To measure it properly in it's pure form (where dosages are in micrograms rather than milligrams), you need extremely high-precision instruments, and optimally a laboratory like environment, where things like air pressure are being controlled.
While I think this development, if true, is very good news, eventually the manufacturers of this stuff are going to start marketing it at a more-manageable concentration. Granted, that increases legal risk to whole supply chain, due to the packages getting larger (one of the 'beauties' of pure Fentanyl is that someone could transport $20,000 worth of it in 2 packets that would occupy a space as small as that between 'arches' of your feet and the bottom of your shoe), but I think it's inevitable that the labs making this stuff are just going to start diluting it.
The real problem is that Fentanyl is a 100% synthetic opioid, which means that it requires no actual 'Poppy Product' (no morphine/codeine/thebaine) as a precursor. Just 'other' chemicals, all of which have other 'valid' uses.
The only real solution to this crisis (assuming we're to remain as a 'free country') is to really, earnestly begin addressing it as public health crisis, stop making addicts into villains, increase expenditures for education dramatically, make it MUCH easier and cheaper for people to get replacement therapy such as buprenorphine and methadone ... and I think we're going to need to seriously ponder the UK approach of letting people register as addicts, and come to designated locations where they're given Rx Heroin (or oxycontin, or whatever), and clean needles for the IV users, and medical supervision ... and they are allowed to just ... use. Safely. Take the opportunity while they're there to give them counseling. Try to get them to switch to methadone or buprenorphine, make it easy and cheap to do so. Or try to get them into any sort of treatment programs that are shown to actually WORK.
We also need non-opioid drugs developed that legitimately ease the pain of opioid withdrawal. That 'tech' has not come far in 20 years, and that's ridiculous. The latest drug they're trying to get $1000's for for one course of treatment ... is just BARELY more effective than Clonidine (and the same method of action), which rehabs have been using for 20+ years.