摘要
为了验证激光诱导击穿光谱(LIBS)快速无损检测农产品中重金属污染物的可行性,对赣南脐橙样品进行了实验室镉铅污染处理。首先对样品LIBS试验参数进行了优化分析,根据美国NIST(National Institute of Standards and Technology)原子光谱数据库,确定试验用的最佳特征谱线位置分别为Cd226.502nm和Pb405.783nm。观测了光谱信噪比和强度随着延迟时间和激光能量的变化规律,综合考虑结果表明,最佳延迟时间和激光能量分别为1300ns和130mJ。利用优化的LIBS试验参数对镉(Cd)和铅(Pb)元素的光谱信息进行了采集。同时,采用原子吸收分光光度计对脐橙表皮中镉铅元素的真实浓度进行了检测,建立了镉铅元素特征谱线强度与真实浓度之间的关系模型,相关系数分别为0.94669和0.96059。由定标模型得到镉铅元素的检测限分别为17.375和22.782μg/g。为了验证模型的准确性,采用3个样品做了定标曲线反演分析,预测值与真实值之间的相对误差保持在10%左右。试验结果表明,LIBS技术能应用于农业安全方面的农产品重金属Cd、Pb的快速无损检测。
Toxic heavy metal cadmium （Cd） and lead （Pb） are found in water and soil primarily due to the effluents of industrial wastewater. Primary products may be contaminated by heavy metal Cd and Pb, which are not essential elements in the human body, and may bring harm to human. In this case, it is necessary to determine Cd and Pb concentration in primary products for the evaluation of nutritional status and the optimization of the growing conditions. The traditional techniques in determining heavy metals require consumption of time and/or reagent, sample preparation as well as laboratory analysis environment. Laser-induced breakdown spectroscopy （LIBS） is a form of atomic emission spectroscopy based on plasma induced by focusing a laser pulse on the sample surface. LIBS has the characteristics such as multi-element analysis, direct measurement without contact with the material to be analyzed, high measuring speed, and no or less sample preparation, which make it a useful tool for rapid, real-time and in-situ measurements. Based on the huge potential of LIBS in elemental analysis, more and more researchers have begun to study the application of LIBS for analysis of agricultural products. In this experiment, the fruits of a common orange （Gannan navel orange） from Ganzhou municipality, Jiangxi Province in China were used. Because the area has better ecological and environmental quality, there is lower Cd and Pb concentration in natural oranges. To prove the feasibility of quantitatively determining Cd and Pb in Gannan navel oranges, the oranges need to be contaminated before the analysis. A LIBS experimental platform was set up in the laboratory . The laser source was a Q-switched Nd：YAG operating at 1064 nm with pulse duration of 10 ns. The spectrometer provided high spectral resolution （full wave at half maximum, FWHM 0.05 nm） in the region from 200 nm to 1100 nm. The charged-coupled device（CCD） detector was triggered with suitable delay time between the laser pulse and the acquisition of plasma emission using a digital pulse delay generator DG535. The spectra of Cd and Pb in navel oranges peel were detected by LIBS. The characteristic spectral lines of Cd and Pb were analyzed based on NIST （National Institute of Standards and Technology） database of USA.The optimal characteristic spectral line were 226.502 nm and 405.783 nm for Cd and Pb, respectively. The variation of signal noise ratio and intensity of spectrum with delay time and laser energy were observed. The results demonstrated that the delay time and laser energy optimized were 1300ns and 130mJ, respectively. At the same time, the real concentrations of Cd and Pb in sample peel were determined by atomic absorption spectroscopy （AAS）.The relationships between spectral intensity and concentrations of Cd and Pb were constructed .The results showed that the correlation coefficient of calibration curves were 0.94669 and 0.96059 for Cd and Pb, respectively. The limit of detection （LOD） were acquired by the models, and the results showed that the LOD were 17.375 and 22.782 μg/g for Cd and Pb, respectively. The models were verified by three predictive samples. The results presented that the relative error was near to 10%.The whole experiment displayed the possibility of LIBS in analyzing heavy metals in agricultural products.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2013年第2期260-265,共6页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(30972052)
新世纪优秀人才支持计划(NO.090168)
江西省主要学科学术和技术带头人培养计划项目(09003900)
关键词
激光应用
光谱
原子吸收光谱
镉
铅
激光诱导击穿光谱
赣南脐橙
定标曲线
laser applications, spectroscopy, atomic absorption spectrometry, cadmium, lead, laser-inducedbreakdown spectroscopy（LIBS）, Gannan navel orange, calibration curve
作者简介
张旭（1987-），男，浙江德清人，主要从事农产品无损检测技术研究。南昌江西农业大学生物光电与应用重点实验室，330045。Email：zx8475396@126．com
通信作者：刘木华，男，教授，博士，硕士生导师，主要从事光学无损检测技术研究。南昌江西农业大学生物光电与应用重点实验室，330045。Email：suikelmh@sohu．com
