Quantitative determination of 21-hydroxy-deflazacort in human plasma using gradient semi-microbore liquid chromatography.
A sensitive and selective liquid chromatographic procedure to quantitate the deflazacort metabolite 21-hydroxy-deflazacort (DF-21OH) in human plasma was developed and validated. DF-21OH and fludrocortisone acetate (internal standard, IS) were isolated from human plasma (2 mL) by solid-phase extraction onto C-18 cartridges. Potential interferences were selectively removed and analytes were eluted with ethyl acetate. Following evaporation, the residue was reconstituted for HPLC analysis. Separation was achieved by gradient elution using a 5 microns YMC Basic column (2.0 x 100 mm) with mobile phases consisting of 20% methanol and 50% acetonitrile in 50 mM phosphate buffer (pH 3) at a temperature of 50 degrees C. Flow rate was maintained at 0.3 mL/min., and analytes were quantified spectrophotometrically at 246 nm. The assay was validated over the range 1.0 to 500 ng/mL DF-21OH. Calibration curves were prepared using a weighted (1/concentration) nonlinear quadratic regression algorithm. Peak-height ratios were proportional to the amount of DF-21OH added to plasma. Assay precision (%RSD) ranged from 4.2 to 11%, with a corresponding assay accuracy (% relative error) of +/- 2.8%. Absolute recovery of DF-21OH from plasma was 78-86% over the concentration range. The minimum quantitation limit was 1.0 ng/mL.
Spectrophotometric and HPLC determination of deflazacort in pharmaceutical dosage forms
O deflazacorte (DFZ) e um farmaco glicocorticoide usado como antiinflamatorio e imunossupressor. Metodos oficiais nao estao disponiveis para a determinacao de DFZ em formas farmaceuticas. Este estudo teve como objetivo desenvolver, validar e comparar metodos por espectrofotometria (UV e colorimetria) e cromatografia liquida de alta eficiencia (CLAE), na determinacao quantitativa de DFZ em comprimidos e suspensao oral. O metodo por UV utilizou etanol como solvente, com deteccao em 244 nm. O metodo colorimetrico foi baseado na reacao de reducao com azul de tetrazolio em meio alcalino, com deteccao em 524 nm. O metodo por CLAE utilizou coluna C18; fase movel constituida de acetonitrila:agua (80:20, v/v), com fluxo de 1,0 mL min-1 e deteccao em 244 nm. Os metodos foram lineares (r > 0,999); precisos (RSD 97%). As analises estatisticas dos resultados obtidos indicaram que os metodos por UV e por CLAE foram estatisticamente equivalentes, enquanto os valores obtidos para o metodo colorimetrico diferiram significativamente dos demais metodos.
Human exposure to methylmercury from crayfish (Procambarus clarkii) in China
Methylmercury (MeHg) accumulation in aquatic food raises global concerns about human exposure to MeHg. Crayfish is the world’s third largest farmed crustacean species and a favorite aquatic food in many countries. However, human health hazard due to MeHg exposure via crayfish consumption is unclear, partly because appropriate survey data are lacking. We report on mercury concentrations and speciation in edible tail muscle of crayfish collected from restaurants in 23 Chinese cities. On average, MeHg constituted 99.1 % of mercury in tail muscle, and MeHg concentrations were comparable with those reported for fish in China. Variation in MeHg concentrations was not attributable to broad geographic region (i.e., provinces) or tail length. For different populations, potential health risk (characterized by hazard quotient or HQ) of MeHg exposure through crayfish consumption depended largely on crayfish consumption rates. In particular, a health hazard (HQ > 1) was found for high-rate consumers (i.e., 95 %ile or higher) in some cities in the middle and lower reaches of the Yangtze River (MLYR), during the peak consumption season. Our results suggest that more attention should be paid to dietary MeHg intake via crayfish consumption in China, particularly for communities with high consumption in MLYR.