样品物理方法前处理提高猪肉中Pb元素的LIBS分析精度研究

摘要

农产品基体复杂,为了减弱水分和有机质对其痕量重金属元素LIBS检测能力的影响,以期提高目标元素LIBS分析灵敏度和预测精度.以实验室含Pb溶液污染处理的新鲜猪肉样品为例,对猪肉样品进行烘干、粉碎、压片处理,比较样品简单的物理方法前处理提高目标元素LIBS探测效果的可行性.通过采集猪肉鲜样和干样的LIBS谱线信息发现,鲜样受水分、有机质成分影响致使其谱线信息背景和噪声信号干扰较大;对于10个浓度梯度的样品,目标元素特征谱线Pb Ⅰ 405.78的LIBS强度信息在鲜样中无明显的差异性,而在干样样品中差异明显并表现出一定的梯度关系.说明LIBS缺乏对鲜样样品低浓度Pb污染的探测能力,干燥处理削弱了水分的影响、浓缩了样品浓度范围,提高了LIBS的检测灵敏度.通过目标元素Pb的真实浓度与其特征谱线LIBS强度线性定量模型分析,干样样品的线性相关系数远大于鲜样样品,此时猪肉干样样品检测限为5.13 mg·kg-1,说明干样样品具有一定的预测精度.整个工作证明猪肉等农产品在经过合适的、简单的物理方法前处理后,有望在LIBS分析灵敏度和检测精度方面发挥应有的潜力,且该物理方法前处理同样适用于其他肉类的LIBS检测分析.%Agricultural products have complex matrix prohibiting the development of LIBS(laser induced breakdown spectroscopy)in detecting its composition,especially tracing toxic heavy metals.The work was aiming at improving the sensitivity and accuracy of LIBS in predicting heavy metals in farm products.Fresh pork was chosen and dipped in Pb solution for making polluted samples.The samples were dried,ground to powder and pressed to pellets to remove the effect of water.The LIBS spectra of fresh and dried pork were collected at the same experimental conditions.The results demonstrated that the intensity of Pb was similar and obscure in fresh samples,but quite strong and clear in dried ones.The linear calibration curve between real content of Pb and intensity of Pb Ⅰ 405.78 showed that the correlation coefficient was poor in fresh pork and good in dried samples and the limit of detection of dried samples is 5.13 mg·kg-1.This experiment testified that the sensitivity and accuracy could be improved after the fresh samples were pretreated by simple physical methods,and it is potential in predicting heavy metals in farm products by LIBS.And this method can also be applied to other meat of detection by LIBS.