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- Posts: 23
- Joined: Tue Apr 30, 2013 8:01 pm
I purchased a second- hand GC-MS (Agilent 689 Leco Pegasus III) but there is a problem about sensitivity.
Mass detector passes all criteria of cal gas (FC-43), but the peak intensity of injected analytes (PAHs) in TIM mode is very low (near 10-20 times lower than that of quadrupole or ion trap gc-ms). The specification for the Pegasus is S/N of 10:1 for mass of 284 for 2 pg HCB (1 µL injection of 2 ppb), but I get S/N of 5:1 for 20 pg of HCB.
I verified all sections of GC such as injector, liner, septum, transfer line,… and increase detector voltage up to 1800 V. All things are apparently correct but the problem still remains.
The vendor says that the detector was damaged two years ago and replaced with a second-hand one. Since MS detector passes all criteria of cal gas tunning, is the low sensitivity related to the detector age? Is there any setting in software for improving sensitivity?
I would greatly appreciate any help.
Thanks
Mass detector passes all criteria of cal gas (FC-43), but the peak intensity of injected analytes (PAHs) in TIM mode is very low (near 10-20 times lower than that of quadrupole or ion trap gc-ms). The specification for the Pegasus is S/N of 10:1 for mass of 284 for 2 pg HCB (1 µL injection of 2 ppb), but I get S/N of 5:1 for 20 pg of HCB.
I verified all sections of GC such as injector, liner, septum, transfer line,… and increase detector voltage up to 1800 V. All things are apparently correct but the problem still remains.
The vendor says that the detector was damaged two years ago and replaced with a second-hand one. Since MS detector passes all criteria of cal gas tunning, is the low sensitivity related to the detector age? Is there any setting in software for improving sensitivity?
I would greatly appreciate any help.
Thanks
