重铬酸钾容量法测定盐碱土中有机碳  

Determination of organic carbon in saline alkali soil by potassium dichromate volumetric method

作　　者：刘春霞[1] LIU Chun-xia(Henan Province Rock&Mineral Testing Centre,Ministry of Land and Resources Key Laboratory of Precious Metals Analysis Technology,Zhengzhou 450012,China)

机构地区：[1]河南省岩石矿物测试中心,国土资源部贵金属分析技术重点试验室,河南郑州450012

出　　处：《化学工程师》2023年第9期33-37,共5页Chemical Engineer

基　　金：河南省自然科学基金资助项目(豫自然资函[2021]157号-4)。

摘　　要：建立了重铬酸钾滴定法测定盐碱土试样中有机碳的方法。通过加入0.1g Ag_(2)SO_(4)消除试样中少量Cl^(-)的干扰,在试样中Cl^(-)含量大于2.0×10^(4)mg·kg^(-1)时,可采用灼烧差减法消除其干扰。实验表明,选择恒温电热板,以0.4mol·L^(-1)重铬酸钾-硫酸消解试样,利用邻菲啰啉作突变指示剂提高测定结果的准确性;采用高温灼烧后的SiO_(2)作为空白有效降低了方法的检出限。方法检出限为0.063%、定量限为0.21%。测定不同性质的国家一级标准物质(土壤、水系沉积物)中有机碳,结果与认定值的相对误差RE为-3.15%~1.15%,对数差△lg C为-0.073%~0.0292%,相对标准偏差RSD(n=12)为0.8%~4.41%。本方法操作简单、快捷经济、准确,检出限低、测定范围广,能够满足地球化学调查项目大通量样品的检测需求。A potassium dichromate titration method was established for the determination of organic carbon in saline alkali soil samples.The interference of a small amount of chloride ions in the sample was eliminated by adding 0.1g Ag_2SO_4,and the interference of chloride ions in the sample could be eliminated by cauterization different subtraction method when the content of chloride ions in the sample was more than 2.0×10^(4) mg·kg^(-1).The experiment showed that selecting a constant temperature electric heating plate,digesting the sample with 0.4mol·L^(-1)potassium dichromate-sulfuric acid,and using o-phenanthroline as a mutation indicator improved the accuracy of the determination results;the detection limit of the method was effectively reduces by using the high-temperature calcined silica as a blank.The detection limit of the method was 0.063%,and the quantification limit was 0.21%.The relative error RE of the results of the determination of organic carbon in different national first-class standard substances(soil,water sediment) and the certified value was-3.15%~+1.15%,the logarithmic diviation lg C was-0.073%~0.0292%,and the relative standard deviation RSD (n=12) was 0.8%~4.41%.The method is simpleast,economical,accurate with low detection limit and wide measurement range,and can meet the detection requirements of large flux samples in geochemical survey projects.

关 键 词：重铬酸钾容量法 有机碳 氯离子 干扰及消除 

分 类 号：O613.71[理学—无机化学]