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Abstract
A method using column switching and reversed-phase high performance liquid chromatography with diode array detection was developed for the screening of 16 diuretics, probenecid and caffeine in urine. First, a 40-μl sample is injected into a short ODS or ODP extraction column with water as eluent and polar matrix components are eluted to waste. The retained compounds are then eluted in backflush mode into the analytical column by means of a column switching valve and a gradient of 0.05 M phosphate buffer (pH 3.1) and acetonitrile. Wavelengths 230, 270 and 360 nm are used for the detection. Recoveries for spiked urine samples were near 100% and relative retention times showed good repeatability. Detection limits were 0.5–2.0 μg/ml.