【作者】 余莉萍；

【导师】 严秀平；

【作者基本信息】 南开大学 ， 分析化学， 2004， 博士

【摘要】 本论文旨在发展原子荧光（AFS）在线联用技术，并将其应用于环境和生物样品中痕量元素的形态分析和汞形态稳定性研究，内容包括以下五章。第一章为文献综述。第一部分简要评述了气相色谱-AFS、高效液相色谱（HPLC）-AFS和毛细管电泳（CE）-AFS在线联用系统的接口技术，总结了这几种联用技术在形态分析中的应用。第二部分综述了Hg（Ⅱ）和甲基汞（MeHg）的贮存稳定性影响因素，讨论了汞损失机理，总结了汞损失的防止方法。第二章成功地把浊点萃取法应用到HPLC-CV（冷蒸气发生）-AFS联用系统中，为HPLC联用系统汞形态分析提供了一种操作简单、费用低廉的样品预富集方法。pH为3.5时，MeHg、乙基汞（EtHg）、苯基汞（PhHg）和Hg（Ⅱ）以吡咯烷二硫代氨基甲酸铵（APDC）络合物的形式被Triton X-114胶束萃取，40℃下平衡10min相分离后，汞化合物被富集到表面活性剂相。采用ODS柱，以甲醇、乙腈和水（65：15：20，v／v／v）混合溶液（pH3.5）为流动相，表面活性剂富集相中的四种汞-APDC络合物在HPLC中得到基线分离。HPLC流出液先与2％m／v K₂S₂O₈-10％v／v HC1混合溶液在200cm的编结反应器（KR）中充分混合，汞-APDC络合物被在线氧化为Hg（Ⅱ），再与KBH₄溶液反应生成汞蒸气，AFS测定。预富集10mL样品溶液得到MeHg、EtHg、PhHg和Hg（Ⅱ）的富集倍数分别为29，43，80和98，检出限（3α）范围为0.1～0.9ng L^-1（以Hg计）。此方法成功地应用于鱼肉样品萃取液中汞化合物的富集和形态分析。第三章应用CE-AFS联用新技术进行了有机锡形态分析。使用50cm长，75μm内径的毛细管，选择50mmol L^-1H₃BO₃-50mmol L^-1Tris-10％v／v甲醇（pH7.10）缓冲体系，添加0.008mmol L^-1CTAB能有效抑制有机锡阳离子在毛细管内壁的吸附，20KV电压下实现了三甲基锡、一丁基锡、二丁基锡和三丁基锡的基线分离。然后以KBH₄为还原剂，把有机锡在线转化为氢化物，AFS测定。有机锡化合物的迁移时间、峰面积和峰高的精密度范围（RSD，n=5）分别为1.7～3.1％、3.8～4.7％和1.6～2.8％。第四章采用流动注射（FI）在线吸附预富集在线氧化洗脱CV-AFS联用技术建立了一种快速、灵敏、费用低廉的天然水样中痕量Hg（Ⅱ）的测定方法。天然水样中痕量的Hg（Ⅱ）通过FI在线形成中性的汞-二乙基二氨基甲酸（Hg-DDTC）络合物并吸附在聚四氟乙烯管编制的KR的内壁上实现预富集。然后用16％v／v HCl-10％v／v H₂O₂混合溶液作为洗脱剂洗脱吸附在KR内的Hg-DDTC络合物。在线氧化洗脱能在冷蒸气发生前有效地把Hg-DDTC络合物氧化分解为容易被KBH₄还原的Hg（Ⅱ），大大提高了冷蒸气发生效率。用3.1mL min^-1流速富集样品60s，得到的检测限（3σ）为4.4ng L^-1，采样频率为36h^-1。MeHg、EtHg和PhHg等有机汞化合物对Hg（Ⅱ）的测定没有干扰。本方法成功地用于测定标准参考物GBW（E）080392（模拟天然雨水）、河水、湖水和海水中的Hg（Ⅱ）。第五章利用CV-AFS和HPLC-CV-AFS联用技术考察了干燥脱水处理鱼肉样品以及调节HCl萃取液pH值对总汞和汞形态的影响。初步实验表明，短时间微波炉和烘箱干燥对新鲜鱼肉中总汞含量没有明显的影响。HCl萃取液的pH降低，甲基汞（保留时间为7.10min）的保留时间提前。这可能是因为酸度变化引起萃取液中的甲基汞发生了形态改变，其根本原因有待更深入的研究。更多还原

