Serious Chemistry Challenge, but hopefully interesting

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p1t1o
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Serious Chemistry Challenge, but hopefully interesting

Postby p1t1o » Wed Nov 28, 2018 2:12 pm UTC

I have a liquid.

It is Propoxylated Glycerol, 1<n<6.5, CAS# 25791-96-2

Using common NMR, IR and HPLC techniques - or any reasonable variant thereof:

Suggest a method that can tell me relative proportions of the different degrees of propoxylation.

Eg: 10-20% 1molar propoxylated; 30-50% 2molar propoxylated etc....

The concentration does not need to be exact, in fact the concentration bands given can be as wide as you like. Actually all I really need is an upper bound.



There is an advanced form of mass-spectrometry called MALDI-TOF - basically a fancy method of ionising substances that minimises fragmentation, so the masses you get out can be held to correspond to the individual fractions - which can apparently do this, but this is an advanced and expensive test that we would have to commission in a 3rd party lab, which we want to avoid.


This is not homework, this is real work. Take a bash at out-smarting a team of professional scientists.


PS: oh and no, we do not have access to any standard materials, other than glycerol itself.

p1t1o
Posts: 941
Joined: Wed Nov 10, 2010 4:32 pm UTC
Location: London, UK

Re: Serious Chemistry Challenge, but hopefully interesting

Postby p1t1o » Thu Dec 06, 2018 10:51 am UTC

Seems like this isnt really possible without a Mass-Spec in the loop, we're going with LCMS.

Nextybrown
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Joined: Fri Feb 22, 2019 11:35 am UTC

Re: Serious Chemistry Challenge, but hopefully interesting

Postby Nextybrown » Fri Feb 22, 2019 11:48 am UTC

p1t1o wrote:Seems like this isnt really possible without a Mass-Spec in the loop, we're going with LCMS.

Have you used Photoemission Method ?
Photoemission is divided into two categories: fluorescence and phosphorescence. Emission of a photon from the singlet excited state to the singlet ground state—or between any two levels with the same spin—is called fluorescence. Emission between a triplet excited state and a singlet ground state—or between any two levels that differ in their respective spin states–is called phosphorescence. Both fluorescence and phosphorescence can be used for qualitative analysis and semi-quantitative analysis.

p1t1o
Posts: 941
Joined: Wed Nov 10, 2010 4:32 pm UTC
Location: London, UK

Re: Serious Chemistry Challenge, but hopefully interesting

Postby p1t1o » Mon Feb 25, 2019 10:31 am UTC

As it happens there was a whole thing where NMR revealed average molecular weight well in excess of what we were expecting, precipitating a discussion with the supplier where we were like "This stuff is WHAT?!" and then another whole thing where we had to change our regulatory requirements because the substance turns out to be in a whole other category from what we expected. So in the end, the question became moot, but it was an interesting problem for a while considering my day-to-day work consists mostly of organising paperwork.


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