Anal. Chem. 2004, 76, 4421-4425
Hadamard Transform Capillary Electrophoresis Combined with Absorption Spectrometry Kazuki Hata, Takashi Kaneta, and Totaro Imasaka*
Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Hakozaki, Fukuoka, 812-8581 Japan
A novel injection device for applying absorption spectrometry to Hadamard transform (HT) capillary electrophoresis is described. A small hole, at the center part of the capillary, functions as an inlet port for the sample. The hole is immersed in a sample solution and the end of the capillary that is usually employed for sample introduction is immersed in a buffer solution. An ultraviolet absorption detector is placed between the sample injection port and the other end of the capillary filled with a buffer solution. A high potential is continuously applied between the injection port and the end of the capillary, which allows the sample solution to be introduced into the separation capillary. By application of a higher potential modulated according to a Hadamard code between both ends of the capillary, the buffer solution is injected into the separation capillary. In some preliminary experiments, this injection device was utilized to introduce a single sample segment into a capillary. As expected, a single peak was observed in the electropherogram for a sample containing a single component. This device was then employed for multiple sample injection in HT capillary electrophoresis. An 8-fold improvement in the S/N ratio was observed when the HT technique was used, in which a 255-order of a Hadamard matrix was used, as expected from theory. The present approach was also utilized for the sensitive detection of a sample comprised of multiple components. Absorption spectrometry is widely used for the analysis of samples that show an absorption band in the ultraviolet or visible region. As a result, it is typically employed for analyte detection in high-performance liquid chromatography (HPLC) and capillary electrophoresis. However, the concentration detection limit is rather poor for capillary electrophoresis relative to HPLC because of the short optical path length (
