Chromatography Forum

Dear All,

I would like to know how u are doing assay of caoted tablets.

We are doing assay of tablets in which it is difficult to crush coating. So can we pass the samples thru sieve to separate caotings and powder.

We were sieving the sample, but our QA/Regulatory objected to it, as they asked for referance for it.

If we are weighing sample with coatings it gives variable results

The simple answer is do a better job of crushing your tablets.

When you say crush are you using a mortar and pestle? I would not recommend sieving unless you think you could validate the procedure.

I have seen variations due to coatings in the past. Our answer was elbow grease and care in handling (don’t stratify the grind) and sampling the grind (analyst technique and spatula choice etc. can introduce bias).

grinding tablets can be physical work but there are other mechanical means availabe (i have not used them) cryo grinders etc.

good luck

Sunjay,

You can use whole tablets instead of crushing or grinding them. To use whole tablets, you need to have a solvent and extraction system (such as shaking or sonication) to get the proper disintegration of the coating so that you will then get sufficient extraction of your analytes.

Did you try a method using whole tablets? And, if you did, how successful were you?

I agree with your QA/regulatory in that the sieving method you describe will not work; there is too much chance for loss of sample and getting low assay results.

If your coating is too hard to crush or grind manually, then try a mechanical means. At one place where I worked, they used coffee grinders for those tablets that were hard to grind (you can get similar devices from various manufactures). They also used the TPW from Caliper (Zymark). It came in both the full automated system and stand alone versions. Check this link for more info: http://www.caliperls.com/products/tpw3- ... tation.htm

One last point, remember that some tablet coatings may get even harder over time. So test out your extraction method on old (stability) samples.

Regards,
Dan

Just to add to Dan's comments we would always assay whole tablets and not faff about taking the coat off - why would you? Most tablets start to disintegrate just sitting in an appropriate aqueous based solvent misture.

For problem tablets, there are also hand held units available for "whizzing" (homogenising) your tablets which is akin to the TPW operation.