Development and evaluation of substoichiometric isotope dilution mass spectrometry as definitive method

将同位素稀释质谱法（IDMS）与亚化学计量学相结合，提出了一种新的分析方法——亚化学计量同位素稀释质谱法（SIDMS）。采用溶剂萃取和离子交换法对痕量铁（III）和铜（II）进行亚化学计量分离，采用微波诱导等离子体质谱（MIP-MS）和ICP-MS进行同位素测定。将这些方法应用于一些环境标准物质，对其准确度、精密度和实用性进行了评价。1)利用基于氢键的协同效应，考察了亚化学计量萃取铁（III）的效果。在过量的3,5-二氯酚作为增效剂的存在下，用亚化学计量量的4-异丙基邻苯二酮提取0.1马克杯水平的Jron（III）。2)考察了有机溶液中铁的MIP-MS测定的最佳条件。将铁的SIDMS应用于海藻标准物质（NIES No.9），铁的测定值与认证值吻合良好。3)对痕量铁（III）进行了亚化学计量离子交换分离。以亚化学计量量的环己烷-1,2-二胺四乙酸酯形成的阴离子铁（III）配合物通过阳离子交换从未反应的铁（III）中分离出来。可以期望用SIDMS测定长水平的铁。4)用二乙基二硫代氨基甲酸锌（II）在四氯化碳中进行亚化学计量提取铜（II），然后用亚化学计量量的钯（II）将提取的铜（II）反提到水相中。铜在10ng水平的测定是可以预期的。5)将铜的SIDMS应用于某海洋沉积物标准物质（NIES No.12）。测定的含量与NIES报告的参考值接近。

A new analytical method, substoichiometric isotope dilution mass spectrometry (SIDMS), was proposed by combining isotope dilution mass spectrometry (IDMS) with substoichiometry. Solvent extraction and ion exchange were studied for the substoichiometric separation of trace iron(III) and copper(II), and a microwave induced plasma mass spectrometer (MIP-MS) and ICP-MS were used for the isotope measurement. By applying these methods to some environmental reference materials, the following were evaluated : accuracy, precision and practicability.1) The substoichiometric extraction of iron(III) was examined using synergistic effect based on hydrogen bond. Jron(III) in 0.1 mug levels was extracted with a substoichiometric amount of 4-isopropyltropolone in the presence of an excess of 3,5- dichlorophenol as a synergist.2) Optimum conditions in the MIP-MS measurement were examined for iron in organic solutions. The SIDMS for iron was applied to a seaweed reference material (NIES No.9), and it was confirmed that the determined value of iron well agreed with the certified value.3) The substoichiometric ion exchange separation was examined for trace iron(III). The anionic iron(III) complex formed with a substoichiometric amount of cyclohexane-1,2-diaminetetraacetate was separated from unreacting iron(III) by the cation exchange. The determination of iron in l0ng levels by SIDMS can be expected.4) Copper(II) was substoichiometrically extracted with zinc(II) diethyldithiocarbamate in carbon tetrachloride, and then the extracted copper(II) was back-extracted with a substoichiometric amount of palladium (II) into the aqueous phase. The determination of copper in 10ng levels can be expected.5) The SIDMS for copper was applied to a marine sediment reference material (NIES No.12). The content determined was close to the reference value reported by NIES.