-
- Posts: 2
- Joined: Tue Apr 01, 2008 12:33 am
Thanks,
Nick
Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.
Kostas Petritis wrote:
Can you try to infuse the methanol with just a syringe pump? This will narrow down where the contamination might be coming from (i.e. LC instrumentation or mass spectrometer or mobile phase)...
mordwink wrote:
We have been having an issue with some contamination in our Agilent 1100 LC system coupled to an API 3000 MS. For multiple compounds, the background noise was extremely high (1000 to 10000 cps) when injecting no sample (just MeOH) without a column. After replacing all parts (tubing, PVDF filter, needle, needle seat, six port valve, etc.), flushing the system with 20% nitric acid, cleaning the MS (plate, quadrupoles, and cone), and flushing for 24 hours with DI water, the signal remains. When we bypass the autosampler and degasser, the signal is not as high but still above 1000 cps. We cannot figure out where else the system could be contaminated. Help please?!
Thanks,
Nick
mordwink wrote:Kostas Petritis wrote:
Can you try to infuse the methanol with just a syringe pump? This will narrow down where the contamination might be coming from (i.e. LC instrumentation or mass spectrometer or mobile phase)...
We tried that, and it is not coming from the MS.
WhiteBloodCells wrote:
Thank you. I have to tell you that my lab measures polyfluorinated compounds with the same instrument for 10 years now. Never had problems with a high noise level. It's also strange, I measure 3000 cps one day and the next day something around 600 cps, next day 2000 and 3000 again (same solvent, same bottle, same tubing, same flow). There is no system behind the noise level. When I measure on these specific masses e.g. for 120 min, I can observe a slowly increasing noise level, but sometimes it's also stagnating. The noise level is very unsteady, but too high.
Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.
Subscribe to our eNewsletter with daily, weekly or monthly updates: Food & Beverage, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.