Sample Introduction and The Injection Chamber

Sample Introduction:

The sample, usually in the form of a solution in the order of 0.5 μl, is introduced into the chromatograph with a microsyringe. Several types of syringe exist because of the diversity of injectors and columns. For gaseous samples, loop injectors similar to those in liquid chromatography can be used. In order to automatic the injection and improve reproducibility-simply changing the user can cause substantial deviations-manufactures provide autosamplers in which the syringe and injection procedure are totally automated. These autosamplers, which can handle several samples, are very reliable. They operate in a cyclic fashion, taking the sample, injecting it rapidly (0.2 second) and rising the syringe. The latter is very important to avoid cross-contamination of successive samples that have similar composition.

A typically 10 μl syringe frequently used in gas chromatography. A guide is used to protect the fragile piston. In some models (0.1 to 1 μl), the plunger enters the needle in order to deliver all of the sample and avoid dead volume effects.

For the analysis of very volatile samples, there is technique known as head space chromatography which can be used either in a static or dynamic mode.