Analysis of aliphatic amines using head‐column field‐enhanced sample stacking in MEKC with LIF detection

This paper describes the use of head-column field-enhanced sample stacking for on-line sample concentration in MEKC; the method has been applied to the determination of C1-C9 aliphatic amines after their pre-capillary derivatization with 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA). The optimum derivatization, on-line concentration and separation conditions for these aliphatic amines were investigated in detail. The optimized molar ratio of CBQCA to amines was found to be 120:1, and 50 mmol/L borate buffer (pH 9.5) was used for derivatization in order to achieve high efficiency. Nine imidazole aliphatic amines were baseline separated within 12 min by using 50 mmol/L of sodium borate (pH 9.5) and 15 mmol/L of SDS as running buffer. Under the optimum conditions, the detection limits of these nine aliphatic amines ranged from 1.2 to 3.8 pmol/L. S/N=3, which was about 49-173-fold lower than those of conventional sample injections. After validation, the developed method was applied to the determination of C1-C9 aliphatic amines in river water with the average recoveries of 86.7-105%.