Quote Originally Posted by davemugnaini
Are you sure the shampoo doesn't work?
I'm positive. Substances trapped within the hair shaft will not be removed by any kind of chemical treatment, without dissolving the hair itself. If you passed, then it was because the levels and/or usage patterns of substances being tested for were below the failure point, that's all. In point of fact, the hairs to be tested are thoroughly washed anyway in strong solvents to remove surface contaminants which may skew the test (which is either gas chromatography or mass spectrometry), before the hairs are cut up into 1/4" pieces, broken down with chemicals, cetrifuged, and the resulting soup extracted for testing.