K. Na-BangchangP. Tan-AriyaR. UbaleeB. KamanikomJ. KarbwangMahidol University2018-07-042018-07-041997-02-21Journal of Chromatography B: Biomedical Applications. Vol.689, No.2 (1997), 433-437157264952-s2.0-0031581910https://repository.li.mahidol.ac.th/handle/123456789/17937A rapid, selective, sensitive and reproducible reversed-phase high-performance liquid chromatography (HPLC) procedure for the quantitative determination of pyrimethamine (PYR) in plasma is described. The procedure involved the two-step extraction of PYR and the internal standard, quinine (QN) with acetonitrile and dichloromethane at basic pH. Chromatographic separation consisted of the mobile phase (methanol-water containing 0.005 M octanesulfonic acid, 50:50, v/v) running through the column (Techopak-10 C18) at a flow-rate of 1.6 ml/min. Detection was at UV wavelength of 240 nm. The mean recoveries of PYR and QN at a concentration range of 50 and 500 ng/ml were 98.9 and 89%, and 94.7 and 96% for PYR and QN. The within-day coefficients of variation were 2.1-5.1% for PYR and 5.9% for QN. The day-to-day coefficients of variation were 2.1-4.1% for PYR and 5% for QN. The minimum detectable concentrations for PYR and QN in plasma were 3 and 10 ng/ml. The method was found to be suitable for use in clinical pharmacokinetic study.Mahidol UniversityChemistryArticleSCOPUS10.1016/S0378-4347(96)00327-1