Abstract: A flow injection analysis (FIA) extraction method has been developed for the analysis of felodipine tablets in connection with dissolution rate testing. The water-soluble oxidation product of felodipine, a pyridine derivative, was extracted into chloroform and measured at 275 nm spectrophotometrically. The FIA-extraction method has been compared with the present liquid chromatographic (LC) method. The sampling rate for the FIA-extraction (60 samples h-1) is 5 times higher than for the LC method. The FIA-extraction method has a standard deviation of 1% for both standards and samples which is the same as for the LC method.

Abstract: A flow injection manifold comprising a 500 µL stainless-steel sample loop, a glass segmentor, a 4-m stainless-steel and nickel (2 m each) extraction coil and a poly(methyl methacrylate)-membrane phase separator was designed. Human serum containing terodiline(I) was injected at 30 samples h-1 into heptane - pentanol (49:1) containing N-t-butyl-1-methyl-4,4-diphenylbutylamine as internal standard (1 mL min-1) that was then mixed with 0.3 M NaOH (0.5 mL min-1) and subsequently segmented with more of the organic phase (0.5 mL min-1). After extraction a fraction of the organic phase (collected at 0.4 mL min-1) was injected (2 or 7 µL) on to a 25-m fused-silica capillary column coated with OV-1701 (cross-linked), at 180°C, with He - H (23:2) as carrier gas (4 mL min-1) and N-selective detection. The extraction was quantitative, i.e., none of the contact materials adsorbed I significantly. The coefficient of variation for 7 determinations of 400 ng mL-1 of I in serum was 3%. The GC determination alone gave a coefficient of variation of 4% (n = 10).