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.
Latorre
R M
RM
Department of Analytical Chemistry, University of Barcelona, Spain.
Saurina
J
J
Hernández-Cassou
S
S
D000596:Amino Acids / Q000032:analysis*; D002021:Buffers; D019075:Electrophoresis, Capillary / Q000379:methods*; D012680:Sensitivity and Specificity
D000596:Amino Acids; D002021:Buffers