二溴对甲基偶氮甲磺光度法同时测定钙和钡

Study on the Simultaneous Spectrophotometric Determinationof Calcium(Ⅱ) and Barium (Ⅱ) with Dibromo-p-methyl-methyl sulfonazo

研究了新显色剂二溴对甲基偶氮甲磺（ＤＢＭ－ＭＳＡ）与钡、钙的显色反应，建立了一种同时测定钙和钡的方法。在０．４ｍｏｌ／Ｌ硝酸介质中，钡、钙与试剂发生灵敏的显色反应，均形成１：２蓝色络合物。钙与试剂形成的络合物最大吸收在６４０ｎｍ，表观摩尔吸光系数为１．８４×１０４，０～３０μｇＣａ２＋／２５ｍＬ符合比尔定律；钡与试剂形成的络合物最大吸收在６３４ｎｍ，表观摩尔吸光系数为７．３１×１０４．绝大多数金属离子不干扰钙和钡的测定，已用于钡硅合金中钙、钡的同时直接测定，结果令人满意．

A new reagent dibromo-p-methyl-methyl sulfonazo (DBM-MSA) was studied as a sensitve and high selective chromogenic reagent for calcium (Ⅱ) and barium (Ⅱ) in this paper. In 0.4mol/L HNO3 medium, DBM-MSA reacted with Ca(Ⅱ) and Ba(Ⅱ) to form a 1: 2 blue complex, respectively. The absorption maximum of calcium complex lies at 640nm withan apparent molar absorptivity of 1.84×10~4, Beer's law is obeyed in the range of 0-30μg Ca2+/25mL. The absorption maxi mum of barium complex lies at 634nm with an apparent molar absorptivity of 7.31×10~4, Beer's law is obeyed in the offersof 0-25μg Ba2+/25mL. RelatiVely large amounts of co-existing ions including noble metal ions can be beared. The proposedmethod has been applied to the simulatneous determination of calcium and barium in silicon barium alloys with satisfactory results.