Heart-cutting 2-D CE using multiple detection points for chiral analysis of native amino acids

A new methodology based on heart-cutting 2-D CE in a single capillary was developed for the chiral separation of a mixture of 22 underivatized amino acids. The first dimension is performed in an achiral BGE (2.3 M acetic acid, pH 2.1) allowing the separation of the analytes as a function of their charge-to-radius ratio. A selected fraction from the first dimension is then separated in the second dimension in the presence of a chiral selector (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid. Since the introduction of the second electrolyte is performed by pressure mobilization, capillaries with small id of 10 microm are used to limit the peak broadening due to Taylor dispersion. Double capacitively coupled contactless conductivity detector is used for monitoring the selection and the isolation of the fraction at the different steps of the analysis (voltage and pressure mobilization steps). This double detection allows calculating the voltage and pressure stop times in real-time analysis. This new methodology is applied with success for the chiral separation of different amino acids (D,L-Tyr, D,L-Trp and D,L-Thr) contained in a mixture of 22 native amino acids.