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Given a sample that is probably modafinil plus common fillers, but could be fake, what reagent tests would best determine whether it contains modafinil? Assume a known-good sample for comparison.

(Modafinil is a sulfur-containing atypical stimulant which has become common in some circles, but which, due to off-label use and the high price of the US name brand, is mostly obtained by mail order from slightly-sketchy websites in India and the UK. There are rumors that some fraction of the modafinil imported this way is fake, but this is only rumor because the effects vary to begin with, and most people don't seem willing to pay for laboratories to do proper testing.)

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    $\begingroup$ Why are you limited to reagent tests? Could you acquire an NMR spectrum of the compound? $\endgroup$ – Mad Scientist Mar 23 '13 at 19:30
  • $\begingroup$ @MadScientist - it sounds like the OP might want a kitchen-level test to distinguish good/bad when he opens the package after delivery. $\endgroup$ – Ben Norris Mar 24 '13 at 11:05
  • $\begingroup$ Yep, pretty much that, with the additional wrinkle that a lot of the testing should be done by third parties who're more cost-sensitive than I am. Saturating the market with reagent test kits is feasible in a way that saturating it with gift certificates for NMR is not. $\endgroup$ – jimrandomh Mar 24 '13 at 12:27
  • $\begingroup$ Which circles is it popular in? $\endgroup$ – Brian Apr 4 '13 at 11:58
  • $\begingroup$ @jimrandomh: Modafinil as a molecule is a sufficiently large and complex organic molecule to mean that I'd be fairly confident that there isn't really going to be a good 'add this to it and only modafinil does X' test. You could consider testing physical properties and something like solubility and pH instead; they're hardly unique, but relatively easy to test. I don't think there's even a good easy reagent test for sulphoxides, unfortunately. $\endgroup$ – Aesin Apr 5 '13 at 0:00
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Honestly, I don't think the average kitchen is equipped to identify (with any accuracy) the presence of this molecule in pills that likely vary in impurities, fillers, etc. depending on the website you buy them from.

With that said, I don't think it's unreasonable that someone could develop an inexpensive testing kit that could at least give a "positive" or "negative".

The area of the molecule I would focus on is not the amide or sulfoxide, but the diphenyl group attached to the sulfoxide. These conjugated rings will absorb UV (literature suggests lambda max around 220-230 nm). So you have a molecule that absorbs UV and is hydrophobic, and you need to separate it from the other pill contents for analysis. One way to do this would be with a mini-TLC kit, where the Modafinil could be detected as dark spots under UV light.

Example Kit:

  • Small vial + cap
  • Organic solvent (this would be determined by your own testing) in dropper bottle
  • TLC plate(s)
  • Small glass capillary (for spotting plates)
  • UV-LED Light
  • Cool UV-protective glasses

Example Procedure:

  1. Crush pill, add to vial
  2. Add a few drops of organic solvent (provided by you in dropper bottle)
  3. Cap vial, shake well (trying to extract Modafinil into organic phase)
  4. Spot TLC plate, elute with appropriate solvent
  5. Compare Rf of spot to the Rf of Modafinil standard (alternatively, the presence or absence of the Modafinil spot may be enough to provide a positive or negative result).

If you are the person developing such a kit, calibration would need to be done using a known "good" sample of the Modafinil. I would be careful to watch for other UV absorbing impurities that may be found in the pills (e.g. reagents from synthesis). You could confirm these results using an HPLC with UV detector or NMR (or whatever other appropriate techniques you have access to).

If all else fails, do as the previous answer says and smell your pee!

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Complex structure

Modafinil is a pretty complex molecule and judging by its structure (see below) I think it will be extremely difficult to find a single reagent test that will identify it.

enter image description here

Post-consumption identification

Interestingly it is much easier to find after consumption, either by the strong sulfur smell of your urine or through chromatography techniques (also here).

'Sketchy' tests

There are apparently some simple tests you can try like dissolving it in hot water and vinegar (which should happen without formation of gas), but these tests are far from fool-proof and might even cause you to think something is a fake while it is not.

Combination of physical/chemical tests as a 'solution'

The best thing to do if you really want 'kitchen-level' tests is to test for a whole range of chemical/physical properties. For example this reference has some information on the pH, water solubility and melting point which are fairly easy to test. Passing the tests will certainly not guarantee anything, but at least it will take away a significant part of the doubts that the product is fake.

Something to consider when designing these tests is that there will always be fillers (e.g. lactose monohydrate, microcrystalline cellulose, pregelatinized starch, croscarmellose sodium, povidone, and magnesium stearate) in the sample so you have to find ways to correct for that.

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