The Method On Sers-Based Rapid Detection For Diquat In Friuts And Vegetables

Fruits and vegetables are essential green foods for people’s daily diet. Recognized as important ingredients to health, they can provide essential vitamins and dietary fiber and play preventive role for a variety of diseases.As a widely used field herbicides, Diquat is heavily soluble and it can cause water pollution when it flows into water,and has moderate irritation to eyes and skin, and a lot of eating and bioaccumulation can cause damage to heart, liver, spleen, lung and other organs. The lethal dose for the human body is 6 g~12 g.Based on the SERS technique for analyzing fruits and vegetables, we establish a rapid detection method of Diquat in this study.The pretreatment is simple, detection is fast and accuracy is high. It provides a convenient technical means for field inspection and supervision of Diquat in fruits and vegetables. Main research contents and results of this paper are as follows:1. By atlas-collecting from the Diquat standard aqueous solution through using portable Raman instrument, we found that Diquat reached its peak at the position of741 cm-1、1008 cm-1、1081 cm-1、1202 cm-1、1246 cm-1、1335 cm-1、1395 cm-1、1541cm-1 and 1593 cm-1, especially at 1593 cm-1. So by this test we confirm that the Diquat reaches its characteristic peak at 1593 cm-1.2. By optimizing the conditions of enhanced substrates, pH, type and concentration of coagulant, amount and orders of adding, etc, the best test condition for Diquat standard solution is the silver sol : 0.1M NaCl(flocculant) : Diquat = 1:1:4, and system pH is 7.0;The detection limit of Diquat aqueous solution is 0.05 μg/kg and within the scope of0.05~1μg/kg, the test result of SERS reads the well liner relationship with relativity of0.9977.3. Based on single-factor test, the best test condition of Diquat in fruits is the silver sol :0.1M NaCl(flocculant) : Diquat=1:1:3, and system pH is 13.0; By testing of the SERS of concentration gradient compared with basal blank, we found that Diquat shows it peak at the level of 1593cm-1. The performance of the peak reads the well liner relationship with Diquat. As for watermelons and the strawberries, Diquat accordingly shows the liner range of 10~150 μg/kg and 0.1~0.5 mg/kg, and minimum limits tested as 10 μg/kg and0.1 mg/kg. The recycling ratio differs all from 86.84~109.32% with relative standard error no more than 5%.4. The best test condition of Diquat in vegetables is the silver sol : 0.1M NaCl(flocculant) : Diquat = 1:1:3 with the system pH of 12.0. The Diquat in the cabbages reads the limits of 3.0 μg/kg, liner range of 3.0~80 μg/kg, and liner relativity of 0.9924.The Diquat in cucumbers reads the limits of 10 μg/kg, liner range of 10~100 μg/kg and liner relativity of 0.9966. And the Doquat in potatoes reads the limits of 0.2 mg/kg, liner range of 0.2~1.0 mg/kg and liner relativity as 0.9983.