Increased throughput in quantitative bioanalysis using parallel-column liquid chromatography with mass spectrometric detection

Use of fast HPLC multiple reaction monitoring cubed for endogenous retinoic acid quantification in complex matrices

Retinoic acid (RA), an essential active metabolite of vitamin A, controls numerous physiological processes. In addition to the analytical challenges owing to its geometric isomers, low endogenous abundance, and often localized occurrence, nonspecific interferences observed during liquid chromatography (LC) multiple reaction monitoring (MRM) quantification methods have necessitated lengthy chromatography to obtain accurate quantification free of interferences. We report the development and validation of a fast high performance liquid chromatography (HPLC) multiplexing multiple reaction monitoring cubed (MRM(3)) assay for selective and sensitive quantification of endogenous RA from complex matrices. The fast HPLC separation was achieved using an embedded amide C18 column packed with 2.7 μm fused-core particles which provided baseline resolution of endogenous RA isomers (all-trans-RA, 9-cis-RA, 13-cis-RA, and 9,13-di-cis-RA) and demonstrated significant improvements in chromatographic efficiency compared to porous particle stationary phases. Multiplexing technology further enhanced sample throughput by a factor of 2 by synchronizing parallel HPLC systems to a single mass spectrometer. The fast HPLC multiplexing MRM(3) assay demonstrated enhanced selectivity for endogenous RA quantification in complex matrices and had comparable analytical performance to robust, validated LC-MRM methodology for RA quantification. The quantification of endogenous RA using the described assay was validated on a number of mouse tissues, nonhuman primate tissues, and human plasma samples. The combined integration of fast HPLC, MRM(3), and multiplexing yields an analysis workflow for essential low-abundance endogenous metabolites that has enhanced selectivity in complex matrices and increased throughput that will be useful in efficiently interrogating the biological role of RA in larger study populations.

An integrated bioanalytical platform for supporting high-throughput serum protein binding screening

Quantification of small molecules using liquid chromatography/tandem mass spectrometry (LC/MS/MS) on a triple quadrupole mass spectrometer has become a common practice in bioanalytical support of in vitro adsorption, distribution, metabolism and excretion (ADME) screening. The bioanalysis process involves primarily three indispensable steps: MS/MS optimization for a large number of new chemical compounds undergoing various screening assays in early drug discovery, high-throughput sample analysis with LC/MS/MS for those chemically diverse compounds using the optimized MS/MS conditions, and post-acquisition data review and reporting. To improve overall efficiency of ADME bioanalysis, an integrated system was proposed featuring an automated and unattended MS/MS optimization, a staggered parallel LC/MS/MS for high-throughput sample analysis, and a sophisticated software tool for LC/MS/MS raw data review as well as biological data calculation and reporting. The integrated platform has been used in bioanalytical support of a serum protein binding screening assay with high speed, high capacity, and good robustness. In this new platform, a unique sample dilution scheme was also introduced. With this dilution design, the total number of analytical samples was reduced; therefore, the total operation time was reduced and the overall throughput was further improved. The performance of the protein binding screening assay was monitored with two controls representing high and low binding properties and an acceptable inter-assay consistency was achieved. This platform has been successfully used for the determination of serum protein binding in multiple species for more than 4000 compounds.

Rapid determination of losartan and losartan acid in human plasma by multiplexed LC-MS/MS

A rapid LC-MS/MS method has been developed and validated for the determination of losartan (LOS) and its metabolite losartan acid (LA) (EXP-3174) in human plasma using multiplexing technique (two HPLC units connected to one MS/MS). LOS and LA were extracted from human plasma by SPE technique using Oasis HLB cartridge without evaporation and reconstitution steps. Hydroflumethiazide (HFTZ) was used as an internal standard (IS). The analytes were separated on Zorbax SB C-18 column. The mass transition [M-H] ions used for detection were m/z 421.0 --> 127.0 for LOS, m/z 435.0 --> 157.0 for LA, and m/z 330.0 --> 239.0 for HFTZ. The proposed method was validated over the concentration range of 2.5-2000 ng/mL for LOS and 5.0-3000 ng/mL for LA with correlation coefficient > or = 0.9993. The overall recoveries for LOS, LA, and IS were 96.53, 99.86, and 94.16%, respectively. Total MS run time was 2.0 min/sample. The validated method has been successfully used to analyze human plasma samples for applications in 100 mg fasted and fed pharmacokinetic studies.

