RESUMO
A sensitive and simple high-performance liquid chromatographic tandem mass spectrometric (LC-MS/MS) method for the determination of verapamil and norverapamil in human plasma was established and utilized in a pharmacokinetic study in healthy patients. Protein was precipitated by methanol in plasma samples, and the analytes and internal standard were separated on an Agilent Zorbax Eclipse C18 column (50 mm×4.6 mm, 5 μm) with a gradient procedure using methanol-acetonitrile (50∶50) as the organic phase and 0.1% formic acid - 5% acetonitrile - 10 mmol·L-1 ammonium formate solution as the mobile phase at flow rate of 0.5 mL·min-1. Electrospray ionization (ESI) and multiple reaction monitoring (MRM) detection modes were used for quantitative detection of verapamil, norverapamil and verapamil-d6 (IS). In the mode of multiple reaction monitoring of positive-ions, the monitoring ion pairs of verapamil, norverapamil and the verapamil-d6 were m/z 445.0→165.2, m/z 441.0→165.2 and m/z 461.1→165.2, respectively. The quantitative lower limit (LLOQ) for the determination of verapamil and norverapamil concentrations in human plasma can reach 0.1 ng·mL-1 in this assay. The calibration curve concentration ranged from 0.1 to 50 ng·mL-1 with high linearity (r2 > 0.997). The matrix effect of verapamil and norverapamil was 99.2%-100% and 101%-102%, respectively. The recovery of verapamil and norverapamil was 86.8%-95.9% and 87.4%-94.8%, respectively. This method has good specificity and high sensitivity. The determination of the verapamil and norverapamil was not subject to the matrix effect and stable extraction recovery was achieved in this assay. This method could be used to determine the concentration of verapamil and norverapamil in human plasma and suitable for human pharmacokinetic studies after approved by ethics committee.
RESUMO
A LC-MS/MS method for quantification of norfloxacin in human plasma had been developed. This method was applied to the pharmacokinetics study of norfloxacin in the human. The plasma sample was precipitated by methanol and ciprofloxacin was used as the internal standard (IS). Chromatographic separation was performed on a Symmetry® C18 column(100 mm×4.6 mm, 5 μm). Mobile phase contains 0.3% formic acid and 5% methanol in deionized water at a flow rate of 0.45 mL·min-1. Norfloxacin and ciprofloxacin (IS) were ionized with an ESI source and operated in positive ion mode. The detected ions were m/z 320.3→302.1 (norfloxacin), m/z 332.3→314.1 (ciprofloxacin). This LC-MS/MS method yielded a linearity over the range of 10-1 000 ng·mL-1 with the lower limit of quantitation (LLOQ) of 10 ng·mL-1. The intra and inter-assay precisions (RSD%) were within the range of 2.64%-7.23% and the accuracy (RE%) was less than ±5.00%. The pharmacokinetic parameters tmax, Cmax, AUC0-t, and t1/2 were 1.28±0.364 h, 627±171 ng·mL-1, 2 938±850 h·ng·mL-1, and 6.01±1.36 h, respectively. This LC-MS /MS method was proven simple, sensitive, rapid and suitable for pharmacokinetics study of norfloxacin in the human and Approved by the Medical Ethics Committee of Liuzhou Workers' Hospital.