Study on ion chromatography (IC) for the low-molecular weight amines]
低分子量有机胺的离子色谱法研究

In this paper the retention behaviors of low-molecular weight amines (methylamine, dimethylamine, trimethylamine, ethylamine, propylamine sec-butylamine, n-butylamine, ethanolamine, diethanolamine, triethanolamine) on Ionpac CS12 column were for the first time studied with modern ion chromatograph. The column is usually used for routine analysis of inorganic cations and it strongly retains these organic amines. So they are difficult to be eluted by dilute aqueous HCl alone. The addition of acetonitrile (ACN) as a modifier can improve the peak shape and resolution. Influences of concentrations (ACN & HCl) on separation and detection were investigated separately and the chromatographic conditions were optimized. Aqueous solution of 20 mmol/L HCl containing 1% or 5% ACN (5% for higher molecular weight amines) was used as the eluant with a flow rate of 1.0 mL/min to optimize the column efficiency. In addition to methylamine, ethanolamine and diethanolamine, all other amines can well be separated from each other. According to the structure they may be divided into three classes: (a) methylamine, dimethylamine and trimethylamine; (b) diethanolamine and triethanolamine; (c) ethylamine, propylamine, sec-butylamine and n-butylamine. The three classes of mixtures were separately injected into the IC system and resolutions being obtained by the developed method were: (a) 1.25 and 1.52; (b) 1.20; (c) 2.45, 2.05 and 2.10 respectively. The new method is characterized by rapidity, convenience, sensitivity and simultaneous determination of some inorganic cations. It was separately used for determination of diethanolamine, triethanolamine, NH4+ in explosive samples and of Na+, K+, MgZ+, Ca2+ in water supply with satisfactory results. The retention mechanism of amines on CS12 column and effect of organic modifier were also preliminarily explored.