Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
Wavy backgrounds
4 views
Skip to first unread message
justyna_000
Nov 19, 2009, 11:13:46 PM11/19/09
to
Dear All.
First time I have approached such an unusual problem. I have LCQ
Advantage (ion trap), and when I record TIC from the very begging of
turning on the machine I see background dropping down from 1e5 to 4e4
in 5min, then going up again to 1e5 in 3-4min. After this 8 min
baseline is stable on level of 1e5, and one have to turn of LC and MS
for around 2h to be able to see this phenomena. The issue appeared
when we had big problem with sensitivity and I washed skimmer ( I am
not sure if the skimmer or some residues which caused this loss of
sensitivity, cause this issue). When I use direct infusion ( syringe
pump) I do not see this problem ( what would suggest that it is not
MS), however if I connect HPLC pumps directly to MS I see smaller,
but still see ^�wave^� ( what would suggest that it is MS). I have
already changed solvents, lines to MS, washed divert valve and ESI
source. However, I still see this unusual behavior. I wonder if any of
you had before this experience, and if you have nay idea if this can
be explained by MS or LC issue. I will be very grateful for any
suggestions.
First time I have approached such an unusual problem. I have LCQ
Advantage (ion trap), and when I record TIC from the very begging of
turning on the machine I see background dropping down from 1e5 to 4e4
in 5min, then going up again to 1e5 in 3-4min. After this 8 min
baseline is stable on level of 1e5, and one have to turn of LC and MS
for around 2h to be able to see this phenomena. The issue appeared
when we had big problem with sensitivity and I washed skimmer ( I am
not sure if the skimmer or some residues which caused this loss of
sensitivity, cause this issue). When I use direct infusion ( syringe
pump) I do not see this problem ( what would suggest that it is not
MS), however if I connect HPLC pumps directly to MS I see smaller,
but still see ^�wave^� ( what would suggest that it is MS). I have
already changed solvents, lines to MS, washed divert valve and ESI
source. However, I still see this unusual behavior. I wonder if any of
you had before this experience, and if you have nay idea if this can
be explained by MS or LC issue. I will be very grateful for any
suggestions.
allend
Nov 20, 2009, 11:41:13 AM11/20/09
to
On Nov 20, 3:13�pm, justyna_000 <sikorska.just...@gmail.com> wrote:
} When I use direct infusion ( syringe
} pump) I do not see this problem ( what would suggest that it is not
} MS), however if I connect HPLC pumps directly to MS I see �smaller,
} but still see ^�wave^�
} When I use direct infusion ( syringe
} pump) I do not see this problem ( what would suggest that it is not
} MS), however if I connect HPLC pumps directly to MS I see �smaller,
} but still see ^�wave^�
Suggests a pump issue, sticking check valve or piston seal starting to
leak, that is exacerbated at higher pressure when the column is in
place.
John Thaden, Ph.D.
Nov 21, 2009, 8:56:16 AM11/21/09
to
On Nov 19, 10:13�pm, justyna_000 <sikorska.just...@gmail.com> wrote:
} Dear All.
} �First time I have approached such an unusual problem. I have LCQ
} Advantage (ion trap), and when I record TIC from the very begging of
} turning on the machine I see background dropping down from 1e5 to 4e4
} in 5min, then going up again to 1e5 in 3-4min. �After this 8 min
} baseline is stable on level of 1e5, and one have to turn of LC and MS
} for around 2h to be able to see this phenomena. The issue appeared
} when we had big problem with sensitivity and I washed skimmer ( I am
} not sure if the skimmer or some residues which caused this loss of
} sensitivity, cause this issue). �When I use direct infusion ( syringe} Dear All.
} �First time I have approached such an unusual problem. I have LCQ
} Advantage (ion trap), and when I record TIC from the very begging of
} turning on the machine I see background dropping down from 1e5 to 4e4
} in 5min, then going up again to 1e5 in 3-4min. �After this 8 min
} baseline is stable on level of 1e5, and one have to turn of LC and MS
} for around 2h to be able to see this phenomena. The issue appeared
} when we had big problem with sensitivity and I washed skimmer ( I am
} not sure if the skimmer or some residues which caused this loss of
} pump) I do not see this problem ( what would suggest that it is not
} MS), however if I connect HPLC pumps directly to MS I see �smaller,
} but still see ^�wave^� ( what would suggest that it is MS). I have
} already changed solvents, lines to MS, washed divert valve and ESI
} source. However, I still see this unusual behavior. I wonder if any of
} you had before this experience, and if you have nay idea if this can
} be explained by MS or LC issue. I will be very grateful for any
} suggestions.
} already changed solvents, lines to MS, washed divert valve and ESI
} source. However, I still see this unusual behavior. I wonder if any of
} you had before this experience, and if you have nay idea if this can
} be explained by MS or LC issue. I will be very grateful for any
} suggestions.
Consider the cycling of room air conditioning/heating.
Chip Cody
Nov 22, 2009, 11:04:30 AM11/22/09
to
Do the waves that you see when the LC is connected directly to the MS
(no column) correspond to the pump cycles? If so, what kind of pulse
damping does your HPLC use?
Steve Cepa
Nov 23, 2009, 2:08:55 PM11/23/09
to
I've seen this on our LCQ also. It was a bad capillary heater.
Unfortunately that LCQ was retired over a year ago and I no longer
have the maintenance log. I can't remember if the controller board had
to be replaced or just the heater.
Unfortunately that LCQ was retired over a year ago and I no longer
have the maintenance log. I can't remember if the controller board had
to be replaced or just the heater.
See if you can monitor the temperature. If you have it at say 180degC,
it should stay within about 1-2 degrees of that. If it's changing over
4-5 deg, you can get this type of behaviour.
-Steve
0 new messages