An automated fluorimetric method for the determination of fluproquazone in plasma and urine.

A rapid and sensitive fluorimetric assay was developed for the quantitative determination of 4-(p-fluorophenyl)-1-isopropyl-7-methyl-2(1H)-quinazolinone(fluproquazone) in plasma and urine. The unchanged drug was extracted from alkalinized plasma or urine into n-heptane containing 0--1.5% isoamyl alcohol followed by a back extraction into 5 N HCl. After oxidation with potassium persulfate the fluorescence measurements were taken at 326 nm excitation and 520 nm emission. Detection limits were about 15 ng/ml plasma and 6 ng/ml urine, using 1 ml plasma and 2 ml urine, respectively. The automated assay had a five times higher sample capacity and better reproducibility (+/- 3%) than the manual assay (+/- 5%). The method was applied to animal studies including assays in milk and proved to be suitable in human studies after oral doses in the therapeutical range.