Simultaneous Quantitation of Paracetamol, Pseudoephedrine and Chlorpheniramine in Dog Plasma by LC-MS-MS

A simple, rapid and sensitive liquid chromatography/electrospray tandem mass spectrometry quantitative detection method, using amantadine as internal standard, was developed for the simultaneous analysis of paracetamol, pseudoephedrine and chlorpheniramine concentrations. Analytes were extracted from plasma samples by liquid–liquid extraction with n-hexane–dichloromethane–2-propanol (2:1:0.1, v/v), separated on a C18 reversed-phase column with 0.1% formic acid–methanol (40:60, v/v) and detected by electrospray ionization mass spectrometry in positive multiple reaction monitoring mode. Calibration curves for plasma were linear over the concentration range 10–10,000 ng mL^?1 of paracetamol, 2–2,000 ng mL^?1 of pseudoephedrine and 0.2–200 ng mL^?1 of chlorpheniramine. The method has a lower limit of quantitation of 10 ng mL^?1 for paracetamol, 2.0 ng mL^?1 for pseudoephedrine and 0.2 ng mL^?1 for chlorpheniramine. Recoveries, precision and accuracy results indicate that the method was reliable within the analytical range, and the use of the internal standard was very effective for reproducibility by LC-MS-MS. This method is feasible for the evaluation of pharmacokinetic profiles of a novel multicomponent sustained release formulation containing 325 mg of paracetamol, 30 mg of pseudoephedrine hydrochloride and 2 mg of chlorpheniramine maleate. It is the first time the pharmacokinetic evaluation of a novel sustained-action formulation containing paracetamol, pseudoephedrine and chlorpheniramine has been elucidated in vivo using LC-MS-MS.     

Determination of Gastrodin and Ligustrazine Hydrochloride in Plasma and Brain Dialysate by LC–Tandem MS

A gradient liquid chromatography-tandem mass spectrometry method has been developed and validated for the determination of gastrodin and ligustrazine hydrochloride in rat plasma and brain dialysates. Zolpidem was used as internal standard. For plasma samples, solid-phase extraction was used and the brain dialysates were collected from freely moving rats using brain microdialysis. Both were followed by HPLC separation and positive electrospray ionization tandem mass spectrometry detection (ESI–MS–MS). Chromatographic separation was achieved on a Symmetry RP-18 column using gradient elution with methanol and water containing 0.5% formic acid and 2 mM ammonium formate. Selected reaction monitoring (SRM) mode was used for quantitation. Good linearities were obtained in the range of 0.05–100 and 0.01–50 μg mL^?1 for gastrodin and ligustrazine hydrochloride in rat plasma, and 0.05–1,000 ng mL^?1 for both in dialysate. The lower limit of quantitation was 0.01 ng mL^?1 for gastrodin and 0.05 ng mL^?1 for ligustrazine. The method is precise and reliable and can be applied to pharmacokinetic studies.     

Sensitive and Selective LC–ESI–MS Analysis of Aesculin in Rat Plasma

A rapid and sensitive liquid chromatography–electrospray ionization mass spectrometry method was developed for the determination of aesculin in rat plasma. The analyses were chromatographed on a Zorbax Extend-C18 analytical column (150 × 2.1 mm I.D., 5 µm) with 30:70 (v/v) methanol–0.1% formic acid as mobile phase. Detection was performed by triple-quadrupole tandem mass spectrometry in multi-reaction-monitoring mode with an electrospray ionization source. The method was validated for accuracy and precision, and linearity in the two matrices was good. The assay was linear in the range 12.5–1,800 ng mL^?1. The lower limit of quantification of aesculin (LLOQ) was 12.5 ng mL^?1. The recovery of aesculin and tinidazole (IS) were well above 85%. The within- and between-batch accuracy was 100–104% and 97–109%, respectively. There were no stability-related problems in the procedure for the analysis of aesculin. The method was successfully used in a preclinical study of the pharmacokinetics of aesculin in rats.     

