Answers to Questions - Forensic Applications of Gas Chromatography - page 139

10. What is Tenax?
Answer: Tenax is a porous polymer for concentration of airborne
organic compounds. It is based on 2,6-diphenyl- p -phenylene oxide.
11. How long would the chromatographic run take to separate com-
pounds using the following temperature programme: 50°C for 2
min, followed by ramp rate of 10°C/min to 220°C, with a final hold
temperature of 2 min?
Answer: The total chromatographic run time can be calculated as
follows:
Temperature difference:
Final temperature - initial temperature = 220°C - 50°C
= 170°C
Ramp rate is 10°C per minute
Therefore, the time for the ramp to be delivered is
170°C/10°C per minute = 17 min
Add all the time together:
Initial hold time = 2 min
Ramp time = 17 min
Final hold time = 2 min
Total time for chromatographic run is 21 min.
12. What is the stationary phase?
Answer: The stationary phase is the film coated on the inner wall of
the capillary column.
13. What are polar compounds composed of?
Answer: Polar compounds are made up mainly of carbon and
hydrogen atoms but also must contain electronegative atoms
such as oxygen, nitrogen and sulphur, as well as double bonds
(e.g., carbon-oxygen).
14. What is the linear dynamic range?
Answer: The linear dynamic range is the extent of the calibration
range over which the concentration rises in a linear manner. It
would be reasonable to quote a linear dynamic range of 10 5 . This
means the instrument detector produces a linear calibration
graph over the concentration range from 0.001 (via 0.01, 0.1, 1,
10) to 100 (in appropriate units).
15. What effect would having a 60 m capillary column have on the sam-
ple components?
Answer: Typically, a longer column (60 m) has a longer analysis
time (e.g., twice the time of a 30 m column to separate the same
compounds under isothermal conditions) but can be extremely
useful for complex samples with a large number of compounds
for separation.