INTRODUCTION TO GC

 

 

GC is one of the tools/instruments used for measuring the separate volatile compound from a mixture. The principle is the interaction between sample, mobile phase and stationery phase.

Sample to be analyzed in a small amount taken by using a micro syringe. Then the micro syringe needle inserted into a hot GC injector port, then sample injected. Injector temperature is set higher than the boiling point (20-30 Celsius deg), so the components of the mixture changed to a gas phase in the injector. Carrier gas, such as Helium, flow from the injector and push the components (in the form of gas) into the GC column. Inside the column, there is components separation and molecules partition between the carrier gas (mobile phase) and stationary phase occurs.

After the components in the mixture through the GC column, then these components going to the detector. Ideally each component going to the detector at different times because of partitioning between the mobile and stationary phases. Detector will send a signal to recorder/PC software (using Chrom Perfect). Peak area or peak height proportional to the number of molecules (concentration) which produces the detector signal.

How to use GC:

Here are the steps using the GC:

• Ensure that we already have a good method, saved in the GC or Software (Chrom Perfect).
  
  • 1. Make sure the GC is in ready state
• 2. Wash the syringe with acetone by taking and throw acetone 3 times.
  3. Pull the sample into syringe, usually 1-2 micro liter is injected into GC.
  4. Make sure the software in a state ready for data acquisition.
  5. Enter the syringe needle (all) into the injector, and inject the samples.
  6. Press the start button on the GC to provide trigger signal to the PC/Software.
  7. Clean the syringe immediately, because there may be some sediment in the syringe.
  8. Wait until all data acquired by software.
  

Note on injection process:

Injector is very hot, be careful, do not touch it.

Syringe needle going through a rubber septum, so we will feel a little resistance, a syringe needle will go entirely in to the GC Injector.

Inject the sample as soon as possible for best results, do not hesitate to inject the sample after syringe needle wal already in the injector.

Pull the syringe as soon as possible after sample was injected.

GC Analysis Results.

The result of analysis can be calculated by comparing peak height or peak area of sample with peak height or peak area of standard solution. Usually concentrations counting and calibration functions are providing by Software, such as Chrom Perfect.