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砷是污染地面水的主要有毒元素之一,有人认为砷(Ⅲ)比砷(Ⅴ)对人体的毒性更大。水中微量砷(Ⅲ)和砷(Ⅴ)的测定多用溶剂萃取或挥发分离后再用原子吸收法或原子荧光法测定,而利用锌还原及二乙基二硫代甲酸银光度法,灵敏度较低。本法以硼氢化钾作还原剂,调节pH为6—7,还原砷(Ⅲ)至砷化氢;然后加盐酸调节pH为2—3,加适量抗坏血酸还原砷(Ⅴ)为砷(Ⅲ),再加入硼氢化钾还原砷(Ⅲ)到砷化氢。两次还原得到的砷化氢用吸收瓶分别收集,以砷钼杂多酸结晶紫分光光度法直接测定。条件试验表明,在pH为6—7时,硼氢化钾只能还原砷(Ⅲ),而在pH≈1时,可以还原砷(Ⅴ),但由于酸性太强,反应速度过快,难以控制而使重现性欠佳,所以需先加入一定量的抗坏血酸还原砷(Ⅴ)到砷(Ⅲ)。本法以电磁搅拌器不断搅拌,可省去通氮气驱赶砷化氢的复杂操作及装置。水中存在的微量金
Arsenic is one of the major toxic elements that pollute surface waters. Some people think that arsenic (III) is more toxic to humans than Arsenic (V). Determination of trace arsenic (Ⅲ) and arsenic (Ⅴ) in water is mostly determined by atomic absorption method or atomic fluorescence spectrometry after solvent extraction or volatilization separation. However, the sensitivity of zinc reduction and diethyldithioformic acid silver photometry is relatively high low. In this method, potassium borohydride is used as a reducing agent to adjust the pH to 6-7 to reduce arsenic (III) to arsine; then hydrochloric acid is added to adjust the pH to 2-3, and arsenic (Ⅴ) , And then add potassium borohydride to reduce arsenic (III) to arsine. The arsine obtained from the two reductions were separately collected by absorption bottles and directly determined by arsenic molybdenum heteropoly acid crystal violet spectrophotometry. The condition tests show that potassium borohydride can only reduce arsenic (Ⅲ) when pH is 6-7, and arsenic (Ⅴ) can be reduced when pH≈1, but it is difficult to control due to too high acidity and too fast reaction rate So that reproducibility is not good, so the need to add a certain amount of ascorbic acid reduction of arsenic (Ⅴ) to arsenic (Ⅲ). This method of continuous stirring with a magnetic stirrer, eliminating the need to drive nitrogen gas arsenide complex operations and devices. Trace gold present in water