Validated LC-MS-MS method for determination of m-nisoldipine polymorphs in rat plasma and its application to pharmacokinetic studies

A sensitive and specific liquid chromatography-tandem mass spectrometric (LC-MS-MS) method has been developed to determine m-nisoldipine in rat plasma. Sample was pretreated by a single-step protein precipitation with acetonitrile, in contrast to the liquid-liquid procedure frequently used for the extraction of 1,4-dihydropyridines from biologic samples. Separation of analyte and internal standard (I.S.) was performed on a Symmetry RP-C(18) analytic column (50 mm x 4.6 mm, 3.5 microm) with a mobile phase consisting of acetonitrile-water (80:20, v/v) at a flow rate of 0.5 ml/min. The API 4000 triple quadrupole mass spectrometer was operated in multiple reaction monitoring (MRM) scan mode using TurboIonSpray ionization (ESI) source. The method was sensitive with a lower limit of quantification (LLOQ) of 0.2 ng/mL, with good linearity (r>or=0.9982) over the linear range of 0.2-20 ng/mL. All the validation data, such as accuracy, precision, and inter-day repeatability, were within the required limits. The method was successfully applied to pharmacokinetic and relative bioavailability studies of m-nisoldipine polymorphs in rats.     

Determination of nimodipine in human plasma by a sensitive and selective liquid chromatography-tandem mass spectrometry method

A sensitive and highly selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed to determine nimodipine in human plasma. The analyte and internal standard nitrendipine were extracted from plasma samples by n-hexane-dichloromethane-isopropanol (300:150:4, v/v/v), and chromatographed on a C(18) column. The mobile phase consisted of methanol-water-formic acid (80:20:1, v/v/v). Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI) source. The method has a limit of quantification of 0.24 ng/ml. The linear calibration curves were obtained in the concentration range of 0.24-80 ng/ml. The intra- and inter-day precisions were lower than 4.4% in terms of relative standard deviation (R.S.D.), and the accuracy ranged from 0.0 to 5.8% in terms of relative error (RE). This validated method was successfully applied for the evaluation of pharmacokinetic profiles of nimodipine tablets administered to 18 healthy volunteers.     

Determination of mitiglinide in rat plasma by high-performance liquid chromatography with UV detection

A selective and sensitive high-performance liquid chromatography method has been developed and validated for determination of mitiglinide (MGN) in rat plasma using 2-(4-biphenylyl) propionic acid (BPA) as internal standard. Liquid-liquid extraction was used for sample preparation. Chromatographic separation was achieved on a C(18) column using acetonitrile and 0.02 mol/l KH(2)PO(4) buffer (pH 4.0) (45:55, v/v) as mobile phase delivered at 1.0 ml/min. The UV detector was set at 210 nm. The assay was linear over the range 0.1-20 microg/ml for MGN. The average extraction recoveries of MGN and BPA from rat plasma were 98.6 and 97.4%, respectively. The developed method has been applied to the pharmacokinetic study of MGN in rats.     

Determination of cryptotanshinone and its metabolite in rat plasma by liquid chromatography-tandem mass spectrometry

A sensitive and selective LC-MS-MS method has been developed and validated for the determination of cryptotanshinone (CTS) and its active metabolite tanshinone II A (TS II A) in rat plasma using fenofibrate (FOFB) as internal standard. Liquid-liquid extraction was used for sample preparation. Chromatographic separation was achieved on a Waters symmetry ODS column using methanol and water (85:15) as mobile phase delivered at 1.0 mL/min. LC-MS-MS analysis was carried out on a Finnigan LC-TSQ Quantum mass spectrometer using atmospheric pressure chemical ionization (APCI) and positive multiple reaction monitoring. Ions monitored were m/z 297.0--> 251.0 for CTS, m/z 295.0--> 249.0 for TS II A, and m/z 361.1--> 233.0 for FOFB with argon at a pressure of 0.2 Pa and collision energy of 25 eV for collision-induced dissociation (CID). The assay was linear over the range 0.1-20 ng/mL for CTS and 0.2-15 ng/mL for TS II A. The average recoveries of CTS and TS II A from rat plasma were 93.7 and 94.7%, respectively. The established method has been applied in a pharmacokinetic study of CTS in rats.     