LC–MS–MS Method to Simultaneously Determine Six Probe Drugs for CYP450 Isozymes in Human Liver Microsomes

Here, we report a rapid and specific method based on high-performance liquid chromatography coupled with tandem mass spectrometry (LC–MS–MS) capable of quantifying six CYP450-specific probe substrates in human liver microsomal incubation mixtures simultaneously. These analytes were prepared by single-step extraction and detected in one run by switching polarity of electrospray ionization mode three times. Following optimization of the chromatographic conditions, the peaks were well separated, and retention times ranged between 2.0 and 8.4 min. The total run time for a single injection was within 9 min. This method was fully validated over linear range of 18.8–3,000.0 ng mL^?1 for diclofenac, 0.8–3,000.0 ng mL^?1 for dapson, 1.5–3,000.0 ng mL^?1 for dextromethorphan, 2.0–4,000.0 ng mL^?1 for omeprazole, 75.0–3,000.0 ng mL^?1 for chlorzoxazone and 0.8–3,000.0 ng mL^?1 for phenacetin using diazepam as internal standard. Samples were prepared by protein precipitation and analyzed on the LC–MS–MS equipped with ESI interface. For each analyte, inter- and intra-day precision (RSD%) were <15 % and accuracy was within 85–115 %. The specificity, precision, accuracy, stabilities and matrix effect were evaluated.     

LC�CMS�CMS Quantitative Determination of Gefitinib in Human Serum and Cerebrospinal Fluid

A specific, sensitive, and rapid method based on high-performance liquid chromatography coupled to tandem mass spectrometry (LC?CMS?CMS) was developed for determination of gefitinib in human serum and cerebrospinal fluid (CSF). The analyte was detected by tandem mass spectrometry operating in positive electrospray ionization mode with multiple reaction monitoring (MRM). Gefitinib was extracted from serum or CSF samples with ethyl acetate using icotinib as internal standard. The method was validated over the concentration range of 1.00?C1,000 ng mL^?1 in human serum and 0.05?C50.0 ng mL^?1 in CSF. For both matrices, inter- and intraday precision (CV%) were less than 15% and accuracy was within 85?C115%. Average extraction recoveries were 78.9 and 61.8% in human serum and CSF, respectively. Linearity, recovery, matrix effects, and stability were validated in the two matrices. The method was successfully used for analysis of clinical samples from lung cancer patients with brain metastases treated with gefitinib in the dosage range of 250?C500 mg day^?1.     

Sensitive and Selective LC-MS-MS Assay for the Quantification of Palonosetron in Human Plasma and Its Application to a Pharmacokinetic Study

A highly sensitive and selective liquid chromatography-tandem mass spectrometry method was developed for the determination of palonosetron in human plasma samples. Chromatographic conditions and mass spectral parameters were optimized in order to achieve a limit of quantification of approximately 0.03 ng mL^?1. Palonosetron and citalopram (internal standard) were extracted by liquid–liquid extraction under alkaline conditions using saturated sodium bicarbonate. Separation was achieved with a Hanbon Lichrospher C₁₈ column and detection was carried out by tandem mass spectrometry using positive electrospray ionization in selected reaction monitoring mode. The target ions of palonosetron and citalopram were to m/z 297.00 → 297.00 and 325.00 → 325.00 respectively. Calibration curves were linear over the range of approximately 0.03–10 ng mL^?1. Precision and accuracy of this method was acceptable. The method was successfully applied to a pharmacokinetic study with healthy Chinese volunteers after intravenous administration of a single dose of 0.125, 0.25 or 0.5 mg palonosetron hydrochloride.     

