June 20, 2024, 01:24:54 AM
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Topic: Problem with zinc determination  (Read 17741 times)

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Offline Potatomuffin

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Re: Problem with zinc determination
« Reply #15 on: May 26, 2010, 06:41:54 AM »
Use Methyl Orange.  The pH change should be sharp so determine the endpoint based on the immediate change to pumpkin orange.

pH changes pH during EDTA titration? No idea what you refer to.

They were talking about back titration from the USP monograph, not the EDTA anymore.

Offline Borek

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Re: Problem with zinc determination
« Reply #16 on: May 26, 2010, 08:24:38 AM »
They were talking about back titration from the USP monograph, not the EDTA anymore.

Perhaps I am missing something, but judging from the posts

I had previously perused the USP (...) the approach is similar chemically

my guess is that USP titration is also using a chelating agent. And back titration was mentioned here:

hit it with an excess of an EDTA salt, add about 100 ml of IPA and back titrate with aqueous mag chloride.

This is again an EDTA titration.
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Offline Potatomuffin

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Re: Problem with zinc determination
« Reply #17 on: May 26, 2010, 06:39:18 PM »
The USP does not use EDTA titration.  What is used as an assay here:

http://fa.kfda.go.kr/standard/egongjeon_standard_view.jsp?SerialNo=313&GoCa=1&currPage=1&stext2=zinc%20oxide&chkoption1=Y&chkoption2=&chkoption3=&chkoption4=&chkoption5=&chkoption6=&chkoption7=&chkoption8=&chkoption0=

Is the same that I have in my USP as well as the food chemical code index monographs.  I'd be interested in seeing the EDTA titration assay for Zinc Oxide because I run into Zinc a lot and sometimes the Atomic Absorption Spectrophotometer is being used for other assays.

Offline Potatomuffin

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Re: Problem with zinc determination
« Reply #18 on: June 02, 2010, 06:26:30 PM »
I decided to open the USP again because I re-read the topic.  I apologize for reading too fast and missing the key term "ointment".  I don't know if your lab uses one, but I find Flame Atomic Absorption to be less of a hassle.

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