Chromatographic Troubleshooting
Baseline symptoms
CContaminated detector gases (hydrogen and air).
CAir currents from a fan or air conditioner blowing across the top of the instrument may interfere with gas exiting from the detector.
This is a possible, though not very likely, cause of noise since detectors are well protected. Switching off the air current source or shielding the detector area identifies this problem.
CAn inadequately tightened collector on an FID or NPD generates noise.
CA contaminated detector results in noise.
2.Noise increases gradually to an unacceptable level:
CThis symptom indicates gradual buildup of the noise source, rather than an abrupt change as discussed above. FI detectors are susceptible to gradual buildup of deposits in the collector. In extreme cases spiking occurs along with increased noise level.
Silicon dioxide deposits are formed when bleed from a silicone column is burned in the flame. This material is removed mechanically. Preventive measures include use of low column loadings, stationary phases with high•temperaturelimit, thorough column conditioning before use, and the lowest possible oven temperatures for the analysis.
CCarbon deposits may form from solvents that burn poorly (primarily chlorinated materials and aromatics). If possible, avoid such solvents. If they are necessary, periodic cleaning of the collector is required.
CGradual noise increase may occur from saturated carrier gas drier or chemical traps. When these approach their capacities, contaminants begin to pass through and create noise. Trap and drier regeneration or replacement eliminates this source of noise.
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