Where can I find information on how to think through test such related substances, HPLC, IR, UV, GC etc?

HPLC user’s guide: http://kerouac.pharm.uky.edu/asrg/hplc/h.
Gas Chromatography (GS) http://en.wikipedia.org/wiki/gas_chromat. . Here you may also find (at the bottom of the article), external links to the other analytical methods.
possibly check here :
http://www.usdoj.gov/dea/programs/forens.