TOC analysis for insoluble compound using NaOH as solvent extraction

i work in pharmaceutical company, and we want to develop TOC analysis for aour clenaing validation. we use mefenamic acid as sample because we produce that medicine.mefenamic acid are insolube in water so we use NaOH as a solvent to do the extraction from the swab. we use TOC siever 900. But we got unstable result for percent recovery. when i increase time for diluting the swab in NaOH the recovery sometimes not increase.

Do you have any idea on how i could fix it? or what happened??

The sample has to neutralized before it is analyzed, since the machine uses both an acid and persulfite channels. You can increase the volume or concentration of the acid to compensate for the alkalinity of the sample.

Thx u for give me a reply.

So i need to change the rate of acid in acidification step?
but what if i use autoreagent when i perform this analysis and its recovery still variative?
did TOC measurement only suitable with purified water as solvent?

please kindly answer my question…i’ve already do literature research about this problem butn i couldnt find the answer…

Water is the only common solvent that does not contain Carbon (that I know), so yes. You can use a 0.1M pH 7 phosphate buffer as a neutralization agent.

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so based on your answer i’ve to try diluting the mefenamic acid in NaOH and then use the buffer to neutralizing the sample before perform the analysis??

Yes. That will work.