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19
Initial Bakeout and Equilibration
The basic procedures and temperature settings described below are for refer-
enced mode operation, but they can also be applied to operation in the single
filament or independent mode. Just make sure that both channels have the
same carrier gas; for instance, do not use helium carrier in one channel and
nitrogen in the other. Also be aware of the possibility of detector cross-talk when
components elute from the columns in concentrations greater than 1%.
Initial Conditioning
1. On the Control screen, set the detector temperature to 220°C.
2. Also on the Control screen, set the power level of both filaments to 90%.
3. Condition the detector by allowing it to bake at these settings for at least
12 hours.
Temperature Settings
4. After the initial bake-out period, set the detector temperature to 100°C or to
the column temperature plus 30°C, whichever is higher.
5. Set the filament temperatures to at least 50°C and as much as 100°C higher
than the detector temperature. Refer to
Figure 11
, which outlines the
relationship between the filament power settings and the actual filament
temperature.
Detector sensitivity
increases
as the temperature differential between the
detector and the filaments increases; howe ver, the lifetime of the filament
decreases
as its temperature increases. Thus, the detector temperature should
be set as low as possible, determined by the boiling point of the highest boiling
component of the sample.
6. Once all temperatures are set, allow plenty of time for the system to equilibrate,
evidenced by a stable baseline. Typical equilibration time for going from a
cold start-up to 130°C detector temperature is approximately five hours.
Detector temperature changes take much longer to equilibrate than do
filament temperature changes.
The test chromatogram accompanying your TCD was obtained under the follow-
ing conditions:
Sample:
~100 ppm blend in Helium balance
Sample volume:
250 μL
Column:
10' x 1/16" x 0.040" molecular sieve 5Å micropacked
Column flow:
6 mL/min
Reference flow:
6 mL/min
Column temperature: 65°C
Detector temperature: 100°C
Filament temperature: 230°C (a power setting of 67%)
Carrier gas:
Helium
Содержание Vici TCD-3
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