【作者】 王志强；

【导师】 刘刚；

【作者基本信息】 中国农业大学 ， 农业电气化与自动化， 2014， 博士

【摘要】 农产品是食品的源头,农产品质量安全关系到人民群众的身体健康和生命安全,而农产品质量安全又直接取决于农产品的产地环境。近年来,随着中国工业的快速发展以及农药化肥在农业生产中的过量施用,农产品产地环境以及主要农产品中的重金属污染问题日益严重,已成为制约我国农业可持续发展的一个突出问题。开展适用于农业生产实际需要的重金属快速检测关键技术研究,将会对农产品产地环境管理、农产品供应链全程可追溯以及保障农产品质量安全具有重要意义。电化学检测技术具有仪器成本低、检测速度快、便于操作、易于实现自动化等优点,因此被广泛应用于环境监测、生物样本分析以及食品药品监控等多个领域。如何利用电化学检测技术实现对农产品及其产地环境中的重金属污染进行快速、准确地检测,是当前农业信息技术研究领域内的一个热点课题。传统的电化学传感器存在诸如检测灵敏度低、稳定性差以及抗干扰能力弱等缺点,同时其检测仪器体积大、成本高,不合适在一线农业生产中推广使用。近年来,电化学、纳米材料学、微电子学和计算机科学的快速发展及多学科融合,为上述问题的解决提供了一种新的途径。本文以主要农产品及其产地环境中重要的土壤和灌溉水为研究对象,将纳米材料技术与电化学传感技术相结合,研究开发了多个高灵敏度、低成本的重金属传感器；针对现有电化学检测仪器存在的诸如设备成本高、体积大等问题,结合微电子技术及虚拟仪器技术,研制了用于电化学重金属快速检测的低功耗、便携式检测仪器；将开发的重金属传感器与便携式检测仪器相结合,构建了一套适合于在农村基层诸如乡镇一级农技站使用的快速、高效、低成本的重金属检测平台。具体研究内容包括以下几个方面：1.研制了一种高灵敏度、低成本的镉离子电化学传感器。采用导电物质分子导线作为粘合剂,制作了一种新型碳糊电极,在电极表面进一步修饰Nafion膜和锡膜,并采用方波阳极溶出伏安法对农田灌溉水中的镉离子进行检测。实验结果分析表明,利用分子导线制作的碳糊电极具有较好的导电性和电化学活性。修饰Nafion膜和锡膜使传感器具备了较好的检测灵敏度、稳定性以及抗干扰能力。在最优检测条件下,传感器的线性工作范围为1.0～80.0μg/L,线性回归方程为ip=-0.2065+0.3621c(ip:μA,c:μgL-1),检测限为0.13μg/L。利用该电极对多个农田灌溉水样本中的重金属镉进行测定,检测结果与原子吸收光谱法测量结果对照分析表明,该传感器具有良好的检测准确性和可靠性。2.采用新型材料离子液体作为粘合剂,结合石墨粉制作了一种新型碳糊电极,在电极表面进一步修饰金膜,然后采用方波阳极溶出伏安法对农田灌溉水中的汞离子进行了检测。实验结果分析表明,利用离子液体制作的碳糊电极具有较好的离子导电性和电化学活性。采用金膜对电极进行修饰提高了传感器对汞离子的检测灵敏性和选择性。在最优检测条件下,传感器的线性工作范围为1.0～80.0μg/L,线性回归方程为ip=0.9535+0.4955c=(ip:μA,c:μgL-1),检测限为0.16μg/L。利用该传感器对农田灌溉水样本中的汞离子浓度进行了测定,检测结果与ICP-MS检测结果对照分析表明,该传感器具有很好的检测准确性。3.研制了一种低成本、高灵敏度的“可抛弃”式电化学传感器,并将其用于对土壤样本中的铅和镉含量进行检测。首先采用丝网印刷技术,结合导电性浆料,制作了一种集成式丝网印刷电极,然后在工作电极表面再修饰碳纳米管/Nafion复合材料,采用原位镀铋膜的方式结合方波阳极溶出伏安法,实现了对重金属铅和镉的同步检测。实验结果分析表明,采用碳纳米管/Nafion复合物质对电极进行修饰后,可有效提高传感器的比表面积以及电子传输率,结合高灵敏、低毒的铋膜,该传感器对重金属铅和镉显示出了良好的检测灵敏性。在最优检测条件下,传感器对铅和镉的线性检测范围为1.0～80.0μg/L,铅离子的线性回归方程为ip=0.0329+0.3721c(ip:μA,c:μgL-1),检测限为0.8μg/L。镉离子的线性回归方程为ip=0.0615+0.6634c,检测限为0.5μg/L。利用该传感器对多个实际土壤样本中的生物有效态铅、镉含量进行了测定试验,结果分析表明该传感器具有集成度高、准确性好等优点,可用于对农田土壤中的铅和镉污染进行快速检验和评估。4.研制了一种基于石墨烯/聚对氨基苯磺酸/锡膜复合修饰的镉离子电化学传感器,并将该传感器用于对大米样本中的镉含量进行检测。制备时以玻碳电极为基底,分别采用电化学沉积法和电聚合方法在电极表面修饰石墨烯和聚合物膜,然后采用原位镀锡膜方式,结合方波阳极溶出伏安法实现了对镉离子的灵敏测量。试验结果分析表明,石墨烯修饰层能够较大的提高电极的比表面积以及表面电子传输率,聚合物修饰层能够提高传感器的阳离子交换能力和抗干扰能力,结合高灵敏、低毒的锡膜,该传感器对镉离子显示出了良好的检测灵敏性。在最优检测条件下,传感器的线性工作范围为1.0～70.Oμg/L,线性回归方程为ip=1.6239c+0.0073(ip:μA,c:μgL-1),检测限为0.05μg/L。多个实际大米样本检测结果分析表明,该传感器具有检测速度快、准确性好、重现性高等优点,可用于对农产品中的镉含量进行高精度定量分析。5.将微电子技术与虚拟仪器技术相结合,研发了一种便携式重金属快速检测仪器系统。该仪器基于电化学方波阳极溶出伏安法原理,由上位机软件和下位机硬件电路组成。上位机软件基于Labview平台开发,主要负责完成向仪器硬件发送检测指令和工作参数、接收下位机采集到的数据以及对检测结果进行分析和定量计算等功能。下位机以MSP430混合信号处理器为控制核心,结合恒电位电路、I/V转换电路、滤波电路、串口通信电路等硬件设备,实现了电化学分析过程中信号的激发以及检测数据的采集和传输功能。采用该仪器对多个实际土壤以及农田灌溉水样本中的铅、镉和汞离子进行了测定试验,结果分析表明,该仪器具有检测精度高、准确性好、速度快、功耗低等优点,较适合于对农产品及其产地环境中重金属进行快速检测和分析。更多还原

【Abstract】 Agricultural products are the source of food, and the quality and safety of agricultural products is related to the health and safety of people. The quality and safety of agricultural products is directly dependent on the agricultural production environment. In recent years, with the rapid development of China’s industrial and the excessive application fertilizers and pesticides in agricultural production, heavy metal pollution has become a serious problem in environment and agricultural products. The development of a heavy metal detection technology, which is rapid, accurate and suitable for agricultural use, is of great importance for the agricultural environmental management, agricultural traceability supply chain and the quality and safety of agricultural products.Electrochemical detection technology possesses many advantages such as low cost, high speed, easy to operate, etc., which was suitable for the environmental monitoring, food and bio-medical analysis. How to use electrochemical detection technology for rapid and accurate detection of heavy metal pollution in farmland environment and agricultural