The GC injector may seem a simple device. It is, however, a complex part of the entire GC system and has four important functions:

Although there are some small differences in design, most injectors of various manufacturers are more or less the same.

The injection port for the sample is attached to a (heated) injector block. A septum seals the system at the injector side. A liner can be inserted into the injector block and installed by means of a nut and a ferrule. The liner operates as the evaporation chamber of the sample and the place where the column can be connected. The injector is connected to the column by means of a nut and a ferrule.

Depending on the amount and type of sample, as well as on the dimension and type of column, various types of injector are available:

• Direct injector: This injector is used for packed columns and wide-bore capillary columns. It is used for liquid samples. These samples can be pure liquid components or solutions of liquid and/or solid samples. Direct injection is practically always carried out at high temperatures and therefore a temperature control unit is required.
• Split injector: This is the most universal and most widely used injector for capillary columns. The split injector is derived from the direct injector and is also based on rapid evaporation.
• Splitless injector: This type of injector is used for highly diluted samples (trace injection).
• Cold on-column injector: This injector is used for direct injection of liquid samples onto capillary columns.

Comparison of GC injectors