Hi Friends

We facing a problem of column to column reproduciblity in Retention time, Resolution, Peak Asymmetry and theoretical plate with same brand. We not even changed the brand. In such case we standardised our each column by changing mobile phase concentration. After changing mobile phase concentration we acheveing our system suitability parameters which mentioned above.

When same brand give such problem than how to change or switch over to other brand column?
Any one can tell what to be consider while changing the other column brand?

hi
can you please provide some details about your experiment, like the column you are using, at what temperature are you maintaing the column, the mobile phase, the sample matrix..etc.etc.

normally branded columns should not give this kind of trouble. Does the retention time remain constant during interday analysis for a particular column?

Have you tried contacting the vendor?

Hi Bookoon

As you ask, details are as follows

Column : Kromasil 100, C8 250 x 4.6 mm, 5 micron.
Column Temperature : Ambient
Mobile Phase : Buffer : Methanol (75:25)
Buffer is 0.4%w/v Disodium Hydrogen Phosphate anhydrous adjusted PH to 3.5 with Phosphoric acid.
Sample : Cyanocobalamin ( Obtained From Fermentation technology)
Yes the retention time remain constant during interday analysis.
Yes, We concern vendor but they says such things should not happened with same brand something wrong from your side.
I hope above data is sufficent.
Can you focus something on this?

Narenda,

Here is what you should do:
Check the information that came with the columns or ask the vendor, if the packing in all your columns comes from the same batch, i.e. the same preparation of packing material. If it did, and you see differences, the problem is on your side. If the packings come from different batches, ask your vendor to supply you with a column from exactly the same batch as your older column and do the same study comparing new and old column. This way you will be absolutely sure, if the problem is a batch-to-batch difference, or if you are comparing a column that has been used a lot to a new column. Your vendor should supply you with free columns for this study.

hi

vitamin samples are always difficult to analyse, due to their unstability.
Is it possible for you to conduct robustness of your method? How much critical is the pH?
I once faced a problem because of a faulty AC in our lab. Since i was not using a column oven (i was using 'AMBIENT' temp) and the AC vent was just above my instrument the Ret.Time of the analyte was shifting. But this is a very typical example and it may not be your case since interday ret. time matches. But that experience taught me to always place the column inside an oven (at a temp of ~30°C).

Right now Uwe Neue has given the best suggestion.
Keep us informed

Hi Uwe Neue

Thanks for your suggestion

I will do the same experiment as you said and I will keep you inform about our findings.

Thanks once again.

Hi Bookoon,

Thanks for suggestion.

Yes, it is possible to conduct robustness test for analytical method. We never did because it is official method in British Pharmacopoiea. Now it seems that we have to do robustness test for analytical method.

It is our observation that even in change of ±0.5 change in pH not making any change.

I will keep you inform about our findings.

Thanks once again.