Allowable Adjustments to Pharmacopoeia Methods for GRADIENT

[etaxene]

Hi...

I can not interpret this phrase from Ph.Eu. Will you help me please?
What is meant by "minor."
And what is meant by "elution power"?
Thank you all

"Minor adjustments of the composition of the mobile phase and the gradient are acceptable, if the system suitability requirements are met, the principle peak(s) elute(s) within ± 15 % of the indicated retention time(s) and the final elution power of the mobile phase is not weaker."

[tkubowicz]

Hello

Please see article about it below:

http://www.chromatographyonline.com/adj ... imitations

Regards

Tomasz Kubowicz

[etaxene]

Hello

Please see article about it below:

http://www.chromatographyonline.com/adj ... imitations

Regards

Tomasz Kubowicz

Thanks but this is USP not PhE

[dblux_]

...
Thanks but this is USP not PhE

Don't be so meticulous
https://az621941.vo.msecnd.net/document ... bafb96.pdf
https://www.phenomenex.com/Info/WebDocu ... w_1_ep.pdf
https://www.phenomenex.com/Info/WebDocu ... _2_usp.pdf

[etaxene]

...
Thanks but this is USP not PhE

Don't be so meticulous
https://az621941.vo.msecnd.net/document ... bafb96.pdf
https://www.phenomenex.com/Info/WebDocu ... w_1_ep.pdf
https://www.phenomenex.com/Info/WebDocu ... _2_usp.pdf

Thank you all. But what I can not understand is what "minor adjustments."
How can I change the composition in gradient phase?

What does it mean " the final elution power of the mobile phase is
not weaker"? I can change only organic phase?

[tom jupille]

It means that the % strong solvent at the end of the gradient must be at least as high as that written in the method.

[tom jupille]

What does it mean " the final elution power of the mobile phase is
not weaker"? I can change only organic phase?

I would interpret that to mean that your final %B must be equal to or higher than the final %B specified in the method.

[lmh]

what on earth is the logic of allowing a free choice of column diameter (subject to keeping the same linear flow of solvent), but only permitting smaller injection volumes? If someone runs a method on a wider-diameter column, they can (and probably should) inject proportionally more. The acceptable injection volume should surely be expressed per cross-sectional area of the column.

[HPLCaddict]

what on earth is the logic of allowing a free choice of column diameter (subject to keeping the same linear flow of solvent), but only permitting smaller injection volumes? If someone runs a method on a wider-diameter column, they can (and probably should) inject proportionally more. The acceptable injection volume should surely be expressed per cross-sectional area of the column.

As you wish:
"When column dimensions are changed, the flow rate may be adjusted as necessary using the following equation:", followed by the proper formula including column diameter and length. One of the few thing Ph.Eur. got right.

The sentence "Injection volume: may be decreased, provided detection and repeatability of the peak(s) to be determined are satisfactory; no increase permitted." only refers to injection volume changes when the column dimensions are NOT changed.
By the way: "free choice of column diameter"? I'd wish that was possible. Only +-25% allowed by Ph.Eur. Which means you're allowed to change from a 4 mm to a 3 mm column, but not from a 3 mm to a 4 mm column. And forget to scale anything to 2 mm columns...

[lmh]

Thanks! I'm lucky enough to work in an environment where it's more important that a method works than that it conforms to particular regulations. Nevertheless, I think it makes sense for those of us in unregulated environments to look at regulated approaches and learn from them (particularly to define what "method works" actually means). We should reject things deliberately rather than through ignorance. The thing that makes it difficult is that there are a lot of things in regulations that are either grotesquely woolly, or apparently wrong. I understand the frustration of moving to 2mm columns: there should be a simple route for minimal revalidation of methods after conversion from 4.6mm to 2mm because on any respectable modern instrument it's quite hard to get wrong. My personal opinion is that changing the analyst is a far more worrying change than changing the column diameter!

It's a pity when people continue to use 5 times as much acetonitrile as they need, in order to run excessively wide columns.

[HPLCaddict]

My personal opinion is that changing the analyst is a far more worrying change than changing the column diameter!

That one made my day Full ACK