Determination of a glycine/NMDA receptor antagonist in human plasma and urine using column-switching high-performance liquid chromatography with ultraviolet, fluorescence and tandem mass spectrometric detection

Increasing sample throughput in pharmacological studies by using dual-column liquid chromatography with tandem mass spectrometry

A robust novel technology of parallel chromatography combined with tandem mass spectrometry was successfully applied to a biological matrix extract for analyte detection. The presented study shows how only by using an additional isocratic pump, a second column and a 10-port valve the throughput is twice of that of a conventional single column system with the same sensitivity. Analytes and matrix were separated and eluting peaks of the first column were detected while the second column was equilibrated. The system was tested and used for the determination of several drugs, metabolites and endogenous compounds (i.e., propiverine, talinolol, scopolamine and leukotrienes).

Effect of the sample matrix on the determination of indinavir in human urine by HPLC with turbo ion spray tandem mass spectrometric detection

The HPLC/tandem mass spectrometric (LC/MS/MS) behavior of indinavir, an HIV protease inhibitor, in human urine is presented as an example of a case where endogenous matrix components were found to interfere with the ionization of the target analyte. The MS/MS system used for these experiments was equipped with a turbo ion spray LC interface. Results from two sample preparation procedures (direct dilution of urine vs urine extraction) and two chromatographic systems (low vs. high capacity factor (k')) for the analytes were compared. Additionally, the precision of the analysis that was achieved while using a stable isotope labeled internal standard is contrasted with the results obtained using an analog of indinavir as internal standard. The results obtained indicated that during development and validation of LC/MS/MS based assays the potential effect of co-eluting 'unseen' endogenous species should be evaluated to ensure that sample preparation and chromatography is adequate to overcome the matrix effect problems.

Development of high-performance liquid chromatography-tandem mass spectrometric methods for the determination of a new oxytocin receptor antagonist (L-368,899) extracted from human plasma and urine: a case of lack of specificity due to the presence of metabolites

The purpose of this work was to develop HPLC-MS-MS methods for the quantification of L-368,899 (1) in human plasma and urine and to evaluate the selectivity of these methods in post-dose samples in the presence of metabolites. Assays were based on double liquid-liquid extraction of the drug and internal standard (I.S., 2) from basified plasma, evaporation of the extracts to dryness, derivatization of the primary amino groups of 1 and 2 with trifluoroacetic anhydride (TFAA) to form trifluoroacetylated (TFA) analogs, and HPLC analysis using tandem mass spectrometer equipped with the heated nebulizer interface as a detector. The derivatization with TFAA was required to eliminate the carryover and adsorption problems encountered when underivatized molecules were chromatographed, and allowed quantitation at low concentration (0.5 ng/ml) in plasma and urine. Initially, assays in control human plasma and urine were validated in the concentration range of 0.5-75 ng/ml, using simplified chromatographic conditions with a 2-min run-time and no separation of the drug from I.S.. Quantitation was based on the high selectivity of detection and multiple reaction monitoring (MRM) using the precursor-->product ion combinations of m/z 651-->152 and m/z 665-->425 for the TFA-derivatized 1 and 2, respectively. However, when selected post-dose urine samples from a clinical study were analyzed using this assay, the area of the I.S. peak was 4 to 7 times larger than the area of I.S. peak in pre-dose urines, indicating the presence of metabolites giving rise to the m/z 665-->425 I.S. peak. A number of metabolites contributing to the I.S. ion pair were separated from 1 and 2 using a longer analytical column, a weaker mobile phase, and by extending the HPLC run-time to 12 min. Under these new conditions, the modified assays both in plasma and urine were validated in the concentration range of 0.5 to 75.0 ng/ml. These assays were selective in the post-dose urine samples in the presence of metabolites.

