Gradient Selection

[aprilcparker]

Hello,

I am developing a method for Cocoamidopropyl Betaine, so far I have achieved decent separation. My peaks are not as clean and symmetrical as I want them but I think this can be resolved using a gradient method. However, I have been reading on switching from isocratic to gradient and it's more analytical than I thought and would like some assistance on choosing a gradient for my method. I can attach the chromat if anyone would like me to. I am currently running a 70:30; MeOH:0.2% TFA as my mobile phase. Any suggestions would be greatly appreciated.

Info- run time = 30min, 1st peak ~3.2min, last peak ~23.1min running at 0.8mL/min ..Let me know if any other information is needed thanks!

[Consumer Products Guy]

Please post chromatograms, or link. I've done some work on CAP betaine myself, and maybe can help. Please list column as well.

30 minutes is a long run by our department assays...

[aprilcparker]

Hello, I sent the chromatography to your email, not sure how to upload images here yet, sorry! [/img]

[Consumer Products Guy]

April - I didn't receive any E-mail from you. Please send to cussboy -at -cox.net

[tom jupille]

instructions on linking to graphics files are here:
viewtopic.php?t=2617

That said, changing a working isocratic method to a gradient is not done that often; any savings in run time are quickly chewed up by the need to re-equilibrate the column for the next injection. And peak shape improvements are often a matter of sweeping the problem under the rug. A smaller particle size / higher purity packing material might be an easier alternative.

[SIELC_Tech]

I have a method for cocobetaine with good symmetry and separation from other products. PLease send me email inquiry.

Kind regards,

[aprilcparker]

This is in response for the gradient for the CAPB… this is a 6% solution of 35% CAPB in 50:50; MeOH:.2% TFA as diluent. Method parameters are:

MP Flow-0.8 mL/min
Gas Flow- 2.6 bar
ELSD temp-90 Deg
Column- Jsphere ODS-H80 (250mm X 4.6mm, 4um)
Current Isocratic- 70:30; Methanol: .2% TFA (pH= 2.3)
20uL injection volume, run time 30 minutes

Any help would be greatly appreciated, let me know if you need any additional information.
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