[cantytoofly]

Hi all,

I've got a question concerning Karl Fischer moisture titrations.

So as a fairly standard practice I use Hydranal Composite 5 for the majority of my products I have to test and Hydranal 5K for ketones / aldehydes.

Does anyone know anything about Explotab / Sodium starch glycolate?

In my specification there's a Loss on Dry value equal to or less than 3.0% (if going by Eu. Ph. it's 10%)
However the Karl Fischer seems to always come out at about 0.1 - 0.2% moisture.

I've looked at CoA and there is a Methanol residue of around 0.2% but - 0.2% methanol + 0.2% moisture doth not 3.0% LOD make.

Are we using the correct titrant? I can't find any rationale in my CAP or specs to point to using something else.

Any input would be greatly appreciated,

Thanks! 

[cantytoofly]

I should add *

Does the Ether group of the Starch glycolate have any aldehyde / ketone effect wrt to the titrant? i.e best to go for none methanol containing titrants?

Or should I maybe swap the reaction medium for something like 1:1 MeOH : CH3COOH - as per amines?

Cheers!

[Arkcon]

So its 0.2% moisture (by your analysis), and 0.2% methanol (by CofA), but loss on drying is 3% (it says?)

Well, that's not impossible, given these are ranges, and the spec is NMT.  However, I think you're using the correct titrant for Karl-Fisher.  If you're in the mood to experiment, you could try spiking in water, at various levels, and seeing which titant and solvent gives accurate results.  You could also submit the sample for residual solvents analysis by GC.  Maybe it is 0.1% water, 0.1% methanol, and they just failed to mention to 2% gasoline impurity .  Also, performing a loss on drying yourself is pretty easy to to, maybe there are other volatile components to take into consideration.

[cantytoofly]

Thanks for the response Arkcon.

The CoA spec limit is <= 3.0% it came in as 2.1% (apparently).
I've got my own LOD in the oven ask we speak to see if it's coming out at anything near their value.
 
Yeah this is my concern - how the F is it losing an extra 1.6% through LOD?

This wouldn't be the first time we've had issues with solvent impurity from this supplier - but not with this excipient (it doesn't smell strange so I dunno)

Oh well back to the drawing board - I doubt the people doing GC are going to be up for running me a sample, enpower /data integrity sucks! So I can't really just "chuck a run on"  

I'm starting to think that whoever came up with the testing roster for this product doesn't actually know what they are talking about lol!

Thanks a lot anyway!