GC Sampling Techniques
Perhaps the most difficult step in any GC analysis is the sample introduction. Solid and liquid samples need to be converted to the gas phase and then transported onto the column. Samples already in the gas phase need to be efficiently diverted or transported into the GC column. The aims of this module include investigating the various sampling techniques available for GC analysis. We will give a detailed description of manual injection and injection troubleshooting and describe the use of autosamplers to increase sample capacity, accuracy, and precision. The principles, primary operating parameters, and practical implementation of a series of sampling techniques are also explained.
At the end of this section you should be able to choose the relevant technique for the introduction of a wide range of sample types and presentations, describe the practical implementation of various sample introduction methods, demonstrate a good understanding of problems that occur in GC injection and describe how these might be practically overcome, explain the general principles of a series of sampling techniques, and identify the major parameters for each of these techniques which require optimization and describe optimization strategies.
Topics include:
- Sampling techniques overview
- Manual injection
- Cold needle technique
- Hot needle technique
- Air gap technique
- Solvent flush technique
- Automatic liquid sampling (autosamplers)
- Gas sampling devices
- Purge and trap autosampers
- Purge and trap adsorbents
- Thermal desorption (TD) autosamplers
- Two-stage thermal desorption
- Two-stage desorption with cold trapping
- Thermal desorption - important parameters
- Solid phase microextraction (SPME)
- Important SPME parameters
- Headspace sampling
- Headspace autosamplers
- Headspace calibration and quantitation