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

Contrary to common perceptions, the reliability of quantitative assays for the determination of drugs in biological fluids using high-performance liquid chromatography with tandem mass spectrometric (LC/MS/MS) detection methods and the integrity of resulting pharmacokinetic data may not be absolute. Results may be adversely affected by lack of specificity and selectivity due to ion suppression caused by the sample matrix, interferences from metabolites, and "cross-talk" effects. In this paper, an example of the effect of the sample matrix on the determination of finasteride (I) in human plasma is presented. The ion suppression effect was studied by analyzing standards of I injected directly in mobile phase and comparing the response (peak areas) of I and an internal standard (II) with the peak areas of the same analytes spiked before extraction into five different plasma pools and standards spiked into the plasma extracts after extraction. The LC/MS/MS analyses were performed using a turbo ion spray interface (TISP) under chromatographic conditions, characterized by minimal (total run time of 2 min, capacity factors, k' of 1.50 and 1.75 for I and II, respectively) and high retention of the analytes (total run time 6 min, k' of 3.25 and 13.25 for I and II, respectively). The absolute peak areas for I and II in different plasmas were calculated, and the slopes and peak area ratios at all concentrations within the standard curve ranges were compared. When analyses were performed under conditions of minimal HPLC retention, the slope of the standard line for one set of plasma samples was substantially different (about 50% higher) from that from other plasma sources. The precision of the assay, expressed as coefficient of variation (CV, %) was also inadequate and varied from 15 to 30% at all concentrations within the standard curve range. When the same experiments were repeated using high HPLC retention, the slopes from different plasma sources were practically the same, and the CV was improved to 6-14%. By increasing k' and providing more chromatographic retention of analytes, the "unseen" interferences from plasma matrix were mostly separated from analytes, practically eliminating the ion suppression. In addition, by eliminating from plasma extracts a number of endogenous components through more selective extraction, the ion suppression was also minimized. The detailed data and the design of these experiments are presented. In addition, development of a highly sensitive assay for I in human plasma at low picogram per milliliter concentrations using LC/MS/MS with a heated nebulizer (HN) interface, instead of a TISP interface, is described. In this case, the effects of sample matrixes were not observed.

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

Contrary to common perceptions, the reliability of quantitative assays for the determination of drugs in biological fluids using high-performance liquid chromatography with tandem mass spectrometric (LC/MS/MS) detection methods and the integrity of resulting pharmacokinetic data may not be absolute. Results may be adversely affected by lack of specificity and selectivity due to ion suppression caused by the sample matrix, interferences from metabolites, and "cross-talk" effects. In this paper, an example of the effect of the sample matrix on the determination of finasteride (I) in human plasma is presented. The ion suppression effect was studied by analyzing standards of I injected directly in mobile phase and comparing the response (peak areas) of I and an internal standard (II) with the peak areas of the same analytes spiked before extraction into five different plasma pools and standards spiked into the plasma extracts after extraction. The LC/MS/MS analyses were performed using a turbo ion spray interface (TISP) under chromatographic conditions, characterized by minimal (total run time of 2 min, capacity factors, k' of 1.50 and 1.75 for I and II, respectively) and high retention of the analytes (total run time 6 min, k' of 3.25 and 13.25 for I and II, respectively). The absolute peak areas for I and II in different plasmas were calculated, and the slopes and peak area ratios at all concentrations within the standard curve ranges were compared. When analyses were performed under conditions of minimal HPLC retention, the slope of the standard line for one set of plasma samples was substantially different (about 50% higher) from that from other plasma sources. The precision of the assay, expressed as coefficient of variation (CV, %) was also inadequate and varied from 15 to 30% at all concentrations within the standard curve range. When the same experiments were repeated using high HPLC retention, the slopes from different plasma sources were practically the same, and the CV was improved to 6-14%. By increasing k' and providing more chromatographic retention of analytes, the "unseen" interferences from plasma matrix were mostly separated from analytes, practically eliminating the ion suppression. In addition, by eliminating from plasma extracts a number of endogenous components through more selective extraction, the ion suppression was also minimized. The detailed data and the design of these experiments are presented. In addition, development of a highly sensitive assay for I in human plasma at low picogram per milliliter concentrations using LC/MS/MS with a heated nebulizer (HN) interface, instead of a TISP interface, is described. In this case, the effects of sample matrixes were not observed.

