chemrox - 15-8-2007 at 22:18
Does anyone know how to mix Frodhe's reagent or what it is? It's used to distinguish among alkaloids and compares with Marquis reagent which I
understand to be 2 drops of formalin and 3 ml con sulfuric.
jim20/20 - 18-8-2007 at 11:40
do you mean froede reagant
Dissolve 0.5 g of molybdic acid or sodium molybate in 100 mL of hot concentrated sulfuric acid.
from
Color Test Reagents/Kits for Preliminary
Identification of Drugs of Abuse
http://www.ncjrs.gov/pdffiles1/nij/183258.pdf
phase_dancer - 18-8-2007 at 13:11
For Froehdes reagent, 'Clarkes Analysis of Drugs and Poisons' states 1.0g in 100mL of conc sulfuric acid. The temperature doesn't need to be high, but
stiring helps. I've found the reagent keeps well for over 2 years if refrigerated.
Here's a few color references;
Color -- Compound
Yellow -- Hydrocodone, pethidine
Yellow–blue -- Oxycodone HCl
Orange -- Diphenhydramine, flurazepam, promazine, trifluoperazine, triflupromazine
Green -- Chlorphentermine, codeine, mescaline, oxycodone, phenyltoloxamine
Yellow–green -- Lysergide
Blue -- Pentazocine
Red -- Amfetamine, chlorpromazine HCl
Grey–red -- Propoxyphene HCl
Purple–red -- Alimemazine, diacetylmorphine, promethazine, propylhexadrine, salicylicacid, tetracycline, thioridazine
Brown -- Ephedrine, mescaline
Red–brown -- Doxepin HCl
Black -- (nothing listed)
Brown–black -- Opium
Green–black --Methylenedioxyamphetamine (MDA) HCl
The following paper is an excellent reference for Froehdes and other reagents, listing reaction color changes for over 200 drugs :
Johns, S. H. et. al., "Spot Tests: A Color Chart Reference for Forensic Chemists," Journal of Forensic Sciences,
Volume 24, No.3, July 1979, pp. 631-649
guy - 18-8-2007 at 14:06
That's cool, how does it work?
@phase_dancer
chemrox - 18-8-2007 at 22:57
@phase_dancer
Thanks for the ref. Could you copy the article and post a link to it?
phase_dancer - 19-8-2007 at 00:34
chemrox; see this link in the reference section.
As for the mechanisms behind the reagent reactions; I was hoping someone else might offer something solid. I've nothing definitive and can find no
reference to the exact mechanisms of this reagent. Mo oxidation states and various ligands produce interesting but also some complex compounds. See
Kirk-Othmer Encylcopedia of Chemical Technology, 4th Ed, vol 16, p 469