Determination of dextromethorphan in biological fluids by liquid chromatography by using semi-microbore columns

A sensitive, specific procedure for the determination of dextromethorphan in plasma and urine in dogs is described. The use of a semi-microbore column, 2.1 mm i.d. X 25 cm resulted in a detection limit of 1 ng/mL in plasma and 25 ng/mL in urine. Plasma (3 mL) is extracted in CCl4 and the drug is back-extracted with 3% acetic acid. The chromatographic separation is carried out using a 5-micron particle size octadecyl-bonded column, and the drug is monitored by a fluorescence detector. The results after 10-mg oral administrations of dextromethorphan to dogs are provided.