ON-COLUMN DOUBLE-BEAM LASER-ABSORPTION DETECTION FOR CAPILLARY ELECTROPHORESIS

Double-beam laser absorption detection in capillary electrophoresis (CE) has been developed. This is based on the direct subtraction of reference and signal photocurrents by an electronic circuit, under feedback control, to reduce background noise. A simple equation for calculating concentrations has been proposed and was confirmed by experimental results. A practical noise-to-signal ratio of 1 x 10(-5) in intensity is achieved. This is 5 times lower than that of commercial CE systems. For absorbance detection, as low as 2 x 10(-8) M malachite green can be detected. This corresponds to a 25-fold improvement of detection limit over commercial systems. This gain in detectability results from both a reduction in intensity fluctuations (noise) and an increase in the effective absorption path length (signal).