health when consumed in excess. This study aimed to investigate the optimal extraction method for the quantitative analysis of PGAs in whole blood by using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and to apply this validated method to postmortem blood.

Methods

A total of 200 µL of human whole blood was prepared for PGA extraction. For validation, a solid-phase extraction (SPE) using Oasis^® PRiME HLB, in which extraction could be performed in three simple steps (sample loading, washing, and elution) was used, with no need for both conditioning and equilibration of columns for sample preparation.

Results

In this method, the limit of detection and the lower limit of quantification (LLOQ) of both α-solanine and α-chaconine were 1 and 2 µg/L, respectively. The calibration curves of the two compounds were obtained with good linearity in the range of 2-100 µg/L. The recovery rates at the LLOQ of α-solanine and α-chaconine were ≥ 91.8% and ≥ 85.9%, respectively. The validation data (intra- and inter-day combined) for accuracy ranged from 93.5 to 106.6% for α-solanine and from 93.9 to 107.7% for α-chaconine. This validated method was successfully applied to one forensic autopsy case, and the concentrations of α-solanine and α-chaconine in the postmortem cardiac blood were 45.1 and 35.5 µg/L, respectively.

Conclusions

This validated UHPLC-MS/MS with SPE for quantitative analysis of PGAs could be useful in forensic toxicology.

A Simple HPLC-MS/MS Method for Determination of Tryptophan, Kynurenine and Kynurenic Acid in Human Serum and its Potential for Monitoring Antidepressant Therapy

The kynurenine pathway, in which tryptophan is metabolized to kynurenine and kynurenic acid, has been linked to depression. A rapid and highly reproducible liquid-chromatography-tandem mass spectrometry (LC-MS/MS) method were established for determining tryptophan, kynurenine and kynurenic acid in human serum. Biological samples were precipitated with methanol before separation on an Agilent Eclipse XDB-C18. The stable-isotope-labeled internal standards (kynurenine-¹³C₄¹⁵N and kynurenic acid-d₅) were used for quantification. Detection was performed using multiple reaction monitoring in electrospray ionization mode at m/z 205.1→188.1 for tryptophan, m/z 209.1→146.1 for kynurenine, m/z 190.1→144.1 for kynurenic acid. Good linearity of analyte to internal standard peak area ratios was seen in the concentration range 1,000-50,000 ng/mL for tryptophan, 100-5,000 ng/mL for kynurenine and 1-60 ng/mL for kynurenic acid. Pooled drug-free human serum was purified using activated charcoal and the method was shown to be linear, with validation parameters within acceptable limits. The newly developed method was successfully used to determine concentrations of tryptophan, kynurenine and kynurenic acid in serum from 26 healthy volunteers and 54 patients with depression. Concentrations of tryptophan and kynurenine were lower in serum from depressed individuals than from healthy individuals.

Study of the estrogenic-like mechanism of glycosides of cistanche using metabolomics

Cistanche deserticola, known as Rou Cong-Rong in China, has been used as a tonic for more than 1800 years, with previous studies demonstrating that glycosides of cistanche (GCs) are a main active component.

Collagenase as an effective tool for drug quantitation in tissues

BACKGROUND

In early drug-discovery research, traditional techniques to analyze drug concentrations in tissues for bioanalytical needs include bead beaters and probe homogenization devices, but are not as effective for tough fibrous tissues. To prepare these tissues, the enzyme collagenase was used to digest the collagen fibers present in epithelial and connective tissue.

RESULTS

The benefits of tissue homogenization using a bead beater following collagenase treatment of samples, as opposed to using bead beating alone, was investigated. Matrix effect, recovery factor and stability with and without collagenase were assessed.

CONCLUSION

Little to no effects on the quality and reliability of collagenase treated samples were observed. This enzymatic approach is a feasible and effective tool for tissue homogenization and subsequent analysis by LC-MS/MS.

Liquid-Phase Microextraction and Gas Chromatographic-Mass Spectrometric Analysis of Antidepressants in Vitreous Humor: Study of Matrix Effect of Human and Bovine Vitreous and Saline Solution