Determination of 5-Hydroxytryptamine, Norepinephrine, Dopamine and Their Metabolites in Rat Brain Tissue by LC–ESI–MS–MS

A liquid chromatography–electrospray ionization tandem mass spectrometry method has been developed to perform the determination of 5-hydroxytryptamine (5-HT), norepinephrine (NE), dopamine (DA) and their metabolites, i.e., 5-hydroxyindole-3-acetic acid (5-HIAA), 4-hydroxy-3-methoxyphenylglycol (MHPG) sulfate, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in rat brain tissue. Analytes were separated on a Thermo C₁₈ column (4.6 mm × 250 mm, 5 μm, SN: 1245575T, Thermo electron corporation, USA) with a mobile phase of 0.05% formic acid/acetonitrile (92:8 for ESI⁺, 82:18 for ESI^?, v/v) at the flow-rate of 0.8 mL min^?1. The LC system was coupled to a Waters Micromass Quattro Premier XE tandem quadruple mass spectrometer. MS acquisition of 5-HT, NE and DA was performed in positive electrospray ionization multiple reaction monitoring (MRM) mode, while negative electrospray ionization MRM mode was used to monitor their metabolites. The calibration curves were linear within the concentration range of 4–4,450 ng mL^?1 for 5-HT, 4–4,110 ng mL^?1 for NE and 4–4,100 ng mL^?1 for DA (r ≥ 0.999). The limit of quantitation was 4 ng mL^?1. 5-HIAA, MHPG, DOPAC and HVA have good linearity within the range of 12–1,000 ng mL^?1(r ≥ 0.998) and the limit of quantitation was 12 ng mL^?1. The intra- and inter-day RSD were lower than 8.45%. The method is sensitive, fast, accurate and usable for quantity determination of monoamine neurotransmitters and their metabolites in neuropsychiatric diseases.     

LC-MS–MS Determination of Pregabalin in Human Plasma

A rapid, sensitive and specific method to quantify pregabalin in human plasma using metaxalone as the internal standard is described. Sample preparation involved simple protein precipitation by using acetronitrile as solvent. The extract was analyzed by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry (LC-MS–MS). Chromatography was performed isocratically on Thermo Hypurity C₁₈ 5 μm analytical column, (50 mm × 4.6 mm i.d.). The assay of pegabalin was linear calibration curve over the range 10.000–10000.000 ng mL^?1. The lower limit of quantification was 10.000 ng mL^?1 in plasma. The method was successfully applied to the bioequivalence study of pregabalin capsules (150.0 mg) administered as a single oral dose.     

Comparative Study of Electrospray and Atmospheric Pressure Chemical Ionization with Liquid Chromatography–Mass Spectrometry for Quantification of Five Antihyperglycemic Agents Utilizing Monolithic Column

Liquid chromatography-mass spectrometry (LC-MS) in atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) modes were studied for a multi-component plasma and urine quantification of 5 antihyperglycemic agents (metformin, pioglitazone, gliclazide, glibenclamide, and glimperide). The separation of the compounds was achieved using Chromolith Performance RP-18e column (100 × 4.6 mm), with gradient mobile phase composition of acetonitrile ?0.1% formic acid. MS parameters for APCI and ESI were optimized individually and were operated in positive mode. The detection limits for the metformin, pioglitazone, glibenclamide, and glimepiride were determined to be 6.84, 6.22, 13.03, and 44.38 ng mL^?1 using LC-ESI-MS; and for LC-APCI-MS, it was determined to be 48.39, 8.02, 17.02, and 144.55 ng mL^?1, respectively. Gliclazide was the only exception as it exhibited a lower limit of detection (LOD) using APCI than ESI which was found to be 5.61 and 23.43 ng mL^?1, respectively. The method was validated for system suitability, linearity, precision and accuracy, specificity, stability, and robustness. The ESI as compared to APCI was found superior in many analytical parameters. The assay has been applied successfully to biological fluids (plasma and urine) of healthy volunteers.     

Simultaneous Determination of Twelve Saponins in Radix et Rhizoma Notoginseng by Rapid Resolution LC-ESI-TOF-MS

Rapid resolution liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry was developed for simultaneous determination of twelve saponins in Radix et Rhizoma Notoginseng (RRN) with macranthoidine A as internal standard. All calibration curves showed good linear regression (r ² > 0.9935) within test range. The limits of detection of the twelve compounds were in the range of 1.53–5.08 ng mL^?1. This method was successfully applied to analyze the saponins in fifteen samples of RRN.     