Liquid chromatographic-tandem mass spectrometric method for the quantitation of huperzine A in dog plasma

A rapid and sensitive LC-MS-MS method for the determination of huperzine A in dog plasma using huperzine B as internal standard has been developed and validated. The analyte and internal standard were extracted from plasma using n-hexane-dichloromethane-2-propanol (300:150:15, v/v/v), chromatographed on a C(18) column (5 microm, 50 mm x 4.6 mm i.d.) with a mobile phase consisting of acetonitrile-methanol-10mM ammonium acetate (35:40:25, v/v/v), and detected using a tandem mass spectrometer with a TurboIonSpray ionization interface. The run time was only 2 min. The assay was linear over the concentration range 0.05-20 ng/ml and intra- and inter-day precision over this range were <5.3% with good accuracy. The limit of detection in plasma was 0.01 ng/ml. The method was successfully applied to define plasma concentration-time curves of huperzine A in dogs after the last dose of an intramuscular injection (10 microg/kg per day for 15 days) of a sustained-release formulation of huperzine A.     

Determination of meloxicam in human plasma by liquid chromatography-tandem mass spectrometry following transdermal administration

A highly sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed to determine meloxicam of low concentration in human plasma. After a simple sample preparation procedure by one-step protein precipitation with methanol, meloxicam and the internal standard piroxicam were chromatographed on a Zorbax SB C(18) column. The mobile phase consisted of acetonitrile-water-formic acid (80:20:0.2, v/v/v). Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via electrospray ionization (ESI) source. The method had a lower limit of quantification of 0.10 ng/ml. The calibration curve was demonstrated to be linear over the concentration range of 0.10-50.0 ng/ml. The assay was specific, accurate (percentage deviations from nominal concentrations were within +/-2.5%), precise (intra- and inter-day relative standard deviation (R.S.D.) <7%). The validated method was successfully applied to the determination of meloxicam in human plasma collected up to 180 h after a transdermal administration of 30 mg meloxicam for evaluation of the pharmacokinetics.     

Rapid and sensitive liquid chromatography-tandem mass spectrometric method for the quantitation of metformin in human plasma

A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS-MS) method for the determination of metformin in human plasma using phenformin as internal standard has been developed and validated. Sample preparation of plasma involved acidification with acetic acid, deproteination with acetonitrile and washing with dichloromethane. Samples were then analyzed by HPLC on a short Nucleosil C18 column (5 microm, 50 mm x 4.6 mm i.d.) using a mobile phase consisting of acetonitrile:methanol:10mM ammonium acetate pH 7.0 (20:20:60, v/v/v) delivered at 0.65 ml/min. Detection was performed using an Applied Biosystems Sciex API 4000 mass spectrometer set at unit resolution in the multiple reaction monitoring (MRM) mode. Atmospheric pressure chemical ionization (APCI) was used for ion production. The assay was linear over the range 1-2000 ng/ml with intra- and inter-day precision of <8.6% and accuracy in the range 91-110%. The limit of detection was 250 pg/ml in plasma. The method was successfully applied to a clinical pharmacokinetic study of an extended-release tablet of metformin hydrochloride (500 mg) administered as a single oral dose.     

Simultaneous determination of four active alkaloids from a traditional Chinese medicine Corydalis saxicola Bunting. (Yanhuanglian) in plasma and urine samples by LC-MS-MS

