Sequential injection sample introduction microfluidic-chip based capillary electrophoresis system

A sequential injection micro-sample introduction system was coupled to a microfluidic-chip based capillary electrophoresis system through a split-flow sampling interface integrated on the micro-chip. The microfluidic system measured 20x70x3 mm in dimension, and was produced using a non-lithographic approach with components readily available in the analytical laboratory. In the H-configuration channel design the horizontal separation channel was a 75 mu m I.D. x 60 mm quartz capillary, with two vertical side arms produced from plastic tubing. The conduits were embedded in silicon elastomer with a planar glass base. Sequential introduction of a series of samples with about 2.5% carryover was achieved at 48 h(-1) throughput with samples containing a mixture of fluorescein isothiocyanate (FITC)-labeled amino acids using SI sample volumes of 3.3 mu l and carrier flow-rate of 2.0 ml min(-1). Baseline separation was achieved for FITC-labeled arginine, phenylalanine, glycine and FITC (laser induced fluorescence detection) in sodium tetraborate buffer (pH 9.2) within 8-80 s, at separation lengths of 25-35 mm and electrical field strengths of 250-1500 V cm(-1), with plate heights in the 0.7-3 mu m range. (C) 1999 Elsevier Science B.V. All rights reserved.