Determination of ZD9583, a thromboxane receptor antagonist, in human plasma and urine by liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry

A liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS-MS) method is described for the determination of a thromboxane receptor antagonist (4Z)-6-((2S,4S,5R)-2-(1-(2-cyano-4-methylphenoxy)-1-methylethyl)-4 -(3-pyridyl)-3-dioxan-5-yl)hex-4-enoic acid (ZD9583, I) in human plasma and urine. Proteins in plasma and urine samples are precipitated using acidified acetonitrile. The resulting supernatant is chromatographed on a C8 reversed-phase chromatography column. Following the diversion of the solvent front from the mass spectrometer by a switching valve, the column eluate is passed on to the mass spectrometer via a heated nebulizer interface where the analyte is detected by multiple reaction monitoring (MRM). The method has a chromatographic run time of less than 2 min, a linear calibration curve with a range of 1-500 ng ml(-1) and intra- and inter-day precision estimates of less than 10% over the calibration range.

Determination of a substance P antagonist in human plasma and urine using high-performance liquid chromatography with ultraviolet absorbance and tandem mass spectrometric detection

A high-performance liquid chromatographic (HPLC) assay using ultraviolet (UV) detection was developed and compared with a HPLC method with tandem mass spectrometric (HPLC/MS-MS) detection for the determination of a substance P receptor antagonist 2(S)-((3,5-bis(trifluoromethyl)benzyl)-oxy)-3(S)-phenyl-4-((3-oxo-1,2,4- triazol-5-yl) methyl)morpholine (Fig. 1, Ia, L-742 694) in human plasma and urine. The drug was isolated from the biological matrix through liquid-liquid extraction. In the HPLC/UV method, the samples were initially injected onto a cyano Hypersil column, and the chromatographic region containing the peaks of interest was heart-cut onto an analytical C-18 Hypersil column via a column switching device. The analyte was quantified by monitoring absorbance at 205 nm. The limit of quantification for I extracted from 1 ml of plasma or urine was 2.5 ng ml-1, and the assays were validated in the concentration range 2.5-500 ng ml-1. The HPLC/MS-MS method were validated in the concentration range 0.2-500 ng ml-1. Both assays provided data with precision, measured as coefficient of variation, better than 10% at all points within the standard curve range and with adequate accuracy.

Determination of a novel growth hormone secretagogue (MK-677) in human plasma at picogram levels by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A sensitive and specific method for the determination of N-[1(R)¿[1,2-dihydro-1-methylsulfonylspiro(3H-indole-3,4'-piper idin)-1'-yl]carbonyl¿-2-(phenylmethoxy)ethyl]-2-amino-2-meth ylpropanamide (MK-677, I), a growth hormone secretagogue, has been developed. The method is based on high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) detection. The analyte and internal standard (II) were isolated from the basified plasma using a liquid-liquid extraction with methyl-tert.-butyl ether (MTBE). The organic extract was evaporated to dryness, the residue was reconstituted in mobile phase and injected into the HPLC system. The MS-MS detection was performed on a PE Sciex API III Plus tandem mass spectrometer using a heated nebulizer interface. Multiple reaction monitoring of parent-->product ion combinations at m/z 529-->267 and 527-->267 was used to quantify I and II, respectively. The assay was validated in human plasma in the concentration range of 0.1 to 100 ng/ml, and the limit of quantification (LOQ) was 0.1 ng/ml. The precision of the assay, as expressed as coefficients of variation (C.V.,%) was less than 7% at all concentrations within the standard curve range, with adequate assay specificity and accuracy. The HPLC-MS-MS method provided sufficient sensitivity to completely map the pharmacokinetic time-course following a single 5-mg oral dose of I.

Low level determination of dorzolamide and its de-ethylated metabolite in human plasma by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A sensitive and specific method for the determination of dorzolamide (I) and its de-ethylated metabolite (II) in human plasma has been developed utilizing high pressure liquid chromatography (HPLC) with tandem mass spectrometric (MS/MS) detection. The analytes and internal standard (III) were isolated from the deproteinized pH 8.0 buffered plasma, using a liquid-liquid extraction with a mixture of ethyl acetate, toluene, and isopropanol. The analytes were then back extracted into 0.085% phosphoric acid (200 microliters) and after washing the acidic extract with hexane, the organic layer was discarded and a fraction (50 microliters) of the acid extract was injected into the LC/MS/MS system. The MS/MS detection was performed on a PE Sciex API III tandem mass spectrometer using a heated nebulizer interface. Multiple reaction monitoring of the parent-->product ion combinations of m/z 325-->199, 297-->199, and 397-->306 were used to quantify I, II, and III, respectively. The assay was validated in the concentration ranges of 0.5-100 and 2.5-100 ng ml-1 of plasma for I and II, respectively. The precision of the assays, expressed as coefficients of variation (C.V.%), were less than 10% over the entire concentration range, with adequate assay specificity and accuracy. The LC/MS/MS method provided a 10-fold increase in the sensitivity of I over the previously reported HPLC/UV method [1].

