Question: what kind of chemicals are used to test blood?

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  1. There are many, many tests for blood ranging from testing for blood types and blood related diseases, through to testing compounds in the blood to confirm illness, organ function, chemical levels and nutrition. Many of these tests don’t use chemicals for detection but tests for things in the blood can be detected directly by using equipment that can detect things in blood directly. Aside from chemicals or equipment that can detect things in blood directly, we can use more ‘biological’ approaches. One example is the ELISA test, which uses antibodies to bind to a target in the blood, and if the target is there, a colour change will occur that indicates the target is in present in the blood sample. Here is a simple sample using a test for the HIV virus in blood:

    In forensic science (more my area!), chemicals can be used to detect if blood is present at the crime scene. One example is the luminol test.
    The chemicals luminol, sodium hydroxide and hydrogen peroxide are mixed together. Crime scene officers then will spray this mix on an area that they think is suspicious. These chemicals react with even the tiniest traces of blood, and the result is that if blood is present it will glow blue. Even with good cleaning, or a fresh coat of paint, traces of blood can remain and last for a very long time, and luminol can detect these! however, there are some drawbacks – luminol can sometimes react with other things and give a false result; and luminol can destroy the DNA in the blood cells that could be used for further tests. However, this chemical test can be really useful in figuring out what has happened at a scene, and where to take samples, even long after the crime scene has been cleaned or a long time has passed! Here’s an example of a before and after where luminol has been used: