Proposed Changes to USP Chromatography Chapter <621> - What do you think?

Hello All, As some of you may know, a Stimuli Article written by Uwe Neue 2009 proposed that a chromatographer can simultaneously adjust the LC column length and particle size to achieve equivalent resolution as the original method. This is in contrast to the existing allowed changes in <621> such as -50% for particle size; +/- 70% for column length, etc. These proposed changes were designed to stimulate discussions around modernizing USP General Chapter Chromatography <621>. In May 2011, the first proposed changes were posted to the Pharmacopeial Forum. This was followed by a 90-day comment period and an Expert Committee Meeting in late 2011. At the end of 2011, the decision to amend or modernize <621> was deferred until USP PF 38(2). USP PF 38(2) was posted on 01-Mar-2012.  In 38(2) is the next proposed chapter <621>. Accessing the USP PF requires a free, one-time registration (Click the Access PF Now button on this page: Once registered you can find the proposed, amended Chapter <621> here: If you do not wish to register, I have created and attached a pdf of the amended Chapter <621>. I'd like to bring your attention to the last sentence under the Particle Size section in the middle of page 17 of the attached pdf. Basically, this proposed, amended chapter prohibits changing the column dimensions in a gradient method. This is restated on page 18 (last sentence): I am curious what the members of the ACQUITY UPLC community think about these proposed changes. Is it sufficient to only be able to transfer an isocratic compendial HPLC method to UPLC, but not a gradient method?  Does any of this matter to you and your company?  Thanks,


  • After reading your post and the proposed changes, yes, it does matter for me regarding gradient runs.  Many of our procedures use gradient conditions to reduce the run time, to improve chromatography and help "wash out" the column of slow-moving excipients.

    As long as the column volumes are the same for the gradient parameters between the two columns and the relative retention times are consistent, I think there should be some allowance to adjust column parameters.

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