CAPILLARY ELECTROPHORETIC DETERMINATION OF TRACE-METALS IN HAIR SAMPLES AND ITS COMPARISON WITH HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND ATOMIC-ABSORPTION SPECTROMETRY TECHNIQUES

Capillary electrophoresis (CE) is compared with high performance liqui d chromatography (HPLC) and atomic absorption spectrometry (AA) for th e determination of trace concentrations of selected metals in human ha ir. CE and HPLC methods are based upon the chelation of the metals wit h 2-(5'-bromo-2'-pyridylazo)-5-diethylamino phenol (5-Br-PADAP) follow ed by ultraviolet-visible (W-Vis) detection. Large volume sample stack ing (LVSS)-CE using injection times of up to 300 s is applied to the s imultaneous determination of Co and Zn providing lower limits of detec tion (LODs) of 4.2 x 10(-8) mol dm(-3) and 6.0 x 10(-8) mol dm(-3), re spectively, than can be achieved by conventional CE. The LVSS procedur e could not be applied to hair samples due to a higher run current exi sting when the sample is introduced into the capillary. Conventional C E with cetyltrimethylammonium bromide (CTAB) present in the run buffer to retain the ligand in solution is used for the determination of met al concentrations in hair samples. Only Zn could be determined in this way as it exists at relatively high levels in hair. Co, Ni and Hg cou ld be detected when spiked hair samples were analysed with estimated L ODs of 5.0 x 10(-7) mol dm(-3), 1.0 x 10(-6) mol dm(-3) and 3.0 x 10(- 5) mol dm(-3), respectively. HPLC was successfully used to determine C o and Cu in hair samples, with levels of 57.6 ppb and 17.31 ppm being found, respectively, and corresponded closely to results produced by A A. Fe also gave a signal together with unidentified coeluting species. In a separate HPLC study the determination of Ni and Hg as their comp lexes with hydrogen peroxide and 5-Br-PADAP was also investigated and LODs of 2.0 x 10(-6) mol dm(-3) and 5.0 x 10(-6) mol dm(-3), respectiv ely, were achieved. AA was used as a reference method to determine lev els of Co, Cu, Fe, Pb and Zn in hair and the results produced were in order of magnitude agreement with accepted literature values.