Optimization of an interface chip for coupling capillary electrophoresis with thermal lens microscopic detection.

This paper presents a capillary-to-microchip connection, which can be used as an interface for coupling capillary electrophoresis (CE) with a thermal lens microscope (TLM). It is difficult to directly apply TLM to samples in a capillary with a curved surface, and such an interface chip at the end of a CE separation column is needed for reliable TLM measurements. The dependence of the TLM signal intensity on the TLM detection point in the interface chip and the dependence of the theoretical plate number of CE separation on the channel dimensions of the interface chip were investigated and optimized with a mixture of 4-dimethylaminoazobenze-4'-sulfonyl (DABSYL)-derivatized amino acids (glycine, alanine, methionine, and proline) as a model sample. By using an optimized interface chip, theoretical plate numbers of DABSYL-glycine, -methionine, -alanine, and -proline were obtained to be 104000, 95000, 104000, and 95000, respectively.