LECO GC-MS

[allene]

Hi all,

I have a Agilent-Leco Pegasus III GC-TOF-MS and I have several problems about that:
1- What adjustments are critical to get a AIC (analytical ion chromatogram)? When I inject 1 ppm of a mixture (three analytes), good AIC chromatogram (high S/N ratio) is achieved but when injecting the sample with half the concentration (0.5 ppm), only the peak of one analyte is seen.

2- Can I turn off the electronic at weekend? About vacuum power?

3- Can I save the helium gas by chaining it ton nitrogen when the instrument is out of use for a week?

4- The intensity of single mass chromatogram is lower than AIC chromatogram, is it acceptable?

Thanks for any help.

[James_Ball]

I don't know the specifics for the Leco, but for any mass spec it is better to leave the vacuum on all the time. Otherwise you will have to deal with pumping out air and water ever time you want to use it, plus the detectors last longer when kept under vacuum.