Your opinion on handling UVCB substances

Off-topic conversations and chit-chat.

2 posts Page 1 of 1
Dear colleagues
There is no sub forum "Regulatory stuff" or so, so I don't know where to put this at best.
I am working in a rather small company who performs all kind of OECD studies for regulatory needs; mainly REACH/ECHA but also EPA and world-wide.
Especially ECHA is very difficult in the last one or two years regarding UVCB substances (for those not familiar with the ECHA wording: "Unknown or Variable composition, Complex reaction products or Biological materials").
For example, in the past it was sufficient for registration to use analysis of organic carbon for the determination of water solubility or monitoring of ecotoxicological studies. Nowadays it is required to provide specific analytical methods for this purpose.

What do you think, or what is your experience on this topic? How meaningful is it to develop and use an LC/MS/MS based method which will pick out one (or two or ten) components of a mixture of largely unknown composition and say: "Yes, now I know the concentration of this mixture in water!"?

I am asking because of a really problematic substance: A Polymer based dispersion (70 % in mineral oil). MW distribution is 500 - 20000 with maximum at about 3000, largely insoluble. Regulatory requirement is Daphnid and algal test and water solubility. TOC is not acceptable (and, of course, not helpful because it is not sufficiently soluble).

Best regards
Did you ever come up with an idea about this?
I'm not a regulatory person, and not the right person to answer, but it hurts seeing a serious question go unanswered.
The answer probably depends on what makes your test substance a UVCB, and it definitely depends on what you're trying to measure. In your case, because it's a polymer which qualifies as a UVCB presumably because it's an inordinately large number of peaks of different masses, but all chemically rather similar, you might be in luck. If you're trying to determine water-solubility, for example, you can probably assume that the solubility varies smoothly with molecular weight. So you could determine the solubility for a handful of peaks across the whole distribution, and use this to predict the solubility of everything in between? You could also, given a natural contaminated water sample, estimate the entire profile of peaks present from an analysis of only three or four across the range. But I'm not sure how helpful this is? Perhaps it's useful if you need to develop a really sensitive assay by triple quad, where you really can't look at every peak.
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