Chromatography Forum

Dear Chromatographers,

I need advise for sample solution prep procedure of film-coated tablets. The film usually hard to be pulverized and tends to be plates.
Which one better in these methods:
- Weigh 10-20 film-coated tablets to get average weight, pulverize, and transfer sample ‘powder’ (only takes the fine powder without film plates) equivalent to one tablet (average weight) to vol flask …
- Pulverize 10-20 film-coated tablets, sieve to eliminate film plates, weigh to get average weight, and transfer sample powder eq to one tablet (av weight) to vol flask …
- Transfer 10-20 film-coated tablets to a vol flask fo such capacity, dissolve, fill to vol and pipette …
First method could give higher conc because the portion of film-coat is replaced by core powder. Second method could give bias because of the missing parts of ‘dusty’ powder in sieve, adhered to tablet coat, powder container, etc. Third method needs large amount of solvent to dissolve the tablets.
I tend to use the third.

Best regards,
SYX

Dear syx
There's another option, and that's to remove the film by scraping or washing with some solvent, than re-weighing to get the average weight of uncoated tablets, powdering and weighing samples.
I would consider this if you need to take (for statistics reasons) multiple samples from a limited number of tablets. If not, I think it is best to take 10 or 20 tablets together in 1 large flask (i.e. your third option).
Good luck
Jan

As described in your third method what if the solvent used to dissolve the drug does not dissolve the excipients and how much of the solvent should we take?

As described in your third method what if the solvent used to dissolve the drug does not dissolve the excipients and how much of the solvent should we take?

It is not necessary to dissolve the excipients when we want to analyze the active substance(s). The question must be: how much of the solvent should we take to dissolve the active substance(s)?

There's another option, and that's to remove the film by scraping or washing with some solvent, than re-weighing to get the average weight of uncoated tablets, powdering and weighing samples

What 'bout washing solvent that be adsorbed by core? It means need more time (or maybe heat) to dry the core before we weigh.

Regards,
SYX

How much of the solvent : if you do not want to take any risks, use 20 times the volume if for instance you would normally weigh 1 average weigth and are putting 20 tablets together now. This is only practical if you were using 50 ml flasks or smaller (means 1 l flasks for 20 tablets). If you do not want to use liters of solvent, check solubility of your standard at higher concentrations (maybe you made a stock solution of your standard...)

Drying the cores : sorry I forgot to mention this. Yes, you should dry the cores before weighing and powdering them, but in my expercience, it's enough to leave them 10-15 minutes at RT. Washing-off the film goes usually very quickly, so no time for the solvent to be absorbed by the cores.

Most film coated tablets should disperse OK in an aqueous solution - after all the film coating was most likely dispersed in water when the tablets were coated in the first place. Check the manufacturing formula to see what was used, but it will probably be water.

Our standard practice would be to place a quantity of tablets into a volumetric flask, add a small quantity of aqueous solution, shake/sonicate to disintegrate the tablets, then make up to volume with suitable aqueous/organic mixture. The final solution would be centrifuged or filtered prior to injection on the HPLC.

The error introduced by the undisolved excipients in the tablets is not significant unless you have really large tablets. You are more likely to introduce error if you try to remove the coating (could remove some active material too) or by grinding the tablets first (the active could be very fine and will be lost during the grinding/weighing/transfer process).

I agree with Tim. I have run many methods for film coated tablets and usulay find that placing the required number of tablets in a flask then adding enough water to cover the tablets works fine. Sometimes sonication is required or alternatively you can put a magnetic strirrer bar in and stir for 15 minutes or so, and wash the sirrer bar with extraction solvent (into the flask) whilst you are making it to volume.

Alternatively if you want to pulverise the tablets Retsch make a ball mill that does a great job.

Chris

Thanx for the help to choose a prep method.

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