A liquid chromatographic method for the determination of promethazine enantiomers in human urine and serum using solid-phase extraction and fluorescence detection.

A LC method was developed for the concurrent assay of R(+) and S(-) promethazine from human urine and serum. The method involves the use of solid-phase extraction for sample clean-up. Chromatographic resolution of the enantiomers was performed under isocratic conditions using a mobile phase of hexane-1,2-dichlorethane-absolute ethanol-trifluoroacetic acid (400:150:100:1, v/v/v/v) at a flow rate of 1 ml min-1 on a brush-type column KK-CARNU. The enantiomers were detected by fluorescence using an excitation wavelength of 250 nm and a 280 nm emission cutoff filter. Chlorpromazine was used as the internal standard for urine analysis. Standard addition was used for promethazine analysis from serum. Drug to internal standard ratios were linear from 0.25 to 10 micrograms ml-1 in urine. Serum levels were linear from 2 to 10 ng ml-1.

High-performance thin-layer chromatographic determination of digoxin and related compounds, digoxigenin bisdigitoxoside and gitoxin, in digoxin drug substance and tablets.

A high-performance thin-layer chromatographic (HPTLC) method for the determination of digoxin and its related compounds digoxigenin bisdigitoxoside (DBD) and gitoxin in digoxin drug substance and tablets was developed. Separation of the three compounds was accomplished on a C18 wettable reversed-phase plate using water-methanol-ethyl acetate (50:48:2, v/v/v) as the mobile phase. The analytes were determined by densitometry using absorbance for digoxin and fluorescence for the two related compounds. All peaks were quantified by peak-height analysis. Linear regression analysis of the data was performed for all three compounds. The calibration range for digoxin was set at 320-480 ng per 5-mm band, equivalent to 80-120% (w/w) of a 400-ng band load, that for DBD was set at 4-12 ng per 5-mm band, equivalent to 1-3% (w/w) of the digoxin load, and that for gitoxin was set at 0.4-1.6 ng per 5-mm band, equivalent to 0.1-0.4% (w/w) of the digoxin load. The limit of quantification (LOQ) for digoxin was 64 ng per 5-mm band with a limit of detection (LOD) of 8 ng per 5-mm band. The LOQs for both DBD and gitoxin were 0.12 ng per 5-mm band with LODs of 0.4 ng per 5-mm band. The linearity range for the digoxin peak height in the absorbance mode was 0-5000 ng per 5-mm band. The linearity range for DBD and gitoxin peak heights in the fluorescence mode was 0-2000 ng per 5-mm band.