[Determination of pentoxifylline and its major metabolites in human plasma using HPLC]. / Stanovenie pentoxifylínu a jeho hlavného metabolitu v plazme l'udí s vyuzitím HPLC.

The present paper describes a rapid, reliable and simple method of pentoxiphyllin in plasma. The worked-out one-step extraction with dichloromethane yields 63% recovery of pentoxiphyllin, 58% recovery of the metabolite and 54% recovery of the internal standard. The employed column with a reverse load of Spherisorb ODS, mobile phase 65% of 0.01 M KH2PO4 and 35% acetonitrile, detection at the wavelength lambda = 273 nm, makes it possible to achieve determination of pentoxiphyllin at the levels commencing with 5 ng.ml-1 of plasma. Reproducibility of determination is 6.8%, or 4.5% in the pentoxiphyllin concentrations of 50, or 100 ng.ml-1.

[Determination of nifedipine and its metabolites in plasma using gas chromatography]. / Stanovenie nifedipínu a jeho metabolitu v plazme metódou plynovej chromatografie.

A method was worked out to determine nifedipine and its metabolite in plasma with the use of the packed chromatographic column 3% OV-101 and the detector of electron capture. The adjustment od plasma is simple. It consists in denaturation of plasma proteins and subsequent simple extraction with benzene. Denaturation of proteins present in canine plasma is carried out with methanol, where as denaturation of human plasma with ammonium phosphomolybdate. The minimal detectable amount of nifedipine is 0.5 ng.ml-1 of plasma and that of its metabolite, 0.1 ng.ml-1 of plasma. As nifedipine is unstable in daylight, the whole extraction of plasma including the withdrawal of blood must be performed in yellow light. At -18 degrees C and in darkness, nifedipine samples in plasma can be kept for 30 days.

Optimization of fluorescence detection for the determination of labetalol in plasma by high-performance liquid chromatography.

A sensitive reversed-phase high-performance liquid chromatographic method for the determination of labetalol has been developed. A mobile phase consisting of citrate buffer (pH 6.5), acetonitrile and 2-propanol and an RP-8 column were used. The sensitivity of the fluorescence detection was enhanced to 1 ng/ml of labetalol in plasma by optimizing the emitted light. General guidelines for optimization of fluorescence detection are discussed.