Determination of the spectrum of low molecular mass organic acids in urine by capillary electrophoresis with contactless conductivity and ultraviolet photometric detection-An efficient tool for monitoring of inborn metabolic disorders

A mixture of 29 organic acids (OAs) occurring in urine was analyzed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection ((CD)-D-4) and UV photometric detection. The optimized analytical system involved a 100 cm long polyacrylamide-coated capillary (50 mu m i.d.) and the background electrolyte of 20 mM 2-morpholinoethanesulfonic acid (MES)/NaOH + 10% (v/v) methanol, pH 6.0 (pH is related to the 20 mM MES/NaOH buffer in water). The LOD values obtained by (CD)-D-4 for the OAs which do not absorb UV radiation range from 0.6 mu M (oxalic acid) to 6.8 mu M (pyruvic acid): those obtained by UV photometry for the remaining OAs range from 2.9 mu M (5-hydroxy-3-indoleacetic acid) to 10.2 mu M (uric acid). The repeatability of the procedure developed is characterized by the coefficients of variation, which vary between 0.3% (tartaric acid) and 0.6% (5-hydroxy-3-indoleacetic acid) for the migration time and between 1.3% (tartaric acid) and 3.5% (lactic acid) for the peak area. The procedure permitted quantitation of 20 OAs in a real urine sample and was applied to monitoring of the occurrence of the inborn metabolic fault of methylmalonic aciduria. (C) 2010 Elsevier B.V. All rights reserved.