A survey of some of the articles which can be found through the PubMed database suggests that, without sophisticated knowledge of chemical analysis and equipment, you really can not get an accurate analysis of drug ingredients found on the illicit market.

An article from the Journal of Forensic Sciences, 2005 Nov;50(6):1342-60, descibes "Proton nuclear magnetic resonance spectroscopy (NMR) methods for determining the purity of reference drug standards and illicit forensic drug seizures." Another article, from the Archiv fur Kriminolgie, 1996 Jan-Feb;197(1-2):16-26, discusses using "liquid chromatography and photodiode array detection." Another article describes the "gas chromatographic signature" of illicit samples (Journal of Forensic Sciences, 2007 Jul;52(4):860-6). You can obtain these articles through an academic library - a reference librarian can help you find them using the citations provided. The articles will provide discussions of how these procedures can be carried out, and the citations at the end of the articles should provide further resources.

These and other articles found in the database discuss the results of such analysis. Since this was not your question, I will only cite the title of one additional article, from the Journal of Emergency Nursing, 2008 Feb;34(1):80-2: "Luck of the draw: common adulterants found in illicit drugs." This gives a sense of how much you, or for that matter "your dealer," typically knows about the ingredients of illicit drugs.