Chromatography Forum

Dear All,

My question is related to the in house qualificationof the working standard.

Can we use present working standard to determine the potency of next working standard?

For ex. For a non-pharmacopeial product , if we have prepared a WS (Lot A5) today against Referance Standard from a supplier and assigned a potency (99.8%) with use before date of 1 year. So we keep few gm of this WS in a vial nicely packed/ sealed with paraffin film, stored in referigerator.

After 1 year we hav selected another batch for WS. Can we use the potency of Lot A5 to qualify new WS (Lot A6).

I would like to know the schme folowed by you, if u can share.


Waiting for your valuable suggestions

Thanks in Advance

I think an auditor would find fault with that approach, on the grounds that errors would tend to accumulate over time.

I would concur with Tom - your approach is too basic to be acceptable to an auditor. In the old days we used to make use of secondary standards, but one too many observations in audits across the company means we now only use primary reference material (either bought in, or extensively tested by a central reference standards group).

A reference material has extensive testing done on it - not just for assay%, but other impurities/degradates, moisture, residual solvents, etc. If you have done similar testing on your "secondary" reference material as was performed on the primary material you tested it against, that would put you in a better position to support using it.

However you also need to prove that your secondary reference material has not degraded over time - how do you know that fridge temperature is sufficient to prevent the standard degrading? One approach would be to retest the secondary reference material against a new batch of primary material after 6 months, 12 months, 18 months, etc. to show there was no change in the purity and no increase in degradates. Ensure you make multiple preparations of all the reference material too so you can show the accuracy and precision of the data you are generating on this ciritical material.

That is not all - you may also need to consider other physical characteristics of the material that may change over time and affect how it behaves when made into a solution.

i would also add to all being said above that your equipments and materials always need to be checked in reference to a standard of a better quality grade then those you wish to use, because like Tim said they are put to more serious testing and have to comply to sticter specs.
otherwise you canot trully show the accuracy and robustness of the equipment and materials that you use.

for that reason you will always need to check you in house WS in relation to a certified reference standard.