Common Faults of Gas Chromatography FID Detector

Before any FID analysis can begin, the flame must be properly ignited - ionization only occurs under the action of the hydrogen flame, so a failed or unstable flame will directly compromise the chromatographic peak. To check whether the flame is lit, hold a small mirror or piece of glass near the detector's vent; if condensation (water droplets) forms, the flame is burning normally. No condensation typically indicates the flame has not been ignited, or that there is gas leakage - check for this using a soap-bubble leak test around fittings and connections.

Next, verify that the gas flow is normal and that the hydrogen-to-air ratio is appropriate, since an incorrect ratio is one of the most common causes of ignition failure. After re-igniting the flame, fine-tune the various flow rates to reach the optimal setting for stable combustion and consistent detector response.

The signal line is the channel that carries the detection signal from the detector to the workstation. If this line is damaged or short-circuited, the signal cannot reach the recorder, and no peak will be displayed. Start by inspecting the connection between the instrument and the workstation for loose contacts or physical damage. You can also use a multimeter to measure the signal output after sample injection - if no signal is detected, the fault is likely internal to the chromatograph, and you should trace the issue to the signal amplification circuitry for further repair.

Insulation resistance between the collector electrode and the instrument housing should measure greater than 1 kΩ. If the reading falls below this threshold, poor insulation is indicated, and the collector electrode should be removed and cleaned individually to restore proper function.

Other frequent contributors to peak failure include damage to the injection septum, chromatographic column failure (particularly common with capillary columns), and wear or damage to the micro-syringe. Routine inspection of these consumable components is a practical way to prevent unexpected downtime.

To isolate electrical noise, disconnect the detector's signal line and observe the baseline in acquisition mode. If the noise disappears or is significantly reduced, the fault originates from the FID detector itself - in this case, replacing the detector or minor components typically resolves the issue. If noise persists, check other circuit-related causes such as power supply damage, loose circuit boards or connectors, or poor instrument grounding. Grounding can be verified with a multimeter; grounding resistance should be less than 5Ω for stable operation.

Again, disconnect the signal line and check baseline behavior in acquisition mode. If the system operates normally with the line disconnected, this points to contamination rather than an electrical fault - check whether the chromatographic column has failed or become contaminated (glass wool, glass liner residue, etc.), or whether the detector's ion collector itself is contaminated. Ion collector contamination is usually caused by carbon deposit buildup, and correcting it requires carefully disassembling the detector and cleaning it with a neutral solvent.