Team:SSHS-Shenzhen/Human Practices/4

2018.igem.org/Team:SSHS-Shenzhen)

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Learning to quickly detect pesticide residues

Date: August 18, 2018

Location: Research lab at Shenzhen University

We wanted to find out the situation of food safety in small farmer’s markets, where food safety control is less strict. We also want to find a simple pesticide residue detection method, which people can use at home. Thus, we performed another round of pesticide residue detection using quick pesticide detection method. Five of our iGEM team members gathered at the laboratory of Shenzhen University to find out methods for quickly detecting pesticide residues on vegetable leaves. We bought three groups of vegetables from three different places to detect pesticide residues. They are from a small farmer's market, a farmer's market and a supermarket (Renrenle supermarket). The three vegetables are Pak Choi, Chinese flowering cabbage, and Water spinach. Arriving at the lab, everyone appeared to be a little overwhelmed. At first glance, detecting residues emerged as a complicated matter.

But when we really got started, we found that the method of quickly detecting pesticide residues is rather simple and convenient. Generally, there are two methods for detecting pesticide residues on vegetable leaves: one is to use a pesticide residue detector; the other is to employ test strips. We chose the second method, thus ordering test strips online and completing our pesticide residue test under the guidance of Deng Zihan's father.

Let's take a look at the process of using those pesticide residue test strips:

Unpack the pesticide residue test strip, take out the eluent and the pesticide residue test strips. Drop 3-5 drops of eluent on one leaf and gently rub it with another leaf. Transfer the eluent onto the white tablet on the test strip and wait for 10 minutes. Fold the test strip in half and press it tightly for 3 minutes. Unfold the strip and interpret the results based on the color change on the white tablet. Compare the strip to a blank control strip. If the white tablet remains uncolored or turns slightly blue, the results are positive. A white color shows a strong positive result, indicating high pesticide residue. A light blue color shows a weak positive result, indicating low pesticide residue. A sky-blue color is identical to the blank control strip, showing a negative result. Our final results are carefully documented. Based on our test results, there were small amount of pesticide residues in the samples we tested.

Although the test strips may not have the precision and accuracy of a pesticide residue detector, they are very convenient and practical as a measure of purchasing food in daily life.