Multiplex multidimensional nanoLC-MS system for targeted proteomic analyses

The present work describes a dual-column and dual-sprayer LC-MS system for high-throughput proteomic analyses. This system consists of two precolumns for sample desalting and two analytical columns. Each column is terminated by a nanoelectrospray emitter mounted on a robotic arm enabling their sequential positioning in front of the sampling cone of the mass spectrometer. The effluent from each emitter is recorded in separate acquisition channels without detectable crosstalk. Gradient elution to both nanoLC columns is delivered by a single HPLC system via a flow splitter. The reproducibility of retention time and peak intensity of the present multiplex system were comparable to those obtainable using a single emitter configuration. Replicate injections of complex tryptic digests (n = 10) indicated that this system provided good reproducibility of retention time and peak intensity on both columns with RSD values of less than 0.9 and 18.6%, respectively. The application of this system is demonstrated for the monitoring of protein expression changes in U937 human monocyte cells with and without phorbol ester administration. Furthermore, we also demonstrated the use of this multiplex system in a 2-D LC configuration to increase sample loading and throughput for the analysis of biomarker samples of higher complexity. Variations in peptide abundance down to two-fold change were identified across salt fractions for spiked tryptic digests present at a level of 50 fmol in 1.5 microg of plasma samples.

Quantitative determination of a novel dual PPAR α/γ agonist using on-line turbulent flow extraction with liquid chromatography–tandem mass spectrometry

Turbulent flow chromatograph (TFC) is a technique for the direct and efficient analysis of drugs and metabolites in biological matrices. We report here TFC on-line with an HPLC-MS/MS assay for the determination of 5-[2,4-dioxothiazolidin-5-yl)methyl]-2-methoxy-N-[[(4-trifluoromethyl)phenyl]methyl]benzamide (I, MK-0767, KRP297, Fig. 1) in plasma. Samples were transferred using an automated system followed by the addition of internal standard (II), prepared in 0.1 M ammonium acetate (pH 4.0). The plasma samples were directly injected onto a C18 turbulent flow column on-line with an HPLC-MS/MS system, and the analytical column used was a ThermoHypersil Keystone C18. Detection was achieved by MS/MS, using positive ionization on a TurboIonSpray probe, operated in multiple reaction monitoring (MRM) mode. The linear range was 4-2000 ng/mL for I when using 50 microL of plasma. The method exhibited good linearity and reproducibility. The method also showed good selectivity and ruggedness when applied to clinical samples, and was successfully cross-validated with a conventional off-line SPE, LC-MS/MS method.

Liquid chromatography–negative ion electrospray tandem mass spectrometry method for the quantification of tacrolimus in human plasma and its bioanalytical applications

A simple, rapid, novel and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of tacrolimus (I) in human plasma, a narrow therapeutic index, potent macrolide immunosuppressive drug. The analyte and internal standard (tamsulosin (II)) were extracted by liquid-liquid extraction with t-butylmethylether using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of 99% methanol and 1% 10mM ammonium acetate buffer. The deprotonate of analyte was quantitated in negative ionization by multiple reaction monitoring (MRM) with a mass spectrometer. The mass transitions m/z 802.5-->560.3 and m/z 407.2-->151.9 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.05-25ng/ml for tacrolimus in human plasma. The lower limit of quantitation was 50pg/ml with a relative standard deviation of less than 20%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. Run time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in comparative bioavailability studies. The tacrolimus plasma concentration profile could be obtained for pharmacokinetic study. The observed maximum plasma concentration (C(max)) of tacrolimus (5mg oral dose) is 440pg/ml, time to observed maximum plasma concentration (T(max)) is 2.5h and elimination half-life (T(1/2)) is 21h.

