Indirect thermo-optical detection for capillary electrophoresis is des
cribed first. A 20 mW helium-neon laser (632.8 nm) was used to provide
the pumping beam and a 2 mW helium-neon laser (632.8 nm) supplied as
the probe beam; Methylene Blue dye was used as a background absorber.
The addition of ethanol to the background electrolyte solution can be
performed to reduce adsorption of Methylene Blue onto the capillary wa
ll. The detection method was applied to the detection of amino acids s
eparated by capillary electrophoresis. The detection limit for lysine
was 5 x 10(-6) mol l(-1) (signal-to-noise ratio, 2).