食品重金属污染日趋严重,常规的实验室化学分析方法难以满足现代农业发展的需求.激光诱导击穿光谱是一种新兴的快速无损检测新方法,但该技术存在检测稳定性、灵敏度和精确度不高的瓶颈问题.本工作以江西特色水果赣南脐橙中的Cu元素为研究对象,探讨采用LIBS技术检测的可行性问题.首先对脐橙样品进行实验室污染处理,再利用优化的试验参数(激光能量120 mJ、光谱采集延迟时间1.14 μs、采集积分时间2 ms)采集样品表皮的LIBS光谱信息,然后利用AAS对激光击打部位果皮进行Cu元素真实含量检测.提取Cu Ⅰ324.7 nm与Cu Ⅰ 327.4 nm作为Cu元素定量分析特征光谱,建立Cu元素真实浓度与Cu Ⅰ 324.7强度、Cu Ⅰ 327.4强度、Cu Ⅰ 324.7与Cu Ⅰ 327.4强度之和的关系模型,并对模型的灵敏度和预测准确度进行了分析.结果显示,三个关系模型的浓度预测相对误差均在7.01%以下,最小分别达到了0.02%,0.01%和0.02%,平均相对误差分别为2.33%,3.10%和2.63%.试验表明,寻找合适的特征变量能明显提高定量分析结果的精确度.此外,该研究有助于为重金属元素在果皮果肉中的传输规律提供理论依据。

Heavy metals pollution in foodstuffs is more and more serious.It is impossible to satisfy the modern agricultural development by conventional chemical analysis.Laser induced breakdown spectroscopy(LIBS) is an emerging technology with the characteristic of rapid and nondestructive detection.But LIBS’s repeatability,sensitivity and accuracy has much room to improve.In this work,heavy metal Cu in Gannan Navel Orange which is the Jiangxi specialty fruit will be predicted by LIBS.Firstly,the navel orange samples were contaminated in our lab.The spectra of samples were collected by irradiating the peel by optimized LIBS parameters.The laser energy was set as 20 mJ,delay time of Spectral Data Gathering was set as 1.2 μs,the integration time of Spectral data gathering was set as 2 ms.The real concentration in samples was obtained by AAS(atom absorption spectroscopy).The characteristic variables Cu Ⅰ 324.7 and Cu Ⅰ 327.4 were extracted.And the calibration model was constructed between LIBS spectra and real concentration about Cu.The results show that relative error of the predicted concentrations of three relational model were 7.01% or less,reached a minimum of 0.02%,0.01% and 0.02% respectively.The average relative errors were 2.33%,3.10% and 26.3%.Tests showed that different characteristic variables decided different accuracy.It is very important to choose suitable characteristic variable.At the same time,this work is helpful to explore the distribution of heavy metals between pulp and peel.