Chlorinated hydrocarbons (organochlorides) are a very large and diverse group of hydrocarbon molecules that also have at least one covalently bound chlorine atom chemically bonded to them. The number of carbon atoms and its consequential three dimensional arrangements as well as the number of chlorine atoms attached will determine the chemical and physical properties of the chlorinated hydrocarbon formed. There is an immense number of possible forms of chlorinated hydrocarbons, allowing this class of compounds to have an extensive range of applications that are of significant economic and practical importance.

Chlorinated hydrocarbons are used predominantly as solvents and have historically been used as industrial degreasers, in fire extinguisher and as refrigerants. They are colourless, volatile liquids with a moderately sweet aroma and partially soluble in but denser than water.

The more common forms of chlorinated solvent contamination of soils and ground waters include;

Tetrachloroethene (PCE, Tetrachloroethylene)

Carbon tetrachloride (Tetrachloromethane or carbon tet)

Trichloroethylene (TCE,Trichloroethene)

1,1,1 - Trichloroethane (TCA, methyl chloroform, chlorothene, Solvent 111)

Dichloromethane (DCM or methylene chloride)

QROS currently utilises two methods to rapidly quantify /semi-quantify their presence in soils on site. The first of these uses a diffusion tube technique which in conjunction with a modified extraction protocol can quantify chlorinated solvents to ppm levels. Determination takes approximately 10-15 minutes and gives an absence/presence indicator, with a Minimum Detection Limit of 10 ppb in water and 0.5 ppm in soil. The method is unable to differentiate between chlorinated solvent types and the data produced assume a given 'typical' mixture of solvents is present. If the contaminate is known to be a single Chlorinated hydrocarbon then quantification can be based on that assumption and a more accurate concentration determined, and like wise for a mixture of chlorinated hydrocarbons if the relative ratios has previously been determined.

A further rapid onsite technique currently under development within QROS utilises a positive ion heated diode system and is sensitive to levels as low as 0.005 ppm and not susceptible to interferences from BTEX or other volatile hydrocarbons. The sensor is also unaffected by moisture levels that would quickly destroy a PID lamp. The unit can be operated as either a "sniffer" providing semi-quantitative data that can be used to identify gross contamination, or as a discreet analyser to provide more quantitative results. The analyser is completely portable and can operate for a day before battery recharge is required