Development of a Packed Precolumn for Capillary Gas Chromatographic Analysis of Amines in Acidic Aqueous Solution

This paper describes an optimization of the analysis of amines in aqueous solution. Direct injection of the acidic sample (HCl 0.12 N) is performed by the coupling of packed precolumn with a capillary column. The basic support efficiently traps residual vapors of hydrochloric acid and water at the injection time; the capillary chromatographic performance is maintained. The precolumn coupling with PoraPLOT Amines capillary column enables a separation and quantification of the lower volatile aliphatic amines (methylamine, dimethylamine, trimethylamine and ethylamine). The ammonia addition to the solution (200 ppm NH₃) reduces amine adsorption in the column. The analysis repeatability is about 5% for a 50μM amine mixture and 21% for the quantification limit of 0.5 μM with a sensitive and specific nitrogen phosphor detector. The precolumn avoids using split injection (sensitivity increased). Other nitrogen compounds can be analyzed by this system: aromatic amines (aniline) and unsaturated nitrogen heterocycles (pyridine). This new technique increases the chromatographic performances in comparison with usual methods; its automation is possible.