DETERMINATION OF CHLORIDE, NITRATE, SULFATE, NITRITE, FLUORIDE, AND PHOSPHATE BY ON LINE COUPLED CAPILLARY ISOTACHOPHORESIS-CAPILLARY ZONE ELECTROPHORESIS WITH CONDUCTIVITY DETECTION

Capillary zone electrophoresis (CZE) on-line coupled with capillary is otachophoresis (ITP) in the column-coupling configuration of the separ ation unit was studied for determination of nitrite, fluoride, and pho sphate persent in a large excess of chloride, nitrate, and sulfate. Su ch distributions of these anions are typical for many environmental ma trices, and it is shown that the ITP-CZE tandem enables the ITP determ ination of the macroconstituents, while ITP-preconcentrated microconst ituents cleaned up from the macroconstituents can be determined by CZE with a conductivity detector. This approach was effective when the co ncentration ratio of macro-microconstituents was less than (2-3) x 10( 4). The limits of detection achieved for the microconstituents (200, 3 00, and 600 pptr for nitrite, fluoride, and phosphate, respectively) e nabled their determinations at low parts per billion concentrations in instances when the concentrations of sulfate or chloride in the sampl es were higher than 1000 ppm. Although in such situations the load cap acity of the ITP column was not sufficient to provide the quantitation s of the macroconstituents, the ITP sample cleanup enabled the CZE det erminations of the microconstituents present in the samples at 10(5)-1 0(6)-fold lower concentrations. Experiments with samples of such extre me compositions showed that anionic impurities from the ITP electrolyt e solutions transferred together with the analytes into the CZE column are probably the main hindrances in extending this dynamic concentrat ion range by decreasing the limits of the detection to a level associa ted with the noise characteristics of the conductivity detector.