A sensitive rapid method for the simultaneous determination of four major active alkaloids (dehydrocavidine, coptisine, dehydroapocavidine, and tetradehydroscoulerine, in abbreviation thereafter called YHL-I, YHL-II, YHL-III, and YHL-IV, respectively) from a Chinese traditional medicine Corydalis saxicola Bunting. (Yanhuanglian) in rat plasma and urine was established and validated. The assay for these substances in plasma and urine was based on HPLC coupled with tandem mass spectrometry (MS/MS) detection using multiple reaction monitoring mode (MRM) with berberine and clenbuterol as internal standards. The plasma and urine sample were deproteinated by adding methanol prior to liquid chromatography where separation was performed on a Luna column (5 microm, 100 x 2.00 mm) and an Agilent Zorbax SB-C18 guard column (5 microm, 20 x 4 mm). The method was validated with the concentration range 1-1000 ng/mL in plasma and 10-1000 ng/mL in urine for the four test compounds, and the calibration curves were linear with correlation coefficients >0.999. The lowest limits of quantitation for all four substances were 1 ng/mL in 0.1 mL rat plasma and 10 ng/mL in 0.1 mL urine. The intra-assay accuracy and precision in plasma ranged from 88.1 to 115.7% and 1.4 to 10.8%, respectively, while inter-assay accuracy and precision for YHL-I, YHL-II, YHL-III, and YHL-IV ranged from 96.2 to 113.2% and 0.4 to 16.9%, respectively. The intra-assay accuracy and precision for YHL-I, YHL-II, YHL-III, and YHL-IV in rat urine ranged from 96.1 to 112.9% and 1.2 to 8.3%, respectively, while inter-assay accuracy and precision ranged from 95.0 to 106.8% and 2.2 to 10.3%, respectively. The method was further applied to assess pharmacokinetics and urine excretion of the four alkaloids after oral and intravenous administration to rats. Practical utility of this new LC-MS-MS method was confirmed in pilot pharmacokinetic studies in rats following both intravenous and oral administration.     

Enantiomeric separation of mirtazapine and its metabolite in rat plasma by reverse polar ionic liquid chromatography using fluorescence and polarimetric detectors connected in series

A simple and rapid reverse polar ionic LC method was developed and validated for simultaneous separation and determination of mirtazapine, an antidepressant drug, and its main metabolite N-desmethyl mirtazapine using fluorescence and polarimetric detectors connected in series. The chromatographic separation was achieved on Chirobiotic V column packed with vancomycin as a stationary phase in an isocratic mode of elution of methanol:glacial acetic acid:anhydrous triethyl amine (100:0.2:0.1, v/v/v) as a mobile phase. The compounds were detected by their excitation at 290nm and emission at 370nm using fluorescence detector while the optical rotation (+/-) of the enantiomers was identified by polarimetric detector. The analytes were extracted from rat plasma by precipitation of proteins and the average yield was 88-111% for mirtazapine and 85-123% for N-desmethyl mirtazapine. The method was linear over the concentration range of 20-5000ng/mL. The method was successfully applied on rat plasma spiked with the enantiomers of mirtazapine and N-desmethyl mirtazapine.     

High-performance liquid chromatographic determination of finasteride in human plasma using direct injection with column switching

A fully automated column-switching high-performance liquid chromatographic (HPLC) method was developed for the quantification of finasteride [N-(1,1-dimethylethyl)-3-oxo-4-aza-5α-androst-1-ene-17β-carboxamide] in human plasma. Plasma samples were diluted with an equal volume of ethylene glycol-water (40:60, v/v), then the diluted sample (150 μl) was injected into the HPLC system without clean-up. The analyte was retained on a pretreatment column, whereas plasma proteins and other endogenous components were washed out to waste. The analyte was transferred to the analytical column in the heart-cut mode and then detected at 210 nm. A quantification limit of 1 ng/ml was attained. There was a linear relationship between peak height and drug concentration in plasma in the range 1–50 ng/ml. This method was validated and applied to the assay of plasma samples to characterize pharmacokinetic parameters in clinical studies.     

