Chemistry Reference
In-Depth Information
• Instrument manufacturer manuals: he purchase of any new instru-
ment also provides the user with an invaluable source of information—
the manual. Within the manual you will find useful troubleshooting
information specific to that instrument brand and model.
It is also essential to have an assortment of tools, cutters and other items
to enable effective installation and manipulation within the instrument. A
comprehensive alphabetical listing of tools and accessories, from a user's per-
spective, is given in the article highlighted in the Further Reading section at
the end of the chapter.
The major issues in GC all occur as a result of one (or a combination) of
the following:
• Operator error (particularly relating to injection technique).
• Sample (and hence its constituents in the form of the solvent and
compounds under investigation).
• Column (in the context of deterioration, wrong stationary phase and
physical characteristics).
• Gas low rates (in terms of leaks with resultant diferent low occurring).
• Electrical issues associated with malfunction of circuit boards.
Ultimately, the most appropriate way to solve any GC problems is to
prevent them. This can be addressed by having a regular maintenance and
upkeep programme. While this does not necessarily preclude problems due
to malfunction, it does allow early warning signs to be acted upon. Some
common areas to be aware of include:
• Quality of gas supply (e.g., N
2
should have <1.0 ppm O
2
, H
2
O, CO
2
,
CO and hydrocarbons).
• Maintenance of gas generator (e.g., N
2
supply).
• Awareness of deterioration in in-line gas puriiers (e.g., oxygen trap,
molecular sieve).
• Regular changing of injection port septum.
• Periodic changing of injection port liner (
Note:
This may be more
frequent depending upon cleanliness of the sample matrix.).
• Establishing a 'standard' solution to conirm column performance
(and hence identify when changes in performance have occurred).
• Periodic maintenance of detector (e.g., cleaning of ion optics of
mass spectrometer).
The major issues in GC that affect the separation and performance of the
instrument can be identified as the following:
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