| Nowadays, food safety problem is very prominent, and especially the problem of pesticide residue. The conventional detection methods of pesticide residues have higher precision, but these methods have some defects such as complex pretreatment, long detection time, high cost, etc. Therefore, these methods are not suitable for on-site rapid detection of pesticide residues in food and agricultural products. In this study,Surface-enhanced Raman spectroscopy(SERS) technology was used to qualitatively and quantitatively analyze the commonly pesticide residues(thiabendazole and triazophos) and prochloraz residue in oranges, and the rapid detection method of pesticide residues in oranges were developed. This study provides a basis for rapid screening equipment development of pesticide residues in orange. The main research contents are as follows:(1) The rapid detection method study of thiabendazole residues in navel orange flesh were studied using SERS combined with Solid Phase Extraction method.SPE-C18 solid phase extraction column was used to filter extraction, and eliminate fluorescence interference of pigment, ribose and other substances. Five characteristic peaks of thiabendazole are identified, namely 785, 1010, 1274, 1330 and 1562cm-1. The standard curve was plotted with the intensity of the peak 1010cm-1 and the SERS signals of thiabendazole standard solutions(1 ~ 50 mg / L) had a good linear relationship. The linear equation was y=813.6x+16268, the correlation coefficient was R2=0.9904. Thiabendazole solutions with orange flesh extract as the matrix can be detected by SERS method in low concentrations of 5mg/L.(2) The methods of qualitative and quantitative analysis of prochloraz residue in navel orange flesh and peel by SERS were studied. Graphitized Carbon, Anhydrous Magnesium Sulfate, PSA and C18 were used to eliminate fluorescent interference of pigment and other material. Five characteristic peaks of prochloraz are identified, namely 427, 829, 1006, 1076 and 1254cm-1.The standard curve was plotted with the intensity of the peak 1077cm-1 and the SERS signals of prochloraz concentration(8~25m /L) had a good linear relationship. The linear equation were y=30.176x+665.51 and y=51.448x+1066.1 respectively, and the correlation coefficient were 0.9747 and0.9849 respectively. The averaged recoveries of prochloraz pesticide residue in navel orange flesh and peel were 94.07% ~ 102.53% and 91.33% ~ 99.57% and relative standard deviations were 4.35%~7.46% and 3.86%~8.95% respectively. The minimum detection concentration for prochloraz pesticides in navel orange flesh and peel were 5mg/L and 8mg/L respectively.(3) The qualitative and quantitative analysis models of triazophos residues in navel orange flesh and peel by SERS were developed. Six characteristic peaks of triazophos are identified, namely 609, 976, 999, 1320, 1408 and 1596cm-1. Acetonitrile was selected as the internal standard and the relative intensity was made by characteristic peak(1409cm-1) of triazophos and characteristic peak(2257cm-1) of acetonitrile, and the quantitative analysis model of triazophos pesticide in navel orange flesh was developed. A good linear relationship was found between the relative intensity and concentration of triazophos in the range of 0.5~20mg/L. The averaged recoveries were 84.44%~95.02%,relative standard deviation was between 0.84% and 6.12% respectively. The model of triazophos pesticide in navel orange peel was established by partial least squares regression model. The correlation coefficient and root mean square error of prediction(RMSEP) were0.9669 and 1.60 mg/L. The model was used to predict the three unknown concentration of navel orange peel triazophos pesticide residues, and compared with the chemical method measured values. The absolute values of the relative error were between 0.08% and 5.98%,and the predict recoveries were 94.36%~104.36%.The minimum detection concentration for triazophos pesticides in navel orange flesh and peel were 0.5mg/L and 0.8mg/L respectively. |
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