Determination of Fulvestrant in Rat Plasma by LC�CMS�CMS: Application to a Pharmacokinetic Study

A reversed-phase liquid chromatography coupled to tandem mass spectrometry (LC?CMS?CMS) method was developed and validated for the determination of fulvestrant in rat plasma. Sample preparation involved a liquid-liquid extraction using 1.0 mL of n-hexane?Cisopropanol (90:10, v/v) to extract the analyte from 0.1 mL of rat plasma. The analytes were separated on a phenyl-based column using the mobile phase consisting of methanol/water containing 5 mM ammonium acetate at the flow rate of 0.3 mL min^?1. The analytes were monitored by tandem mass spectrometry under electrospray negative ionization mode. Linear calibration curves were generated over the fulvestrant concentration ranges of 0.05?C10.0 ng mL^?1 in rat plasma. The accuracy and within- and between-day precisions were within the generally accepted criteria for bioanalytical methods (<15%). This developed and validated assay method was successfully employed to characterize the plasma concentration-time profile of fulvestrant after its intramuscular administration in rats at a dose of 10 mg kg^?1.     

LC�CMS�CMS Method for Quantification of Hydralazine in BALB/C Mouse Plasma and Brain: Application to Pharmacokinetic Study

A rapid, sensitive and accurate high performance liquid chromatography method using tandem mass spectrometry detection for hydralazine in BALB/C mouse plasma and brain was developed and validated. The method involved a derivatization with 2,4-pentanedione at 50 °C for 1 h, and a step of solid phase extraction to purify and concentrate hydralazine derivative. Chromatographic separation was carried out on an Agilent ZORBAX SB-C18 column by elution with methanol?C0.01 mol L^?1 ammonium acetate (60:40, v/v). The multiple reaction monitoring transition used for quantification was m/z 225.2 ?? 129.5 in the electrospray positive ionization mode. Good linearity was obtained over the concentration range of 10?C200 ng mL^?1. The limits of detection were 0.49 and 1.05 ng mL^?1 for hydralazine in mouse plasma and brain, respectively. The limits of quantitation were 1.5 and 3.18 ng mL^?1 for hydralazine in mouse plasma and brain, respectively. Sample analysis time was 6 min including sample separation. The method was successfully applied to a pharmacokinetic study following intraperitoneal injection of hydralazine in BALB/C mice at the dose of 20 mg kg^?1.     

Determination of Quinine and Doxycycline in Rat Plasma by LC�CMS�CMS: Application to a Pharmacokinetic Study

A fast, sensitive, and specific LC?CMS?CMS method for determination of quinine (QN) and doxycycline (DOX) in rat plasma has been developed and validated. QN, DOX, and cimetidine (internal standard, IS) were extracted from the plasma by protein precipitation. The compounds were separated on a C₁₈ column with methanol?C0.1% aqueous formic acid 70:30 (v/v) as mobile phase at a flow rate of 0.5 mL min^?1 (split 1:3). Detection was by positive electrospray ionization (ESI+) in multiple reaction monitoring (MRM) mode, monitoring the transitions 325.0 ?? 307.0, 445.0 ?? 428.1, and 252.8 ?? 159.0, for QN, DOX, and IS, respectively. The analysis was carried out in 2.0 min and the method was linear in the plasma concentration range 5?C5,000 ng mL^?1. The mean extraction recoveries for QN, DOX, and IS from plasma were 89.4, 90.5, and 86.3%, respectively. The method was validated for linearity, precision, accuracy, specificity, and stability; the results obtained were within the acceptable range. The proposed method was successfully applied to the determination of QN and DOX in rat plasma samples to support pharmacokinetic studies.     

