I was reading an article about an independent pharmaceutical watchdog group called Valisure which recently released a report stating that they found Benzene, a toxic substance, in many bottles of consumer sunscreen. (Full report here: https://www.valisure.com/blog/valisure-news/valisure-detects-benzene-in-sunscreen/ )
Valisure LLC has tested and detected high levels of benzene, a known human carcinogen, in several brands and batches of sunscreen, which are considered drug products by the Food and Drug Administration (FDA), as well as in after-sun care products, which are generally regulated by FDA as cosmetics. Benzene is known to cause cancer in humans according to the U.S. Centers for Disease Control and Prevention, the U.S. Department of Health and Human Services, the World Health Organization, and other regulatory agencies
As a layman, it made me marvel at how they are able to do this. What is the process by which a chemist is able to start with a complicated multi-ingredient substance like sunscreen, and determine that it contains a particular molecule, like benzene?
Is there some kind of litmus paper that ONLY reacts with something containing benzene, and not ANY other substance? Or do they mix in substances known to react ONLY with the other sunscreen ingredients, leaving benzene behind? This sounds like it would be incredibly complicated.
I'd love some more insight about how this works