products is a valuable research topic in agricultural information technology. However, the traditional electrochemical sensors have some disadvantage such as low sensitivity, poor stability as well as weak anti-interference capability, while the conventional electrochemical instruments are large volume and high cost, which are not suitable for on-site use. In recent years, the rapid development and cross-integration in electrochemistry, nano-materials, microelectronics and computer science provides a new way to solve the above problem.In this study, we mainly focus on the research of heavy metals in major agricultural products and farmland irrigation water and soil environment. We combined the nano-materials technology with electrochemical sensing technology, and develope a variety of heavy metals electrochemical sensors which is high sensitivity, low-cost, and suitable for agricultural use. To solve some of its underlying problems in electrochemical detection devices, we combined the microelectronic technology with virtual instrument technology, and developed a low-power, portable detection equipment for electrochemical detection of heavy metal. At last, the developed sensors and portable testing instruments was constitute together and formed a fast, efficient and low-cost heavy metals detection platform which was suitable for the usage in agricultural production. The main contents include the following aspects:1. A high-sensitivity, low-cost cadmium ion electrochemical sensor was developed. Conductive material-molecular wires was used as a binder to produce a new type of carbon paste electrode, the electrode surface was further modified with Nafion and tin film, and then employed to determination of cadimium in agricultural irrigation water by using square wave anodic stripping voltammetry. Experimental results showed that the prepared electrode possessed excellent electrochemical performance and increased electron transfer rate due to the introduction of molecular wire as a binder, and exhibited a better sensitivity and stability as well as high resistance to surfactants due to the synergistic effect of Nafion and stannum film. Under the optimal conditions, the stripping peak currents showed a good linear relationship with the Cd(II) concentration in the range from1.0to80.0μg/L with a detection limit of0.13μg/L (S/N=3), and the linear regression equation was ip=-0.2065+0.3621c (ip:μA,c:μgL-1). The developed electrode was further applied to the determination of Cd(II) in agricultural water samples with satisfactory results. The test results show that the sensor has the advantage of high sensitivity, good accuracy, low cost and easy fabrication.2. A new type of carbon paste electrode was fabricated by using new materials-ionic liquid as binder. The electrode surface was further plated with gold film, and then used to determination of mercury ions in farmland water environment by square wave anodic stripping voltammetry. Experimental results showed that the prepared electrode possessed good electrical conductivity and electrochemical activity due to the introduction of ionic liquid as binder, while the gold film greatly improved the detection selectivity and sensitivity for the mercury ions. Under optimal conditions, the linear detection range of the sensor was1.0～80.0μg/L, the linear regression equation was ip=0.9535+0.4955c (i:μA,c:μgL-1), and the detection limit was0.16μg/L. The sensor was further applied to determine of mercury ion in irrigation water and the results indicted that the electrode has the advantages of high detection accuracy, low cost, and simple preparation.3. We developed a low-cost, high-sensitivity "disposable" electrochemical sensors, and