Simultaneous Determination of Pregabalin, Sildenafil and Its Active Metabolite in Rat Plasma Utilising SPE Followed by LC�CMS�CMS

A sensitive and selective analytical method for the quantification of pregabalin, sildenafil and the active desmethyl metabolite of sildenafil (UK-103320) has been developed. The method can simultaneously quantify the three analytes within the expected in vivo concentration ranges using 50 ??L of rat plasma. It utilises solid-phase extraction followed by high performance liquid chromatography coupled with tandem mass spectrometry. Quantitation in rat plasma demonstrated good accuracy and precision over the following dynamic ranges for each analyte: pregabalin (70?C10,000 ng mL^?1), sildenafil (1?C2,000 ng mL^?1) and UK-103320 (1?C2,000 ng mL^?1). For each analyte, the following lower limits of quantitation were obtained: 70 ng mL^?1 for pregabalin and 1 ng mL^?1 for sildenafil and UK-103320, respectively. The method was successfully used to analyse plasma samples from rats when pregabalin and sildenafil were administered in combination.     

HILIC-MS-MS for the Quantification of Pidotimod in Human Plasma

A method for fast, sensitive, and specific hydrophilic interaction chromatography combined with tandem mass spectrometry (HILIC-MS/MS) was developed for the first time to determine the level of pidotimod in human plasma. With rosiglitazone as internal standard, analysis was carried out on a HILIC column (150 mm × 2.1 mm, 3.5 ??m) using a mobile phase consisting of methanol:0.2% formic acid (60:40, v/v). Detection was carried out by tandem mass spectrometry using electrospray ionization (ESI). Linear calibration curves were obtained in the concentration range of 11.2?C1.12 × 10⁴ ng mL^?1 for pidotimod, with a lower limit of quantification of 11.2 ng mL^?1. The intra- and inter-day precision values were high, with standard deviations lower than 15%, and the accuracy, in terms of relative error, ranged from ?10.5 to 9.4% at all quality control (QC) levels.     

Rapid and Sensitive UPLC-MS–MS for the Determination of Trimetazidine in Human Plasma

A specific and sensitive UPLC-MS–MS was developed for the determination of trimetazidine in human plasma. The sample preparation was based on a single-step liquid–liquid extraction with acetic ether. The chromatographic separation was on a C₁₈ analytical column (50 mm × 2.1 mm, 1.7 μm) with acetonitrile and 10 mM ammonium acetate (30:70, v/v) as the mobile phase, and a triple-quadrupole mass spectrometer equipped with an electrospray ionization source (ESI) applied for detection. The method was linear over the concentration ranges of 0.25–100.00 ng mL^?1 for trimetazidine, and the lower limit of quantification (LLOQ) was 0.25 ng mL^?1. The intra- and inter-day relative standard deviation (RSD) were less than 15% and the relative error (RE) were all within 15%. Finally, this method has been successfully applied to analyze plasma samples from a bioequivalence study with 18 volunteers.     

Determination of Atovaquone in Human Plasma by LC-MS-MS and Its Application to a Bioequivalence Study

A sensitive and selective method for the determination of atovaquone in human plasma was developed and validated. The procedure employed the use of an internal standard (chlorothalidone) and a solvent extraction step. Detection was by electrospray ionization tandem mass spectrometry with multiple reaction monitoring. The method showed a linear range from 50 to 2,000 ng mL^?1. The extraction recovery was determined to be 84.91 ± 6.42% (SD), the intra- and inter-day assay accuracy (relative error) was within 7.57% and precision (RSD) was below 6.06%. The method was successfully employed to analyze plasma samples and evaluate the pharmacokinetics of atovaquone in human volunteers.     

