SURFACE-CHARGE REVERSED CAPILLARY ZONE ELECTROPHORESIS OF INORGANIC AND ORGANIC-ANIONS

Anions commonly found in biological fluids such as chloride, citrate, phosphate, bicarbonate, lactate, aspartate and glutamate, were determi ned within 60 s by means of capillary zone electrophoresis and indirec t UV detection using 10 mM of chromate, pH 8.0, as both carrier electr olyte and chromophore. The lower mass detection limit was 0.5 pmol. In order to avoid a gradual shift of the pH and, in consequence, driftin g ionic mobilities due to the formation of hydroxyl ions at the cathod e, 1 mM of 5,5-diethylbarbiturate was added to the background electrol yte. Moreover, fused silica capillaries were coated with a 0.0003% sol ution of hexadimethrine bromide for two minutes between runs to revers e electroendosmotic flow which otherwise would counteract the electrop horetic migration of the anions and, hence, increase time of analysis. It is concluded that charge-reversed capillary zone electrophoresis i n concert with indirect UV detection is superior to ion chromatography and conductivity detection in the determination of inorganic and orga nic anions in biological fluids both with regard to selectivity, sensi tivity and speed of analysis.