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BDD Moderators: Keif’ Richards
FT-IR Spectrometer Analysis
- Thread starter dylan007
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IR is more about identifying the main material present rather than purity and is as reliable as anything else provided....
1 the sample in the machine is the same as the rest of the material
2 you have the IR spectrum is of a pure sample of reference compound. Otherwise it is down to how good at interpretation of IR spectra you are, most people are pretty poor beyond identifying some of the common groups.
NMR is much easier to interpret, and provides some measure of purity as well.
FT-IR alone is pretty worthless in this case. If you have an idea of what your substance might be, and a reference material or spectrum of the substance in question, you can get a fairly reliable identification by comparison of spectra.
It's possible to intrepret the spectrum of an unknown and propose a structure, but I wouldn't call it identification unless you can match it with a reference spectrum. Even then, you can't always distinguish between isomers. I spent a lot of time poring over IR spectra in my younger days, but I haven't touched an FT-IR since I left the uni.
HPLC-UV is fine for purity assessment, but again you'd need a reference material to do it properly (i.e. by quantitative determination). Some contaminants/solvents would not show up in your chromatogram, and evaluating the peak area of target compund vs peak areas of contaminants will only give you a ballpark figure, at best. Often referred to as "HPLC purity", it tends to produce falsely high results.
GC-MS with an experienced operator is hard to beat. Interpretation of spectra and preferably library search can give you a pretty reliable ID even if you don't have the reference material. True purity tests will require a reference material, but purity assessment by comparison of target and contaminant peaks ("GC-MS purity") is also possible and gives decent results unless the product contains a lot of solvents or other volatiles.
NMR is great too, but NMR spectra aren't exactly easy to interpret, especially if you've got a lot of contaminants. A couple of years back, I had a chance to play with one of those nifty Bruker LC-MS-NMR hybrids for metabolite ID, but I ended up going back to plain GC-MS and LC-MS(/MS) for ID and occasionally 2D-NMR for additional confirmation.
It's possible to intrepret the spectrum of an unknown and propose a structure, but I wouldn't call it identification unless you can match it with a reference spectrum. Even then, you can't always distinguish between isomers. I spent a lot of time poring over IR spectra in my younger days, but I haven't touched an FT-IR since I left the uni.
HPLC-UV is fine for purity assessment, but again you'd need a reference material to do it properly (i.e. by quantitative determination). Some contaminants/solvents would not show up in your chromatogram, and evaluating the peak area of target compund vs peak areas of contaminants will only give you a ballpark figure, at best. Often referred to as "HPLC purity", it tends to produce falsely high results.
GC-MS with an experienced operator is hard to beat. Interpretation of spectra and preferably library search can give you a pretty reliable ID even if you don't have the reference material. True purity tests will require a reference material, but purity assessment by comparison of target and contaminant peaks ("GC-MS purity") is also possible and gives decent results unless the product contains a lot of solvents or other volatiles.
NMR is great too, but NMR spectra aren't exactly easy to interpret, especially if you've got a lot of contaminants. A couple of years back, I had a chance to play with one of those nifty Bruker LC-MS-NMR hybrids for metabolite ID, but I ended up going back to plain GC-MS and LC-MS(/MS) for ID and occasionally 2D-NMR for additional confirmation.
thanks for the reply on the different methods of testing a chemical, i hold this in high regard, however i have a question for you...
when going to buy chemicals from my source i was told... Research product, foil sealed and accompanied by "full batch data sheet" and "FT-IR Spectrometer Analysis" to prove legality and purity
on this quote above would you say this is reliable and are most likely to be receiving the desired chemical.
i would appreciate a reply, as you seem to be someone who actually knows what they are talking about
MurphyClox
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GC-MS and NMR will fail if the adulterant is either an insoluble compound (well, in this case one should see insolubles swimming around, if the sample was chosen big enough; if not, you'll see nothing) or an inorganic salt. What if the compound in question was laced with 10% NaCl?
The best way to obtain purity-data is IMHO GC-MS and a decent elemental analysis. The combination beats nearly everything.
- Murphy
The best way to obtain purity-data is IMHO GC-MS and a decent elemental analysis. The combination beats nearly everything.
- Murphy
Sounds sketchy to me. An enclosed FT-IR spectrum can by no means prove the legality and purity of the product. Provided that you know which substance your product should contain, and assuming that the FT-IR analysis was properly done and on this particular batch of material, anyone with a bit of experience with FT-IR should be able to say whether the spectrum is "consistent with" or "not consistent with" the stated content. That's a far cry from proving the identity of the compound, though.
It also says very little about purity. Some impurities might stick out in the IR spectrum, if they're present at sufficiently high concentration, but anything below say 5-10% by weight of the main compound would usually not be visible. So in theory, your product could very well contain significant amounts of harmful or illegal substances even if the IR spectrum appears clean.
