tullis onstott wrote the following about electron energy:

> Dear isotopers,
>
> Have any of you who analyse the isotopic composition of CO2, tried
> increasing you electron energy to around 100ev to see if it improves the
> ionization efficiency?  Are there any pubs out there on this?  I'm curious
> to know if the increase in sensitivity comes at a price of less linearity.

In my experience, the optimum sensitivity for a VG-type (Optima,
PRISM, SIRA, 602 etc). running dual inlet gasses will occur when the
eV is set at about 60V.  Pumping up to 100 is almost always
detrimental to sensitivity, and peak shape, so would suggest that
"happier" ionisation occurs at the lower setting.  In continuous flow
conditions, on the other hand, the eV setting is always at, or close
to the maximum possible value.  100-120V.  Probably because you have
to "punch" the electrons through a Helium "soup".

All technical terms used by permission

Totty  <8^)