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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: thermoman on October 15, 2012, 01:54:41 PM

Title: loss on drying of tripotassium citrate monohydrate
Post by: thermoman on October 15, 2012, 01:54:41 PM

I'm having a problem with the loss on drying test of tripotassium citrate monohydrate.
The specification is between 3.0-6.0% after drying for 4h at 180c. The result I'm getting is about 2.1%. This batch was tested a year ago and the result was 4.9%. I have done the test twice, and got the same result. when I'm trying to determine the assay on dry basis , I'm getting a result of about 100.1% with the L.O.D result of 4.9 and about 97% (out of spec)  with the L.O.D result of 2.1%.
what am I doing wrong?
I hope the massage is clear.

Title: Re: loss on drying of tripotassium citrate monohydrate
Post by: Stepan on October 16, 2012, 06:56:34 AM

Try to take a sample from different part of the storage container - close to the middle. It might happens that top layer adsorbed CO2 and potassium carbonate doesn't want to brake down at 180C. If this is a case: a) contamination is more pronounced on the layer of citrate which exposed to air - on the surface. b) dissolve small portion of salt in water and add acid to resulting solution acidity below pH 3, you should observe bubbling of CO2.

Title: Re: loss on drying of tripotassium citrate monohydrate
Post by: curiouscat on October 16, 2012, 08:44:27 AM

Quote from: thermoman on October 15, 2012, 01:54:41 PM

I hope the massage is clear.

I rather hope not.. ;)