Sample introduction
The most common injection method is where a microsyringe is used (Figure 2.3) to inject a very small quantity of sample in solution (e.g. 05 L), through a rubber septum into a flash vaporizer port at the head of the column. For gaseous samples,
The most common injection method is where a microsyringe is used (Figure 2.3) to inject a very small quantity of sample in solution (e.g. 05 L), through a rubber septum into a flash vaporizer port at the head of the column. For gaseous samples,
loop injectors are used similar to those described in liquid chromatography (cf. paragraph 3.4). To better control the reproducibility of the injections – simply changing the user can lead substantial deviations, when in manual mode – most instruments are provides with autosamplers in which the syringe movements are automated (Figure 2.1). The assembly operates in a cyclic fashion, taking the sample, injecting it rapidly (0.2 s) and rinsing the syringe. The latter is important to avoid cross-contamination of successive samples that have similar composition.
A sampling technique known as ‘headspace’, of which there are two modes, static and dynamic, is very widespread in GC for the qualitative and even quantitative analyses of volatile constituents present in some samples (cf. Chapter 21).
A sampling technique known as ‘headspace’, of which there are two modes, static and dynamic, is very widespread in GC for the qualitative and even quantitative analyses of volatile constituents present in some samples (cf. Chapter 21).