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用湿法测定样品中的汞,一般均需要消化过程,使有机汞转为无机汞,然后用原子吸收法或萃取比色法测定.消化方法有H_2SO_4—KMnO_4法,HNO_3—H_2SO_4—KClO_3法,HNO_3—H_2SO_4—V_2O_5法……等.这些方法,消化后一般均用盐酸羟胺消除氧化剂,在双硫腙比色法中,由于反应产生的游离氯,能使双硫腙氧化褪色而影响测定(1),不少文章(2)(3)介绍使用Na_2SO_3除去残存微量氯气,但效果不好,CharIes(2)认为过量Na_2SO_3会导致汞的结果偏低,因此只能按计算量加入.有些文章(4)(5)介绍用盐酸羟胺还原后开盖放置半小时,以去除残余氯.经试验我们发现了两对新的还原剂——尿素、硫酸亚铁(用在V_2O_5法),草酸钠、硫酸亚铁(用在H_2SO_4—KMnO_4法),它们无需特别放置能有效地除去上述氧化剂的干扰,消化后、结合使用CHCI_3—CCI_4混合溶剂的双硫腙比色法(6)能方便和准确地测定土壤及污水中痕量汞.
The determination of mercury in the sample by the wet method generally requires the digestion process to convert the organic mercury into inorganic mercury and then determined by the atomic absorption method or the extraction colorimetric method. The digestion methods include the H_2SO_4-KMnO_4 method, the HNO_3-H_2SO_4-KClO_3 method, HNO_3-H_2SO_4-V_2O_5 method ... etc .. These methods are generally digested with hydroxylamine hydrochloride to eliminate the oxidant, in the dithizone colorimetric method, due to the reaction of free chlorine, dithizone oxidation can fade and affect the determination of ( 1), many articles (2) (3) introduce the use of Na_2SO_3 to remove traces of residual chlorine, but the results are not good. CharIes (2) thinks that the excess of Na_2SO_3 will lead to the low result of mercury and therefore can only be calculated by calculation. (4) (5) Introduction Were exposed to hydroxylamine hydrochloride to open the lid for half an hour to remove residual chlorine.We found two pairs of new reductants - urea, ferrous sulfate (used in the V 2 O 5 method), sodium oxalate , Ferrous sulfate (used in H_2SO_4-KMnO_4 method), they do not need special place to effectively remove the interference of the above oxidant, after digestion, combined with CHCI_3-CCI_4 mixed solvent dithizone colorimetric method (6) can be convenient and accurate Determination of trace mercury in soil and sewage.