Analysis of urine samples containing cardiovascular drugs by micellar liquid chromatography with fluorimetric detection

A simple direct injection chromatographic procedure with fluorimetric detection is successfully applied to the determination of mixtures of 4 diuretics (amiloride, bendroflumethiazide, piretanide, and triamterene) and 6 beta-blockers (acebutolol, atenolol, labetalol, metoprolol, nadolol, and propranolol), which are usually administered in combinations for the treatment of hypertension, in urine samples. The procedure makes use of C18 columns and micellar mobile phases of sodium dodecyl sulphate (SDS), propanol, and phosphate buffer at pH 3. The adequate resolution of most drugs is obtained with a chemometrics approach where the retention is modeled as a first step using the retention factors in only 5 mobile phases. Afterward, an optimization criterion that takes into account the position and shape of the chromatographic peaks is applied. A mobile phase of 0.11M SDS--8% propanol could resolve mixtures of 8 drugs and was adequate for the analysis of the combinations of diuretic and beta-blocker usually prescribed. However, a mobile phase of larger elution strength, such as 0.15M SDS--15% propanol, is preferred for the analysis of mixtures of amiloride-metoprolol, amiloride-labetalol, and triameterene-propranolol. The method is sensitive enough for the routine analysis of diuretics and beta-blockers at therapeutic urine levels with limits of detection in the 0.5-28-ng/mL range. Urinary excretion studies show that the detection of most drugs is possible up to 24-72 h after their ingestion.