Abstract
A pressurized CEC (pCEC) coupled with onโcolumn chemiluminescence (CL) detection was developed for direct determination of amino acids, which was based on the principle of an enhanced effect of Cu(II)โamino acid complexes on the CL reaction between luminol and hydrogen peroxide in alkaline solution. The effects of some important factors on pCEC separation and CL intensity were systemically investigated. Baseline separation of amino acids including Lโhistidine (LโHis), Lโthreonine (LโThr), and Lโtyrosine (LโTyr) was achieved by using a monolithic column with a mobile phase of 5.0ร10^โ3^ mol/L phosphate buffer at pH 8.0 that contained 25% v/v methanol and 5.0ร10^โ4^ mol/L luminol and 1.0ร10^โ5^ mol/L Cu(II) at an applied voltage of โ5 kV. The calibration curves of the analytes by plotting the peak height against corresponding concentration were linear over the range of 3.2ร10^โ6^ โผ๏ธ 3.2ร 10^โ4^ mol/L for LโHis, 4.1ร10^โ6^ โผ๏ธ 4.1ร10^โ4^ mol/L for LโThr, and 6.0ร10^โ7^ โผ๏ธ 3.0ร10^โ4^ mol/L for LโTyr. The LODs for LโHis, LโThr, and LโTyr were 6.4ร10^โ7^, 8.4ร10^โ7^, and 3.0ร10^โ7^ mol/L (S/N = 2), respectively. The proposed method was applied to the analysis of amino acid injection sample with satisfactory results. Mean recoveries for three amino acids were from 84.3 to 89.6%.