Chromatography Forum

Hi, all,

I was run the same thing (everything is same in term of concentration, injection volume, instrument method, etc) before and after shutdown and restart the instrument together with UV detector. The response (in term of area) showed 6 times difference. is this possible or any other reason explain this? thanks a lot.

Was the change in area a decrease or increase? Were there any other changes that you noticed? Per your post, the 'shutdown and restart' seem, at least to you, to be involved in this change. Was there anything that precipitated this event? Did something cause you to need to restart the instrument? Did you notice anything odd before or after the restart? Have you re-prepped and re-run standards and compared them to previous injections to determine if this change in area is a one-time event?

If you had, for instance, a power outage, and you had not saved some important changes to a method (specifically, injection volume), then upon restart the instrument may have loaded the old version of the same method you had been running, but with the previous injection volume (say, 100 uL vs. 20 uL). Just a thought. You may want to check each parameter to make sure it really is "the same as" before the shutdown.

Thanks for reply.

Nothing changed in the method and sample except the system restarting. I compared the instrument method attached to each specific injection.

I ran the same sample with all the setting the same, it looks good. Then I decided to repeat with more injections to confirm the method. I restart the system due to the system looks not fully communicating with the computer. I expect area change after restart the system, but not so much as 6 times more.

It is even better, but just curious about the reason.

How old is the detector lamp and how long after restarting did you inject the samples?

meillid, why did you expect an area change after restarting the instrument?