-
- Posts: 1
- Joined: Fri Dec 15, 2017 7:16 pm
How often people develop LC method which has flow rate chang
Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.
6 posts
Page 1 of 1
How often people develop LC method with flow rate change during the run? Is it common for complex method development or rare cases?
-
- Posts: 3503
- Joined: Mon Aug 30, 2004 11:43 pm
I developed and validated HPLC methods for over 35 years.
Rarely did I have a procedure where the flow rate increased at a certain timepoint to help a later-eluting analyte to elute. Most often I increased the flow rate after the analyte eluted if the pressure was low enough, and I had later-eluting stuff to get off the column. This could be faster to re-equilibrate than initiating a gradient.
And of course a gradient could not be used when we had a single pre-mixed mobile phase.
Rarely did I have a procedure where the flow rate increased at a certain timepoint to help a later-eluting analyte to elute. Most often I increased the flow rate after the analyte eluted if the pressure was low enough, and I had later-eluting stuff to get off the column. This could be faster to re-equilibrate than initiating a gradient.
And of course a gradient could not be used when we had a single pre-mixed mobile phase.
-
- Posts: 404
- Joined: Wed Nov 09, 2016 12:43 am
Flow programming is very 'rare' (it is an indication of a poor method). It is more advantageous to increase the composition of the organic phase slowly during a gradient method (shorter too) in order to 'boot' the target molecule off the column.
-
- Posts: 3475
- Joined: Mon Jan 07, 2013 8:54 pm
- Location: Western Kentucky
When I first started working with EPA Method 1694 I noticed they used flow rate changes (0.150ml/min then 0.250 ml/min then 0.300 ml/min then back to 0.150ml/min). That was the first time I ever saw it, and even though I am running the method I don't use the flow program I use a different column and gradient elution.
It seems to be something Waters likes to do with their "UPLC" instrument methods.
It seems to be something Waters likes to do with their "UPLC" instrument methods.
The past is there to guide us into the future, not to dwell in.
-
- Posts: 686
- Joined: Mon Apr 29, 2013 4:37 pm
- Location: 39° 44' 44" N / 75° 32' 48" W
Hi KhareM,
Another older Waters method that employed a flow rate change was the AccQ.Tag kit method for amino acid analysis, in the middle of a gradient program.
I agree with these other folks above--it is less usual to vary flow rate during an elution program in HPLC than not.
Another older Waters method that employed a flow rate change was the AccQ.Tag kit method for amino acid analysis, in the middle of a gradient program.
I agree with these other folks above--it is less usual to vary flow rate during an elution program in HPLC than not.
MattM
-
- Posts: 114
- Joined: Fri Oct 22, 2010 8:53 pm
- Location: San Francisco Bay Area, United States
Agree with the other posts here. The only time I use a change in flow-rate in a method is to hasten column washing/re-equilibration if possible. Never for analytes - suggests a poor method.
6 posts
Page 1 of 1
Who is online
In total there is 1 user online :: 0 registered, 0 hidden and 1 guest (based on users active over the past 5 minutes)
Most users ever online was 1117 on Mon Jan 31, 2022 2:50 pm
Users browsing this forum: No registered users and 1 guest
Most users ever online was 1117 on Mon Jan 31, 2022 2:50 pm
Users browsing this forum: No registered users and 1 guest
Latest Blog Posts from Separation Science
Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.
Subscribe to our eNewsletter with daily, weekly or monthly updates: Food & Beverage, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.
- Follow us on Twitter: @Sep_Science
- Follow us on Linkedin: Separation Science