Quantitative Analysis Of Heavy Metals In Gannan Navel Oranges Based On Laser-induced Breakdown Spectroscopy Technology

Food safety and environmental pollution problems directly affect human health, has caused the global attention. Gannan navel oranges are listed as Jiangxi geographical landmark protection products. So it’s great significance to detect the harmful heavy metals content by real-time, on line and in situ means. The traditional’methods in detecting heavy metals of oranges are time-consuming, contaminative and etc., while LIBS technology is rapid, environmental friendly and etc. in quantificationaly analyzing heavy metals content of agricultural products. Therefore this paper seeks to probe LIBS quantitative analysis of heavy metals in navel oranges. The theoretical analysis and experimental research about LIBS platform for experimental parameters of detecting navel oranges, the Pb and Cr content in navel oranges skin were done in this work.Firstly, this topic research background and significance were expounded, and the LIBS technologies with its advantages for real-time, fast, nondestructive detecting heavy metals in agricultural products were introduced. LIBS research status at home and abroad determined this paper content.Secondly, paper expounded several mechanism of plasma forming, plasma radiation mechanism and model and some commonly quantitative analysis methods. The LIBS experimental detection platform was shown and LIBS working principle, main components were introduced. In order to obtain the optimal work parameters for LIBS experiment in navel oranges, heavy metal solution soaking navel oranges experiment, spectral data processing and analysis were needed. By orthogonal analysis of the spectral intensity and relative standard deviation, or signal to background ratio, the optimal parameters values for laser energy, delay time, pulse cumulative times and repetition frequency were determined.Again, the quantitative analysis models for LIBS detecting Pb and Cr in navel oranges skin were further studied in the paper. According to the method and principle for choosing elements characteristics analytical spectral lines, and analyzing spectral data by LIBS experiment, Pb Ⅰ405.78nm and Cr Ⅰ425.43nm were chosen to be the analytical lines. Navel orange samples after soaking in heavy metal solution of chemical dissolution process and atomic absorption spectrophotometer monitoring were introduced to obtain Pb and Cr actual content in skin at the same time. Use of external standard method established LIBS quantitative analysis of Pb and Cr linear regression equation, the correlation coefficient and detection limit were0.98623,12.89mg/kg and0.97202,10.13mg/kg respectively. Five test samples on Cr element of the linear regression equation verification, which got the relative errors between predicted mean and reference, a minimum of0.81%and a maximum of10.60%, also the relative standard deviation for repeated measure value between7.39%to11.14%, conform to the present research status, further verified the feasibility for LIBS technology quantitative analysis of the heavy metals in navel oranges.Finally, the research conclusions were summarized, and some suggestions on the further work and hope were presented.