Application of Hadamard transformation to MEKC

Abstract

The Hadamard transform (HT) technique, which permits the S/N in CE to be improved, was applied to MEKC. Multiple sample injection of fluorescent analytes according to a Hadamard code sequence was performed using an optically gated sample injection technique, in which a sample plug was produced based on photodegradation by irradiation with an intense laser beam. The capillary and reservoirs were filled with a sample solution containing buffer components and SDS as a pseudostationary phase. A preliminary study confirmed that fluorescein ion could be photobleached in the presence of SDS. The optically gated sample injection technique was then applied to multiple sample injection, based on a Hadamard matrix. The S/N in the electropherogram obtained by HT-MEKC was improved substantially compared to that obtained by a single injection method. When the technique was applied to the separation of several amino acids labeled with FITC, the S/N ratio for each amino acid was enhanced, without any evidence of degradation in separation resolution. Moreover, HT-MEKC was applied to the analysis of amino acids contained in a Japanese beverage, resulting in improved S/Ns for the amino acids.

Laser‐Induced Fluorometry for Capillary Electrophoresis

“…When using cyclodextrin (CD) as a chiral selector, FITC‐labeled glutamic acid enantiomers are clearly separated in the transformed data with enhanced S/N ratios. Furthermore, Hadamard transformation using optically gated sample introduction was applicable to the MEKC separation of amino acids . Therefore, HT‐CE with optically gated sample introduction is useful for the sensitive detection of FITC‐labeled analytes with no degradation of resolution in the separations.…”

MEKC: A powerful tool for the determination of amino acids in a variety of biomatrices

“…To conclude this paragraph, we would like to mention the work by Hata et al . 82, who demonstrated the applicability to a MEKC separation of Hadamard transformation (HT), a technique that permits the S / N to be improved. A sample solution containing Phe, Glu, and Asp, labelled with FITC, was used in a demonstration of HT‐MEKC separation; 30 mM sodium borate buffer (pH 9.0) containing 30 mM SDS was the running buffer employed.…”

Cross-correlation capillary electrophoresis in unmodified commercial equipment

“…It has been used in conventional CE [18,19] and in microchip CE [14,17,21,22]. Hata et al have even reported using cross-correlation CE technique for MEKC analyses [23]. All cross-correlation CE experiments reported before have been done using some sort specific sample injection device that is not available in commercial equipment.…”