离子交换色层法测定低浓度铵态氮水样的氮同位素研究  

Determination of Nitrogen Isotope of Water Samples with Low Ammonium Nitrogen by Ion Exchange Method

作　　者：胡婧[1] 刘卫国[1,2] 

机构地区：[1]中国科学院地球环境研究所,黄土与第四纪地质国家重点实验室,陕西西安710075 [2]西安交通大学人居环境与建筑工程学院,陕西西安710049

出　　处：《岩矿测试》2013年第3期495-501,共7页Rock and Mineral Analysis

基　　金：黄土与第四纪地质国家重点实验室开放基金(Y15200B214);中国科学院地球环境研究所创新基金(Y151121214)

摘　　要：采用氯化铵、氯化钾为原料的离子交换色层法结合扩散法处理低浓度铵态氮水样,测定其铵态氮同位素时,减小全流程空白、避免同位素分馏、获取准确的铵态氮同位素值是需解决的关键问题。本文建立一套尽可能密闭的离子交换系统,避免了在大气环境下低浓度铵态氮水样在离子交换色层预处理过程中的污染;采用蠕动泵过柱的方法,调节蠕动泵的转速控制氯化铵溶液的过柱速率为1.2 L/h,洗脱速率为0.2 L/h,缩短了样品处理时间,减少了空气对铵态氮样品的污染,样品中的NH4+可完全被阳离子交换树脂吸附,铵态氮回收率为93.5%～102.8%,且不会引起氮同位素分馏;将优级纯氯化钾试剂置于450℃马弗炉中灼烧24 h,降低了氯化钾试剂引入的铵态氮污染。建立的方法使全流程的铵态氮空白浓度低于检出限0.02 mg/L,解决了在大气环境下采用离子交换色层法处理低浓度铵态氮水样的污染问题,加速了样品前处理的过程,提高了样品处理效率。When theδ^15N-NH4 in water samples is pretreated by using the ion exchange and diffusion method with NH4Cl and KCl, the key problem is how to reduce the blank, avoid isotopic fractionation and yield accurate isotope results. In this study, a closed ion exchange system was set up to prevent the small amount of NH4 contamination to the water samples. Furthermore, the sample and elution flow rates of 1.2 L/h and 0.2 L/h respectively were achieved by adjusting the speed of a peristaltic pump. Thus, both the experiment time and the contamination were reduced. In addition, all of the NH4 in the sample is absorbed on the ion exchange resin and the N recoveries were from 93.5% to 102.8%. Therefore, the whole process will not cause isotopic fractionation. The blank introduced by KC1 was reduced by being heated at 450℃ for 24 h. As a result, the blank ion exchange was reduced to below the detection limit of 0.02 mg/L by using the closed ion exchange system. The problem of contamination for water sample pretreatment in air was solved. The process was accelerated and efficiency was improved.

关 键 词：低浓度铵态氮水样 铵态氮同位素 离子交换色层法 扩散法 元素分析仪-同位素比值质谱法 

分 类 号：P641[天文地球—地质矿产勘探] O628[天文地球—地质学]