The detector



Abstract Possible sources for detector problems are discussed, examples of effects are given as well as how to prevent and solve problems.

LevelBasic

Possible GC detector problem areas are:

(Link for more details on detection principles)

A good detector for the gas chromatography should comply with a number of requirements:

  • Universal or selective. Dependent on the application, a detector should detect all chemical components which emerge from the column or should detect only a specific group. 
  • Sensitivity. Small amounts of sample (nanogram or picogram amounts) should be 'observed'. 
  • Accurate. Deviant signals, given by the detector, should stay within acceptable limits. 
  • Reproducibility. A detector should give a similar signal if two identical components in the same amounts pass through the detector independent of the time of measurement. 
  • Speed. Components pass, after they leave the column, the detector rapidly. This should not cause any problems regarding the accuracy and the separation. 
  • Reliability. One should be able to rely on a detector.

All the requirements mentioned here for the detector have their limits. The more we require of the system, the closer we get near the limits and inaccuracy and unreliability increase. The more we require, the more problems we can expect. Errors will reinforced if parameters oppose each other.

The limits of the detector characteristics are not fixed, they depend on:

  • Detector type,
  • Sample,
  • Carrier gas,
  • Age, the usage and maintenance.

It is recommended (as of course is valid for all parts of the system) to handle it sensibly and efficiently. The efficiency, the accuracy and the reliability of the entire system are influenced by the performance of the detector.

General trouble shooting for GC detectors:

  1. Check all settings of the detector, electronics and data system
  2. Change the column flow/pressure and observe the results / baseline
  3. Disconnect the column from the detector!
  4. Run a blank temperature program
  5. Inject sample solvent only

Link: More on detectors.

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