Developments of microfluidic paper-based analytical devices (μPADs) for water analysis: A review

Water pollution is a serious environmental problem affecting millions of people, and the demand for frequent water quality monitoring is increasing. The need for analytical platforms that combine high sensitivity, selectivity and accuracy with low cost, portability and user friendliness remains a challenge. Microfluidic paper-based analytical devices (μPADs) are recognised as a powerful analytical platform that can satisfy these requirements. The aim of this review is to provide a detailed overview of the μPADs that have been developed for the determination of important water quality parameters, such as nutrients, metals and organic contaminants, in a range of waters. A description of the fabrication and detection methods selected for these applications is provided, and the performance of the μPADs with respect to their precision and accuracy is critically assessed. The potential of these devices for real-life applications is also critically examined, particularly if they can determine the concentrations specified in water quality guidelines or the maximum recommended concentrations for various waters, as well as if they are suitable for field applications.