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The injector, which is the sample’s entrance to the chromatograph, has different functions: to vaporize and entrain the sample mixed with the carrier gas at the head of the column. Depending on the way injection is conducted and on its rapidity, it can impact the quality of analysis.

Injectors differ depending on the nature of samples and types of analyses. Historically, the first injectors, called direct vaporization injectors, were intended for packed columns or macrobores, in which the carrier gas flow rate must be at least 6–7 ml/min. Any model of this type comprises a metal tube with a glass sleeve (called the insert). It is swept by the carrier gas and heated to a sufficient temperature so that the less volatile solutes of the sample vaporize. The sample is introduced with a microsyringe, piercing the septum placed at the entrance of the injector (Figure 2.4). The other end is connected directly to the column. Once all of the sample has been introduced with a syringe, it is immediately volatilized and enters the column, swept along by the carrier gas.