Hydrocarbon Sensors for Liquids with Mid-IR Fibres

The on-line and in situ detection and quantification of organic compounds dissolved in water is a task which has a big importance in industrial and environmental applications like process control or pollution monitoring. There is a growing need to monitor hazardous substances like chlorinated and polycyclic aromatic hydrocarbons in cooling water or waste water in order to protect waste water treatment plants. Recycling of process water can lead to strong cost savings, but it is often necessary to determine the water quality with respect to concentrations of organic substances. Current methods used for the detection of hydrocarbons include discontinuous sampling followed by laboratory analysis like headspace gaschromatography. There are also on-line measurement systems available, for instance for the TOC-measurement (Total Organic Carbon) of waste water or cooling water. Other on-line systems based on UV-stimulated fluorescence are very sensitive (e.g. to cyclic hydrocarbons), but like to TOC measurements they are not specific. In general, it can be stated that there is still a need for cost effective techniques which are capable of continuous measurements with high sensitivity and specificity. The approach presented here which makes use of the high specificity and sensitivity of infrared spectroscopy in comination with a solid phase extraction technique is a step in this direction.