In forensic bioanalytical methods, there is a general agreement that calibrators should be prepared by fortifying analytes in matrix-based blank samples (matrix-based). However, in the case of vitreous humor (VH), the collection of blank samples for the validation and for routine analysis would require the availability of many cadavers. Besides the difficulty of obtaining enough blank VH, this procedure could also represent an ethical issue. Here, a study of matrix effect was performed taking into consideration human and bovine vitreous and saline solution (SS) (NaCl 0.9%). Tricyclic antidepressants [amitriptyline (AMI), nortriptyline (NTR), imipramine (IMI) and desipramine (DES)] were used as model analytes and were extracted from samples by means of liquid-phase microextraction and detected by gas chromatography-mass spectrometry. Samples of human and bovine VH and SS were prepared in six different concentrations of antidepressants (5, 40, 80, 120, 160 and 200 ng/mL) and were analyzed. Relative matrix effect was evaluated by applying a two-tailed homoscedastic Student's t-test, comparing the results obtained with the set of data obtained with human VH and bovine VH and SS. No significant matrix effect was found for AMI and NTR in the three evaluated matrices. However, a great variability was observed for IMI and DES for all matrices. Once compatibilities among the matrices were demonstrated, the method was fully validated for AMI and NTR in SS. The method was applied to six VH samples deriving from real cases whose femoral whole blood (FWB) was analyzed by a previously published method. An average ratio (VH/FWB) of ∼ 0.1 was found for both compounds.

Chromatographic behavior of co-eluted plasma compounds and effect on screening of drugs by APCI-LC-MS(/MS): Applications to selected cardiovascular drugs

Chromatographic behavior of co-eluted compounds from un-extracted drug-free plasma samples was studied by LC–MS and LC–MS/MS with positive APCI. Under soft gradient, total ion chromatogram (TIC) consisted of two major peaks separated by a constant lower intensity region. Early peak (0.15–0.4 min) belongs to polar plasma compounds and consisted of smaller mass ions (m/z<250); late peak (3.6–4.6 min) belongs to thermally unstable phospholipids and consisted of fragments with m/z<300. Late peak is more sensitive to variations in chromatographic and MS parameters. Screening of most targeted cardiovascular drugs at levels lower than 50 ng/mL has been possible by LC–MS for drugs with retention factors larger than three. Matrix effects and recovery, at 20 and 200 ng/mL, were evaluated for spiked plasma samples with 15 cardiovascular drugs, by MRM–LC–MS/MS. Average recoveries were above 90% and matrix effects expressed as percent matrix factor (% MF) were above 100%, indicating enhancement character for APCI. Large uncertainties were significant for drugs with smaller masses (m/z<250) and retention factors lower than two.

Biological sample preparation: attempts on productivity increasing in bioanalysis

Sample preparation is an important step of any biomedical analysis. Development and validation of fast, reproducible and reliable sample preparation methods would be very helpful in increasing productivity. Except for a few direct injection methods, almost all biological samples should at least be diluted before any analysis. Sometimes dilution is not possible because of the low concentration of the target analyte in the sample, and alternative pretreatments, such as filtration, precipitation and sample clean up using different extraction methods, are needed. This review focuses on the recent achievements in the pretreatment of biological samples and investigates them in six categories (i.e., dilution, filtration/dialysis, precipitation, extraction [solid-phase extraction, liquid–liquid extraction], novel techniques [turbulent flow chromatography, immunoaffinity method, electromembrane extraction] and combined methods). Each category will be discussed according to its productivity rate and suitability for routine analysis, and the discussed methods will be compared according to the mentioned indices.

Choosing the appropriate matrix to perform a scientifically meaningful lipemic plasma test in bioanalytical method validation

Laurence Mayrand-Provencher has obtained a Master of Science in Chemistry from Université de Montréal. With over 3 years of experience as a scientist in the bioanalysis industry, he is now a scientist in method development at Algorithme Pharma. His experiences have led him to conduct robust and effective method development of bioanalytical assays, specifically in the LC–MS/MS field.

Many regulatory agencies include in their guidelines the need to investigate the effect of lipemic plasma on the reliability of the data as part of a bioanalytical assay validation. Lipids can cause matrix effect, specificity and recovery issues, which can potentially lead to inaccurate data if left unaccounted for. However, finding the appropriate matrix type to be used to perform a lipemic plasma test is a major challenge, as the differences between those commercially available are not well known. The work reported herein describes the differences in lipid content between normal plasma, synthetic lipemic plasma mixes, and two types of natural lipemic plasma. The results obtained show that natural plasma with high triglycerides content should be used to perform a scientifically meaningful lipemic plasma test.

Free analyte QC concept: a novel approach to prove correct quantification of free therapeutic protein drug/biomarker concentrations

Quantification of free drug concentrations is highly challenging due to the dynamic drug–ligand equilibrium, which may result in incorrect results. Current QC concepts do not adequately cover all of the important influencing factors: the assay itself (format and procedure); the calibration concept; the sample preparation; and the sample storage. Here, we propose a ‘free analyte QC concept’ that enables quantitative testing of these four factors and, thus, provides best possible proof of correct free drug quantification. The principle of the free analyte QC concept and an example of its application for a free drug assay is described. A comparison of this novel approach with current approaches and how the new concept fits (or does not fit) with current regulatory guidelines is discussed.

