Operating in EI Mode 4
5977B Series MSD Operating Manual 91
The MSD can be used to measure actual column flow. You inject a small
amount of air or other unretained chemical, and time how long it takes to
reach the MSD. With this time measurement, you can calculate the column
flow. (See “To Calibrate Column Flow Linear Velocity” on page 52.)
Controlling JetClean Hydrogen Flow
The JetClean option uses hydrogen gas for cleaning the ion source. The
JetClean system MFC sends hydrogen to the annular space surrounding the
column in the GC/MS interface where it then enters the ion source body. The
flow rate is controlled by the MassHunter GC/MS Acquisition software. The
JetClean system is only supported on turbo based systems using an EI Inert
source, or an EI HES. (See “To Set the Operation Mode for the Optional
JetClean System” on page 106.)
Venting the MSD
A program in the DS guides you through the venting process. It turns off the
GC and MSD heaters and diffusion pump heater or the turbo pump at the
correct time. It also lets you monitor temperatures in the MSD and indicates
when to vent the MSD.
The MSD will be damaged by incorrect venting. A diffusion pump will
backstream vaporized pump fluid onto the analyzer if the MSD is vented
before the diffusion pump has fully cooled. A turbo pump will be damaged if it
is vented while spinning at more than 50% of its normal operating speed.
Make sure the GC/MSD interface and the analyzer zones are cool (below 100 °C)
before you vent the MSD. A temperature of 100 °C is hot enough to burn skin; always
wear cloth gloves when handling analyzer parts.
If hydrogen is used as a carrier gas or JetClean system supply, the carrier and
JetClean system supply shutoff valves must be closed before turning off the MS
power. If the foreline pump is off, hydrogen will accumulate in the MS and an
explosion may occur. Read “Hydrogen Safety” on page 23 before operating the MSD
with hydrogen gas.
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