Development and validation of a liquid chromatography-mass spectrometric method for the determination of DPC 423, an antithrombotic agent,in rat and dog plasma

A sensitive and selective LC-MS-MS method for the determination of DPC 423 (I), an antithrombotic agent, is described. This method used a solid-phase extraction from 0.1 ml plasma with an Isolute C(2) cartridge. HPLC separation was carried out on a YMC ODS-AQ C(18) column (50x2 mm) at a flow-rate of 300 microliter/min with an analysis time of 5 min. Compounds were eluted using a mobile phase of H(2)O/CH(3)CN/HCOOH: 66:34:0.1 (v/v/v), pH 4.0. A structural analogue of I was used as the internal standard to account for variations in recovery and instrument response. Mass spectrometric detection was carried out with a PE Sciex API III(+) triple quadrupole mass spectrometer equipped with a Turbo IonSpray source as the LC-MS interface. Good intra-day and inter-day assay precision (<10% CV) and accuracy (<10% difference) were observed over a concentration range of 0.005-2.5 microM in plasma. The extraction recoveries were approximately 90% and the method was found to be linear for the assay (r(2)>0.999). The method has been successfully applied to discovery and preclinical pharmacokinetic studies, including a dose range-finding study and toxicokinetic exposure studies in rat and dog.     

Quantification of CPT13 in rat plasma using LC-MS/MS for a pharmacokinetic study

A new, simple, sensitive and specific reversed-phase high performance liquid chromatographic (HPLC) method using tandem mass spectrometry detection was initially developed and validated for the analysis of 10-(2-pyrazolyl-ethoxy)-(20S)-camptothecin (CPT13) in rat plasma. Pretreatment of the sample obtained from plasma involved a single protein precipitation step with using acetonitrile containing 0.1% formic acid. An aliquot of 20 μl was injected into a C-18 column. The chromatographic separation was achieved using the mobile phase consisting of acetonitrile:water (35:65) at a flow rate of 1.0 mL/min. The total run time for each sample was 10 min, and camptothecin (CPT, IS) and CPT13 were well separated with retention times of 5.1 min and 5.6 min, respectively. Detection was performed using a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via an electrospray ionization (ESI) source. The calibration curve was linear (r2 = 0.9998) over the concentration range of 1-1000 ng/mL, with a LLOQ of 1 ng/mL for CPT13. The inter- and intra-day precision (%R.S.D.) were <2.58% and 6.28%, respectively, and the accuracies (%) were within the range of 97.34-110.67%. CPT13 in rat plasma was stable when stored at -20 °C or 4 °C for three freeze-thaw cycles, The method was employed for the first time during pharmacokinetic studies of CPT13 in rats following a single intravenous dose (0.1 mg/kg) and three different oral doses (50 mg/kg, 30 mg/kg, and 10 mg/kg). This fully validated method was successfully applied to a pharmacokinetic study of CPT13 in rats.     

Simultaneous determination of the new anticancer agent amidox and its metabolites in rat bile and plasma by high-performance liquid chromatography

A new reversed-phase ion-pair high-performance liquid chromatography method was developed to study the first-pass hepatic metabolism of the anti cancer drug amidox in bile. Separation of the metabolites was achieved on a Spherisorb C₁₈ column after liquid-liquid extraction using a linear gradient system of heptanesulfonic acid in potassium phosphate monobasic (pH 4.0) with increasing amounts of methanol (0–40%). The method was further applied to a pharmacokinetic study of amidox in rats after 200 mg kg⁻¹ intraperitoneal administration. Using 50 μl of rat bile and 300 μl of rat plasma the limit of detection for amidox was 60 ng and 85 ng, respectively, and the assay was linear from 0.1 to 150 μg ml⁻¹. This method appears to be sensitive enough to be used in further pharmacokinetic studies of amidox in human volunteers.     

Analysis of alpha-lipoprotein cholesterol in 50 microl of plasma

A micromethod for quantitation of alpha-lipoprotein cholesterol was devised for gas-liquid chromatography to minimize plasma sample size and facilitate lipid studies using capillary blood from children or small animals. alpha-Lipoprotein cholesterol was measured by gas-liquid chromatography in 20 micro l of the centrifuged supernate obtained after addition of 5 micro l of mixed heparin-manganese chloride solution 1:1 (v/v) to 50 micro l of plasma. Comparison of venous alpha-lipoprotein cholesterol measured by gas-liquid chromatography with venous alpha-lipoprotein cholesterol measured by conventional heparin-manganese precipitation and ferric chloride (colorimetric) cholesterol determination gave a correlation coefficient of 0.98 for 80 plasma samples. Capillary alpha-lipoprotein cholesterol and venous alpha-lipoprotein cholesterol were closely correlated in 31 patients (r = 0.97).     

