text: The sampler can be deployed in the field for extended periods of time ranging from days to weeks. The specific pollutants of interest are sequestered by the samplers and these are retained on the receiving phase disk. After retrieval from the environment the pollutants are eluted from the disk and analysed in the laboratory using conventional instrumental methods. In order to obtain TWA concentrations the sampler must first be calibrated in the laboratory so as to ascertain the uptake rate (usually measured as the volume of water cleared per unit time i.e. L/h for the analyte) of the pollutant of interest. Chemcatcher® has been used in a range of aquatic environments; however, most work to date has been in monitoring the TWA concentrations of priority and emerging pollutants in surface waters.
  The use of passive sampling devices, such as Chemcatcher® or polar organic chemical integrative sampler (POCIS), has a number of advantages over the use of spot or bottle sampling for monitoring pollutants in the aquatic environment. The latter technique gives only an instantaneous concentration of the pollutant as the specific time of sampling. Passive samplers, depending on their mode of use, can give either the TWA or equilibrium concentration of the pollutant over the deployment period. The measurement of TWA concentrations can give a better indication of the long-term environmental conditions and enables improved risk assessment. Chemcatcher® can be used to monitor both polar and non-polar compounds.