Picogram determination of a novel dopamine D4 receptor antagonist in human plasma and urine by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A sensitive and specific assay for the determination of 3-[[4-(4-chlorophenyl)piperazin-1-yl]methyl]-1H-pyrrolo[2,3-b]p yri dine (I, L-745,870), a potential antipsychotic agent, has been developed, utilizing high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) detection. The analyte and the internal standard (II, 3-[[4-(4-trifluoromethyl)piperazin-1-yl]methyl]-1H-pyrrolo[2,3-b] pyridine) were isolated from a basified biological matrix using liquid-liquid extraction with methyl-tert.-butyl ether. The organic extract was evaporated to dryness, the residue was reconstituted in a mobile phase and injected into the HPLC system. The chromatographic conditions used for the analysis were a Keystone Scientific C18 BDS 150 x 4.6 mm, 5 microns column with a mobile phase consisting of a 40:60 (v/v) mixture of acetonitrile and water containing 10 mM ammonium acetate and 0.1% formic acid pumped at a flow-rate of 1.2 ml/min, yielding retention times of 3.4 and 5.0 min for I and II, respectively. The MS-MS detection was performed on a PE Sciex API III Plus tandem mass spectrometer using a heated nebulizer interface. Multiple reaction monitoring using the parent-->product ion combinations of m/z 327-->131 and 361-->131 were utilized to quantitate I and II, respectively. The assays were validated in the concentration range of 0.1 to 100 and 0.5 to 500 ng/ml for plasma and urine, respectively. The precision of the assays, expressed as coefficients of variation were less than 10% over the entire concentration range, with adequate assay accuracy, sensitivity and specificity to determine the pharmacokinetics in human subjects following a single 1-mg dose.

Determination of an in vivo metabolite of a human immunodeficiency virus protease-inhibitor in human plasma by high-performance liquid chromatography with tandem mass spectrometry

A method for the determination of a metabolic of the human immunodeficiency virus protease inhibitor indinavir, in human plasma is described. Isolation of the analyte and the internal standard from plasma was achieved via liquid-liquid extraction with a mixture of isopropanol-chloroform (5:95, v/v). The analytes were chromatographed under reversed-phase conditions on a Waters Symmetry C, column. A Sciex API III+ tandem mass spectrometer equipped with a heated nebulizer was used as a detector and was operated in the positive ion mode. Multiple reaction monitoring using the precursor-->production combinations of m/z, 523.4-->273.4 and 512.4-->345.2 was used to quantify analyte and internal standard, respectively. The method was validated in the concentration range of 5-500 ng/ml plasma with adequate assay precision and accuracy. The assay was used to analyze samples collected during drug interaction studies of indinavir.

Simultaneous determination of unlabeled and deuterium-labeled indinavir in human plasma by high-performance liquid chromatography with tandem mass spectrometric detection

A method for the simultaneous determination of indinavir and its hexadeuterated analog (d6-indinavir) in human plasma is described. Isolation of the analytes and internal standard from plasma was achieved via liquid-liquid extraction with methyl-t-butyl ether. The analytes were chromatographed under reversed-phase conditions on a BDS-Hypersil C8 column. A Sciex API III+ tandem mass spectrometer equipped with a turbo ion-spray interface was used as the detector. Multiple reaction monitoring using the parent-->product ion combinations of m/z 614-->465, 620-->471 and 654-->505 were used to quantify indinavir, d6-indinavir, and internal standard, respectively. The method was validated, using 1-mL aliquots of plasma, in the concentration range in plasma of 1 to 200 ng/mL. Precision of the assay, as measured by the coefficient of variation, ranged from 0.9 to 4.3% and 0.9 to 6.2% for indinavir and d6-indinavir, respectively. Indinavir assay accuracy ranged from 95.8 to 105.0% of nominal, whereas the accuracy of the assay for d6-indinavir ranged from 97.4 to 104.0% of nominal. The assay was used to support a clinical study in which the stable isotope technique was used to determine the bioavailability of indinavir.