Interfacing monolith-based electrochromatography in microchips with inductively coupled plasma mass spectrometry for elemental speciation

The feasibility of microchip-based electrochromatography interfaced with ICP-MS (mu-EC-ICP-MS) for elemental speciation was first reported, which was achieved by using a homemade nanoflow nebulizer and heated single pass spray chamber. A polymer monolith (poly(butyl methacrylate) (BMA)-co-ethylene dimethacrylate (EDMA)-co-2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)) was fabricated in a 50 mm microchannel by UV-initiated polymerization. The monolith not only eliminated the laminar flow induced by the nebulizer suction but also ensured variable-volume electrokinetic injection. Factors affecting the EOF rate such as the AMPS percentage and electrochromatographic conditions were optimized. The mu-EC-ICP-MS system offered satisfactory resolutions and reproducibilities (<4.4%) by individually using multiple metallic cations and iodine anions as the models. Detection limits of 0.036-0.075 mu g L-1 for mercuric and methylmercuric ions and 0.15-0.22 mg L-1 for arsenite, arsenate, monomethylarsenate and dimethylarsenate were obtained. Mercury speciation in certified fish tissue and arsenic speciation in reference human urine by using the proposed mu-EC-ICP-MS system proved its good applicability in elemental speciation.