Determination of Imidol in Rat Plasma by UPLC�CMS�CMS and Its Application in a Pharmacokinetic Study

A rapid, sensitive and accurate ultra-performance liquid chromatography/tandem mass spectrometry method was developed and validated for the quantitative determination of imidol in rat plasma for the first time. The analyte and internal standard were extracted from plasma by liquid?Cliquid extraction with diethyl ether. The separation was performed on a BEH C₁₈ column (50 mm × 2.1 mm, 1.7 ??m). The detection was carried out by electrospray ionization mass spectrometry in positive ion mode with multiple reaction monitoring. Linear calibration curves were obtained in the concentration range of 2.5?C2,500 ng mL^?1, with the lower limit of quantification of 2.5 ng mL^?1. The intra- and inter-day precision (RSD) values were below 8% and accuracy (RE) was from ?7.9 to 6.3%. After strict validation, the method was applied successfully to the pharmacokinetic study of imidol in rats after oral and intravenous administration, respectively.     

Determination of Pilocarpine in Human Plasma by LC�CAPCI�CMS�CMS and Application to a Pharmacokinetic Study

A sensitive, specific and rapid high performance liquid chromatography?Catmospheric pressure chemical ionization source-tandem mass spectrometry (LC-APCI-MS-MS) method for the determination of pilocarpine in human plasma was developed and validated. The method is based on liquid?Cliquid extraction, followed by a reversed-phase liquid chromatographic separation, and detected by means of tandem mass spectrometry. The linear calibration curve covered a concentration range of 2?C500 ??g L^?1. The intra- and inter-day precisions for pilocarpine were <10% and the accuracies were between 90 and 110%. The method was applied successfully to a pharmacokinetic study involving 20 healthy Chinese male volunteers after oral administration of 6 mg pilocarpine.     

LC�CMS�CMS Quantitative Determination of Brivudine in Human Plasma and Its Application to Pharmacokinetic Studies

A sensitive and specific liquid chromatography?Celectrospray ionization?Ctandem mass spectrometry method has been developed and validated for the identification and quantification of brivudine in human plasma using diclofenac as an internal standard. The method involves extraction with ethyl acetate. The analyte was separated on a C₁₈ column and analyzed in multiple reaction monitoring mode with a negative electrospray ionization interface using the [M?CH]^? ions, m/z 332.8??m/z 80.9 for brivudine, m/z 293.6??m/z 249.5 for diclofenac. The method was validated over the concentration range of 5.54?C2,836 ??g L^?1 for brivudine. The intra-and inter-day precisions were less than 8.91% in terms of relative standard deviation (RSD), and the accuracy was within ?4.22% in terms of relative error (RE). The lower limit of quantification (LLOQ) was 5.54 ??g L^?1 with acceptable precision and accuracy. There were almost no matrix effects. Recovery of brivudine spiked in drug-free plasma was higher than 77.17%. The method was used to study the pharmacokinetic profile of brivudine in human plasma after oral administration of brivudine tablets.     

LC�CMS Method for Determination of Amphotericin B in Rabbit Tears and Its Application to Ocular Pharmacokinetic Study

A rapid and sensitive LC?CMS?CMS method was developed for the quantification of amphotericin B in rabbit tears using natamycin as internal standard. The analyte and internal standard were extracted from the tear sample using a solid phase extraction method. Chromatographic separation was achieved on a Phenomenex Luna 3 ??m CN column (100 × 2 mm, 3 ??m) using 3.5 mM ammonium acetate (pH 4):methanol (10:90) as mobile phase. The assay was validated with a linear range of 0.1?C3.2 ??g mL^?1 for amphotericin B using 10 ??L of tear sample. The intra- and inter-day assay precision ranged from 2.49 to 4.37 and 2.17 to 5.59%, respectively, and intra- and inter-day assay accuracy was between from 0.27 to 3.32 and ?0.51 to 3.72%, respectively. The method was successfully applied to the pharmacokinetic studies of amphotericin B eye drops in rabbit tears.     

