Sensitivity enhancement by on-line preconcentration and in-capillary derivatization for the electrophoretic determination of amino acids

✍ Scribed by Rosa M. Latorre; Javier Saurina; Santiago Hernández-Cassou

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 488 KB
• Volume: 22
• Category: Article
• ISSN: 0173-0835
• DOI: 10.1002/1522-2683(200112)22:20<4355::aid-elps4355>3.0.co;2-t

✦ Synopsis

Sensitivity enhancement by on-line preconcentration and in-capillary derivatization for the electrophoretic determination of amino acids

This study describes an application of on-line preconcentration by large-volume stacking in combination with in-capillary derivatization for enhancing spectrophotometric detection sensitivity in capillary electrophoresis. The method is illustrated by an example dealing with the determination of amino acids with 1,2-naphthoquinone-4-sulfonate as a labelling agent. Samples are dissolved in water in order to create a stacking process based on differences in the conductivity between this medium and a concentrated running buffer. The in-capillary derivatization is accomplished following a sandwich procedure in which the sample is inserted between two segments of reagent. Amino acid derivatives are obtained and separated in a fused-silica capillary with a sodium borate electrolyte buffer using 2-propanol as an organic modifier. The method is applied to the analysis of amino acids in pharmaceutical and feed samples. A good concordance between the predicted values and those obtained with the standard method is observed, with overall quantification error below 5%. The proposed procedure allows the detection limits sensitivity to be enhanced in 1000-fold with respect to conventional precapillary derivatization.