Chromatography Forum

Hi all

Im doing some method development for our GCMS system and was following the literature reference to set our MS settings. The literature was using the Agilents GCMS where as ours is Shimadzu QP2010 plus GCMS

and The results was a very noisy background as shown



The peak shown here is my target compound

Since I am not very familiar with MS setups any tips which parameters should I tweak first to reduce the noise levels? the current MS setting for the above is:

Ion Source Temp 250°C
Interface: 300°C
Detector gain mode: Relative
Detector gain: 0.000kV
Threshold: 1000

Acquisiton mode: Scan
Event time: 0.5 sec
scan speed: 1250
Start m/z: 30
End m/z: 580

When do you click on the noise in the chromatogram what do you see?
Silicone related compound or something else?
Do you see it in every run?

Tarapan,

It looks like electronic noise to me. Fairly consistent in pattern and trending downward at the very high temp. Having said that, a spectra (as noted by bhuvfe) would be very helpful. Also, I would not start at 30 AMU. Obviously what you are looking for is reasonably heavy so I would suggest something more like 45 or 50 AMU as the low mass.

Best regards,

AICMM

Although it is difficult to compare between intruments, the noise is not excessive - your vertical scale is quite short. So maybe the proble is that the signal is too low. How much of the analyte are you putting onto the column ?

Peter

Heres the spectra at noise "peak" and noise "valley"


Spectra at one of background "peak"


Spectra at one background "valley"

bhuvfe and AICMM: the background noise is mostly silicon related compounds

Peter apps: The target compound should be around 0.5 microgram on column.

0.5 ug on the column - then you really do have a problem, but not with the noise, with a very weak response to the analyte. Please check your calculations to make sure that this is not 0.5 ng

Peter