偶氮氯磷mA-溴化十六烷基吡啶光度法测定化探样品中钍

Spectrophotometric Determination of Thorium in Geo-chemical Exploration Samples with Chlorophosphon-azo-mA and Cetypyridinium Bromide

铀试剂Ⅲ光度法测定钍一般能满足岩石矿物分析要求,但对ppm级钍的化探样品的分析,由于试剂质量问题难以达到要求。偶氮氯膦Ⅲ虽然灵敏度较高,但需用有机溶剂萃取,且稀土和铀的干扰严重。偶氮氯膦mA[2-(4—氯—2—膦酸—苯偶氮)—7—(3—乙酰苯偶氮)—1,8—二羟基萘—3,6—二磺酸)]作为稀土元素的显色剂[1,2].

This paper reports a new method for the spectrophotometric determination of trace thorium with chlorophosphonazo-mA and cetylpyridium bromide(CPB).In dilute formic acid medium at pH 1-3 thorium forms a blue-violet colour ternary complex with the above mentioned reagent.The complex exhibits maximum absorption at 680 nm and the value of molar absorption coefficient is found to be 1.41×10^(5).The concentration of thorium obeys Beer’s law in the range of 0-25μg/25 ml.When 743 cation exchange resin is used a 5%sodium citrate-0.05%EDTA solution is recommended as new eluant for separation and concentration of thorium.The precision is better than±4.79%.