Agilent’s single quadrupole is available in three versions, with diffusion or turbo pump. The diffusion pump system has slightly less sensitivity than turbo pump systems, and can only be run with 0.25 columns, but in addition it is a rock solid system.
Turbo-pump systems may accept up to 4mL/min carrier gas, and there is therefore also the possibility to operate with 0.32 columns. If you want the ultimate sensitivity, the turbo pump system also comes with a “High Efficiency source (HES)” ion source.
Our general recommendation is a diffusion pump system if you want a robust system where maximum sensitivity is not required, and you can do with 0.25 columns. If you want a system with optimal sensitivity, chemical ionization and/or running 0.32 columns, a turbo pump system should be selected.
We also like to mention here, that there has been a significant move towards more and more real sensitivity over the past generations of mass detectors:
Agilent 5973 MS: 60:1 s/n for 1-pg OFN scanning from 50-300 amu at nominal m/z 272 ion.
Agilent 5975 MS: 600:1 s/n for 1-pg OFN scanning from 50-300 amu at nominal m/z 272 ion.
Agilent 5977B MS (extractor): 1500:1 s/n for 1-pg OFN scanning from 50-300 amu at nominal m/z 272 ion. IDL (see below): 10fg.
Agilent 5977B MS (HES source): A new parameter has been introduced by Agilent, the Instrument Detection Limit(IDL). Therefore the Detection Limit is not directly comparable to previous s/n measurements. IDL for 5977B HES is 1.5fg,