Isotachophoresis and isotachophoresis-zone electrophoresis of food additives on a chip with column-coupling separation channels

The use of a poly(methylmethacrylate) chip, provided with two separation ch annels in the column-coupling (CC) arrangement and on-column conductivity d etection sensors, to isotachophoresis (ITP) and ITP-ZE separation and deter mination of food additives was studied. A group of preservatives and taste intensifying components examined in this study included benzoate, sorbate, p-hydroxybenzoic acid esters (parabens), and glutamate, while various food products and cosmetics represented different matrices (proteins, fat, organ ic acids, carbohydrates, salts). ITP on the CC chip was found suitable for the determination of glutamate in the food products with only a minimum sam ple preparation (dilution, filtration). It also provided a rapid and simple procedure for the determination of parabens in cosmetics. On the other han d, ITP experiments with benzoate and sorbate revealed that sample preparati ons providing high analyte/matrix concentration ratios are essential when t hese food preservatives are to be determined by ITP on the chip. ITP-ZE com bination on the same chip provided a solution to this problem by integratin g an efficient ITP sample preparation (concentration of the preservatives a nd removal of the main part of the matrix), capable of processing muL sampl e volumes, with a final ZE separation and sensitive detection (low mu mol/L limits of detection) of the preservatives. In both ITP and ITP-ZE separati ons on the CC chip no interference from food matrices was found.