A simple LC-MS/MS method for determination of kynurenine and tryptophan concentrations in human plasma from HIV-infected patients

BACKGROUND

Indoleamine 2,3-dioxygenase, catalyzing tryptophan (Trp) metabolism through the kynurenine (Kyn) metabolic pathway, plays important roles in immune suppression and the CNS. In this article, we report a simple, rapid and specific LC-MS/MS method for accurate determination of Kyn and Trp concentrations in human plasma from HIV-infected patients.

RESULTS

The human plasma sample (100 µl) was mixed with Kyn-d4 and Trp-d5 internal standards and then precipitated with trifluoroacetic acid. The supernatant was directly analyzed by LC-MS/MS. The assay using surrogate matrix calibrators was validated for precision, accuracy, matrix effect, extraction efficiency and stability. Some assay validation issues for endogenous substance bioanalysis using an LC-MS/MS method are discussed.

CONCLUSION

A simple, specific and reproducible LC-MS/MS method has been developed and validated for measuring Kyn and Trp in human plasma samples.

Aging of biological matrices and its effect on bioanalytical method performance

Apart from the well-known matrix effects that can occur in ESI LC–MS, biological matrices may have other effects influencing the quantitative reliability of bioanalytical methods. In this paper, six case studies are presented that show the effect that aging, that is the change in properties and composition of biological matrices over time, can have on the performance of bioanalytical methods. It is shown that selectivity can be affected due to the formation or disappearance of endogenous compounds. Stability can be influenced because of the decrease (or increase) of enzyme activities and recovery can be impacted if the extractability from binding sites in the matrix is enhanced or decreased. A general discussion on the importance of these matrix effects is provided as well as a perspective on how to properly address them in the method-development and validation stages of regulated bioanalysis.

Simultaneous determination of a novel anxiolytic agent buagafuran and one metabolite in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry

A robust and validated ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method has been developed for the simultaneous determination of buagafuran and one metabolite (M1) in human plasma. The two analytes were extracted from plasma samples using tert-butyl methyl ether after addition of the internal standard and chromatographed on an Acquity UPLC BEH C18 column (2.1mm×50mm, 1.7μm) thermostatted at 35°C with methanol-water (75:25, v/v) as the mobile phase at an isocratic flow rate of 0.4mL/min. The detection was performed on an API 5500 mass spectrometer coupled with electrospray ionization (ESI) source in positive mode. The multiple reactions monitoring (MRM) transitions of m/z 245.2→109.1 and m/z 279.1→243.1 were used to quantify buagafuran and M1, respectively. The assay was validated over the concentration range of 0.5-200ng/mL for the two analytes. Precision and accuracy are in accordance with the generally accepted criteria for bioanalytical methods. The extraction recovery and the matrix effect were investigated. This method was successfully applied to support a clinical study where multiple oral doses were administrated to healthy Chinese volunteers to investigate the pharmacokinetics, safety and tolerability of buagafuran.

Strategies for dealing with hemolyzed samples in regulated LC–MS/MS bioanalysis

There is a consensus in industry that there is a need to assess the impact of hemolysis on the bioanalytical method. However, due to the difficulty to prepare standardized hemolyzed QC samples and the fact that no apparent conclusion can be made from hemolysis assessments during method validation, we propose that the assessments are conducted during method development and sample analysis. The use of a stable-labeled internal standard is highly recommended to identify the hemolyzed samples with potential issues of matrix effects. When an internal standard response is abnormal, dilution or standard addition can be used to confirm the data accuracy of the hemolyzed samples. An incurred sample reanalysis test is also recommended for hemolyzed samples to ensure the reproducibility of a hemolysis-‘insensitive’ method. The number of hemolyzed samples selected for incurred sample reanalysis is study dependent. All these additional steps can determine the ‘reportability’ of the bioanalytical data. For regulated studies, it is important to document all hemolysis tests in appropriate ways based on GLP requirement.

Regulated drug bioanalysis for human pharmacokinetic studies and therapeutic drug management

Regulated drug bioanalysis (i.e., determination of drug concentrations in biological matrices for regulated studies) usually refers to animal toxicokinetics, bioavailability/bioequivalence and clinical pharmacokinetic studies. However, there is another important regulated drug bioanalysis – therapeutic drug management (TDM). In the USA, TDM is regulated by Clinical Laboratory Improvement Amendments. In this article, we review and compare human pharmacokinetic sample analysis and TDM sample analysis. The US FDA/Bioanalytical Method Validation Guidance and the American Association for Clinical Chemistry/TDM Roundtable Recommended Generic Assay Validation Guidance are also compared. Some regulated drug bioanalysis issues, such as terminology, validation concepts and acceptance criteria, are discussed. Fostering interaction between bioanalysts from pharmaceutical science and clinical chemistry and reducing the regulatory gaps between different agencies for drug bioanalysis is our objective.