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The sample is injected directly into the capillary column (cold on‐column or COC). It is vaporized just after introduction. A special microsyringe, whose needle (steel or silica) is just 0.15 mm in diameter, is necessary for penetrating the column, which is cooled to 40°C before being allowed to return to its normal operating temperature. This process, useful for fragile compounds, is difficult to master in order to correctly eliminate the solvent(s). It is known not to discriminate between compounds of different volatilities (Figure 2.6). The injector has a special duckbill septum. While it is useful for thermally labile compounds, there is a risk of column pollution if nonvolatile compounds are present.