Comparison of LC–UV, LC–ELSD and LC–MS Methods for the Determination of Sesquiterpenoids in Various Species of Artemisia

Simple and specific analytical methods for the quantitative determination of sesquiterpenoids from various species of Artemisia plant samples were developed. By LC–UV, LC–ELSD, the separation was achieved by reversed-phase chromatography on a C18 column with water and acetonitrile both containing 0.025% trifluoroacetic acid as the mobile phase. In the LC–MS system, trifluoroacetic acid was replaced by 0.1% formic acid. The wavelength used for quantification of sesquiterpenoids with a diode array detector was 205 nm. The limits of detection by LC–MS was found to be 5, 10, 25, 50, 50 ng mL^?1. The limits of detection by LC–UV and LC–ELSD were found to be 5.0, 3.0, 100, 100, 7.5 μg mL^?1, by LC–UV and 50, 25, 30, 100 and 75 μg mL^?1 by LC–ELSD. LC–mass spectrometry coupled with electrospray ionization (ESI) interface is described for the identification and quantification of sesquiterpenoids in various plant samples. This method involved the use of the [M + H]⁺ ions of sesquiterpenoids in the positive ion mode with extractive ion monitoring.     

Development and Validation of Atorvastatin by LC–ESI–MS and Application in Bioequivalence Research in Healthy Chinese Volunteers

The aim of this research was to develop a sensitive liquid chromatographic–electrospray ionization–mass spectrometric (LC–MS) method for direct measurement of the concentration of Atorvastatin in human plasma. Plasma samples (1 mL) were extracted with 3 mL ethyl acetate, and by a simple reversed-phase chromatography. Pitavastatin was used as internal standard (IS). The LOQ was 0.25 ng mL^?1 (RSD 4.24%). The assay was linear from 0.25–20 ng mL^?1. And the correlation coefficient for the calibration regression line was 0.9996 or better. Intra-day and inter-day accuracy were better than 15%. The method has been successfully used for a pharmacokinetic study with human subjects. A two-period crossover designed bioequivalence research was also progressed in healthy Chinese volunteers. Among the pharmacokinetic data obtained, T _max was 1.36 ± 0.68 h for reference formulation and 0.81 ± 0.54 h for test formulation. C _max was 8.54 ± 5.06 ng mL^?1 for reference formulation and 9.54 ± 3.68 ng mL^?1 for test formulation. t _1/2 was 8.50 ± 2.74 h for reference formulation and 9.24 ± 3.17 h for test formulation. AUC _0?48h was 54.77 ± 21.82 h ng mL^?1 for reference formulation and 55.66 ± 20.91 h ng mL^?1 for test formulation. The method was successfully applied to the study of pharmacokinetics of Atorvastatin in healthy Chinese volunteers.     

LC–ESI–MS Determination of Imperatorin in Rat Plasma After Oral Administration and Total Furocoumarins of Radix Angelica dahuricae and its Application to a Pharmacokinetic Study

A simple, rapid, sensitive and reliable liquid chromatography–electrospray ionization mass spectrometry method for the quantification of imperatorin in rat plasma after oral administration and total furocoumarins of Radix Angelica dahuricae has been established. The plasma samples were deproteinized by adding internal standard (IS) osthole solution, which was prepared by acetonitrile. The analysis was performed on a Shim-pack C₁₈ column (150 × 2.0 mm i.d., 5 μm) using acetonitrile and 0.5% formic acid solution (70:30, v/v) as a mobile phase. The detection was performed on a quadrupole mass spectrometer detector with an ESI interface operated in the selected ion monitoring mode. The linear quantification range of the method was 2–4000 ng mL^?1 in rat plasma with a correlation coefficient greater than 0.99, the limit of detection (LOD) was 0.5 ng mL^?1 and the lower limit of quantification (LLOQ) 2 ng mL^?1. The intra- and inter-day relative standard deviations (RSD) were less than 2.5 and 3.5%, respectively. The recoveries were above 90%. The validated method was successfully applied to a pharmacokinetic study of imperatorin in rats after oral administration and total furocoumarins of Radix Angelica dahuricae.     

