Determination of Trace Elements by Solid-phase Spectrophotometry after Collection on a membrane filter

1.海水中铀(VI)的测定铀(VI)以3-[4-(5-溴-2-pyridylazo)-3-hydroxy-N-propylanilino]propanesufonate(5-Br-PAPS)，)]的络合物形式，与塞菲拉明和高氯酸根离子形成离子对沉淀，固相分光光度法测定铀。在pH为7的乙二胺缓冲溶液中加入反式环己烷-1，2-二氨基四乙酸乙酯，可提高方法的选择性。除碳酸盐离子外，其他痕量元素和海水中的主要成分均不影响铀的测定。用超声波搅拌除去酸化海水样品中的二氧化碳离子，消除了碳酸盐离子的干扰。海水样品中铀的浓度为3.26ug/L，30-50毫升海水中铀的相对标准偏差为2.2%(n=21)。2.在pH 5的过氧化氢存在下，在乙二胺四乙酸和过量锌(II)的配体缓冲溶液中，钴(II)与2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(5-Br-PADAP反应。反应混合物用高氯酸酸化至pH 1.8，钴(III)-5-溴-PADAP在膜过滤器上收集。滤膜上的络合物用固相分光光度法测定。白葡萄酒中无机微量元素和主要成分不影响钴(II)的测定。酒样与水的比例为1：1可消除酒精的影响。10个不同的葡萄酒样品中钴的浓度在2.4-5.6mugLAMBDA之间。

1.Determination of uranium(VI)in seawaterUranium(VI) was collected on a membrane filter as a complex with 3-[4-(5-bromo-2- pyridylazo)-3-hydroxy-N-propylanilino]propanesufonate(5-Br-PAPS), together with the ion-pair precipitate formed between Zephiramine and perchlorate ions, and determined by solid-state spectrophotometry. The selectivity of the method could be improved with the use of trans-cyclohexane-1,2-diaminetetraacetic acid and an ethylenediamine buffer solution of pH 7. Except for carbonate ion, other trace elements and the major constituents of seawater did not affect the determination of uranium. The interference from the carbonate ion was eliminated by the removal of the ion as carbon dioxide from the acidified seawater sample with ultrasonic agitation. The concentration of uranium in a seawater sample was found to be 3.26 mugLAMBDA with a relative standard deviation of 2.2% (n=21) for 30-50 ml of seawater.2.Determination of cobalt(II) in white wineCobalt(II) was made to react with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(5-Br- PADAP) at pH 5 in the presence of hydrogen peroxide and a ligand buffer solution composed of ethylenediaminetetraacetic acid and an excess of zinc(II). The reaction mixture was then acidified to pH 1.8 by the addition of perchloric acid and the cobalt(III)-5- Br-PADAP was collected on a membrane filter. The complex on the filter was determined by solid-phase spectrophotometry. Inorganic trace elements and major constituents of white wine did not affect the determination of cobalt(II). The effect of alcohol could be eliminated by 1:1 dilution of wine samples with water. The concentration of cobalt in 10 different wine samples was in the range 2.4-5.6 mugLAMBDA.