过硫酸铵氧化-二苯碳酰二肼分光光度法测定总铬

摘要

In Water and Wastewater Analysis（Fourth Edition）,the total chromium was determined with oxidation of ferrous ammonium sulfate using ammonium sulfate titration.The detection limit of this method is 1 mg/l which is much higher than the measured values of total chromium in general industrial wastewater（less than 0.5 mg/l）.Determination of total chromium by potassium permanganate oxidation method is easy to generate manganese dioxide,a kind of brown precipitate.Therefore,the acid digestion of wastewater samples is adopted by oxidizing trivalent chromium into hexavalent chromium using ammonium sulfate.Under the catalyst effects of silver nitrate and manganese sulfate as indicator,diphenylcarbazide spectrophotometric method achieved good effect.This method lowers the detection limit to 0.003 mg/l.It is easy to operate,simple and accurate.%《水和废水分析方法第四版》中，用过硫酸铵氧化硫酸亚铁胺滴定法测定总铬，此方法检出限为大于1mg／1，远高出了一般工业废水总铬的测定值，不适用于测定一般工业废水总铬（小于0．5mg／1）高锰酸钾氧化法测定总铬又易生成棕色的二氧化锰沉淀。因此，采用强酸消解废水样，用过硫酸铵氧化三价铬成六价铬，在硝酸银的催化作用下，以硫酸锰做指示剂，酸溶液中，过硫酸铵氧化三价铬，用二苯碳酰二肼光度法测定，有很好的效果。这样大大降低了方法检出限（0．003mg／1），易操作，方法简单，准确度高，满足了废水监测的需要。