Separations of inorganic anions based on their complexations with alpha-cyclodextrin by capillary zone electrophoresis with contactless conductivity detection

Capillary zone electrophoresis (CZE) separations of inorganic anions based on their host-guest complex equilibria with alpha-cyclodextrin (alpha-CD) w ere investigated. alpha-CD employed as a host was found to influence select ively the effective mobilities most of the studied anions (chloride, bromid e, iodide, sulfate, nitrite, nitrate, fluoride, phosphate). Its complexing ability combined with a low pH of the carrier electrolyte solution provided working conditions suitable for rapid CZE separations of the anions. For e xample, iodide and chloride present in the injected sample in a concentrati on ratio of ca. 1:2.10(3) could be separated in less than 100 s and seven o f the above anions (alpha-CD failed to resolve chloride and bromide) were b aseline-resolved in less than 120 a. A high overall selectivity of the carr ier electrolytes combining the host-guest equilibria with a low pH in the a nalysis of highly complex samples is illustrated by CZE separations of inor ganic anions present in milk. Here, no interferences to the separations of inorganic anions due to co-migrations of organic acids present in milk were observed also when a 200 nl volume of a diluted (1:10) milk sample was loa ded onto the column. A contactless conductivity detector used for the detec tion of anions in this work proved very reliable. Under our separating cond itions it provided for the studied anions concentration limits of detection in the range of 0.5-1.4 mu mol/l (a 200-nl sample injection volume) when t he separations were carried out in a 300 mu m I.D. capillary tube made of p olytetrafluoroethylene. (C) 1999 Elsevier Science B.V. All rights reserved.