|关键词||海岸带水体 新型电极 伏安分析法 溶解态总铁|
1. 一步电还原法制备还原氧化石墨烯-金纳米粒子（rGO-AuNPs）修饰电极灵敏检测海岸带水体中的溶解态总铁。本实验采用2-（5-溴-2-吡啶偶氮）-5-二乙氨基酚（5-Br-PADAP）为络合剂。该络合剂可在酸性缓冲溶液中与铁离子络合，rGO提供大的比表面积，AuNPs加速电子传递。在最佳实验条件下，该电极测定铁离子的线性范围是0.03~3 μmol/L，检出限是3.5 nmol/L。该修饰电极具有良好的重现性和重复性，已经成功应用于实际海岸带水体中溶解态总铁的测定。
2. 两步法制备还原氧化石墨烯/金膜（rGO/AuF）修饰电极检测海水中的溶解态总铁。海水呈弱碱性，pH为8左右。为了更加准确地检测海水中的溶解态总铁，本实验采用2,3-二羟基萘（DHN）为络合剂，该络合剂适用于在碱性缓冲溶液中与铁离子络合。KBrO3为催化剂，在最佳实验条件下，得到测定铁离子的标准工作曲线。该电极对铁离子的检测线性范围是分段的，分别为0.01~0.1 μmol/L和0.1~1 μmol/L。该方法的检测结果与伏安极谱仪的检测结果能很好的吻合，并且已经成功应用于海水中溶解态总铁的测定。
3. 典型海岸带河水中溶解态总铁浓度检测及分布研究。采用金电极为工作电极，5-Br-PADAP为络合剂，5-Br-PADAP与Fe(III)络合速度快（< 3 min），并且金电极对该络合物具有很好的响应。通过优化测试条件，该方法的线性范围为0.01~1 μmol/L，检出限为1.2 nmol/L。 该方法测试结果与分光光度法的测试结果基本吻合，并已成功应用于烟台大沽夹河（干湿两季12个站点）溶解态总铁的测定，并探讨了溶解态总铁与溶解氧、盐度等特征常数的关系。金电极结合吸附溶出伏安法有望实现海岸带河水中溶解态总铁的监测。
; The coastal waters include river/water ditches, offshore area, reservoirs, salina, lakes/pond and so on. They are important for the coastal zone area. Iron is one of the essential micronutrients for organisms in ecological system. Iron plays an important factor in plant metabolism and chlorophyll synthesis. Besides, it is believed to be a limiting factor for primary productivity in marine ecosystems. Thus, accurate analysis of iron in coastal waters has great significance in studying coastal biogeochemistry cycle and realizing coastal environment monitoring.
Many techniques have been developed to determine iron. However, most of these methods need expensive and bulky devices which restrict their use for in situ determination. Moreover, some methods suffer from serious matrix interferences. Electrochemical stripping voltammetry has been widely regarded as a sensitive technique for iron determination due to its simple equipment, low detection limit, fast and accurate detection, easy automation and suitable for in situ determination. Therefore, electrochemical method take an increasing significant role in trace iron determination. The choice of working electrode is the key problem in electrochemical methods. The mostly used working electrode is mercury electrode, however, it has some drawbacks including toxicity and difficulties in the handling.
In this thesis, novel electrodes were proposed in view of the problem of iron determination. The established methods have been successfully applied to the determination of total dissolved iron in coastal river waters and coastal sea waters. The main contents are as follows:
1. An electrochemical sensor based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) modified electrode via one single step was developed for determination of total dissolved iron in coastal waters. 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) was used as complexing agent of iron, 5-Br-PADAP can be complexed with iron in acidic buffer solution. rGO was acted as a support provided large specific surface area for AuNPs, which would facilitate the electrochemical reduction of Fe(III)-5-Br-PADAP. Under the optimized conditions, the responses of Fe(III) at this established sensor were linear in the range of 0.03~3 μmol/L with a detection limit of 3.5 nmol/L. The fabricated sensor also had excellent reproducibility and repeatability, it has been successfully applied to the determination of total dissolved iron in real coastal waters.
2. The reduced graphene oxide (rGO) and gold film (AuF) modified electrode via two steps was used for the determination of total dissolved iron in coastal sea waters. Sea water is slightly alkaline, the pH is about 8. In order to accurately determine total dissolved iron in coastal sea waters, 2,3-dihydroxynaphthalene (DHN) was used as complexing agent of iron, the complexing agent applied to reacting with iron in alkaline buffer solution, potassium bromate was used as a catalyst. Under the optimized conditions, the liner range of the electrode is segmented (0.01~0.1 μmol/L and 0.1~1 μmol/L). The results of this method are in agreement with the polarography, it has been successfully applied to determine total dissolved iron in coastal sea waters.
3. The concentration and distribution of total dissolved iron in typical coastal river waters. Gold electrode was used as working electrode. 5-Br-PADAP was used as complexing agent of iron with a short chelating reaction time (< 3 min), while gold electrode has a good response to this complex. Under the optimized conditions, the response of Fe(III) at the electrode was linear in the range of 0.01 μmol/L to 1 μmol/L with a detection limit of 1.2 nmol/L. The results of this method were in agreement with the spectrophotometry. Besides, this method has been successfully applied to determine total dissolved iron in Dagujia river of Yantai, China (twelve sampling stations in dry season and wet season). The relationship between the concentrations of total dissolved iron with dissolved oxygen and salinity were also discussed. Experiments showed that the gold electrode combined with adsorptive stripping voltammetry can be adopted for determination of total dissolved iron in coastal river waters.
|朱云. 新型电极检测海岸带水体溶解态总铁研究[D]. 北京. 中国科学院大学,2017.|