AbstractA method for determining Picumast, an antiallergic drug, in plasma by HPLC and column switching has been developed. The system consisted of two precolumns, an analytical column, three pumps, an autosampler and a fluorescence detector. The precolumns (17 × 4.6 mm i.d.) were packed with LiChroprep RPR (a moderately polar reversed phase) and the analytical column with Nucleosil ODS (RP 18, 5 μm). The columns were connected according to the alternating precolumn technique. The mobile phase consisted of 30% CH3CN/70% 0.05M KH2PO4, pH 2.5, with a flow gradient. Detection wavelengths were 333 nm for excitation and 383 nm for emission. The retention times of Picumast, M1 and M2 were 12, 3.6 and 4.0 min, respectively. Total run time was 15 min. The limit of detection was 3 ng/mL for M1 and 1 ng/mL for M2 and Picumast using an injection volume of 150 μL. The recoveries vary between 89% and 97% with standard deviations between 2.4 and 3.