Gas Chromatography with Mass Selective Detector, Flame Ionization Detector, Electron Capture Detector and Thermal Conductivity Detectors

Organic Compound Analysis

Most of the organic analyses that we conduct are for organic priority pollutants such as pesticides, PCBs, PHCs, BTEX, and other petroleum products. Gas Chromatography (GC) is the standard methodology. From sample matrices such as soil, water, plants and fish, the analyte's are extracted into organic solvents, separated from interfering substances (cleaned up), concentrated and run on the GCs.

Using a variety of different detectors, excellent sensitivity and specificity can be achieved for a whole spectrum of  compounds. The use of automated sample carousels means that the GCs can be left unattended for overnight operation.

Automated sample analysis on Agilent GC

The ASU possesses or otherwise has access to seven automated GC systems.  In addition, we have a Pyrolizer accessory for special (non-volatile) samples and a purge and trap unit for volatile organic compounds (VOCs).

For details on how a pyrolizer works:

How to Analyse Unknown Samples by Pyrolysis GC/MS, by Joeri Vercammen, Valérie Winne and Myriam Madani,

'Purge and Trap' GC/MS is used to look at volatile organic compounds. Typically, the organic compounds have to be concentrated prior to analysis and this is done by purging the analytes of interest from a sample using an inert gas. This purging process removes the compounds from the sample matrix and deposits them to an absorbent cartridge. This is then heated rapidly and the organics are removed into the GC/MS system in concentrated form.

Soxhlett Extraction

This glass apparatus was invented in 1879 and is still in use today. It uses the principle of 'continuous extraction' to repeatedly cycle solvent through a 'thimble' containing a material to be extracted.

See Wikipedia: Soxhlett Apparatus

Plant sample extraction, by soxhlett

Detectors and how they work

The Electron Capture Detector (ECD)

From Agilent: eInspirations newsletter,2010 

The Flame Ionisation Detector (FID)

See UCDavis ChemWIKI for a complete description of how the FID works.

The Thermal Conductivity Detector (TCD)

See UCDavis ChemWIKI for a complete description of how the TCD works.

Sample Preparation For GC Analysis

There are many 'method specific' methods we use to prepare our organic samples for GC analysis. Two of our primary solvent extraction methods utilize accelerated solvent extraction (ASE) or soxhlett extraction  techniques.

Dionex ASE200 Solvent Extractor

Typical PCB Chromatogram

Reproduced from "β-cyclodextrin enhanced phytoremediation of aged PCBs-contaminated soil from e-waste recycling area"
Yingxu Chen^{* a}, Xianjin Tang^a, Sardar Alam Cheema^a, Wenli Liu^b and Chaofeng Shen^a