Towards deployable analytical systems for nutrient monitoring in natural waters

The freshwater environment is intrinsically linked to human, animal and plant life and is an indispensable resource for the economy. Effective water quality monitoring is therefore one of the cornerstones of environmental protection and this importance is reflected within both European and global legislation. Nutrient pollution in water bodies can be seen as one of the largest global problems which effects the freshwater environment. Current legislation and policies governing water quality depend on grab sampling techniques, providing only instantaneous data which can result in a non-representative estimate of the nutrient pollution load status of a water body. In order to fully satisfy the water sectors need for comprehensive analysis, management and protection, effective portable in-situ nutrient monitoring systems are required. The focal point of this research was based around the current need which exists for inexpensive, robust in-situ nutrient monitoring solutions for the freshwater environment. The primary goal was to develop a low-cost, field deployable, automated IC system for nutrient anion analysis. Complimentary to this work, portable systems based on colorimetry for nutrient analysis were also explored. Through this research, a portable low-cost nitrate test kit has been developed which is based on a modified version of the Griess assay and employs zinc as a reducing agent. The developed method was validated according to ISO17025 accreditation guidelines and reliably detected nitrate in a range of freshwater samples. A portable, lightweight capillary IC system for anion analysis in water was also developed and demonstrated in a laboratory setting. The IC uses low-cost, miniaturised components and through a modular design enables flexible system modification. Progressing from this capillary system, a new low-cost, UV absorbance detector incorporating a 235 nm light emitting diode (LED) was developed for portable ion chromatography. The detector enabled selective, fast determination of nitrite and nitrate in a range of natural waters. In an attempt to develop a portable system for ammonium analysis, a multi-material 3D printed microfluidic reactor with integrated heating was fabricated and used with colorimetry to facilitate fast ammonium determination. Although the analytical range for ammonium xxii determination was narrow, the developed 3D printed heater represents a novel contribution in the area of 3D printed analytical systems. Finally, an IC which is low-cost, automated and fully deployable was developed which allows for in-situ analysis of nitrite and nitrate in a wide variety of natural waters. The system employed 3D printed pumps for eluent delivery and the 235 nm LED based optical detector which was developed during the course of the research. The system was deployed at various locations around the world and achieved an analytical performance comparable to accredited benchtop instrumentation.