Rapid Detection of Trace Dimethoate Pesticide Residues Based on Colorimetric Spectroscopy
LI Wen1, 2, SUN Ming1, LI Min-zan1*, SUN Hong1
1. Key Laboratory of Modern Precision Agriculture System Integration Research, Ministry of Education, China Agricultural University, Beijing 100083, China 2. College of Computer Science and Information Engineering, Beijing Technology and Business University, Beijing 100048, China
Abstract：In order to detect dimethoate pesticide residues rapidly and safely, a feasible method based on colorimetric spectroscopy was developed. Because dimethoate is one of organophosphorus pesticides containing sulfur, its sulfenyl can react with Pd2+ to produce a yellow complex named palladium sulfide. PdCl2 was used as the color agent, which was dissolved in acetic acid instead of the common concentrated hydrochloric acid. The dimethoate solution was prepared by dissolving the commercial pesticides into distilled water at different concentrations. The pesticide samples were reacted with the same amount of PdCl2 solution respectively. The absorbance spectra of the samples after coloring reaction were measured in the region of 300～900 nm by a spectrophotometer. The result showed that the effect of using acetic acid instead of concentrated hydrochloric acid was not only safe but also preferable, and 0.5 mg·kg-1 was the minimum concentration of the pesticide that could be distinguished in the spectra. The result met the pesticide residue detecting requirements of part fruits and vegetables in the national standard GB2763—2012 regulations. Further studies on random 40 dimethoate samples from 0.5 to 88 mg·kg-1 were carried out. Thirty samples were randomly selected to establish the training model and remaining 10 samples were used to test the model. The preprocessing methods were carried on the spectrum data such as normalization and smoothing to get a better effect through comparison their prediction results with the correlation coefficient (r) and the root mean square error of cross-validation (RMSEP). The principal component analysis (PCA) method and partial least squares(PLS)method were used to establish prediction models respectively in the different wave ranges. By calculating the correlation coefficient of dimethoate samples in 350～900 nm the maximum of 0.957 2 was obtained at wavelength 458 nm, so 453～463 and 400～600 nm were selected as feather regions. Experiments showed that the effect of SG preprocessing on the absorbance spectra in the region of 350～900 and 400～600 nm was obvious, and PLS method were better than PCA method. The optimum model was obtained in the region of 400～600 nm, when principal component number was 4, the training set r=0.994 1, RMSEP=2.770 3 and the validation set r=0.993 3, RMSEP=2.214 8. This method was safe in operation and the colorimetric reaction time was 2 min, which provided theoretical and technical support for further studying on development of rapid, safe organophosphorus pesticide detection instrument.
李 文1, 2，孙 明1，李民赞1*，孙 红1 . 微量乐果农药残留比色光谱快速检测方法 [J]. 光谱学与光谱分析, 2015, 35(07): 2029-2033.
LI Wen1, 2, SUN Ming1, LI Min-zan1*, SUN Hong1 . Rapid Detection of Trace Dimethoate Pesticide Residues Based on Colorimetric Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 35(07): 2029-2033.
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