Farmers often use insecticides, also known as pesticides, to keep insects from damaging or eating their crops. The Environmental Protection Agency establishes maximum insecticide residue levels in our food, and the Food and Drug Administration and the Department of Agriculture send inspectors to monitor insecticides on the nation’s crops. While growers are required to use only government-approved insecticides in a safe and consistent manner, there can still be residues even after you scrub and rinse the produce. An insecticide test kit allows you to detect the presence of insecticides in fruits and vegetables to get an idea of what you are consuming.
Obtain and unpack an insecticide test kit. There will be test tubes, an alcohol lamp, vials, tongs, test strips, acetone, glass slides, eyedroppers, capillary tubes, a color chart and two bottles containing different test solutions, which you will use in the order described in the test kit’s instruction sheet.
Cut a sample of the fruit or vegetable that you want to test for insecticide residue. Place a small amount of the fruit or vegetable, about 5 grams, into a test tube. Add 5 mL of acetone to the test tube, put a cap on the tube, and shake it up to extract material from the fruit or vegetable sample. Let the test tube rest for about 15 minutes, and then remove the cap.
Pour the acetone with the fruit or vegetable extract into a vial. Using tongs, hold the vial over an alcohol lamp to heat the liquid until it evaporates to one-tenth of the initial amount. Aim an electrical fan at the vial as well to help speed up the evaporation.
Add a drop of the test kit’s first solution to a strip of test paper with an eyedropper, and set it aside to dry. Dip a capillary tube (a thin piece of glass like the kind used to apply iodine from a first aid kit) into the vial holding the concentrated extract, and use it to place five drops onto the treated test strip. Sandwich the test strip between two glass slides, and hold them with tongs over the alcohol flame for a minute. Let them cool down for about three minutes.
Lift off the top slide and add one drop of the test kit’s second test solution to the test strip. It will now change color. Match the test strip’s color with a color chart (color schemes may vary depending on which company made your test kit) to determine what insecticide, if any, is present.
- Environmental Protection Agency: Pesticides and Food – What the Pesticide Residue Limits are on Food
- North Carolina State University; Pesticide Residues on Fresh Fruits and Vegetables: What’s the Risk?; Angela Fraser; 2004
- GT Pesticide Test Kit: Introduction to Basic Testing
- Glory Science: Pesticide Test Card
About the Author
Julius Vandersteen has been a freelance writer since 1999. His work has appeared in “The Los Angeles Times,” “Wired” and “S.F. Weekly.” Vandersteen has a Bachelor of Arts in journalism from San Francisco State University.