基于激光诱导击穿光谱的洋葱在线原位检测

激光诱导击穿光谱(Laser-induced breakdown spectroscopy, LIBS)是一种分析多元素的光学技术,可用于新鲜蔬菜的快速检测.以洋葱为例,采用LIBS对其含有的元素进行了在线原位检测.用乙酸铅溶液污染洋葱以模拟大气湿沉降的重金属污染现象,并进行重金属Pb元素检测.使用主成分分析(principal components analysis, PCA)和反向传播人工神经网络(back-propagating artificial neutral network, BP-ANN),以洋葱、大蒜、小葱为样品进行区分检测.洋葱光谱中的特征谱线包括Si、Fe、C、Mg、Al、Ca、Ti、Sr、Ba、Na、Li和K等元素,以及N、H、O的谱线和CN分子谱带.不同浓度梯度乙酸铅溶液污染的洋葱样品中都能检测出Pb元素,其相对强度与溶液浓度成比例.此外,PCA的结果表明洋葱、小葱、大蒜的区分效果明显,BP-ANN交叉验证的识别率为89.47%.结果证明LIBS在对元素进行快速分析时具有较好的识别能力,是检测新鲜蔬菜的有效手段.

Online in situ detection of onion by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is an optical technique for the analysis of multiple elements, and can be used for rapid detection of fresh vegetables. Taking onion as an example, LIBS is used to carry out online in situ detection of the elements contained in onion. The onion is contaminated with lead acetate solution to simulate the heavy metal pollution in the wet precipitation, and the heavy metal element Pb is detected. Usingprincipal components analysis (PCA) and back-propagating artificial neutral network (BP-ANN), onion, garlic and scallion are selected as samples for discriminative detection. The characteristic lines of onion spectrum include Si, Fe, C, Mg, Al, Ca, Ti, Sr, Ba, Na, Li and K, as well as the H, O, N lines and CN molecular bands. Pb can be detected in onion samples contaminated by lead acetate solutions with different concentration gradients, and its relative strength is proportional to the solution concentration. In addition, the result of PCA shows that there is a clear distinction among onion, garlic and scallion, and the effective rate of BP-ANN cross validation is 89.47%. The results show that LIBS has a good recognition ability in the rapid analysis of elements, and is an effective means to detect fresh vegetables.