Abstract: In this work, a system for high sensitivity absorbance measurements on microfluidic chips was developed with a detection volume of 240 nL. Long optical path-length(1.7 cm effective path length) was achieved on the chip by using an integrated liquid core waveguide(LCW) silica capillary coated with Teflon AF. The performance of the system was tested by using o-phenanthroline-Fe(Ⅱ) complex as a model sample with spectrophotometric detection, achieving a detection limit of 8 nmol/L for the complex. The absorbance of samples ranging from 0.03—50 μmol/L is linear(R 2=0.999 4) and showed good repeatability with a RSD of 0.8%(n=5). The sensitivity of the chip-LCW system was a factor of 1.7 higher than conventional spectrophotometry using a 1 cm cell. The present system can be applied in continous flow or flow injection analysis systems.

Key words: Microfluidic chip, Liquid core waveguide, Absorbance detection