摘要
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~-,SO_4~(2-) and Br~-) and matrix in seawater were removed by setting an appropriate valve switching time,while the C_2O_4~(2-) was collected a concentrator column. Thirdly,the C_2O_4~(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 C_2O_4~(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.
引文
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