Normal Problem and Solution in GC Test

More than 90% of gas chromatographic problems occur in the inlet, and it is necessary to see which problems may occur in the inlet.

Problem No.1: Leak

If there is a leak, the pressure on the inlet may not be maintained, and the instrument will alarm. If the problem cannot be solved in time, the instrument will automatically turn off the pressure. Leakage is two-way. The carrier gas will leak out and the air will leak in. The air entering the chromatographic system, especially oxygen, is highly destructive, especially at high temperatures, where oxygen in the system can damage the stationary phase coating of the column. It results in much shorter of column life.

The main leak points as following:

1. Septum; the holes in the septum will become larger and larger after repeated use, and the seal will be problematic. For gas chromatography running around the clock, it is better to replace one septum per day.
2. O-ring outside the liner; long-term heating and cooling will also lead to rubber aging, sealing is reduced, O-rings need to be replaced in time.
3. Column seal; After repeated tightening, the sealing performance will also be reduced, try not to reuse it as many times as possible.

Problem No.2: Block

In general, the carrier gas and gas samples will not block the pipeline. Only when the sample contains some high-boiling compounds, some samples will condense in the split flow path due to untimely discharge, resulting in blockage of the pipeline or Partial blockage, which directly affects the accuracy and stability of the split ratio. The chromatographic results is that the repeatability of peak area is not good.

Problem No.3: Sample Residue

Although we have purged through the septum and shunted to minimize sample residue, there are many stubborn samples where the sample remains, including septa, liners, shunt plates, and even the front of the column. Replacing these consumables on the inlet can effectively solves the problem of sample residue. Selecting more inert liner and column also avoids sample residue better.