Please, even if it is not harmful in small measures, give me some tests which are simple enough to find out some chemicals in food items like vegetables, fruits, etc. that we get from the farms.
Actually by harmful I mean the simplest chemicals that can be detect using simple lab techniques which cause simple or complex unwanted effects in the body. as long as the tests are simple I don't care what effects they cause.
What are the different ways to detect harmful chemicals in food? I need to find at least 5 tests for different chemicals for my chemistry investigatory for my final exams. I have only chemicals available in a standard lab in my hand.