title: Fabrication of a monolithic sampling probe system for automated and continuous sample introduction in microchip-based CE.
abstract: A fabrication process for producing monolithic sampling probes on glass chips, with tip diameters of a few hundred micrometers was developed, using simple tools including a glass cutter and a bench drill. Microfluidic chips with probes fabricated by this approach were coupled to a linearly moving slotted-vial array sample presentation system for performing continuous sample introduction in the chip-based CE system. On-chip horizontal tubular reservoirs containing working electrolyte and waste were used to maintain a stable hydrostatic pressure in the chip channels during prolonged working periods. The performance of the system was demonstrated in the separation of FITC-labeled amino acids with LIF detection, by continuously introducing a train of different samples without interruption. Throughputs of 30-60/h were achieved with <1.0% carry-over and reproducibilities in peak height of 3.6, 3.3, and 3.5% RSD for arginine, FITC, and phenylalanine, respectively (n = 11). Continuous analysis of a mixture of FITC-labeled amino acids for 2 h, involving 60 analytical cycles, yielded an RSD of 7.5 and 6.8% for arginine and FITC (n = 60), respectively. An extremely low sample consumption of 30 nL for each analysis was obtained. Separation efficiencies in plate numbers were in the range of 0.8-2x10(5)/m. In addition to the application in sample introduction, the sample/reagent introduction system was also used to produce working electrolyte gradients during a CE separation to improve the separation efficiency. Comparing with isocratic electrophoresis separation, gradient CE demonstrated better separation efficiencies for a mixture of FITC-labeled amino acids.
authors.affiliation: Institute of Microanalytical Systems, Zhejiang University, Hangzhou, PR China.
authors.forename: Qiao-Hong
authors.initials: QH
authors.lastname: He
authors.forename: Qun
authors.initials: Q
authors.lastname: Fang
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Du
authors.forename: Zhao-Lun
authors.initials: ZL
authors.lastname: Fang
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001331:Automation; D004573:Electrolytes; D046209:Electrophoresis, Microchip / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D005898:Glass
chemical_list: D000596:Amino Acids; D004573:Electrolytes; D005456:Fluorescent Dyes; D016650:Fluorescein-5-isothiocyanate