马铃薯中重金属元素铅和铬的激光诱导击穿光谱快速绿色检测研究

发布时间：2018-07-25 13:47

【摘要】：随着现代物质生活水准的提升,绿色安全的农产品已然成为人们日常生活关注的焦点,农产品的质量安全与否直接关系到人们的身体健康。蔬菜中重金属残留超标对人体有重大的影响,而且残留在蔬菜中的重金属元素无法通过浸泡清洗和煮沸的方式去除的,食用了含有残留重金属元素的果蔬对人体的危害极大,重金属在人体内具有累积性,潜伏期长。马铃薯是我国的五大主食之一,同时也是全球第三大粮食作物,仅次于小麦和玉米,马铃薯中的营养价值高、生长环境适应能力强、产量高。但是种植在污染土壤的马铃薯会对重金属元素有富集作用,进而影响到马铃薯的品质。为此,急需发展一种全新的绿色快速有效的物质成分检测技术。激光诱导击穿光谱(LIBS)技术以其快速、绿色环保、多元素同时检测等优点受到越来越多的研究者的关注。因此,本工作以验证LIBS检测技术在农产品中应用的可行性为研究目的,以马铃薯中的重金属元素铅和铬为研究对象展开。首先搭建了LIBS快速检测试验装置,为了使LIBS在农产品重金属检测中获得较好的检测效果,对LIBS试验装置参数(如光纤采集角度、聚焦点位置等)进行调节。然后探讨湿样马铃薯样品中的含水量对LIBS检测灵敏度的影响,对比干样和湿样马铃薯样品的LIBS检测结果可知干样马铃薯样品检测的灵敏度和稳定性明显优于湿样马铃薯样品。因此,为了提高马铃薯LIBS检测的灵敏度和稳定性,对湿样马铃薯进行真空冷冻抽湿、粉碎研磨等简单的预处理,然后将马铃薯粉末进行手动压片制样。其次对LIBS试验采集参数进行了优化,分析了光谱采集延迟时间,光谱采样门宽和激光能量值对LIBS信号采集的影响,最终确定光谱采集延迟时间,光谱采样门宽和激光能量值的最佳参数值为2μs、8ms和90mJ。最后针对96个污染马铃薯样品的LIBS光谱数据,分别进行3点到17点平滑处理,将平滑后的数据分别进行标准正态变量变换、均值中心化、求导去噪(一阶求导和二阶求导)和多元散射校正预处理;然后分别应用一元线性回归、偏最小二乘法和联合区间偏最小二乘法建立了的马铃薯样品Pb、Cr重金属元素LIBS光谱信号强度与其浓度关系的模型,进行预测值与实际值的比较。试验结果表明激光诱导击穿光谱用于马铃薯重金属元素检测是可行的,为激光诱导击穿光谱技术在其它农产品重金属中的快速检测提供了理论依据和技术支持。
[Abstract]:With the improvement of modern material living standards, green and safe agricultural products have become the focus of our daily life, and the quality and safety of agricultural products have a direct bearing on people's health. Heavy metal residues in vegetables have a significant impact on the human body, and the residual heavy metal elements in vegetables can not be removed by soaking and boiling. Eating fruits and vegetables containing residual heavy metal elements is very harmful to human body. Heavy metals are accumulated in the human body and have a long incubation period. Potato is one of the five staple foods in China, and it is also the third largest food crop in the world, which is second only to wheat and corn. The potato has high nutritional value, strong adaptability to the environment and high yield. But potato grown in contaminated soil can enrich heavy metal elements and affect the quality of potato. Therefore, it is urgent to develop a new green rapid and effective material composition detection technology. Laser induced breakdown spectroscopy (LIBS) technology has attracted more and more attention due to its advantages of fast, green and multi-element simultaneous detection. Therefore, the purpose of this study was to verify the feasibility of the application of LIBS detection technology in agricultural products, and the heavy metal elements lead and chromium in potato were studied. In order to get better detection effect of LIBS in agricultural products, the parameters of LIBS test device (such as the angle of optical fiber acquisition, focus position) were adjusted. Then, the effect of water content in wet potato samples on the sensitivity of LIBS detection was discussed. Compared with the LIBS detection results of dry and wet potato samples, the sensitivity and stability of dry potato samples were obviously better than that of wet potato samples. Therefore, in order to improve the sensitivity and stability of potato LIBS detection, the wet potato was pretreated by vacuum freezing and grinding, and then the potato powder was made by pressing the sample manually. Secondly, the acquisition parameters of LIBS test are optimized, and the effects of spectrum acquisition delay time, spectral sampling gate width and laser energy value on LIBS signal acquisition are analyzed. Finally, the spectrum acquisition delay time is determined. The optimum parameters of spectral sampling gate width and laser energy value are 2 渭 s ~ 8ms and 90mJ. Finally, the LIBS spectral data of 96 contaminated potato samples were smoothed from 3 to 17:00, and the smooth data were transformed into standard normal variables and the mean value was centered. The derivation denoising (first order and second order derivation) and multivariate scattering correction are preprocessed, and then the linear regression is used respectively. The relationship between the LIBS signal intensity and the concentration of Pb Cr heavy metal elements in potato samples was established by partial least square method and combined interval partial least square method, and the predicted values were compared with the actual values. The results show that laser induced breakdown spectroscopy is feasible for the detection of heavy metals in potato, which provides a theoretical basis and technical support for rapid detection of heavy metals in other agricultural products by laser induced breakdown spectroscopy.
【学位授予单位】：江西农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S532;TN24;O433

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