The Froehde reagent is used as a simple spot-test to presumptively identify alkaloids, especially opioids, as well as other compounds. It is composed of a mixture of molybdic acid or a molybdate salt dissolved in hot, concentrated sulfuric acid, which is then dripped onto the substance being tested.
The United States Department of Justice method for producing the reagent is the addition of 100 ml of hot, concentrated (95–98%) sulfuric acid to 0.5 g of sodium molybdate or molybdic acid.
The Virginia Department of Forensic Science method uses 0.5 g ammonium molybdate per 100 ml H2SO4 (conc.)
Unheated sulfuric acid can be used to prepare the reagent in a less dangerous manner, but 2–4 hours must be allowed for the molybdate to dissolve.
+ Final colors produced by Froehde Reagent with various substancesSubstance Color Amphetamine No reaction or RedCathinone No reactionMethcathinone No reaction4-MMC No reaction 3-FMC No reactionMDMA BlackMethylone Bright yellowMDPV Bright yellowButylone Yellow > Green3,4-DMMC Light brownNaphyrone OrangePMA Pale greenPMMA Pale green4-MeO-PCP Light yellowMethoxetamine Yellow - Green3-HO-PCE Black5-MeO-DALT Yellow4-AcO-DALT Yellow > Green4-HO-MET Yellow > Green4-HO-MIPT Yellow > Green4-AcO-DET Yellow > GreenaMT Yellow5-IT Red brown5-APB Dark purple6-APB PurpleCamfetamine Tan > Dark yellowMethiopropamine Light brownMDAI Green > Black5-IAI OrangeAllylescaline Green > Black (fast)2C-T-2 Orange > Purple2C-B Yellow2C-P Greenb-methoxy-2C-D RedAcetaminophen Pale blueAspirin Greyish purple or Blue > PurpleAlimemazine Purple redChlorphentermine GreenChlorpromazine HCl Very deep redContac HCl Moderate olive brownDimethoxy-meth HCl Very yellow greenDiphenhydramine OrangeDoxepin HCl Deep reddish brownDristan Light bluish greenEphedrine BrownExedrine Brilliant blueFlurazepam OrangeLSD Moderate yellow green, Yellow GreenMace Light olive yellowMDA HCl Greenish blackMescaline Green or brown or light yellowMeperidine GreyModafinil Deep orange/redMorphine monohydrate Deep purplish Red > SlateHeroin HCl Deep purplish red > GreenOpium Brownish blackOxycodone HCl Strong yellow - Blue or GreenCodeine HCl Very dark Green > Red - BrownHydromorphone Blue > PurpleHydrocodone Light YellowPentazocine BluePethidine YellowPhenoxymethylpenicillin BluePhenyltoloxamine GreenPromazine OrangePromethazine Purple redPropoxyphene HCl Dark greyish red or BrownPropylhexadrine Purple redSugar Brilliant yellowSalicylic acid Purple redTetracycline Purple redThioridazine Purple redGuaifenesin Green with purple streaksMethapyrilene PurplePyrilamine PurpleTrifluoperazine OrangeTriflupromazine Orange
See also Reagent testing Drug checking Dille–Koppanyi reagent Folin's reagent Liebermann reagent Mandelin reagent Marquis reagent Mecke reagent Simon's reagent Zwikker reagent
References