EFFECT OF SURFACTANT CONCENTRATION ON THE DETERMINATION OF TRANS,TRANS-MUCONIC ACID IN URINE BY CATIONIC MICELLAR ELECTROKINETIC CHROMATOGRAPHY WITH THERMO-OPTICAL ABSORBANCE DETECTION

Abstract

A rapid method is described for the determination of trans,trans-muconic acid (2,4–hexadienedioic acid), a biomarker of benzene exposure in urine, by micellar electrokinetic chromatography (MEKC) with thermo-optical absorbance (TOA) detection. Addition of the cationic surfactant cetyltri–methylammonium bromide (CTAB) to a pH 7.0 background electrolyte induces a reversal in the direction of electroosmotic flow (EOF), from cathode to anode. The negatively charged trans,trans-muconic acid ion migrates rapidly (< 3 min) toward the anode owing to its electrophoretic mobility supplemented by the surfactant–induced anodic EOF.

A rigorous investigation into the effect of CTAB concentration on EOF showed that 0.05 to 5 mM surfactant permits trans,trans-muconic acid to elute before most endogenous urine components. For a urine sample doped with 0.8 mg/L trans,trans-muconic acid, the relative standard deviations of the analyte migration time and peak height were 1.5 % and 5.7 % respectively (n=6), for this home–built analysis system. The detection limit (3 SD) was 0.1 mg/L (7×10⁻⁷ M) trans,trans-muconic acid based on calibration standards and the linear dynamic range extended to 50 mg/L.

ACKNOWLEDGMENTS

The authors would like to thank Dr. X. C. Le, Department of Public Health Sciences, University of Alberta, for his helpful comments and suggestions regarding this study. This work was first presented at the 43^rd International Conference on Analytical Sciences and Spectroscopy (Abstract No. 16–4), August 10–13, 1997, Montréal, Canada. Funding for this research was provided by the Natural Sciences and Engineering Council of Canada and an FCAR Québec (Fonds pour la formation de chercheurs et l'aide à la recherche) grant for the establishment of new professors.