Hydrophilic interaction liquid chromatography/positive ion electrospray ionization mass spectrometry method for the quantification of perindopril and its main metabolite in human plasma

A validated method based on liquid chromatography/positive ion electrospray–mass spectrometry (LC-ESI/MS) is described for the quantification of perindopril and its active metabolite, perindoprilat, in human plasma. The assay was based on 500-μL plasma samples, following solid-phase extraction using Oasis HLB cartridges. All analytes and the internal standard (trandolapril) were separated by hydrophilic interaction liquid chromatography using a SeQuant Zic-HILIC analytical column (150.0?×?2.1 mm i.d., particle size 3.5 μm, 200 Å) with isocratic elution. The mobile phase consisted of 10% 5.0 mM ammonium acetate water solution in a binary mixture of acetonitrile/methanol (60:40, v/v) and pumped at a flow rate of 0.10 mL min^?1. Quantitation of the analytes was performed with selected ion monitoring (SIM) in positive ionization mode using electrospray ionization interface. The assay was found to be linear in the concentration range of 5.0–500.0 ng mL^?1 for perindopril and perindoprilat. Intermediate precision were found less than 3.5% over the tested concentration ranges. A run time of less than 6.0 min for each sample made it possible to analyze a large number of human plasma samples per day. The method is the first reported application of HILIC in the analysis of angiotensin-converting enzyme inhibitors and can be used to quantify perindopril and perindoprilat in human plasma covering a variety of pharmacokinetic or bioequivalence studies.     

Simultaneous Determination of Ebastine and Its Active Metabolite (Carebastine) in Human Plasma Using LC–MS–MS

A sensitive and rapid LC–MS–MS method was developed for the simultaneous determination of ebastine and carebastine in human plasma. Solid-phase extraction was used to isolate the compounds from the biological matrix followed by separation on a Symmetry C18 column under isocratic conditions. The mobile phase was 10 mM ammonium formate in water/acetonitrile (40:60, v/v). Detection was carried out using a triple-quadrupole mass spectrometer in positive electrospray ionization and multiple reaction monitoring mode. The method was fully validated over the concentration range of 0.1–10 ng mL^?1 for ebastine and 0.2–200 ng mL^?1 for carebastine in human plasma, respectively. The lower limit of quantification (LLOQ) was 0.1 ng mL^?1 for ebastine and 0.2 ng mL^?1 for carebastine. For ebastine and carebastine inter- and intra-day precision (CV%) and accuracy values were all within ±15% and 85–115%, respectively. The extraction recovery was on average 60.0% for ebastine and 60.3% for carebastine.     

Simultaneous Determination of Berberine and Palmatine in Rabbit Plasma by LC-MS–MS and Its Application in Pharmacokinetic Study After Oral Administration of Coptidis and Coptidis–Gardeniae Couple Extract

A valid and sensitive LC-MS–MS method is adopted for pharmacokinetics study of berberine and palmatine in rabbit plasma. After mixing with internal standard tetrahydroberberine, plasma samples were pretreated with 1.5 mL acetonitrile. Chromatographic separation was on a C₁₈ column using a mixture of water (containing 10 mmol L^?1 ammonium acetate, pH 3.5) and acetonitrile (50∶50, v/v) as mobile phase. The detection was performed by selected ion monitoring mode via electrospray ionization source operating in the positive ionization mode. The method was linear over the concentration range of 2.0–200.0 ng mL^?1 for berberine and 1.0–100.0 ng mL^?1 for palmatine. The lowest limits of quantitation (LLOQ) were 2.0 ng mL^?1 for berberine and 1.0 ng mL^?1 for palmatine. The intra- and inter-day precision values were less than 14.3% and the deviations were within ±11.0%. The fully validated LC-MS–MS method has been successfully applied to a pharmacokinetic study of berberine, palmatine in rabbit plasma after oral administration of Coptidis and coptidis–gardeniae couple extract. The results indicated that the plasma profiles of the two compounds in rabbit confirmed to one-compartment open model and the combinational utilization with Gardeniae could increase the bioavailability of berberine and palmatine, the two major active components of Coptidis.