文摘
The present investigation describes the analytical performances of a microfluidic device comprising an enrichmentcolumn, a reversed-phase separation channel, and ananoelectrospray emitter embedded altogether in polyimide layers. This configuration minimizes transfer linesand connections and reduces postcolumn peak broadening and dead volumes. This compact and versatile modular nanoLC-chip system was interfaced to both ion trapand time-of-flight mass spectrometers, and its analyticalpotentials were evaluated in the context of proteomicsapplications. The figures of merit of this system in termsof peak capacity, reproducibility, sensitivity, and lineardynamic range of peptide detection were determinedusing tryptic digests of complex protein extracts includingalbumin- and immunoglobulin-depleted rat plasma samples. The analysis of peak profiles for more than 600peptide ions reproducibly detected across replicatenanoLC-chip-MS runs (n = 10) indicated that this systemprovided good reproducibility of retention time and peakintensity with RSD values of less than 0.5 and 9.1%,respectively. Variation in peptide abundance as low as2-fold changes was identified for spiked tryptic digestspresent at levels of 2-5 fmol in plasma samples. Sensitivity measurements were performed on dilution series ofprotein digests spiked into rat plasma samples andprovided a detection limit of 1-5 fmol. The modularconcept of the microfluidic systems also facilitated theintegration of two-dimensional chromatography (strongcation exchange/C18) thereby increasing the sample loading and selectivity of the nanoLC-chip-MS system. Theapplication of this integrated device was evaluated forcomplex rat plasma samples to compare the number ofprotein identifications obtained using one- and two-dimensional nanoLC-chip-MS/MS.