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Topic: Determination of mixture content  (Read 473 times)

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Offline Orcio_87

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Determination of mixture content
« on: March 19, 2022, 10:25:46 AM »
I have two mixtures, both of them contains compound "x" and compound "y" but - I do not know how much of "x" and how much of "y" these mixtures cointain.

Also - I measured properties of these mixtures.

Problem is....

Properties of first compund "x" is unknown (and I do not have it), but - I have pure (100 %) compound "y"...

Can I use it somehow to determine composition of both mixtures ?

Like...

Mixture 1. has measured value 2000

Mixture 2. has measured value 1000

Pure compound "y" has value 100, so mixture contains a % of x and b % of y, and second mixture c % of "x" and d % of "y" ?

I am not sure.. is it problem with my mathematics or is it just a problem with too many unknown variables ?

(I dont want to waste the time for something that cannot be solved)

Offline Borek

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Re: Determination of mixture content
« Reply #1 on: March 19, 2022, 03:30:27 PM »
Assuming linearity of the response you can try standard addition method.
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Offline rjb

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Re: Determination of mixture content
« Reply #2 on: March 19, 2022, 04:21:06 PM »
This seems similar in some ways to a question I posed previously in which I asked about methods for estimation of purity for a compound where a reference standard is not available https://www.chemicalforums.com/index.php?topic=110887.0

In my case, a chance conversation with a colleague led me to considering qNMR as a possible option for dealing with this kind of situation. From what I understand, with qNMR there is no requirement for a reference standard (which suits your purposes as well as mine) and the technique can be carried out using a suitable internal standard with pretty high levels of accuracy and precision, apparently without the response factor and matrix effect issues that are present with many other techniques.

NMR is a bit of a dark art as far as I'm concerned which is why it didn't spring to mind initially, but will try to let you know if it works for me when/if I ever get my samples to actually give it a try, but might be worth consideration if you are set up for NMR...

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