Ruiz Encinar Jorge, Rodriguez Gonzalez Pablo, García Alonso J Ignacio, Sanz-Medel Alfredo
Department of Physical and Analytical Chemistry, Faculty of Chemistry, Julian Claveria, Oviedo, Spain.
Anal Chem. 2002 Jan 1;74(1):270-81. doi: 10.1021/ac010551n.
Different liquid-solid extraction techniques, including room-temperature leaching with mechanical shaking, ultrasonic, and microwave-assisted extractions, have been evaluated for the quantitative speciation of tin for mono-, di-, and tributyltin (MBT, DBT, and TBT, respectively) in PACS-2 and BCR-646 certified reference materials. A methanol-acetic acid mixture was used as the extractant reagent in all cases. For this purpose, a mixed spike containing 119Sn-enriched MBT (79.7 At%), 118Sn-enriched DBT (86.7 At%), and 119Sn-enriched TBT (83.1 At%), was synthesized, characterized, and used for isotope dilution analysis. The isotopic composition of the mixed spike was determined by gas chromatography/ICPMS after aqueous ethylation using sodium tetraethylborate, and the determination of the concentration of the different species in the spike was performed by means of reverse isotope-dilution analysis using natural MBT, DBT, and TBT standards. In the analysis of the certified sediments, the sample was spiked with the mixed spike, extracted under different conditions, derivatized with sodium tetraethylborate, and extracted into hexane, and the isotope ratios 120/118 and 120/119 were measured as peak area ratios for all butyltin species after GC/ICPMS. Mass bias was corrected using a derivatized natural standard every three sample injections. Sequential degradation reactions during extraction (from TBT to DBT, from DBT to MBT, and from MBT to inorganic tin) were assumed, and mathematical equations were developed that allowed the determination of the correct species concentration and the decomposition factor for each of the transformation reactions. For ultrasonic extraction and mechanical shaking, negligible degradation reactions were observed. However, for microwave assisted extractions, degradation factors up to 7% (TBT to DBT) and 16% (DBT to MBT) were obtained for both reference materials when high-MW energy was applied in the extraction step. For the three extraction techniques tested, the DBT and TBT concentration values obtained for PACS-2 closely matched the certified values. However, for MBT the concentrations found by microwave and ultrasonic extraction were much higher than the certified value. This was not the case for mechanical shaking. The results obtained for BCR-646 using microwave assisted extraction were in good agreement with the certified values for all tin species.
已对不同的液固萃取技术进行了评估，包括室温机械振荡浸提、超声辅助萃取和微波辅助萃取，以对PACS - 2和BCR - 646标准参考物质中的单丁基锡、二丁基锡和三丁基锡（分别为MBT、DBT和TBT）进行锡的定量形态分析。在所有情况下均使用甲醇 - 乙酸混合物作为萃取试剂。为此，合成了一种含有富集(^{119}Sn)的MBT（79.7原子%）、富集(^{118}Sn)的DBT（86.7原子%）和富集(^{119}Sn)的TBT（83.1原子%）的混合标样，对其进行了表征，并用于同位素稀释分析。混合标样的同位素组成通过使用四乙基硼酸钠进行水相乙基化后，采用气相色谱/电感耦合等离子体质谱法测定，标样中不同形态的浓度通过使用天然MBT、DBT和TBT标准物质的反向同位素稀释分析来确定。在对标准沉积物进行分析时，向样品中加入混合标样，在不同条件下进行萃取，用四乙基硼酸钠进行衍生化，然后萃取到己烷中，在气相色谱/电感耦合等离子体质谱法测定后，测量所有丁基锡形态的(^{120}/^{118})和(^{120}/^{119})同位素比值作为峰面积比。每进样三个样品就使用衍生化的天然标准物质校正质量偏差。假定萃取过程中存在连续降解反应（从TBT到DBT，从DBT到MBT，从MBT到无机锡），并建立了数学方程，可用于确定每种转化反应的正确形态浓度和分解因子。对于超声萃取和机械振荡，观察到的降解反应可忽略不计。然而，对于微波辅助萃取，当在萃取步骤中施加高微波能量时，两种参考物质的降解因子分别高达7%（TBT到DBT）和16%（DBT到MBT）。对于所测试的三种萃取技术，PACS - 2中获得的DBT和TBT浓度值与认证值紧密匹配。然而，对于MBT，微波萃取和超声萃取得到的浓度远高于认证值。机械振荡则并非如此。使用微波辅助萃取对BCR - 646获得的结果与所有锡形态的认证值高度一致。
