碱熔-钼锑抗分光光度法测定土壤磷指示剂的改良

Improvement of Indicator for Determination of Total Phosphorus in Soil by Alkali Fusion-Mo-Sb Anti Spectro-photometric Method

由于碱熔-钼锑抗分光光度法测定土壤中的总磷方法中,溶液的酸度决定磷钼蓝的形成及稳定,因此pH指示剂很重要。但是2,4-二硝基酚指示剂几乎不溶于冷水,经加热溶解冷却后有固体颗粒析出,影响pH显色判断,并且它又属易制爆化合物,其储存、使用的程序繁琐,给日常分析测试工作增加负担和难度。本文研究溴百里酚蓝做指示剂,使用程序便捷,颜色变化对比鲜明,易判断,不影响分析结果。

pH indicator is of great importance to the method for determination of total phosphorus in soil by alkali fusion–Mo-Sb anti spectro-photometric method in view of the formation and stability of phosphomolybdate blue determined by the acidity of solution.But the 2,4-dinitrophenol indicator is almost insoluble in cold water and precipitates out solid particles after heating,dissolving and cooling which affects pH judgment.The storage and use procedure of the 2,4-dinitrophenol indicator as an explosive compound are very tedious.This study uses bromothymol blue as an indicator which is characterized by easy to use,color changes with a sharp contrast and doesn’t affect the analysis.