Volatile Organics Analysis (VOA)

Volatile organic chemicals which boil at relatively low temperatures, up to 120-150^oC, can be easily determined using gas chromatography-mass spectrometry (GCMS).  Using GCMS,  contaminants can be identified from their mass spectrum while the concentrations are measured from their response.  (See the DEHP example below.)

One of the typical methods of extracting volatile organic chemicals from samples is called "purge and trap" or dynamic headspace.  An aqueous based sample or a solid dissolved or suspended in water is purged with helium.  Low boiling compounds are carried with the helium to a porous polymer trap where they are adsorbed.  The trap is then heated and back-flushed into a GCMS system.  Detection limits are usually in the 1-10 ug/L range or less.

Purge and Trap GCMS

for solvents such as acetone, chloroform, benzene, toluene, etc.
Click here for a common analyte list.

Semi-Volatile Organics Analysis (SVOA)

In this case, samples are generally extracted with methylene chloride, the extract concentrated, and then the extract is analyzed by GCMS.  Depending on the type of sample, detection limits may range from ug/g (ppm) to ug/kg (ppb).

The example below shows a chromatogram of diethylhexyl phthalate (DEHP), a common plasticizer for PVC.  The mass spectrum in the box is a molecular fragmentation pattern which identifies this peak as DEHP.  The size of the peak in the chromatogram relates to the amount in the sample.

Example analytes include:

• phenols, chlorinated phenols, nitrophenols
• phthalate esters and other plasticizers
• naphthalene, anthracene, and other PNAs
• paint solvents such as cellosolves and other glycol ethers 
• antioxidants and preservatives
• odorants
• pesticides and PCBs, such as DDT, dichlorovos, etc.
• petroleum hydrocarbons such as mineral spirits and kerosene

Click here for a common analyte list.

Non-Volatile Organic Compounds

This is the most difficult group to determine.  These compounds require a variety of methods, most based on liquid chromatography (HPLC),  LCMS, and FTIR.  A full description of these techniques is beyond the scope of this article.  Links to other web pages are given in the neighboring table.

• polymers
• silicones
• pesticides
• antioxidants and preservatives
• organic ions such as citrate, ascorbate, etc.
• drugs
• sugars
• organometallic compounds
• lubricants
• amino acids, peptides, proteins

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