33
Appendix B: Basic TCD Operation via Serial Commands
Initial Bakeout and Equilibration
Initial Conditioning
4. Set the detector temperature to 220°C:
Type
TS 220
<enter> on the command line.
5. Set the power level of both filaments to 90%;
Type
FA
90
<enter> for filament A.
Type
FB
90
<enter> for filament B.
6. Condition the detector by allowing it to bake at these settings for at least
12 hours.
Temperature Settings
7. After the initial bake-out period, set the detector temperature to 100°C or to
the column temperature plus 30°C, whichever is higher.
8. Set the filament temperatures to at least 50°C and as much as 100°C higher
than the detector temperature.
Refer to
Figure 8
on page 20,
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; however, 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.
9. 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
Balancing the Channels
11. Use the console command “ZS” to “zero” the system, which automatically ad-
justs Channel B, then adjusts Channel A-B to 0 Volts.
An alternate method, if you need to set the outputs to something other than 0
volts, is to use the “ZA” and “ZB” to set the level of each channel independently.
12. The results of the adjustment process will be shown in the console window.
After completion, the detector will be ready for analytical use.
