Determination of amino acids in urine by capillary electrophoresis with indirect UV detection

This study has described a relatively simple method for determination of 14-18 amino acids (AA's) by CE with indirect UV detection using both myristyltrimethyl-ammonium bromide (MTAB)-coated and uncoated capillaries. The method used either salicylate or benzoate as UV-absorbing additive in carbonate buffer and the non-absorbing AA's were detected indirectly at 230 nn. The optimization of the assay conditions was demonstrated with an MTAB-coated capillary using salicylate-carbonate as separation buffer. Factors that affect indirect signal response and migration behavior of AA's such as buffer concentration, pH, and the relative amount of UV-absorbing additive in buffer have been studied. Comparison of MTAB-coated and uncoatd capillaries on the analysis of AA's has been made. It has been found that the limits of detection of 18 AA's by the method were in the order of 53.6 to 785 pg injected. The method developed was used in the determination of AA's in urine sample and preliminary results were provided.