There's of course no guarantee that the enclosed spectrum is representative for the supplied batch of material. That goes for GC-MS or NMR as well, it's dead easy to supply false data to customers who don't know or don't care. However, a decent GC-MS or NMR spectrum with the batch number and date printed in the file header would to me indicate that the supplier is probably serious. An FT-IR spectrum with no link to the product or batch number would to me indicate the opposite. An FT-IR spectrum is next to worthless on its own, and there's a good chance they just toss it in because it looks fancy to anyone not in the know. Any serious synth outfit should have access to proper equipment to certify their products. If FT-IR is the best they've got, they ought to be too embarrased to show it.
Now if I may ask, what's this "full batch data sheet"? A homemade MSDS of some sort, maybe? Anyway, I'd love to see it.
Just to keep things in a a kind of perspective... if you by coke or speed on the street, it doesn't usually come with a certificate of analysis and "full batch data sheet". At least not where I'm from. So a grainy FT-IR and a dodgy data sheet might sound like a step in the right direction, right? And who cares what's in this shit anyway as long as it gets you high as fuck? It's like sausages, we're happy to stuff them down our necks, but we'd rather not know what kind of crap they put in them.
Well I don't eat sausages and I want to know what's in my drugs, but that's just me.
It also says very little about purity. Some impurities might stick out in the IR spectrum, if they're present at sufficiently high concentration, but anything below say 5-10% by weight of the main compound would usually not be visible. So in theory, your product could very well contain significant amounts of harmful or illegal substances even if the IR spectrum appears clean.
There's of course no guarantee that the enclosed spectrum is representative for the supplied batch of material. That goes for GC-MS or NMR as well, it's dead easy to supply false data to customers who don't know or don't care. However, a decent GC-MS or NMR spectrum with the batch number and date printed in the file header would to me indicate that the supplier is probably serious. An FT-IR spectrum with no link to the product or batch number would to me indicate the opposite. An FT-IR spectrum is next to worthless on its own, and there's a good chance they just toss it in because it looks fancy to anyone not in the know. Any serious synth outfit should have access to proper equipment to certify their products. If FT-IR is the best they've got, they ought to be too embarrased to show it.
Now if I may ask, what's this "full batch data sheet"? A homemade MSDS of some sort, maybe? Anyway, I'd love to see it.
Just to keep things in a a kind of perspective... if you by coke or speed on the street, it doesn't usually come with a certificate of analysis and "full batch data sheet". At least not where I'm from. So a grainy FT-IR and a dodgy data sheet might sound like a step in the right direction, right? And who cares what's in this shit anyway as long as it gets you high as fuck? It's like sausages, we're happy to stuff them down our necks, but we'd rather not know what kind of crap they put in them.
Well I don't eat sausages and I want to know what's in my drugs, but that's just me.
Top_Cat
Bluelighter
Once the vendor in question gets the spectrometer fine-tuned and running, it should be providing pretty accurate... they're trying to be legit (supposedly)
^^their batch data sheet is as you expect (substance confirmation sheet really)
*I've had experience with them in the past*
^^their batch data sheet is as you expect (substance confirmation sheet really)
*I've had experience with them in the past*
fryingsquirrel
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Assuming it isn't just of photocopy they got off the net of course.
Top_Cat
Bluelighter
nah they have the machine itself... I was asked to help them calibrate it..
Top_Cat
Bluelighter
hey don't like sending out single gram samples...
you have to go to their offices for something like that..
On second thought, let's step it up one notch. My mind reading skills feel pretty sharp today, and think I know which product the OP has in mind. We won't mention any sources or leads, of course, but I'm guessing that this product is sold through an internet site at which they've been kind enough to post the FT-IR spectrum. Awfully decent of them to provide us with such entertainment. The analysis appears to have been done in Iran, and it shows no apparent link to the product or vendor (so I think we're safe discussing it). The quality isn't too bad, just a tad grainy, the wavenumber axis is reversed (at least compared with what I'm used to) and there is no mention of the acquisition mode. I presume it's a KBr disc. I'm not familiar with the software and I can't read the Farsi text at the bottom.
Dear OP, if you're with me thus far, would you care to copy the FT-IR spectrum onto an independent server and post it here for us to discuss? Just make sure there are no leads pointing back towards the source. I won't do it myself in case my guess was incorrect, and I don't want to litter your thread with irrelevant images.
Since I'm too impatient to wait for the image and for the mods' permission to discuss it, I'll give myself a head start.
Assuming that we are talking about the spectrum mentioned above:
First of all, this is certainly not (2,3)-epithio-17-methyl-17-ol-N-benzyloxycarbonyl-d-proline. I guess you've figured that out already, as there is no such animal.
