【摘要】 为了给铅同位素示踪技术在研究茶叶中重金属铅来源的应用奠定基础,通过大量的茶叶炭化、灰化条件试验和铅的分离、纯化、富集与质谱测定试验,拟定了一套茶叶中铅同位素比值的测定方法:将称好的茶叶置于瓷坩埚中,在电热板上小火炭化完全后,移入马弗炉中灰化,用盐酸溶解灰分,转化为混合酸介质,然后上柱分离解吸,蒸干并上质谱测定。该法打破传统,改用盐酸溶解灰分,克服了用硝酸溶样总是有棕色沉淀物的难点。利用这一流程测得的茶叶样品的207Pb/206Pb的精度(2σ)优于±0.05%。208Pb强度一般均在1V以上。监控分析流程的国际标准物质NBS981的207Pb/206Pb为0.91449±0.00004(其证书值为0.91464±0.00033),全流程本底铅为1.6×10-8量级。更多还原

【Abstract】 To lay a foundation for the application of Pb isotope tracing to studying the main sources of the heavy metal Pb, a large number of carbonization and ashing tests of teas as well as isolation and accumulation of Pb and their mass spectrometry measurement experiments are conducted, and a set of method of measuring Pb isotope compositions in teas is developed. Firstly, the porcelain crucibles with weighed teas are put on an electric hot plate with voltage between 130～145 V to make complete carbonization of the tea samples, then the crucibles are put into a muffle for the ashing of the carbonized teas; secondly, the ashes of the teas are dissolved using hydrochloric acid, which overcomes the difficulty that there is always brown precipitate when repeatedly using nitric acid to dissolve the samples; thirdly, the solutions are dried and are added with mixed acid of HCl and HBr, then centrifuging, and are put through the anion-exchange-resin columns, and the eluting solutions are dried; fourthly, the Pb isotopic ratios are measured with mass spectrometry. The standard deviations in 2σof 207Pb/206Pb of the teas are better than ±0.05%. The intensities of 208Pb ions are usually higher than 1 V. Fifteen analyses of the National Bureau of Standards SRM981 over a 3-week period gives the following results: 207Pb/206Pb=0.914 49±0.000 04 (the national standard reference value of NBS 981 is 0.914 64±0.000 33). Processing blanks range from 16 to 18 ng of lead.更多还原