Effect of Surfactants on detection and separation of 4-Cl-7-nitrobenzofurazan derived amino-acids by chip-based capillary electrophoresis

The effect of various surfactants and solvents on the fluorescence properties of the 4-chloro-7-nitrobenzofurazan (NBD-CI) derived amino-acids was studied. The experimental conditions for the derivatization reaction between NBD-CI and amino acids,and those for chip-based capillary electrophoresis separation-laser induced fluorescence detection (CCE-LIF) of the amino acid derivatives were optimized. It was found that above their critical micelle concentrations, cationic surfactant CTMAB sensitized the fluorescence intensity of NBD-Cl derived arginine, glutamic acid, and aspartic acid, while non-ionic surfactant Brij-35 did the fluorescence intensity of the NBD-Cl derived phenylalanine and arginine. It was observed that six NBD-Cl derived amino acids of arginine, phenylalanine, alanine, glycine, glutamic acid and aspartic acid were CCE separated separated within 70 s in a 15-mmol/L, pH 9.2 borate buffer containing 5 mmol/L Brij-35 and 20% acetonitrile additives, the resolution of the partially overlapped alanine and glycine derivatives being 0.91, and the detection limits of the six derived amino acids were 0.27 - 1.6 mu mol/L..