Updated November 22, 2019
By Julius Vandersteen
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.
FAQs
To the filtrate add 1ml freshly prepared ferrous sulphate solution and warm the contents. Then, add 2-3drops of ferric chloride solution and acidity with the dil. Hydrochloric acid if a blue or green precipitate or colouration is obtained, it indicated the presence of nitrogen containing insecticide.
How do you detect pesticides in vegetables? ›
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.
How do you detect pesticides in food? ›
Conventional methods for pesticide residue and metabolite detection mainly include gas chromatography, high-performance liquid chromatography, and chromatography–mass spectrometry.
How do you test for pesticides presence? ›
The pesticide residues are usually analyzed by the following methods:
- Gas Chromatography – Mass Spectrometry Coupled (GC-MS), especially for volatile compounds in complex samples.
- Liquid Chromatography – Mass Spectrometry Coupled (LC-MS), suitable for non-volatile compounds (thermally unstable molecules)
Chromatographic methods that are commonly used in determination and separation of target pesticides and herbicides include gas chromatography (GC) and liquid chromatography (LC). Mass spectrometry (MS) is used as an additional technique coupled with GC and LC in order to enhance the detection performance.
How do you test for pesticides in plants? ›
Compare the treated plants to untreated (or water-sprayed/drenched) plants nearby to see if there are any differences. Examine the flowers and youngest leaves most closely and check the underside of the foliage as well. Look for symptoms such as yellowing, distortion, brown spotting or bronzing, stunting or edge burn.
How can we avoid pesticides in fruits and vegetables? ›
PEELING and TRIMMING: Peel fruits and vegetables when possible to reduce dirt, bacteria, and pesticides. Discard outer leaves of leafy vegetables. Trim fat from meat and skin from poultry and fish because some pesticides residues collect in fat.
How do you know if food is pesticide free? ›
To be sure that the food you're buying is chemical-free, look for the organic seal. It means that the U.S. Department of Agriculture (USDA) has certified that the food contains no chemical fertilizers, pesticides, herbicides, hormones, drugs, or genetically modified organisms (GMOs).
Do fruits and vegetables absorb pesticides? ›
Pesticides don't always stop at the peel. While the peel can act as a barrier that slows pesticide absorption, some pesticides can penetrate deep into the fruit or vegetable.
What are the standard test methods for pesticides in food or water? ›
Gas and liquid chromatography (GC and LC) coupled to mass spectrometry (MS) are ideal for the identification and quantification of known and unknown compounds within a sample. As such, these techniques are widely used for pesticide residue analysis.
Most of the methods suggested by the Environmental Protection Agency (EPA) for the detection of pesticides in water are based on analytical techniques, such as high-performance liquid chromatography (HPLC) [58,59], gas chromatography (GC) [44,60,61,62], micellar electrokinetic chromatography (MEKC), enzyme-linked ...
Which fruits and vegetables absorb the most pesticides? ›
Here's the full list of the top 12 fruits and vegetables with the most pesticides this year. “More than 90 percent of samples of strawberries, apples, cherries, spinach, nectarines and grapes tested positive for residues of two or more pesticides,” EWG's report states.
How do you know if produce is pesticide free? ›
Shoppers can keep their eyes out for a few visible signs of pesticide testing. The most apparent is a USDA organic badge, signifying farmers grew the product without pesticides. Other seals and third-party certifications to look for include the Non-GMO Project and FDA-approved label.
Are all fruits and vegetables sprayed with pesticides? ›
Top takeaways for consumers: Almost 65 percent of Clean Fifteen fruit and vegetable samples had no detectable pesticide residues. Avocados and sweet corn were the cleanest produce – less than 2 percent of samples showed any detectable pesticides.
