Attomole Amino Acid Analysis: Capillary-Zone Electrophoresis with Laser-Based Thermo-Optical Detection

Abstract

To analyze minute samples of complex biological mixtures, it is necessary to utilize an analytical technique which combines high selectivity and sensitivity. In the analysis of attomole quantities of amino acids, we combine capillary-zone electrophoresis for high-resolution separation with laser-induced thermo-optical measurements for high-sensitivity detection. Capillary-zone electrophoresis provides theoretical plate counts greater than 200,000 within a 40-minute separation. However, to achieve this separation efficiency, it is necessary to utilize a detector with subnanoliter volume. Crossed-beam thermo-optical detection directly on the 50-µm-diameter capillary tube results in high-sensitivity detection with minimal detector volume. Detection limits of 40 attomoles of methionine, injected onto the column, are obtained with a 130-mW argon-ion pump laser.