马一嘉,罗冰虹,谭凯馨

硫在作物生长过程中必不可少的营养元素之一,主要参与作物生理代谢及生长发育。因此,土壤中硫的含量一直是人们关注的热点,快速准确的检测方法也成为人们研究土壤中硫的关键。在高温燃烧碘量法测定土壤硫含量中,碘酸钾溶液滴定亚硫酸时,对于低含量样品,滴定终点的判断较为困难。通过大量的试验,采用硫代硫酸钠滴定吸收器中反应后剩余的碘酸钾溶液,滴定终点由蓝色消失为无色。终点便于肉眼的观察,提高了分析结果的准确性和再现性；采用EXCEL中的LINEST函数回归标准物质滴定校准工作曲线,方法简便快速。通过国家一级标准物质的分析验证,方法准确度高、精密度好,适用于大批量土壤样品中低含量硫的测定。

Optimization of method for determination of total sulfur in soil by high temperature combustion iodine method

In combustion iodimetry method for the determination of sulphor content in soil, when sulfurous acid titrated by potassium iodate in the low content samples, the titration end point is difficult to judge. The host of experiments, the use of sodium thiosulfate reactiong absorber remaining in the potassium iodate solution, the titration end point disappears from blue to colorless, for facilitating visual observation, the analysis results to improve the accuracy and reproducibility. Using excel linest function of the standard of material titration curve calibrated work method was simple, The method has been tested by the determinationg of Sulphor in national standard reference materials and the results are in good agreement with certified values. The improved method is suitable for large quantities of soil samples with low sulfur content determination.