LASER-INDUCED CAPILLARY VIBRATION FOR ULTRAMICROANALYSIS

A highly sensitive, novel method for ultramicroanalysis of flowing liquid sample in a capillary tube is reported. An intensity-modulated argon laser beam of 70-mW power was Irradiated on the capillary tube in which liquid sample was flowing, and the beam deflection signal of a He-Ne probe laser beam passing just over the tube could be detected. The signal generation mechanism was clarified as not due to ordinary photothermal effects but to vibration of the capillary tube itself based on measured tension dependences and resonant peaks in frequency characteristics of the signals. The signal amplitude was found to be proportional to the absorbance of the sample. As the detection volume of the method was 1.0 X 102 pL for a 50 μm i.d. capillary tube, the detection limit of the absorbance was 1.5 X 10–5, which corresponded to an absolute amount of 6.0 fg (13 amol) for sunset yellow dye. © 1990, American Chemical Society. All rights reserved.