Development of a prototype Chemical-Optical Sensor for the detection of Organic Micro-Pollutants in Drinking water

Water utilities take surface water in for the production of drinking water. As soon as Early Warning
Systems (EWS) detect pollution, intake is stopped.
This report describes the research activities on the development of the direct detection of micropollutants
with an opto-chemical based sensor. Such an opto-chemical sensor can be part of a EWS.
The opto-chemical sensor used is the Mach-Zehnder Interferometer (MZI), an evanescent field
measurement based system. Refractive index changes of 10-7 can be detected, corresponding with the
detection of molecules of 100 – 200 D at a concentration of 0.1 – 1 μg/L.
The measurement of refractive index does not indicate the type of compound responsible for the
pollution. Therefore it is needed to introduce a selective coating on top of the sensor surface that contains
selective elements like antibodies. The development of an interface layer for the detection of atrazine is
described as well as the direct measurements of atrazine on a functionalised MZI system. Within this
research a detection limit for the direct detection of atrazine of 5 μg/L is achieved. The reproducibility of
these measurements is low indicating that additional research efforts are needed before a MZI-based
measurement system can be part of an early warning system.