Gow-Mac 580 series, Operating Manual

Page: 40 / 68

GOW-MAC Instrument Co. 40
H. Injection Instructions for use with GSV and S/B-P Valves
If the instrument has GSV and S/B-P valves, it is equipped with a porous polymer (PP) (i.e.,
Porapak , Chromasorb , Hayesep) column and a molecular sieve 5A (MS5A) column. They
are connected via the series/by-pass valve. When the S/B-P Valve is in the series position the
columns are connected in series and the sample passes through both columns before entering
the detector.
When the S/B-P Valve is in the By-Pass position, the sample by-passes the MS5A column and
passes directly through the PP column to the detector.
An analysis which requires the separation of O
2
, N
2
, CH
4
, CO, and CO
2
would normally require
two separate injections to complete the separation.
The porous polymer column will not separate O
2
, N
2
, or CO from each other but will pass them
right through the column. The Molecular Sieve 5A column will separate H
2
, O
2
, N
2
, CH
4
, and CO
but will not allow CO
2
to pass through (CO
2
is adsorbed onto the MS5A).
A S/B-P Valve with PP and MS5A columns will allow the separation of H
2
, O
2
, N
2
, CH
4
, CO and
CO
2
with one injection and one valve change
First an injection of certifi ed standard of H
2
, O
2
, N
2
, CH
4
, CO and CO
2
is made with the S/B-
P Valve in the B-P position. The porous polymer column will separate this standard into four
components H
2
, Air (O
2
, N
2
, or CO), CH
4
and CO. The separation of the Air and CH
4
may not be
baseline on a 1/8” column but this is not important. The retention time from the point of injection
to the valley between the CH
4
and CO
2
peak should be recorded.
After the above retention time is known, a sample containing H
2
, O
2
, N
2
, CH
4
, and CO can be
injected into the instrument with the S/B-P Valve in the Series position. At the time of the above
recorded retention time been reached the S/B-P Valve should be switched to the By-Pass
position.
In this analysis the H
2
, O
2
, N
2
, CH
4
and CO have been allowed to pass through the PP column
onto the MS5A column. When the valve is switched from Series to By-pass these components
are trapped on the MS5A, while the slower eluting component CO
2
comes off the PP column.
After the last component comes off the PP column the S/B-P Valve is switched to the series
position and the H
2
, O
2
, N
2
, CH
4
and CO are eluted from the MS5A column.