Integrated Optical Sensors for Pesticide Analysis

Abstract

Integrated optical transducers for the measurement of interactions between biological molecules and the specific detection of chemical and biochemical species are the subject of growing interest. Potential applications include environmental monitoring, industrial process control and medical diagnostics. Integrated optical devices are capable of delivering the high detection sensitivity achievable through optical techniques in a compact and robust format; this format also has advantages for the fabrication of multianalyte sensors through the integration of multiple transducers on a single chip. Several types of integrated optical sensor have been described, eg. Refs. 1, 2. In this paper we apply two newly-developed types of integrated optical sensor to the detection of low concentrations of triazine pesticides in aqueous solution using a modified competitive immunoassay procedure. One sensor is based on a two-waveguide directional coupler structure, the other on a Mach-Zehnder interferometer (MZI) combined with a three-waveguide coupler. Pesticides are identified as priority pollutants because of their widespread use and persistence in the environment; the European Union (EU) currently specifies a maximum concentration for individual pesticides of 0. 1 μg/l in drinking water, and a maximum concentration of 0.5 μg/1 for the sum of pesticides (including their metabolites). There is thus a general need for fast, reliable and portable methods of analysis that are capable of identifying single pollutants at low concentrations or of rapidly screening samples for a group of pollutants.