I mean if they're making stuff that is designed to alter your production of red blood cells, is that 2% of stuff likely to be inert or be stuff that has an effect on you?
What's the usual purity percentage of say, OTC aspirin?
e.g. https://uk.answers.yahoo.com/question/index?qid=201008170449...
This is mostly deliberate, but acetic acid is a common contaminent in the manufacturing process.
It's not FDA approved and probably made in lab with the same stringent quality controls as the clandestine ones in China pumping out similar things.
The 98% purity thing shows that they weren't willing to put in the extra investment to run enough solvent washes / whatever to not poison their customers.
Then why does it come in pill form? And why do they only sell it to researchers - including those doing clinical trials?
It is available to researchers as they are able to use it in non-human assays, experiments and studies.
[1] https://www.caymanchem.com/app/template/Product.vm/catalog/1...
There really aren't other offerings online for this chemical and I doubt that the suppliers are doing back alley deals with research teams in the US.
Someone in the supply chain knows exactly what this compound is for. They know people are buying it to be consumed. They commissioned a foreign lab to have it produced. They could have found a pharm grade lab to produce it. They didn't, because the margins are high on quasi-illicit substances produced in Chinese labs.
It was a cheap synthesis to get tons of the stuff on the market quickly with a huge margin. It's certainly meant for human use.
Of course, it depends on what the impurity is. If it's ethanol, you can have a few percent. If it's a suspected carcinogen, the level might be in ppm.
Peptide drugs will also typically be cyclized with sulfur bridges, so they don't get destroyed by proteases before doing whatever it is they are supposed to do. They're also pH adjusted.
So once the initial synthesis is complete, your purity may be pretty low. You then run your mix of desired molecule plus oodles of incomplete reaction products through a HPLC column a few times, and take the fraction that has the right molecular weight, until the desired purity is reached.
After doing so, whatever is left is going to be a high fraction of the molecule you want, and a tiny fraction of coincidentally similar peptides, which will probably be inert in the body and quickly destroyed by proteases.
If the drug is from an organic synthesis, the 2% impurity is going to depend on the synthesis processes used. It might be leftover catalyst that can't easily be separated, or stereoisomers, or incomplete reaction products.
For regular pharmaceuticals, that 2% is likely to be harmless. For home-made krokodil, that 2% could cause your skin to rot and fall off. Chinese biochem labs will send you pretty much anything you ask for, but you'll have to do your own QC on it. You're not going to win a consumer protection lawsuit there, and the only weapon you have for compliance is to stop paying them and switch labs.
An OTC aspirin tablet is going to start with x% pure acetylsalicylic acid. The dosage mass per tablet is added. Then inert, known-safe binders and fillers are added, like cellulose and dextrose, to make the dosage amount more convenient for handling and swallowing. The original impurity amount is swamped by fillers, so you really just need to know the percentage to determine what mass of the powder you need to add per tablet to get the correct dose. If your aspirin starts at 50% pure, you add 300 mg of it to get a 150 mg dose. Then you add 700 mg of filler to make a 1 g tablet. If it's 98% pure, you add 153 g to get a 150 mg dose, and add 847 mg of filler. The only concern would be whether the original impurities are more dangerous than the filler you use.
Typical impurities for synthesized acetylsalicylic acid are salicylic acid (unreacted starting reagent), ortho- or para- substituted salicylic acid, which may be esterified, acetic acid, salicylic acid ester dimer, and ethyl salicylate. The impurities will mostly be salicylic acid and vinegar. Salicylic acid is a metabolite of aspirin anyway, and is also antipyretic, analgesic, anti-imflammatory. A lower-purity batch of aspirin probably won't be dangerous to use. But for different drugs, the impurities will be different! If the impurity could be a deadly poison, there's a big difference between 98% pure and 90% pure.