Amino acids determination using capillary electrophoresis with on-capillary derivatization and laser-induced fluorescence detection

Free amino acids have been derivatized on-capillary with 3-(2-furoyl)quinoline-2-carboxaldehyde (FQ) and analyzed using a laboratory-made capillary electrophoresis apparatus with laser-induced fluorescence detection. Several parameters that control on-capillary derivatization of amino acids, including pH, mixing time, reaction time, concentration of the derivatization reagents (potassium cyanide and FQ) and solvent of FQ, as well as the temperature of mixing and reaction were optimized. Repeatabilities better than 1.8% for migration time and 7.8% for peak height were obtained. Assay detection limits for the different amino acids ranged from 23 nM for glycine to 50 nM for lysine and glutamic acid. The methods developed were applied to the analysis of several amino acids in pharmaceutical preparations and plasma samples. Results showed a good agreement with those obtained using an amino acid autoanalyzer for the same samples.