Determination of Revaprazan in Human Plasma by LC�CMS�CMS and Application to a Pharmacokinetic Study in Chinese Volunteers

A sensitive, specific, and rapid liquid chromatography?Celectrospray ionization?Ctandem mass spectrometry (LC?CESI?CMS?CMS) method was developed for determination of revaprazan in human plasma. Plasma samples were simply treated with methanol to precipitate, and then isolated supernatants were directly injected into the LC?CESI?CMS?CMS system. A Thermo Hypurity C18 column (150 × 2.1 mm, 5 ??m) with mobile phase of methanol?Cwater (70:30, v/v) containing 0.05% formic acid was used for chromatographic separation. Mass-spectrometric quantification was carried out in multiple reaction monitoring (MRM) mode, monitoring the m/z transitions 363.1 ?? 245.1 for revaprazan and 531.2 ?? 489.2 for ketoconazole (internal standard, IS) in positive ion mode. The linear calibration curves covered a concentration range of 2?C1,000 ??g L^?1. The intra- and interday precisions (percentage relative standard deviation, RSD%) for revaprazan at three quality control levels were all <5%, and the accuracies were between 90% and 110%. The method has been successfully applied to a pharmacokinetic study involving 12 Chinese volunteers, and the main pharmacokinetic parameters of revaprazan in Chinese population are reported for the first time.     

Simultaneous Determination of Pethidine and Atropine in Rabbit Plasma by LC�CMS�CMS and Its Application to a Pharmacokinetic Study after Intramuscular Administration

A sensitive and selective liquid chromatography?Ctandem mass spectrometry method for the determination of pethidine and atropine in rabbit plasma was developed and validated. The analytes and internal standard (IS) are extracted from plasma by liquid?Cliquid extraction using ethyl acetate, and separated on a Zorbax SB-Aq column (2.1 × 150 mm, 3.5 ??m) using acetonitrile?C0.1% formic acid as mobile phase with gradient elution. Electrospray ionization source was applied and operated in positive ion mode, and multiple reaction monitoring mode was used for quantification using target fragment ions m/z 247.8 ?? 219.7 for pethidine, m/z 289.9 ?? 123.8 for atropine and m/z 295.0 ?? 266.8 for IS, respectively. The assay is linear over the range of 5?C1,000 ng mL^?1 for pethidine and atropine, with a lower limit of quantification of 3 ng mL^?1 for pethidine and 5 ng mL^?1 for atropine. Intra-day and inter-day precision are less than 11% and the accuracy are in the range of 90.4?C106.3%. Furthermore, the newly developed method is successfully used for the determination of pethidine and atropine in rabbit plasma for pharmacokinetic study.     

Determination of Chlorantraniliprole Residues in Corn and Soil by UPLC�CESI�CMS/MS and Its Application to a Pharmacokinetic Study

A rapid, highly sensitive, and selective method was developed for the determination of the insecticide chlorantraniliprole (CAP) in corn and soil using ultra-performance liquid chromatography?Ctandem mass spectrometry (UPLC?CMS/MS). Samples were extracted with acetonitrile, and aliquots were cleaned with solid-phase extraction cartridges. Two precursor-product ion transitions for CAP were measured and evaluated to provide maximum confidence in the results. Average recovery for soil, corn grain, and corn straw at different levels (5 or 10, 40, and 100 ??g kg^?1) ranged from 74.9 to 97.5%, with intra-day relative standard deviation (RSD) values of 1.9?C11.3% and inter-day RSD values of 4.7?C10.4%. Coefficients of determination (R ²) of 0.9988 or higher were achieved for CAP in soil, corn grain, and corn straw matrix calibration curves, from 5 to 1,000 ??g L^?1. The CAP limits of quantitation in soil, corn grain, and straw were determined to be 5, 10, and 10 ??g kg^?1, respectively, which were much lower than the maximum residue levels established by the Environmental Protection Agency of United States. UPLC?CMS/MS was used to determine the CAP residues in real corn and soil for studies on their dissipation. The trial results showed that the half-lives of CAP changed from 12.6 to 23.1 days in soils and ranged from 4.9 to 5.4 days in corn straws in the districts of Henan and Shandong, and the average levels of CAP residues in corn grains were all <0.01 mg kg^?1 with a harvest withholding period of 180 days.     

LC–MS–MS Analysis of Strictosamide in Rat Plasma, and Application of the Method to a Pharmacokinetic Study

A rapid and simple high-performance liquid chromatographic tandem mass spectrometric method has been developed and validated for analysis of strictosamide in rat plasma. Chromatographic separation was achieved on a C₁₈ column by gradient elution with mixtures of methanol, water, and acetonitrile containing 0.05% acetic acid. Digoxin was used as internal standard. Selected reaction monitoring (SRM) was used for MS quantitation. Linearity was good in the range 0.05–20 ng mL^?1 in rat plasma. The lower limit of quantitation was 0.04 ng mL^?1. The method is precise and reliable and can be applied to pharmacokinetic studies.     

