离子色谱-非抑制电导法同时测定铵盐、四乙基铵、甲基三乙基铵

Simultaneous Determination of Ammonium, Tetraethylammonium and Triethylmethylammonium by Ion Chromatography with Non-suppressed Conductivity Detection

建立了离子色谱非抑制电导法同时分离测定铵根与两种季铵盐四乙基铵、甲基三乙基铵的方法。分别实验了在亲水性和疏水性阳离子交换色谱柱上三种铵类的分离效果,研究了使用不同淋洗液和流速情况下离子的分离情况,结果表明使用SH-Cation-101型疏水性阳离子色谱柱,淋洗液采用甲烷磺酸(5.0mmol/L),其中加入乙腈(7%),于0.8mL/min的流速条件下,三种铵类物质分离良好,其中结构极为相似的两种季铵盐四乙基铵和甲基三乙基铵分离度达到1.5以上,分离时间短,3种物质在13min内实现完全分离。采用国产离子色谱仪非抑制电导法检测,无需使用抑制器,成本低,操作简便可行。检测结果的灵敏度高,线性范围铵根为0.5～50mg/L,四乙基铵和甲基三乙基铵为5～500mg/L,相关系数均高于0.999,相对标准偏差均在3%以内,平均加标回收率在98.5%～101.2%。

A new method for simultaneously separating and determining ammonium and two kinds of quaternary ammonium salts（tetraethylammonium and triethylmethylammonium） using ion chromatography with non-suppressed conductivity detection was developed. The separation efficiency of the three kinds of ammonium on hydrophilic and hydrophobic cation exchange column as well as the effects of eluent and flow rate on separation were tested. The results showed that the best separation conditions were： SH-Cation-101 type hydrophobic cation chromatography column; （5.0 mmol/L） methylsulfonic acid containing 7% acetonitrile as eluent; and a flow rate of 0.8 mL/min. The degree of separation for the tetraethylammonium and triethylmethylammonium which have very similar structure was more than 1.5. The separation time is short, e.g, it only took 13 minutes for the three substances were completely separated. Analytical tests by ion chromatography with non-suppressed conductivity detection was completed with a domestic ion chromatography instrument. The method does not need a suppressor and is low-cost, simple and easy to follow. The method had high sensitivity. The linear range for ammonium was 0.5-50 mg/L, and for tetraethylammonium and triethylmethylammonium were 5-500 mg/L. The correlation coefficients were all above 0.999. The precision was less than 3% and average recoveries were between 98.7%-105.3%.