Analytical Sciences

Abstract − Analytical Sciences, 15(6), 525 (1999).

Sub-Zeptomole Detection in a Microfabricated Glass Channel by Thermal-Lens Microscopy
Kiyoshi SATO*, Hiroaki KAWANISHI*, Manabu TOKESHI**, Takehiko KITAMORI* , ** and Tsuguo SAWADA*
*Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Hongo, Tokyo 113-8656, Japan
**Integrated Chemistry Project, Kanagawa Academy of Science and Technology, Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan
A thermal-lens microscope which we developed was applied to an ultramicro quantity determination of a dye in an aqueous solution filling a microchannel (150 mm wide and 100 mm deep) fabricated in a quartz glass substrate. The detection volume, which corresponded to the confocal volume, was estimated to be 1.3 fl. The detection limit of the dye molecules was 160 ymol, and the calibration line showed good linearity in the sub-zmol-to-zmol region. This detection sensitivity is equivalent to that of laser-induced fluorometry. The thermal-lens signal measured in the microchannel was more stable than that measured in a liquid micro space between a slide glass and a cover glass, which was much wider than the microchannel. This may have been due to a suppression of convection in the microchannel. The thermal lens method can be applied to non-fluorescent chemical species, and is thus very suitable detection method for integrated chemistry systems. (Keywords: Thermal-lens microscope, microchannel, integrated chemistry laboratory convection)