Highly sensitive determination of saquinavir in biological samples using liquid chromatography-tandem mass spectrometry

A selective and sensitive method for the determination of the HIV protease inhibitor saquinavir in human plasma, saliva, and urine using liquid-liquid extraction and LC-MS-MS has been developed, validated, and applied to samples of a healthy individual. After extraction with ethyl acetate, sample extracts were chromatographed isocratically within 5 min on Kromasil RP-18. The drug was detected with tandem mass spectrometry in the selected reaction monitoring mode using an electrospray ion source and 2H(5)-saquinavir as internal standard. The limit of quantification was 0.05 ng/mL. The accuracy of the method varied between -1 and +10% (SD within-batch) and the precision ranged from +4 to +10% (SD batch-to-batch). The method is linear at least within 0.05 and 87.6 ng/mL. After a regular oral dose (600 mg) saquinavir concentrations were detectable for 48 h in plasma and were well correlated with saliva concentrations (r(2)=0.9348, mean saliva/plasma ratio 1:15.1). The method is well suited for low saquinavir concentrations in different matrices.     

Sensitive liquid chromatography-tandem mass spectrometry method for the determination of cefixime in human plasma: application to a pharmacokinetic study

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed to determine cefixime ((6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-(carboxymethoxyimino)acetamido]-8-oxo-3-vinyl-5-thia-1-azabicyclo-[4,2,0]-oct-2-ene-2-carboxylic acid) in human plasma. After a simple protein precipitation using acetonitrile, the post-treatment samples were analyzed on a C(8) column interfaced with a triple quadrupole tandem mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase consisted of acetonitrile-water-formic acid (40:60:0.5, v/v/v). The analyte and internal standard cefetamet were both detected by use of selected reaction monitoring mode. The method was linear in the concentration range of 0.05-8.0 microg/ml. The lower limit of quantification was 0.05 microg/ml. The intra- and inter-day relative standard deviation across three validation runs over the entire concentration range was less than 12.7%. The accuracy determined at three concentrations (0.05, 0.80 and 7.2 microg/ml for cefixime) was within +/-2.0% in terms of relative error. Each plasma sample was chromatographed within 3.5 min. The method herein described was successfully applied for the evaluation of pharmacokinetic profiles of cefixime capsule in 24 healthy volunteers.     

Development of a plasma high-performance liquid chromatographic assay for LY303366, a lipopeptide antifungal agent, and its application in a dog pharmacokinetic study

An HPLC assay for plasma analysis of LY303366 (I), a semi-synthetic lipopeptide antifungal related to echinocandin B (ECB), was developed to support the selection and subsequent preclinical development of I. The method involved extraction of I from plasma with the aid of solid-phase extraction (SPE) cartidges followed by reversed-phase HPLC with UV detection at 300 nm. The method is simple, selective and is applicable to dog, rat, mouse and rabbit plasma. Validation studies using dog plasma showed that the values obtained for parameters of linearity, precision and accuracy were within acceptable limits. Based on analysis of 0.3 ml of plasma, the lower limit of quantitation was 20 ng/ml. The method has been successfully applied to determine the pharmacokinetic parameters of I in the dog following intravenous (i.v.) and oral administration. Compared to first generation ECB antifungal agents, the results of the i.v. dog study indicated a 50% reduction in clearance of the drug from plasma (0.1 l/h/kg) and an 18-fold increase in the volume of distribution at steady state (1.8 l/kg). When administered orally, compound I had an absolute bioavailability of 9%; however, plasma levels remained above the MIC for C. albicans (0.005 μg/ml) through 48 h. Given the excellent potency of I and its broad spectrum of activity relative to first generation ECB antifungal agents, the assay results for I indicate the potential for its use as a broad spectrum i.v. and oral antifungal agent.     