As for what it is... well it's only a poorly resolved FT-IR spectrum and I can't do magic (aside from maybe read your mind), but it does indeed seem plausible that it's the spectrum of stimulant drug. There's a phenyl with a probable methyl substituent, an alkyl side chain and what appears to be the salt of a secondary amine. There seems to be a conjugated ketone as well, although the C=O stretch overtone is missing. No other functional groups are present as far as I can tell. I'd say the spectrum is consistent with a substituted cathinone. I'm not sure about the substitution pattern, but the upfield shift of the OOP C-H bend points towards a para-methyl, or perhaps ethyl. Obvious suggestions would be mephedrone or either of its N-ethyl or 4-ethyl analogues which are now on the market, but it might very well be another cathinone or something entirely different. I couldn't say for sure, even if I had reference spectra to compare with. That's why someone invented GC-MS.
@MurphyClox, unless you want to identify your contaminants, you don't really need that elemental analyser. The purity can be reliably and accurately determined by GC-MS alone. You start out with a known (weighed) amount of your sample, then of course you need a reference standard of known purity and a quantitative method employing an internal or external standard calibration (single point or curve). It's not much different from quantitative analysis of drugs in biological fluids, other than that the sample material needs to be diluted of course, and that the result is usually presented in % by weight rather than e.g. ng/mL or nmol/L. If your drug was cut with 10 % NaCl and nothing else, quantitative analysis by GC-MS or any other reliable method would give you a purity of 90% by weight (+/- uncertainty). Granted, it would't give us a clue about what those last 10 % might be.
Dear OP, if you're with me thus far, would you care to copy the FT-IR spectrum onto an independent server and post it here for us to discuss? Just make sure there are no leads pointing back towards the source. I won't do it myself in case my guess was incorrect, and I don't want to litter your thread with irrelevant images.
Since I'm too impatient to wait for the image and for the mods' permission to discuss it, I'll give myself a head start.
Assuming that we are talking about the spectrum mentioned above:
First of all, this is certainly not (2,3)-epithio-17-methyl-17-ol-N-benzyloxycarbonyl-d-proline. I guess you've figured that out already, as there is no such animal.
As for what it is... well it's only a poorly resolved FT-IR spectrum and I can't do magic (aside from maybe read your mind), but it does indeed seem plausible that it's the spectrum of stimulant drug. There's a phenyl with a probable methyl substituent, an alkyl side chain and what appears to be the salt of a secondary amine. There seems to be a conjugated ketone as well, although the C=O stretch overtone is missing. No other functional groups are present as far as I can tell. I'd say the spectrum is consistent with a substituted cathinone. I'm not sure about the substitution pattern, but the upfield shift of the OOP C-H bend points towards a para-methyl, or perhaps ethyl. Obvious suggestions would be mephedrone or either of its N-ethyl or 4-ethyl analogues which are now on the market, but it might very well be another cathinone or something entirely different. I couldn't say for sure, even if I had reference spectra to compare with. That's why someone invented GC-MS.
@MurphyClox, unless you want to identify your contaminants, you don't really need that elemental analyser. The purity can be reliably and accurately determined by GC-MS alone. You start out with a known (weighed) amount of your sample, then of course you need a reference standard of known purity and a quantitative method employing an internal or external standard calibration (single point or curve). It's not much different from quantitative analysis of drugs in biological fluids, other than that the sample material needs to be diluted of course, and that the result is usually presented in % by weight rather than e.g. ng/mL or nmol/L. If your drug was cut with 10 % NaCl and nothing else, quantitative analysis by GC-MS or any other reliable method would give you a purity of 90% by weight (+/- uncertainty). Granted, it would't give us a clue about what those last 10 % might be.
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MurphyClox
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Alcyone said:
Yep Sir, I totally agree, but availability of pure references could be the difficult part, in particular when speaking about 'novel' RCs with hardly any spectroscopic data or commercially available samples at hand (read: reliable source like Tocris or Sigma).
IF there is a pure sample available, I would go with your suggestion, too.
- Murphy
Actually, that would be "Yep Ma'am", if I may say so Sir.
Ok Alcyone once again thanks for your reply! i see you have taking interest into the post and are wondering which Sample "FT-IR analysis" photo that i have seen!
Ok lets get this straight first "the picture is a sample FT-IR analysis photo they provide and they have it on every product page, i think this is to show an example of what you will receive with your product"
ok here is the image
is this what your talking about Alcyone?
Ok lets get this straight first "the picture is a sample FT-IR analysis photo they provide and they have it on every product page, i think this is to show an example of what you will receive with your product"
ok here is the image
is this what your talking about Alcyone?
Yes indeed.
Do I understand you correctly that this spectrum is just an example and not necessarily consistent with the spectra they'll ship with their products? Posting random FT-IR spectra on their product pages is beyond stupid if you ask me. It certainly doesn't add to their credibility.
MurphyClox
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Oh! Please accept my apologies, Ma'am! I wasn't aware...Actually, that would be "Yep Ma'am", if I may say so Sir.
Top_Cat
Bluelighter
yeh the pictures went up before I believe they had the spectrometer calibrated..
I love the symbol for not for human consumption is a figure exploding from the inside out