Failure analysis of gas chromatography: the solution of no peak in sample feeding

No peak in sample means that no peak is detected after the sample is put in, and only a straight line is drawn at the baseline.

Note: when it is found that the sample does not peak, it should first consider whether the carrier gas enters the instrument (including the HPLC column and detector), otherwise it may cause damage to the HPLC column or contaminate the detector.

Therefore, when it is found that the sample can not peak out, the temperature of the thermostat tank of the HPLC column should be immediately lowered to allow the HPLC column to cool down. When using TCD, the tungsten current must be turned off first. The inspection of other items shall not be carried out until the carrier gas system is determined to be normal.

A. Check whether the detector's flame is extinguished, and if so, reignite; If the point is not on fire or is easily extinguished after burning, please check the following items:

 1). Check whether the ignition coil is red. If it is not red, it should be part of the ignition pole fault.

 2). Check whether the flow of various gases is normal, and try to increase the flow of hydrogen appropriately.

 3). When using TCD by gas chromatograph, check whether the current Settings of TCD tungsten wire and tungsten wire are normal.

B. Check the connection between the ion signal line and the detector, amplifier circuit board, and the connection between the output signal line and the instrument, integrator/workstation.

C. When the zero setting is abnormal, it is necessary to consider whether the circuit system fails. Please check whether the signal line fails, the amplifier circuit board fails, the output signal line fails, and the integrator fails.

D. If conventional solvents such as incoming methane do not peak or the retention time becomes slow, after confirming that the temperature of the HPLC column box has dropped to around room temperature, the gas chromatograph should be checked for the following items:

 1). Check whether the HPLC column is broken.

 2) check whether the carrier gas flow is normal and enter the HPLC column, FID detector and other parts.

E. For other reasons, please check the following items:

 1). The syringe is abnormal.

 2). Check whether the analytical conditions such as HPLC column temperature, sampler temperature, detector temperature and range setting are appropriate.