Simultaneous multi-optical path cell for resource-efficient water quality analysis using commercial reagents

Abstract

Monitoring phosphate levels in aquatic systems is crucial due to its role in environmental eutrophication and the classification of phosphorus as a critical raw material by the European Union. This degree thesis presents the design, optimization and successful analytical validation of a new simultaneous multiple optical path system integrated with digital image colorimetry (smartphone) that uses commercial reagents for the generation of coloured compounds. The simultaneous multiple optical path cell allows determinations to be made by preparing a single standard of known concentration and with a single dilution of the sample. In this approach, the variation of the concentration is replaced by the variation of the optical path in the application of the Lambert Beer law. The developed configuration allows decentralized, low-cost and sustainable monitoring of phosphate in water resources. The study included in this work evaluates the capability of commercial procedures for the determination of phosphate concentration, the capability of the use of smartphones as colourimetric detectors and the parameters of the most convenient colour spaces for each determination are determined. The capability for the quantification of the use of different optical paths is also studied. For this application, a cell with multiple simultaneous optical paths is designed and evaluated. The optimized procedure is applied to the determination of different types of water achieving results of quality equivalent to those obtained with spectrophotometric determinations in the laboratory. The accompanying image (Figure 21) corresponds to the cell with multiple simultaneous optical paths.