Validated LC–MS–MS Method for Quantitative Determination of Batifiban in Human Plasma and Its Application to a Pharmacokinetic Study

Batifiban is a new platelet GPIIb/IIIa receptor antagonist. In this work, an analytical method based on liquid chromatography and electrospray ionization tandem mass spectrometry has been firstly developed and validated for the quantitative measurement of batifiban in human plasma to support the investigation of this compound. Separation of analyte and the internal standard eptifibatide was performed on a Thermo HyPURITY C18 column (150 × 2.1 mm, 5 μm) with a mobile phase consisting of formic acid 0.1% (v/v)–acetonitrile (40:60, v/v) at a flow rate of 0.25 mL min^?1. The Waters QuattroMicro API triple quadrupole mass spectrometer was operated in multiple reaction monitoring mode via positive electrospray ionization interface using the transition m/z 819.2 → m/z (623.9 + 159.4) for batifiban and m/z 833.4 → m/z (645.7 + 159.3) for IS. The method was linear over the concentration range of 2.45–5,000 μg L^?1. The intra- and inter- day precisions were less than 15% in terms of relative standard deviation, and the accuracy was within 8.5% in terms of relative error (RE). The lower limit of quantification (LLOQ) was identifiable and reproducible at 2.45 μg L^?1 with acceptable precision and accuracy. The validated method offered sensitivity and wide linear concentration range. This method was successfully applied for the evaluation of pharmacokinetics of batifiban afer single oral doses of 55, 110 and 220 μg kg^?1 batifiban to 36 Chinese healthy volunteers.     

LC–MS–MS Determination of Troxerutin in Plasma and Its Application to a Pharmacokinetic Study

A highly sensitive liquid chromatography–tandem mass spectrometry (LC–MS–MS) method for the determination of troxerutin in human plasma using tramadol as internal standard (IS) has been developed and validated. Sample preparation involved liquid–liquid extraction with ethyl acetate–isopropanol (95:5, v/v). The analyte and IS were separated by RP–LC with gradient elution using 10 mM ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.9 mL min^?1. LC–MS–MS in the positive ion mode employed multiple reaction monitoring of the transitions at m/z 743.2→435.3 and m/z 264.1→58.0 for troxerutin and IS, respectively. The assay was linear in the concentration range 0.01–10 ng mL^?1 with precision and accuracy within assay variability limits as per FDA guidelines. The assay was successfully applied to a pharmacokinetic study involving oral administration of 300 mg troxerutin to eight healthy Chinese volunteers.     

Simultaneous Determination of Escin Ia and Its Isomer Isoescin Ia by LC�CMS�CMS: Application to a Pharmacokinetic Study of Escin Ia in Rats

A rapid and sensitive LC?CMS?CMS method for the simultaneous determination of escin Ia and isoescin Ia in rat plasma, urine, feces and bile samples was developed and validated. Analytes and telmisartan [internal standard (IS)] were extracted by solid-phase extraction on C₁₈ cartridges. Components in the extract were separated on an HC-C₁₈ column (5 ??m, 150 × 4.6 mm i.d.) using 10 mM ammonium acetate?Cmethanol?Cacetonitrile (40:30:30, v/v/v) as the mobile phase. The method demonstrated good linearity from 5 ng mL^?1 (LLOQ) to 1,500 ng mL^?1 for both escin Ia and isoescin Ia. Intra- and inter-day precision measured as RSD was within ±15%. Recoveries and matrix effects of both escin Ia and isoescin Ia were satisfactory in all four matrices examined. The method was successfully applied to a pharmacokinetic study in Wistar rats after a single intravenous administration of escin Ia at the dose of 1.0 mg kg^?1.     

