重铬酸钾容量法测定地质样品中的有机碳

Determination of Organic Carbon in Geological Samples by Potassium Dichromate Volumetric Method

目前,地质样品中有机碳的测定方法有干烧法(高温电炉灼烧)和湿烧法(重铬酸钾氧化)两大类。干烧法要求实验条件苛刻、操作繁琐、不易掌握、受碳酸盐的干扰,湿烧法虽然操作比较简单,但方法受样品中还原性物质的干扰,如氯根、亚铁等,通过优化熔矿温度、熔矿时间、熔剂浓度的选择,考察氯离子的干扰实验。结果表明,样品中含氯化物低的样品通过加入0.1 g硫酸银消除干扰,样品中含氯化物高的样品通过高温灼烧减量消除干扰。氧化指示剂选用邻菲啰啉或苯二氨基苯甲酸。方法的相对标准偏差(RSD)在0.80%~4.4%,准确度(RE)在-3.2%~1.2%,方法适用于土壤、水系沉积物、岩石等地质调查样品中有机碳的测定。通过标准物质验证,方法技术指标满足地质行业规范(DZ/T 0130.4—2006)中有机碳的分析要求,建立了一种简单、快捷、经济、准确的测定地质样品中有机碳的测定方法,满足地球化学调查批量样品生产的需要。

At present,the determination methods of organic carbon in geological samples include dry burning method(high temperature electric furnace burning)and wet burning method(potassium dichromate oxidation).The dry burning method requires harsh experimental conditions,cumbersome operation,difficulty in mastering,and is interfered from carbonate.Although the operation of the wet burning method is relatively simple,the method is disturbed by the reducing substances in the sample,such as chlorine,ferrous,etc.The interference test of chloride ion was carried out by optimizing the melting temperature,melting time and flux concentration.The results showed that samples with low chloride content were eliminated by adding 0.1 g of silver sulfate to eliminate interference,and the samples with high chloride content were eliminated by high temperature ignition reduction.The oxidation indicator was selected as phenanthroline or phenyldiaminobenzoic acid.The relative standard deviation(RSD)of the method was between 0.80%and 4.4%,and the accuracy(RE)was between-3.2%and 1.2%.This method was suitable for the determination of organic carbon in soil,stream sediment,rock and other geological survey samples.Through the verification of standard materials,the technical indicators of the method meet the requirements of organic carbon analysis in the geological industry standards(DZ/T 0130.4—2006).A simple,fast,economical and accurate method for the determination of organic carbon in geological samples was established to meet the needs of geochemical survey batch sample production.