By Olivia on Tuesday, January 23, 2001 - 06:22 am:
I have seen many times in the Pharmacopoeias suggestions about the run time of the related substances analysis: twice the retention time of the main peak, 2.5 times, etc.
Can anyone tell me if there is a guideline which mentions this point? And which criterium should I adopt for a gradient analysis?
By shirishpatel on Friday, April 6, 2001 - 05:29 am:
i am also searching the logic behind all this things but not successful yet
if you got it e mail to me ata shi_ri@usa.net
By Anonymous on Tuesday, April 10, 2001 - 05:56 am:
As far as I know, there is no limit set for total run time. Some chemists prefer 2x the Rt of the drug peak. But, as long as you can prove there are no late eluting peaks, you can shorten your run as much as you need or can. (Run stressed/specificity samples to evaluate late eluters!) This applies to both gradient and isocratic.
By Anonymous on Thursday, April 19, 2001 - 08:26 am:
Run time usually depends from Rt last impurity. We usually check retention time last impurity for 5-6 hours. The Mobile phase has lowest solvent concentration in the rugedness test range.
By Anonymous on Saturday, July 21, 2001 - 05:45 am:
There is no limit in the time of analysis run. Is a balance between time "you can't waste" and time your column is re-aconditionated for a new analysis. In my opinion you have to wash the column after your analysis and follow if some peak elutes from it.
In my experience I prefer use a gradient to wash the column after the peak of my compound is eluted and then reaconditionate the column. My peak has a retention time of 7 minutes, but the run time is 25 minutes. Washing column between injection has given me better results.
By Anonymous on Thursday, July 26, 2001 - 06:36 pm:
The question is what you need to quantitate. If peak is eluted, you're done. But if there are other peaks that make you wash the column, you need to know that these peaks are no interest for analysis.
By Anonymous on Monday, July 30, 2001 - 11:38 am:
My question is for Anonymous two up that washes the column after each injection. Have you ever run a precision study on your method without washing verses with washing? It seems to me that your experience is costing you at least 2/3 in productivity. If your method requires this kind of column clean up and reconditioning, you may want to look for a new one.
By M.R.Shyam Sundar on Sunday, December 30, 2001 - 10:33 pm:
The run time can be determined based on your process and a mainly the stress studies.
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