Ben-Mei Chen

Quantification of prochlorperazine maleate in human plasma by liquid chromatography–mass spectrometry: Application to a bioequivalence study

A sensitive and specific method using a one-step liquid-liquid extraction with dichloromethane followed by liquid chromatographic-electrospray ionization-mass spectrometric was developed and validated to determine prochlorperazine maleate in human plasma using amitriptyline hydrochloride as an internal standard. The samples were separated using a Thermo Hypersil-Hypurity C18 reversed-phase column (150mmx2.1mm i.d., 5mum). A mobile phase containing 10mM ammonium acetate (pH 3.6)-methanol-acetonitrile (27:68:5, v/v/v) was used isocratically eluting at a flow rate of 0.22ml/min. The average extraction recovery of prochlorperazine and internal standard were 81.8+/-2.2% and 79.5+/-3.7%, respectively. Prochlorperazine maleate and internal standard were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 0.20 to 6.40ng/ml with r(2)=0.9989. The limit of quantification for prochlorperazine maleate in the plasma was 0.20ng/ml. The established method has been successfully applied to a bioequivalence study of two prochlorperazine maleate formulations in 18 healthy male Chinese volunteers.

Fingerprint of Hedyotis diffusa Willd. by HPLC-MS.

A HPLC-MS fingerprint method has been developed based on the consistent chromatographic features of the major chemical constituents among 10 batches of Hedyotis diffusa Willd. Chromatographic separation was conducted on a Hypersil-Keystone Hypurity C(18) column using methanol:water:acetic acid as the mobile phase. Major compounds, including oleanolic acid, ursolic acid and ferulic acid, were analysed by HPLC-MS. Their analysis was ascertained by comparison with data derived from the standard compounds. The HPLC-MS fingerprint was successfully applied to analyse and differentiate samples from different geographical origins, or processing methods. H. diffusa was well distinguished from Hedyotis chrysotricha by HPLC-MS. Therefore the establishment of fingerprint of H. diffusa is critical in assessing and controlling its overall quality.

Determination of mianserin in human plasma by high performance liquid chromatography–electrospray ionization mass spectrometry (HPLC–ESI/MS): Application to a bioequivalence study in Chinese volunteers

This study aims to develop a standard protocol for the bioequivalence study of mianserin hydrochloride tablets--a tetracyclic antidepressant drug. For this purpose, a rapid, convenient and selective method using high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI/MS) has been developed and validated to determine mianserin in human plasma. Mianserin and the internal standard (I.S.), cinnarizine were extracted from plasma by N-hexane:dimethylcarbinol (98:2, v/v) after alkalinized with sodium hydroxide. LC separation was performed on a Thermo Hypersil-Hypurity C18 (5 microm, 150 mm x 2.1 mm) with the mobile phase consisting of 10mM ammonium acetate (pH 3.4)-methanol-acetonitrile (35:50:15, v/v/v) at 0.22 ml/min. The retention time of mianserin and cinnarizine was 3.4 and 2.1 min, respectively. Quadrupole MS detection and quantitation was done by monitoring at m/z 265 [M+H]+ for mianserin and m/z 369 [M+H]+ for cinnarizine. The method was validated over the concentration ranges of 1.0-200.0 ng/ml for mianserin. The recovery was 81.3-84.1%, intra- and inter-day precision of the assay at three concentrations were 9.6-11.4% with accuracy of 97.5-101.2% and the lower limit of quantitation (LLOQ) detection was 1.0 ng/ml for mianserin. The stability of compounds was established in a battery of stability studies, i.e., short-term and long-term storage stability as well as freeze-thaw cycles. This method proved to be suitable for the bioequivalence study of mianserin hydrochloride tablets in healthy human male volunteers.

Determination of Fluoxetine in Human Plasma by Liquid Chromatography–Mass Spectrometry and Its Application

Abstract A rapid, simple, and specific liquid chromatography–electrospray ionization–mass spectrometric method has been developed and validated for the determination of fluoxetine in human plasma. The method was validated with a linear range of 0.5–100 ng mL−1, and the lowest limits of quantification were 0.5 ng mL−1 for fluoxetine. The extraction efficiencies were about 65% and recoveries of method were in the range of 94.0–97.5%. The intraday relative standard deviation (RSD) was less than 11% and interday RSD was within 12%. The method has been successfully applied to the evaluation of pharmacokinetics and bioequivalence of fluoxetine.

Quantitative determination of erythromycylamine in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study of dirithromycin

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of erythromycylamine in human plasma was developed and validated. Erythromycylamine in plasma (0.2 mL) was extracted with ethyl acetate, the organic phase was transferred to another clear 1.5 mL Eppendorf tube and evaporated to dryness under gentle nitrogen stream at 45 degrees C, and the residue was dissolved in 100 microL of mobile phase. The samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150 mm x 2.1 mm I.D., 5 microm). A mobile phase containing 10 mM of ammonium acetate (pH = 6.4)-acetonitrile-methanol (50:10:40, v/v/v) was used isocratically eluting at a flow rate of 0.2 mL/min. Erythromycylamine and its internal standard (IS), midecamycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 4.5 to 720 ng/mL with r = 0.9997. The limit of quantification for erythromycylamine in plasma was 4.5 ng/mL with good accuracy and precision. The mean extraction recovery of the method was higher than 75.1% and 72.7% for erythromycylamine and IS, respectively. The intra-day and inter-day precision ranged from 5.2% to 6.4% and 5.6-9.3% (relative standard deviation, RSD), respectively. The established method has been successfully applied to a bioequivalence study of two dirithromycin formulations for 18 healthy volunteers.