Application of external micro-spectrophotometric detection to improve sensitivity on microchips

Gáspár, Attila; Bácsi, István; Garcia, Erika F.; Braun, Mihály; Gomez, Frank A.
September 2009
Analytical & Bioanalytical Chemistry;Sep2009, Vol. 395 Issue 2, p473
Academic Journal
The goal of this work was to increase the sensitivity of a UV–Vis spectrophotometer by decreasing the background noise and lengthening the optical path. A microphotometer has been modified to precisely select very small parts of a microfluidic channel pattern of a chip and to measure light absorbance on a magnified area of the selected part of the channel. The viability of combining a projection microscope and a spectrophotometer for external absorbance measurements on disposable PDMS chips was studied. Besides the external direct detection above a microfluidic channel, the optical pathlength was lengthened by detecting in the region of the perpendicular exit port. Increasing the cross-sectional area of the zone of irradiation improved the signal-to-noise ratio and the limits of detection (LOD).


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