By ruthy6186 on Tuesday, November 4, 2003 - 08:13 pm:
Suppose that you were working in a criminal or research lab and you were handed an unidentified substance vial and were told that it probably possessed 5 prescription/illegal drugs. How would you go about proceeding to identify these drugs given a specific solvent (such as pet. ether/acetone) used to dissolve them? How could you quantitatively confirm the presence of these drugs when making your toxicology report to the chief lab inspector? Be specific!
By Anonymous on Tuesday, November 4, 2003 - 10:09 pm:
The best people to solve this homework are either Dr. Quincy in Los Angeles or Dr. Grissom in Las Vegas!
By Anonymous on Wednesday, November 5, 2003 - 05:45 am:
How about the group in Miami? Or maybe Mark Harmon in the Navy?
By Almost Criminalist-only resolved 99% of polygraph questions in 1976 on Wednesday, November 5, 2003 - 07:27 am:
Wait a minute, Anonymous 1: Sam did all the work and Quincy got all the credit. Grissom and his crew, like Quincy, do stuff way beyond the scope of their jobs, such as questioning suspects. Also, Ruthy, you mean qualitatively confirm the presence, quantitatively is how much. Yes paper or TLC could give an indication of presence of some or all of these 5 drugs, but court of law proof demands GCMS identification, I believe.
By mgoodwin on Wednesday, November 5, 2003 - 11:31 am:
First diagnosis is generally a visual inspection. Is it a white powder? Vegetation material? And protocol is driven from there.
Spot chemical rxns and TLC can be used to eliminate an unknown as a possible controlled substance, but not for definitive determination.
Today GC/MS is widely used for definitive determination. Though perhaps a less specific detector like FID could be used should a the drug have the same retention time as a standard on 3 diverse columns (say PDMS, Carbowax, trifluoro)...especially if visual, spot chems and TLC also check as positive.
Inject the sample and repeat again with the standard (often a NIST library hit is not good enough for court). Do they have the same MS pattern and retention time?
With some drugs, knowing if it is free base, or HCl salt requires additional testing sometimes performed on a FT-IR. Cocaine free base and HCl can be determined there...GC/MS will not.
For quantitation, I've seen toxicologists use GC/FID since it has a better linear response to concentration. Though I imagine a stable isotope drug standard could be used with the MS too.
As I am not a drug forensic chemist, I don't know more detail than this. However, at your request, I could email you a phone # to a forensic laboratory. perhaps they can answer more specifically or recommend a book.