Isotachophoretic determination of chromium(VI) at low parts per billion concentrations.
Factors important in the isotachophoretic determination of CrVI at low ppb concentrations were studied. To increase the selectivity of the analysis, the use of photometric detection at a 405 wavelength was preferred. Losses of CrVI due to adsorption were found to be the main potential source of analytical errors at the concentration levels of interest. The presence of sulphate in the sample solution at ca. 10(-4) M concentration eliminated the losses due to adsorption on the walls of the sample handling glassware. In analysis with a low pH of the leading electrolyte, adsorption of CrVI on the walls of the separation compartment also played a role; addition of naphthalene-1,3,6-trisulphonate to the sample solution considerably reduced this disturbance. When the precautions concerning adsorption were taken, the detection limits for CrVI were in the range 4-5 ppb (depending on the pH of the leading electrolyte) for a 30-microliters sample volume. The calibration graphs were linear over the concentration range 10(-7)-5 X 10(-6) M with good correlation coefficients. The reproducibilities of the determinations within this concentration range were 2-3% or better. The practical utility of capillary isotachophoresis in the trace determination of CrVI in drinking water and wastewater samples seems promising.
D002857:Chromium / Q000032:analysis*; D004586:Electrophoresis; D010783:Photometry
D002857:Chromium