Change buffer in mobile phase

[capozzi]

Hi,

I wonder if there is a possibility of changing the buffer of mobile phase below:

9.52 g monopotassium phosphate in 1000 ml of water
Pentane-1-sulfonic acid sodium salt 2mL in 100 mL of water
Diethylamine 20ml
pH 3.5 with ortho-phosphoric acid
Column Lichrospher 100 RP18 (250mm x 4,0 x 5µm)

There is a better option?

[Blazer]

You are going to have to give much more background information before anyone can give you a useful answer. Just asking if there is a better option without telling us WHY you want a better option will not help us to help you.

Why do you want to change the buffer? Are you having problems? If so, what type of problems? Is this method validated?

[capozzi]

You are going to have to give much more background information before anyone can give you a useful answer. Just asking if there is a better option without telling us WHY you want a better option will not help us to help you.

Why do you want to change the buffer? Are you having problems? If so, what type of problems? Is this method validated?

Actually, I wanted to try to change that buffer because it greatly decrease the efficiency of the column Lichrospher.

And yes, this method is validated, however, the chromatographic profile is not something good.

This method was validated for the follow drugs:

Metamizole
Caffeine
Isometheptene

Thanks

[tom jupille]

If the method is validated, and if you are meeting the system suitability criteria, then whether the efficiency is "good" or not is irrelevant; it is, by definition, suitable for the purpose.

If you are *not* meeting system suitability and you change the buffer, then you will have to revalidate the method (the exception is that for USP methods, you can change ionic strength by 10%). There is no easy way to choose a "better" buffer; in effect, you will be redeveloping the method.