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砷是影响石油重整催化剂活性的有害元素。二乙基二硫代氨基甲酸银(Ag-DDC)光度法测定微量砷,近年来采用氯仿和三乙胺等有机碱代替吡啶,但多采用锌粒作为发生砷化氢的还原剂,还原时间长(40分～1小时)重现性欠佳。国内用硼氢化钠固体压片作还原剂的测定方法已有报导,但未见用注射法加入硼氢化钾溶液作为还原剂进行光度法测定的文献。我们在硫酸介质中,注入硼氢化钾溶液还原,用氮气吹出AsH_3,使还原时间缩短为3分钟,提高了结果的重现性。另外,将5毫升吸收液装入3厘米比色皿中进行吸光度测定,使测定灵敏度提高3倍。本法检出下限0.1微克砷,用于石油中ppb至ppm级砷的测定,相对标准偏差小于8.4%。
Arsenic is a harmful element that affects the activity of the petroleum reforming catalyst. Trace arsenic is determined by silver dithiocarbamate (Ag-DDC) spectrophotometry. In recent years, organic bases such as chloroform and triethylamine are used instead of pyridine. However, zinc particles are mostly used as reductant for arsine, and reduction time Long (40 minutes to 1 hour) poor reproducibility. Domestic sodium borohydride solid tablet as reducing agent determination method has been reported, but no injection by adding potassium borohydride solution as a reducing agent for photometric determination of the literature. We in the sulfuric acid medium, injected potassium borohydride solution reduction, nitrogen purged AsH_3, the reduction time reduced to 3 minutes, improve the reproducibility of the results. In addition, 5 ml of the absorbing solution was filled into a 3 cm cuvette to measure the absorbance, thereby increasing the assay sensitivity by a factor of three. The law detected a minimum of 0.1 microgram arsenic, used in the determination of ppb to ppm arsenic in petroleum, with a relative standard deviation of less than 8.4%.