【Abstract】 This dissertation deals with atomic fluorescence spectrometry （AFS） based on-line hyphenation techniques for speciation analysis and stability study of mercury species. It consists of the following chapters.In Chapter 1, on-line hyphenation techniques of AFS with gas chromatography, high performance liquid chromatography （HPLC） and capillary electrophoresis （CE） were reviewed with emphasis on the interface design and analytical applications. Factors affecting the stability of inorganic mercury and methylmercury during storage were reviewed. Several possible proposed mechanisms for mercury losses and various reported approaches for prevention of such losses were discussed.In Chapter 2, cloud point extraction was applied for simultaneous preconcentration of Hg（II）, methylmercury （MeHg）, ethylmercury （EtHg） and phenylmercury （PhHg） prior to HPLC-CV （cold vapor）-AFS. The four mercury species were taken into complexes with ammonium pyrrolidine dithiocarbamate （APDC） in Triton X-114 medium and concentrated in the surfactant-rich phase by bringing the solution to the temperature of 40℃. Baseline separation of the enriched complexes was achieved on an ODS column with a mixture of methanol, acetonitrile and water （65:15:20, v/v/v） as the mobile phase （pH 3.5）. A post-column oxidation of the elute solution from HPLC, in the presence of K₂S₂O₈ in HCl, was applied to convert organomercury compounds into Hg（II） for cold vapor generation. The preconcentration of 10 mL of sample solution gives enhancement factors of 29, 43, 80 and 98 for MeHg, EtHg, PhHg and Hg （II）, respectively. Detection limits （3σ） ranged from 0.1 to 0.9 ng L^-1 （as Hg）. The developed method was successfully applied to the speciation of mercury in real fish samples.In Chapter 3, CE coupled with hydride generation （HG）-AFS was developed for the speciation analysis of organotin compounds. The four organotin cations of trimethyltin, monobutyltin, dibutyltin and tributyltin were completely separated by CE in a 50 cm×75μm i.d. fused-silica capillary at 20 kV and using a mixture of 50 mmol L^-1 H₃BO₃-50 mmol L^-1 Tris-10% v/v methanol （pH 7.10） as electrolyte. 0.008 mmol L^-1 CTAB added to the electrolyte suppressed the adsorption of the organotin cations on the inner wall of capillary. The generated hydride species were on-line detected with AFS. The relative standard deviation （RSD, n = 5） were in the range of 1.7 to 3.1% for migration time, 3.8 to 4.7 % for peak area response, and 1.6 % to 2.8% for peak height response for the four organotin species.In Chapter 4, a rapid, sensitive, and cost-effective method was developed for the determination of trace mercury in water samples by on-line coupling of flow injection sorption preconcentration with oxidative elution to CV-AFS. Trace Hg（II） in aqueous solution was preconcentrated by on-line formation of mercury diethyldithiocarbamate complex （Hg-DDTC） and adsorption of the resulting neutral complex on the inner walls of a PTFE knotted reactor. A mixture of 16% v/v HCl and 10% v/v H₂O₂ was used as the eluent to remove the adsorbed Hg-DDTC from the KR, then convert on-line the Hg-DDTC into Hg（II） prior to its reduction to elemental mercury by KBH4 for subsequent on-line CV-AFS detection. No serious interferences from the organomercury species of methylmercury, ethylmercury and phenylmercury up to 0.5 mg L^-1 were observed for the preconcentration of Hg （II） in the developed system. With a sample loading flow rate of 3.1 mL min^-1 for a 60 s preconcentration, a detection limit （3a） of 4.4 ng L^-1 was achieved at a sample throughput of 36 samples h^-1. The method was successfully applied to the determination of mercury in a certified reference material, GBW（E） 080392, and a number of local natural water samples.In Chapter 5, CV-AFS and HPLC-CV-AFS were used to study the stability of mercury species in fish samples during sample treatment. From the preliminary results obtained it can be concluded that fresh fish sample show good stability against temperature during microwave oven and oven drying. On the other hand, significant species interconversion takes place during the pH adjustment of fish sample extract. This implies that the HC1 leaching provides a source of error in mercury species determination because of species interconversion. More effort should be made to solve the problems associated with the stability of mercury species.更多还原