further applied to determine lead and cadmium content in soil samples. First, an integrated screen-printed electrodes was fabricated by using screen printing technology and conductive paste, the working electrode surface was then modified with carbon nanotube/Nafion composite membranes, after in situ plating bismuth film, the electrode was used to sensitive detection of lead, cadmium ions by square wave anodic stripping voltammetry. The results showed that the carbon nanotubes/Nafion composite material greatly expanded the the surface area and improved the electron transfer rates of electrode. By combing the high sensitivity and low toxicity of bismuth film, the sensors exhibited better detection sensitivity and signal stability for the measurement of lead and cadmium. Under optimal conditions, the linear detection range of the sensor was1.0～80.0μg/L for lead and cadmium. The linear regression equation was ip=0.0329+0.3721c(ip:μA,c:μgL-1) and ip=0.0615+0.6634c for lead and cadimium with detection limit of0.8μg/L and0.5μg/L, respectively. This sensor was then applied to analysis of bioavailable lead and cadmium content in soil samples, the results show that the detection method is fast, accurate and low cost which suitable for rapid testing of lead and cadmium in farmland soils.4. We developed a graphene/poly(p-aminobenzene sulfonic acid)/tin film composite modified electrochemical sensors. This sensor was applied to the determination of cadmium content of rice samples. The glassy carbon electrode was used as substrate, and a graphene and polymer film was modified on the electrode surface by using electrochemical deposition and polymerization methods, respectively. After in situ depositing tin film, this sensor was used to measurement of cadmium ions by square wave anodic stripping voltammetry. It was found that the graphene layer greatly improved the specific surface area and surface electron transfer rate of the electrode, while the polymer layer enhanced the cation exchange capacity and anti-interference capability of sensor. By combing the high sensitivity, low toxicity tin film, this sensor exhibit good sensitivity and signal stability for the analysis of cadmium ion. Under optimal conditions, the linear detection range of the sensor was1.0～70.0μg/L, the linear regression equation was ip=1.6239c+0.0073(ip:μA, c:μgL-1), with detection limit of0.05ug/L. Actual rice sample analysis results showed that the method was fast, accurate and sensitive, which suitable for quantitative analysis of cadmium content in agricultural products.5. A portable instrument system for rapid detection of heavy metals was developed by using the microelectronics technology and virtual instrument technology. The instrument was based on the principle of electrochemical square wave anodic stripping voltammetry. The system is made up of the PC software and hardware circuit. PC software was developed on Labview software platform, which the major function was sending commands and parameters to the hardware, receiving the data, and analysis and quantitative calculation. The hardware was combined the MSP430MCU with potentiostat circuit, Ⅰ/Ⅴ converter circuit, filter circuit, serial communication circuit and other hardware devices, which achieved the generation of electrochemical excitation signal and the processing and transmission of data. This instrument was further used for analysis of lead, cadmium and mercury ions in actual soil and irrigation water samples. Experimental results showed that the system possessed many advantages such as high precision and speed, low power consumption, which was suitable for rapid evaluation and measurement of heavy metals in in real samples.更多还原