| 其他摘要 | Heavy metal pollution has increasingly become a potential ecological risk in environmental waters due to its high toxicity, unbiodegradation and accumulation for tens of thousands of times. Therefore, heavy metal pollution has attracted worldwide attention. Coastal zone is one of the most vulnerable areas which are susceptible to human activities not only in river basins but also in the coastal zone. With coastal urbanization and the development of large scale industry, a large number of industrial and domestic sewage are poured into the coastal zone, which causes severe pollution to offshore environment. Developing timely, accurate detection of trace heavy metal in coastal zone is an important prerequisite for effective prevention and control of heavy metal pollution and facilitates lowering the environmental risk of heavy metal pollution, it also alleviates the pressure of heavy metal pollution. Electrochemical stripping voltammetry has been widely regarded as a sensitive technique for trace heavy metal detection due to its combined preconcentration procedure with voltammetric analysis and multi-elements determination at the same time. Being simple, low-cost, easy to carry and operate, voltammetric analysis is suitable for online, fast and automated testing. Working electrode is the core of the electrochemical analysis as the quality and the reliability of measurements depend mainly on this sensor. In recent years, with heavy metal detection method tend to be on-site, fast, simple, portable, screen printed electrodes which integrate three electrodes on one stripe are promising alternatives to traditional bulk electrodes. Since the appearance of screen-printing technology in the late 19th century, Bare screen printed electrode are not favorable for heavy metal accumulation, the general way is to modify SPE surface with mercury film, bismuth film, other noble metal film, nanomaterial because the modifying substances can improve surface properties, functionalize the surface, dramatically increase the sensitivity and selectivity of detection and mechanical stability. A major drawback associated with SPEs is the lack of reproducibility due to difference between batch and batch (e.g., surface area and electrode thickness) and the change of measurement conditions. In order to improve the accuracy and sensitivity, run-to-run variations should be correct due to uncertainties. The main contents of the research are as follows: 1. Bismuth as internal standard for reliable detection of trace lead at screen-printed electrode Bismuth as internal standard, IPb/IBi stripping voltammetry current ratio was determined in buffer solution (pH 4.5) using square wave anodic stripping voltammetry with bismuth and lead co-plating on the electrode surface in situ. Bismuth as internal standard, IPb/IBi stripping voltammetry current ratio was determined in pH 4.5 buffer solution using square wave anodic stripping voltammetry with bismuth and lead co-plating on the electrode surface in situ. Various experimental parameters upon the stripping signal were investigated in details. Under optimized conditions, the response ratio IPb/IBi against the concentration of lead was linear in the 2-200 μg/L concentration range. On one hand, the addition of bismuth can greatly minimize the variations between batches and the changes of measurement conditions, on the other hand, makes for the accumulation of lead because bismuth can form alloy with lead and can reach baseline separation. The practical application of this method was carried out for the determination of lead in river water samples and the results were consistent with the values obtained by ICP-MS. 2. Development of an electrochemical system for alert-type point of care testing of lead decision in tap water Combined with screen printed electrode and custom USB electrochemical system (ECS), bismuth served as internal standard is used for the construction of alert-type point of care testing method to decide whether the lead level has excessed a regulated threshold. The threshold is obtained by determining standard solution containing 10 g/L Pb2+ with square wave anodic stripping voltammetry (SWV). Three electrode pretreatment methods as well as the interference and removal of Cu2+ are discussed. The results indicated that a remarkable decreased charge transfer resistance from 4348 to 715 was observed after electrode was pretreated at 1.8 V for 2 min and the peak current increased 1.6-fold with peak potential separation decreasing from 212 mV to 113 mV. The detrimental effect of 6.5-fold Cu2+ can be circumvented effectively by adding 2.0 mmol/L Fe(CN)64-. The proposed method is applied to the decision of Pb2+ in tap water samples and to give a Yes/No signal. ICP-MS analysis is performed to validate the reliability, and the results are satisfying. Simple, rapid and portable, the platform holds great potential for the application in daily life. |
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