title: Liquid-chromatographic analysis for methylphenidate (Ritalin) in serum.
abstract: We describe a "high performance" liquid chromatographic method for quantitating methylphenidate in serum. The internal standard, 4,5-diphenylimidazole, and  serum or plasma sample are extracted in chloroform, evaporated, and redissolved in 20 mmol/L potassium phosphate (pH 3.5)/high-purity acetonitrile, 80/20 by vol. A centrifuged aliquot is chromatographed on mu-Bondapak C-18 with the phosphate/acetonitrile solvent as mobile phase, a flow rate of 1.6 mL/min, and a column temperature of 40 degrees C. Absorbances are read at 192 nm. This method reliably measures concentrations greater than 20 micrograms/L and has analytical recoveries of 74%.
mesh_terms: D002648:Child; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006801:Humans; D007202:Indicators and Reagents; D008297:Male; D008774:Methylphenidate / Q000097:blood*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D007202:Indicators and Reagents; D008774:Methylphenidate