LC–MS Method for the Quantification of Clonazepam in Rat Plasma

A sensitive and specific high-performance liquid chromatography–tandem mass spectrometry method has been developed and validated for the determination of clonazepam in rat plasma. Clonazepam and internal standard diazepam were extracted from plasma samples by a single-step protein precipitation. The chromatographic separation was performed on a Dikma ODS-C18 reversed-phase column at 40 °C. The mobile phase composed of a premix of solvent A (0.1% formic acid–4 mM ammonium acetate–water)–solvent B (acetonitrile) (13:87, v/v) at a flow-rate of 0.7 mL min^?1. Positive electrospray ionization was utilized as the ionization source. Clonazepam and the internal standard were determined using multiple reaction monitoring of precursor → product ion transitions at m/z 316.0 → 270.0 and m/z 285.1 → 193.2, respectively. The lower limit of quantification was 0.25 ng mL^?1 using 50 μL plasma samples and the linear calibration range was from 0.25 to 128 ng mL^?1. The within- and between-batch RSDs were lower than 15% and the relative recoveries of clonazepam ranged from 97.4 to 104.7%. The mean extraction recoveries of clonazepam and IS were 79.7 and 77.6%, respectively. The method has been successfully applied to the pharmacokinetic studies in rat after oral administration of clonazepam.     

LC–Tandem-MS Development and Validation for the Determination of Tegaserod in Beagle Dog Plasma and Its Application to a Pharmacokinetic Study

A sensitive and selective liquid chromatography-tandem mass spectrometry method for quantitative determination of tegaserod was developed and validated over the linearity range 1.0–200.0 ng mL^?1 with 0.5 mL of plasma using diphenhydramine as an internal standard. Liquid–liquid extraction using ethyl ether was used to extract the drug and the internal standard from plasma. The mass spectrometer was operated under the selected reaction monitoring mode using the atmospheric pressure chemical ionization technique. The mobile phase consisted of methanol–water–formic acid (80:20:1, v/v/v), at a flow rate of 0.6 mL min^?1. In the positive mode, tegaserod produced a protonated precursor ion at m/z 302 and a corresponding product ion at m/z 173. The internal standard produced a protonated precursor ion at m/z 256 and a corresponding product ion at m/z 167. The intra- and inter-day accuracy at all levels fell in the ranges of 100.72–102.75% and 100.61–105.45%, and the intra- and inter-day precision were in the ranges of 4.20–5.74% and 1.90–4.17%, respectively. The method was successfully applied to a pharmacokinetic study of tegaserod after an oral administration of two kinds of tegaserod preparations to beagle dogs.     

Development of an LC Method for Simultaneous Analysis of Cinnamic Acid and Paeonol in Rat Plasma, and Its Application to a Pharmacokinetic Study after Intragastric Administration of Guizhi–Fuling Capsule

A specific and accurate high-performance liquid chromatographic method for analysis of cinnamic acid (CA) and paeonol (PN) in rat plasma has been developed and validated. Plasma samples were pretreated by protein precipitation with methanol, and the supernatant was injected for reversed-phase separation on a C₁₈ column with acetonitrile–0.1% phosphoric acid 24:76 (v/v) as mobile phase at a flow-rate of 1.0 mL min^?1. Phenylbutyric acid was used as the internal standard. Good linear relationships were obtained between response and concentration in the range 0.130–52.0 μg mL^?1 (r = 0.9980) and 0.1785–71.4 μg mL^?1 (r = 0.9950) for CA and PN, respectively. Intra-day and inter-day assay precision (RSD, n = 6) at three concentrations was not above 15.1% for either CA and PN, and accuracy was from 94.3 to 104.7% and from 103.3 to 113.1% for CA and PN, respectively. Mean recovery of CA and PN from plasma samples was 87.5 and 86.8%, respectively, and recovery of the internal standard at a concentration of 1.00 mg mL^?1 was 88.5%. Results from a stability study suggested CA and PN were stable under the experimental conditions used. Finally, the validated method was successfully applied to a pharmacokinetic study of CA and PN in rats after intragastric administration of Guizhi–Fuling capsule. The results obtained would be very useful for evaluation of the clinical efficacy of GFC.