Determination of arsenate by sorption pre-concentration on polystyrene beads packed in a microfluidic device with chemiluminescence detection

A highly sensitive chemiluminescence (CL) method for the determination of arsenate in water based on a simple microfluidic device was developed. The method was based on sorption pre-concentration of arsenate as a form of vanadomolybdoarsenate heteropoly acid (VMoAs-HPA) ion-paired with hexadecyltrimethylammonium bromide on the surface of polystyrene beads packed in a microfluidic device monitored by chemiluminescence detection. The composition of the VMoAs-HPA complex was studied by varying the concentrations of ammonium molybdate, ammonium vanadate and sulfuric acid with a variable-size simplex optimization process, of which the optimum concentrations were 6.3 × 10−5, 5.0 × 10−6 and 1.0 × 10−2 M, respectively. In this work, 1.0 × 10−3 M ethylenediaminetetraacetic acid was added to all work solutions to remove the interferences of the other metal ions on the CL detection. The integration of sorption pre-concentration not only increased the detection sensitivity but also eliminated the interference from phosphate and chromate. The calibration plot was linear from 1.0 × 10−7 to 5.0 × 10−5 M As(V). The limit of detection was 8.9 × 10−8 M As(V) (S/N = 3). The time required for one analysis run was as short as 5 min. The relative standard deviation was 5.9% (n = 9). This method was successfully applied to the determination of arsenate in mineral-, drinking- and tap-water samples.