Method development in high-performance liquid chromatography for high-throughput profiling and metabonomic studies of biofluid samples

"Metabonomics" has in the past decade demonstrated enormous potential in furthering the understanding of, for example, disease processes, toxicological mechanisms, and biomarker discovery. The same principles can also provide a systematic and comprehensive approach to the study of food ingredient impact on consumer health. However, "metabonomic" methodology requires the development of rapid, advanced analytical tools to comprehensively profile biofluid metabolites within consumers. Until now, NMR spectroscopy has been used for this purpose almost exclusively. Chromatographic techniques and in particular HPLC, have not been exploited accordingly. The main drawbacks of chromatography are the long analysis time, instabilities in the sample fingerprint and the rigorous sample preparation required. This contribution addresses these problems in the quest to develop generic methods for high-throughput profiling using HPLC. After a careful optimization process, stable fingerprints of biofluid samples can be obtained using standard HPLC equipment. A method using a short monolithic column and a rapid gradient with a high flow-rate has been developed that allowed rapid and detailed profiling of larger numbers of urine samples. The method can be easily translated into a slow, shallow-gradient high-resolution method for identification of interesting peaks by LC-MS/NMR. A similar approach has been applied for cell culture media samples. Due to the much higher protein content of such samples non-porous polymer-based small particle columns yielded the best results. The study clearly shows that HPLC can be used in metabonomic fingerprinting studies.

Quantification of the anti-leukemia drug STI571 (Gleevec) and its metabolite (CGP 74588) in monkey plasma using a semi-automated solid phase extraction procedure and liquid chromatography-tandem mass spectrometry

Signal Transduction Inhibitor 571 (STI571, formerly known as CGP 57148B) or Gleevec received fast track approval by the US Food and Drug Administration (FDA) for treatment of chronic myeloid leukemia (CML). STI571 (Gleevec) is a revolutionary and promising new oral therapy for CML, which functions at the molecular level with high specificity. The dramatic improvement in efficacy compared with existing treatments prompted an equally profound increase in the pace of development of Gleevec. The duration from first dose in man to completion of the New Drug Application (NDA) filing was less than 3 years. In addition, recently, FDA approved Gleevec for the treatment of gastrointestinal stromal tumor (GIST). In order to support all toxicokinetic (TK) studies with sufficient speed to meet various target dates, a semi-automated procedure using solid phase extraction (SPE) was developed and validated. A Packard Multi-Probe I and a SPE step in a 96-well plate format were utilized. A 3M Empore octyl (C(8))-standard density 96-well plate was used for plasma sample extraction. A Sciex API 3000 triple quadrupole mass spectrometer with an atmospheric pressure chemical ionization (APCI) interface operated in positive ion mode was used for detection. Lower limits of quantification of 1.00 and 2.00 ng/ml were attained for STI571 and its metabolite, CGP 74588, respectively. The method proved to be rugged and allowed the simultaneous quantification of STI571 and CGP 74588 in monkey plasma. Herein, assay development, validation, and representative concentration-time profiles obtained from TK studies are presented.

High-speed gradient parallel liquid chromatography/tandem mass spectrometry with fully automated sample preparation for bioanalysis: 30 seconds per sample from plasma

In this work, a high-throughput and high-performance bioanalytical system is described that is capable of extracting and analyzing 1152 plasma samples within 10 hours. A Zymark track robot system interfaced with a Tecan Genesis liquid handler was used for simultaneous solid-phase extraction of four 96-well plates in a fully automated fashion. The extracted plasma samples were injected onto four parallel monolithic columns for separation via a four-injector autosampler. The use of monolithic columns allowed for fast and well-resolved separations at a considerably higher flow rate without generating significant column backpressure. This resulted in a total chromatographic run cycle time of 2 min on each 4.6 x 100 mm column using gradient elution. The effluent from the four columns was directed to a triple quadrupole mass spectrometer equipped with an indexed four-probe electrospray ionization source (Micromass MUX interface). Hence, sample extraction, separation, and detection were all performed in a four-channel parallel format that resulted in an overall throughput of about 30 s per sample from plasma. The performance of this system was evaluated by extracting and by analyzing twelve 96-well plates (1152) of human plasma samples spiked with oxazepam at different concentrations. The relative standard deviation (RSD) of analyte sensitivity (slope of calibration curve) across the four channels and across the 12 plates was 5.2 and 6.8%, respectively. An average extraction recovery of 77.6% with a RSD of 7.7% and an average matrix effect of 0.95 with a RSD of 5.2% were achieved using these generic extraction and separation conditions. The good separation efficiency provided by this system allowed for rapid method development of an assay quantifying the drug candidate and its close structural analog metabolite. The method was cross-validated with a conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay.