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By csang on Tuesday, August 24, 2004 - 11:53 pm:
Hi,
I'm having some problem here with the Bruker MS and hopefully someone could advice me what could be the problem here,
Few months ago, I was analysing some complex microbial protein using LC MS/MS and was identifying proteins by the hundreds, however after the MS was being "cleanned" a couple months ago (the skimmer and octopole were removed and sonicated using proponal) I was not able to obtain the same results again.
Apparently the two observable difference now and then was the accumulation time at the start of the LC MS experiment and unstable nanospray emitters.
I remembered the accumulation time was always less than 10ms to reach a targeted ion of 100 000 (using ion-charge control). Now accumulation time always hovers around 200ms. The explaination I got was that the system is now cleanner that's why it needs more time to fill up the ion trap??
For the nanospray emitter (I am using a new box of SilicaTip from new objectives), I noticed the spray now is not always stable and I am always seeing splitting streams and a emitter can at most be used 10 times before it has to be changed again. Even if the spray is stable, I was not able to get good identification.
Really appreciate if someone could shed some light in this area, especially if you are using Bruker esquire HCT as I really need to compare the parameters of the MS.
Thanks a million!!
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By MG on Friday, August 27, 2004 - 01:16 pm:
The longer accumulation time could be due to fewer ions being sampled, which could in turn be caused by a problem introduced when the instrument was cleaned. Did Bruker advise you to sonicate the octopole? I remember hearing that these shouldn't be sonicated, because it could cause the rods to go out of alignment. I've not used that particular model but have used the original Esquire.
Hi,
I'm having some problem here with the Bruker MS and hopefully someone could advice me what could be the problem here,
Few months ago, I was analysing some complex microbial protein using LC MS/MS and was identifying proteins by the hundreds, however after the MS was being "cleanned" a couple months ago (the skimmer and octopole were removed and sonicated using proponal) I was not able to obtain the same results again.
Apparently the two observable difference now and then was the accumulation time at the start of the LC MS experiment and unstable nanospray emitters.
I remembered the accumulation time was always less than 10ms to reach a targeted ion of 100 000 (using ion-charge control). Now accumulation time always hovers around 200ms. The explaination I got was that the system is now cleanner that's why it needs more time to fill up the ion trap??
For the nanospray emitter (I am using a new box of SilicaTip from new objectives), I noticed the spray now is not always stable and I am always seeing splitting streams and a emitter can at most be used 10 times before it has to be changed again. Even if the spray is stable, I was not able to get good identification.
Really appreciate if someone could shed some light in this area, especially if you are using Bruker esquire HCT as I really need to compare the parameters of the MS.
Thanks a million!!
-------------------------------------------------------------------------------------------------------
By MG on Friday, August 27, 2004 - 01:16 pm:
The longer accumulation time could be due to fewer ions being sampled, which could in turn be caused by a problem introduced when the instrument was cleaned. Did Bruker advise you to sonicate the octopole? I remember hearing that these shouldn't be sonicated, because it could cause the rods to go out of alignment. I've not used that particular model but have used the original Esquire.