Determination of the substance P receptor antagonist CP-122, 721 in plasma by narrow-bore high-performance liquid chromatography-ionspray tandem mass spectrometry

A simple, highly sensitive and specific LC-MS-MS assay was developed for the determination of CP-122,721 (I) in rat and human plasma. I and a structural analog, CP-129,943 (II, internal standard), were extracted from plasma with methyl tert.-butyl ether (MTBE). The dried MTBE extracts were reconstituted and analyzed using a narrow-bore (2.1 mm I.D.) YMC basic HPLC column and a mobile phase of acetonitrile-20 mM ammonium acetate, pH 5 (50:50, v/v). Column effluents were monitored by ionspray tandem mass spectrometry. Multiple reaction monitoring (MRM) using the parent to product ion combinations of m/z 381 → 205 and 395 → 219 was used to quantitate I and II, respectively. The assay exhibited a linear dynamic range of 0.2–100 ng/ml. Absolute recoveries from plasma were above 80% for both I and II. The precision and accuracy values for the method were within ±3 and ±9%, respectively. Sample analysis times were less than 5 min from one injection to the next. The assay has proved to be applicable to the pharmacokinetic study of I in rats.     

A high-performance liquid chromatography-tandem mass spectrometry assay of the androgenic neurosteroid 3alpha-androstanediol (5alpha-androstane-3alpha,17beta-diol) in plasma

The testosterone metabolite 3alpha-androstanediol (5alpha-androstane-3alpha,17-diol) is a potential GABA(A) receptor-modulating neurosteroid with anticonvulsant properties and hence could act as a key neuromodulator in the central nervous system. However, there is no specific and sensitive assay for quantitative determination of the androgenic neurosteroid 3alpha-androstanediol in biological samples. We have established a liquid chromatography-tandem mass spectrometry (LC-MS-MS) assay to measure 3alpha-androstanediol in rat plasma. Standard 3alpha-androstanediol added to rat plasma has been successfully analysed with excellent linearity, specificity, sensitivity, and reproducibility. The sensitivity of the method was < 10 ng/ml with a detection limit of 2 ng/ml (6.8 nmol/l) and a linear range of 10-2000 ng/ml. The method was used for the analysis of testosterone-induced increase in plasma 3alpha-androstanediol levels in rats. Testosterone produced a dose-dependent elevation in plasma 3alpha-androstanediol, which was almost completely prevented by pretreatment with the 5alpha-reductase inhibitor finasteride, indicating that 3alpha-androstanediol is synthesized from testosterone via a 5alpha-reductase pathway. This LC-MS-MS method allows accurate, high-throughput analysis of 3alpha-androstanediol in small amounts (200 microl) of plasma and possibly other biological samples.     

Precolumn o‐Phthalaldehyde‐N‐acetyl‐L‐cysteine Derivatization Followed by RP‐HPLC Separation and Fluorescence Detection of Sitagliptin Enantiomers in Rat Plasma

An indirect reversed‐phase high‐performance liquid chromatographic separation and fluorescence detection of sitagliptin enantiomers in rat plasma was developed and validated. Deproteinized rat plasma containing racemic sitagliptin was derivatized with o‐phthalaldehyde and N‐acetyl‐L‐cysteine under alkaline conditions, converted to diastereomers, and separated on a Lichrospher 100 RP‐18e column using 20 mM phosphate buffer and methanol (45:55 v/v) as a mobile phase under isocratic mode of elution at a flow rate of 1.0 mL/min. Fluorescence detection was performed at 330 and 450 nm as excitation and emission wavelengths, respectively. The method was linear in the range of 50–5000 ng/ mL for both enantiomers. The intra‐ and interday accuracy and precision were within the predefined limits of ≤15% at all concentrations. The method was successfully applied to a pharmacokinetic study of sitagliptin after 5 mg/kg oral administration to Wistar rats. Robustness of the method was evaluated using design of experiments. Chirality 25:883–889, 2013. © 2013 Wiley Periodicals, Inc.