Open Access Research article

Fast responsive, optical trace level ammonia sensor for environmental monitoring

Tobias Abel, Birgit Ungerböck, Ingo Klimant and Torsten Mayr*

Author Affiliations

Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, Graz, 8010, Austria

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Chemistry Central Journal 2012, 6:124  doi:10.1186/1752-153X-6-124

Published: 26 October 2012

Abstract

Background

Ammonia is a ubiquitous chemical substance which is created in technical and biological processes and harmful to many different organisms. One specific problem is the toxicity of ammonia in fish at levels of 25 μg/l - a very common issue in today’s aqua culture. In this study we report a development of a fast responsive, optical ammonia sensor for trace concentrations.

Results

Different hydrogels have been investigated as host polymers for a pH based sensing mechanism based on fluorescent dyes. A porous hydrophobic fluoropolymer membrane was used as an ion barrier cover layer to achieve a good ammonia permeability. The sensor’s sensitivity towards ammonia as well as crosssensitivity towards pH-value and salinity, and the temperature dependency have been determined. Two different methods to reference fluorescence signals have been employed to eliminate intensity-based measurement drawbacks.

Conclusion

The presented sensor features high sensitivity and a fast response even at concentrations near 1 ppb. No cross sensitivity towards pH and salinity could be observed and temperature dependency was determined as compensateable. Both referencing approaches prove themselves to be able to provide a simple use of the sensor for in-field applications.

Keywords:
Optical sensor; Ammonia sensor; Fluorescence sensor; Fish farming; Aqua culture; Dual lifetime referencing; Two wavelength ratiometric referencing

Graphical abstract