Portable thermal lens spectrometer with focusing system

摘要

A portable thermal lens spectrometer with a precise focusing system was developed. Astigmatism of the reflected excitation beam from the microchip was used for depth direction focusing. For width direction focusing, the scattering effect of the transmitted probe beam by a microchannel edge was used. The focusing system was evaluated with a 250 mum wide x 50 mum deep microchannel. Focusing resolutions for depth and width directions were 1 and 10 mum, respectively. The repeatability of the thermal lens signal (40 muM xylenecyanol solution) was proved to be similar to1% coefficient of variance when using these focusing methods. The limit of detection for a xylenecyanol solution was 30 nM, and the absorbance was 4.7 x 10(-6) AU. The sensitivity was 20-100 times higher than that obtained by spectrophotometry. In consequence, a practical thermal lens spectrometer was realized.