Varian 4000 GC, Hardware Operation Manual

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The COLTEST test mixture contains the following compounds at levels of 1 to
5 ng/µL.
No. Compound Formula Integer
Weight Quantitation
Mass
1 Decane C
10
H
22
142 57
2 1-octanol C
8
H
18
O 130 69
3 Undecane C
11
H
24
156 71
4 Nonanal C
9
H
18
O 142 67
5 2,6-dimethylphenol C
8
H
10
O 122 107
6 2-ethylhexanoic acid C
8
H
16
O
2
144 73
7 2,6-dimethylaniline C
8
H
11
N 121 106
8 decanoic acid, methyl ester C
11
H
22
O
2
186 74
9 undecanoic acid, methyl
ester C
12
H
24
O
2
200 87
10 Dicyclohexylamine C
12
H
23
N 181 138
11 dodecanoic acid, methyl
ester C
13
H
26
O
2
214 143
12 Hexachlorobenzene C
6
Cl
6
282 284
You can also effectively separate the individual components in the mixture for
subsequent data manipulation, e.g., library searches and quantitation.
Troubleshooting Common Chromatographic
Problems
The COLTEST mixture includes polar or active compounds such as 1-octanol,
2,6-dimethylphenol, and 2,6-dimethylaniline. Also present are some non-polar or
inactive compounds such as decane and dodecane at approximate levels of 1
ppm in hexane. Analysis of the mixture yields information about solvent tailing,
column efficiency, dead volume, active sites in the injector/column, etc. You can
use the analysis to troubleshoot common chromatographic problems. The
following table identifies many of the problems, and proposes solutions.
Correcting Solvent Tailing or Broadening Problems
Possible Cause Solution
Poor column installation
resulting in dead volume
in the injector Reinstall the column in the injector. Make sure you have a
good cut on the column by examining the column under
magnification.
Solvent flashing in hot
injector. Reduce the injection speed. If possible, reduce the injector
temperature. If you are using sandwich injection, reduce the
solvent plug to 0.5 µL.
Septum purge line is
plugged Check that the septum purge flow is 3.5-4.5 mL/min with a
10-psi head pressure. If necessary, adjust the valve setting.
Injector is not purged
properly following
splitless injection For a splitless injection, the vent flow should be at least
70 mL/min. The injector should be switched to the split mode
30 to 90 sec after the injection.
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