Application
News
No. G323
The Nexis GC-2030 gas chromatograph has begun to
support packed columns. The detectors compatible
with packed columns are a flame ionization detector
(FID) and a thermal conductivity detector (TCD).
As an example of SUS packed column TCD analysis
using the Nexis GC-2030, this article introduces gas
analysis using a Molecular Sieve 5A (MS-5A) column.
K. Kawamoto
Packed Column Support System
An SUS column which can be used for the Nexis GC-
2030, a system compatible with packed columns, is the
same as that used for the GC-14, GC-17 or GC-2014, and
it can be shared between these instruments.
For the TCD for packed columns (PTCD-2030), a column
is connected to the sample vaporization chamber (SINJ)
and the carrier gas flow rate is controlled by the
Advanced Flow Controller (AFC).
Fig. 1 shows the appearance of the instrument equipped
with the PTCD-2030 and an example of connecting an
SUS column and an empty pipe to the analysis line and
reference line, respectively. Also, it is possible to
eliminate the effect of baseline drift identified in a
column temperature program analysis by connecting
the same type of column as that for the analysis line on
the reference side.
Gas Analysis
Gas samples were analyzed using an SUS packed
column (MS-5A). As samples to be analyzed,
approximately 1000 ppm (v/v) each of H
2
, CH
4
, CO and
C
2
H
6
were prepared using He as the base gas. The
samples were prepared by repeatedly taking a certain
volume of the target ingredient using a gas-tight
syringe and adding it to a bag filled with He, which
served as the blank. In the analysis, 1 mL of each gas
sample was aspirated by a gas-tight syringe and
injected manually. Since ambient gas was mixed into
the bag or syringe (needle) during these operations, N
2
or O
2
, which was not added intentionally, was also
analyzed.
Analysis Conditions
Table 1 lists the configuration of the instrument used
for analysis and the analysis conditions.
Table 1 Instrument Configuration and Analysis Conditions
Gas Chromatography
Packed Column Analysis of Gases Using
Nexis™ GC-2030 (TCD)
Fig. 1 Appearance of Instrument with PTCD-2030 and Example
of SUS Column Installation
Model : Nexis GC-2030APT
Injection Mode : Direct
Injection Volume : 1 mL (gas-tight syringe)
Injection Temp. : 120 °C
Carrier Gas : He
Carrier Gas Control : 40 mL/min
Column :
MS-5A 60/80
(2 m × 3 mm I.D.)
* Reference line measurement was
performed via a directly connected
single column
Detector : Thermal Conductivity Detector (TCD)
Detector Temp. : 220 °C
Current : 100 mA
Column Oven Temp. : 60 °C (5min) - 10 °C/min – 200 °C (6min)
In gas analysis using a TCD, as the mount of sample
injected increases, this may cause greater baseline drift
associated with sample injection, and the peak of the
compound whose retention time is short is affected by
the drifting baseline. To reduce baseline drift, an
effective countermeasure is to change the carrier gas
control from flow rate control to pressure control, as is
the case with analysis using the GC-2014. In this
situation, we recommend to install an advanced
pressure controller (AUX APC) for pressure control.
