Chromatography Forum

Hi all,

We recently were able to acquire a Waters Alliance 2695/Quattro Micro LC-MS-MS system, however we were not able to acquire any service with it. It was sitting unused for probably 5 years. I am trying to rehabilitate it, and have replaced as many o-rings and other small replaceable parts in the LC pumps as possible to pass the diagnostic tests, and have cleaned the MS up to the hexapole, and I'm afraid to dig in too much farther. I have a method for some extremely small, extremely polar analytes--very small organophosphate metabolites--that worked on another Quattro, but I can't seem to get any sort of decent response at all. I've optimized my MS/MS conditions, and they aren't far off from the conditions in the method I have, so I suspect that the MS is ok. But the responses I get from samples injected onto the LC don't really seem to give the response I would hope for. I'm not sure if I just don't know what I'm doing, or if there is a problem in the system, and if there is a problem in the system, where it is. I have some contact with Waters, but clearly am not high priority. I need to find a test protocol with expected results. Does anyone know where I could find such a thing for this instrument?
Thanks!
M

Hi,

I sugest you would run the same sample on both machines.
If the `good` machine gives good responses and the the other doesn`t then it would be a hardware problem. if both give low response check your stocksolution then.

If the old machine gives low responses i would first tune the MS again with a calibrant mix. once it is tuned you could inject the sample directly into the massspectrometer without using a column. Then check the if the responses are ok.

Grtz

TheProphet

I'd try chloramphenicol (CLF) as analyte, since it is the compound Waters uses as their ESI- sensitivity benchmark using direct infusion . May be you can get the MS conditions and specifications from them. In my experience ESI- is much more prone to loss of sensitivity than ESI+ so that should take care of the MS. For the whole LC/MS system I'd also use CLF. A 20 ul injection of a 5 ng/ml standard should give a nice peak (S/N better than 10 for the most abundante transition). If I recollect correctly CLF can be detected in a DAD so it'd give you information on how the LC is doing.

Good luck.