一步离子交换-多接收电感耦合等离子体质谱法测定高钙生物样品的硼同位素组成

One-step Ion-exchange Separation and Measurement of Boron Isotope Ratios in High Calcium Biological Samples with by MC-ICP-MS

硼是生物样品(牙齿或骨骼)中重要的微量元素,其含量和同位素组成可以指示宿主的食物摄入、迁移和健康信息,因此生物样品中的硼同位素是重要的环境示踪剂。但生物样品中钙含量较高(>90%),无法采用常规的硼特效树脂分离流程进行硼同位素的分离富集。本文采用醋酸-醋酸铵缓冲液(pH=6.0)替代以往使用的氨水作为树脂再生溶液,将硼特效树脂吸附硼的pH值从8~9降至6.0,从而避免了富含钙的生物样品在碱性条件下(pH=8~9)容易生成沉淀的难题,只需一步离子交换就能富集生物样品中的硼。样品经分离后其中的硼同位素采用多接收电感耦合等离子体质谱(MC-ICP-MS)的"标准-样品-标准"交叉法进行测定。结果表明:采用一步离子交换法分离富集,MC-ICP-MS测定生物样品(牙齿)中硼同位素的测试精度小于0.42‰,达到与其他分离和测试方法相同的水平。该方法不仅适用于牙齿和骨骼等高钙生物样品的硼同位素示踪,且为高钙土壤和海洋沉积物样品的分析提供了借鉴。

BACKGROUND:Boron is an important trace element in high calcium biological samples,such as teeth and bones.Boron content and isotopic composition are important environmental tracers.However,the calcium content in biological samples is relatively high(>90%),and it is impossible to separate and enrich boron isotopes by using the conventional boron-special resin separation process.OBJECTIVES:To establish an efficient method for treatment of boron isotopes in high calcium samples.METHODS:An acetic acid-ammonium acetate buffer(pH=6.0)was used as a resin regeneration solution to replace ammonia.The adsorption pH of boron resin,boron-special resin(Amberlite IRA 743)was dropped from 8-9 to 6.0,thus the precipitation was avoided during digestion of the high calcium biological samples under alkaline conditions.Only one step of ion exchange is necessary to enrich boron in biological samples.The boron isotope of samples after separation was determined by multi-collector inductively coupled plasma-mass spectrometry(MC-ICP-MS)using a standard-sample-standard bracketing method.RESULTS:A one-step ion exchange method was used for separation and enrichment.The analytical accuracy of MC-ICP-MS for the determination of boron isotopes in teeth was less than 0.42‰,reaching the same level as other separation and determination methods.CONCLUSIONS:This method is not only suitable for boron isotope tracing of high calcium biological samples such as teeth and bones,but also provides a reference for the analysis of high calcium soil and marine sediment.