Pneumatic Microvalve-Based Hydrodynamic Sample Injectionfor High-Throughput Quantitative Zone Electrophoresis in Capillaries

摘要

A hybrid microchip/capillary electrophoresis (CE) system was developed to allow unbiased and lossless sample loading and high-throughput repeated injections. This new hybrid CE system consists of a poly(dimethylsiloxane) (PDMS) microchip sample injector featuring a pneumatic microvalve that separates a sample introduction channel from a short sample loading channel, and a fused-silica capillary separation column that connects seamlessly to the sample loading channel. The sample introduction channel is pressurized such that when the pneumatic microvalve opens briefly, a variable-volume sample plug is introduced into the loading channel. A high voltage for CE separation is continuously applied across the loading channel and the fused-silica capillary separation column. Analytes are rapidly separated in the fused-silica capillary, and following separation, high-sensitivity MS detection is accomplished via a sheathless CE/ESI-MS interface. The performance evaluation of the complete CE/ESI-MS platform demonstrated that reproducible sample injection with well controlled sample plug volumes could be achieved by using the PDMS microchipinjector. The absence of band broadening from microchip to capillaryindicated a minimum dead volume at the junction. The capabilitiesof the new CE/ESI-MS platform in performing high-throughput and quantitativesample analyses were demonstrated by the repeated sample injectionwithout interrupting an ongoing separation and a linear dependenceof the total analyte ion abundance on the sample plug volume usinga mixture of peptide standards. The separation efficiency of the newplatform was also evaluated systematically at different sample injectiontimes, flow rates, and CE separation voltages.