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Simple Test

No one wants to eat pesticides, but testing food and water takes time and money. Scientists in Hamilton, Ontario have developed a test for pesticides that is as simple as dipping a small strip of paper in a sample of food or water and waiting for a few minutes. Most pesticides affect the nervous system by interfering with the enzyme acetylcholinesterase, so the strips have this enzyme on one end and IPA on the other. IPA is a compound that turns blue when acetylcholinesterase breaks it down.

Here’s how it works: the enzyme end is dipped into a sample, and the IPA end is dipped into water. Capillary action causes the moisture from the two ends to flow into each other, and the resulting colour tells you if you have pesticides or not. If it turns blue, there are no pesticides and the acetylcholinesterase was able to break down the IPA. If there are pesticides present they will not allow as much of the acetylcholinesterase to work, so the shade of blue will be lighter. It will vary depending on the amount of pesticides present.

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Article condensed from:  The New York Times, Tuesday, December 29, 2009

“A Simple Paper Test May Detect Pesticides”

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Here’s a simple activity that illustrates this process: First find a coffee filter, some markers, and a cup of water. Next, cut the coffee filter into strips about an inch wide. Then, choose two different coloured markers and draw a tiny circle on each end of the coffee filter strip. Colour them in. Finally, dip each end of the strip into water for 2 seconds and lay it flat. Watch and wait. What happens to the colours as the water moves in the strip? This movement of water is called capillary action, the key mechanism in these pesticide-testing strips.

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