An on-line microfluidic device coupled with inductively coupled plasma mass spectrometry for chromium speciation

In this study, an on-line polyoxometalate cluster (POM)/microfluidic (MF) separation system coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection was developed for the determination of trivalent [Cr(III)] and hexavalent [Cr(VI)] chromium species in aqueous samples. In this system, a POM-immobilized MF device was used to separate the chromium species prior to their determination through ICP-MS. Several parameters were investigated to optimize the performance of the system: the adsorption pH, the adsorption and elution flow rates, the elution solution, the adsorption capacity, and the reaction chamber volume. Under the optimized conditions (carrier solution: deionized H2O; adsorption/elution flow rates: 0.2/1.2 ml L-1; reaction chamber volume: 30 mu L), the linearity (> 0.9987), precision (< 3.69%; n = 7), and accuracy (95.93-108.60%) of this analytical procedure were quite high. To confirm its practical utility, the novel POM-MF separation system was applied to the successful determination of chromium species in real-world samples (including spiked tap water).