April 13, 2021, 02:47:23 AM
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Topic: Purity of analytical standards  (Read 215 times)

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Offline denisa174

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Purity of analytical standards
« on: March 22, 2021, 05:37:20 AM »
Hello,

I have a question about purity of a standard. I need to buy a formic acid. I've found 99% (acidimetric) and 99% (alkalimetric) pure acids. What does "alkali-, acidimetric" here mean? Is that a method of determination of the purity or is it anything else?

Next question about the formic acid is: Do you have some tip for CE standard?

Thanks

Offline chenbeier

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Re: Purity of analytical standards
« Reply #1 on: March 22, 2021, 07:37:00 AM »
Its the method by titration.

Offline Borek

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Re: Purity of analytical standards
« Reply #2 on: March 22, 2021, 09:43:56 AM »
Its the method by titration.

Using titration to determine main component is a rather poor approach.

Assume you go 99.9% with titration error three orders of magnitude lower, so 99.9±0.1%. Does it tell you anything about amount of impurities?

Now assume you got the impurity as 0.1% with - again - an error three orders of magnitude lower, so 0.1±0.0001%. Do you see why this information is much better?
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Offline chenbeier

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Re: Purity of analytical standards
« Reply #3 on: March 22, 2021, 09:49:11 AM »
I think it didnt tell about impurities. It tell about the grade. Its 50, 80 or  99 % HCOOH. For impurities need other methods like HPLC,IR UV/Vis, AAS for metals, etc.

Offline Borek

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Re: Purity of analytical standards
« Reply #4 on: March 22, 2021, 10:00:12 AM »
The 99% grade is given, no need to check it.
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Offline chenbeier

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Re: Purity of analytical standards
« Reply #5 on: March 22, 2021, 10:05:23 AM »
I think here is a misunderstanding. The question was 99% acidimetric, what does it mean? It means it was determined by a titration isnt it. Of course normaly it hasnt to be checked,

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