柱切换离子色谱法测海水中的草酸根离子

Determination of Oxalate in Seawater Using Ion Chromatography Couple of Column Switching Technique

建立了柱切换离子色谱法测海水中草酸根离子的方法。采用Dionex Ion Pac AS11-HC(4 mm×250 mm)阴离子分离柱和AG11-HC(4 mm×50 mm)保护柱分离海水中草酸根,采用20 mmol/L KOH淋洗液,流速为1.0 m L/min等度淋洗,通过柱切换除去海水中大部分的高浓度阴离子(Cl^-、SO_4^(2-)和Br^-),分离出的C_2O_4^(2-)收集于富集柱,然后经过阀切换,将目标离子从富集柱上洗脱,进入阴离子分析柱分离,此时淋洗液换成30 mmol/L Na OH溶液,流速为0.8 m L/min等度淋洗,电导法检测。结果表明,在线性范围为0.5~10.0 mg/L内其相关系数为0.999 4,相对标准偏差为1.48%(n=6),最低检出限为4.35μg/L(S/N=3),所得样品回收率为85.3%~110.0%。该实验方法简单方便,且具有较好的重现性和较低的检出限,可用于检测海水中的草酸根离子。

A method for determination of oxalate in seawater by ion chromatography coupe of column switching was established.Sample separation method was as follows： firstly,seawater was injected on an analytical column（ Dionex Ion Pac AS11-HC,4 mm×250 mm） and a guard column（ AG11-HC,4 mm×50 mm）,the elution was 20 mmol/L KOH at a 1. 0 m L/L flow rate.Secondly,high concentration anions（ Cl^-,SO4^2- and Br^- and matrix in seawater were removed by setting an appropriate valve switching time,while the C2O4^2- was collected a concentrator column. Thirdly,the C2O4^2- in concentrator was eluted on a Dionex Ion Pac AS19（ 4 mm×50 mm） and a AS19（ 4 mm×250 mm） column by another valve switching,the elution was 30 mmol/L Na OH at a 0. 8m L/L flow rate.Finally,the C2O4^2- was separated by chosen column and detected using conductivity detection.Under the separation conditions,the method showed good linearity（ r = 0. 999 4） in the range of 0. 5 - 10. 0 mg/L and satisfactory repeatability（ RSD =1. 48%,n = 6）.The limit of detection was 4. 35 μg/L（ S/N = 3）.The utilization of the method was demonstrated by the analysis of seawater,with satisfactory spiked recoveries of ammonium between 85. 3% and 110. 0%. The result showed that the single pump column-switching system was convenient and practical for the determination of low level.