Separation of polyphosphates and polycarboxylates by capillary electrophoresis in a carrier electrolyte containing adenosine 5′-triphosphate and cetyltrimethylammonium bromide with indirect UV detection

Abstract

A capillary electrophoresis method was developed for the separation of polyanions of environmental concern, such as polyphosphates [ortho-(P1), pyro-(P2) and tripoly-(P3)] and polycarboxylic acids (nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid and citrate) which are used as builders in detergents. A carrier electrolyte consisting of adenosine 5′-triphosphate as the UV chromophore for indirect detection at 260 nm and cetyltrimethylammonium bromide as modifier to reverse the electroosmotic flow was used. The changes in the effective mobilities of some solutes and common UV chromophores with pH were either predicted theoretically or determined experimentally. Differences in effective mobilities of the solutes were used to optimize the pH for their separation. Baseline separation for all of the solutes was achieved. Detection limits for all of the solutes were in the range 2·10 -5-5·10 -5 M. Application of the developed method to real samples was demonstrated by separation and determination of polyphosphates (P1, P2 and P3) in a commercial detergent. For sample preparation, only simple dilution with water and filtration were needed.