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    Fabrication of Google-trackable colorimetric test strips for detecting water leakages
    (2020) Gcolotela, Zodidi; Mdluli, Phumlane Selby; Mlambo, M.
    South Africa is a water scarce country due to the shortage of rainfall. This scarcity is further exacerbated by the loss of water through leakage from faulty pipes. The consequence is the high amount of revenue lost through leakages and the negative health implication from water unavailability. Given this concern, it becomes highly imperative to address the water wastage through leaks by timely identifying and fixing household leaking pipes. While different method of detecting water leaks have been proposed in the literature, they are, however, expensive and difficult to implement. Hence, it is therefore sensible for South Africa to make use of leading leakage detection technology on pressurised systems, which can rapidly alert operators to leaks and breakages, and detect leaks in old, low-pressure reticulation systems. In the last decade, paper-based microfluidic device had become highly useful for environmental monitoring, health diagnosis, and food safety due to their simplicity, ease of use, and cheap application. This study is focused on the fabrication of a trackable microfluidic device (μPADs) to detect water leaks A quantitative research approach and an experimental design were followed. The µPADs were prepared by printing patterns of wax (100 μm width) on the paper surface and melting the wax into the paper to form hydrophobic barriers and put on a hot plate for the wax to penetrate the paper. Solutions of lower to higher pH were also prepared and were introduced to the chlorophenol red test strips and a range of colours from yellow (lower pH) to purple (higher pH) were obtained. Colour change for chlorophenol paper is irreversible and is based on pH variation and not on the amount of water available in a solution. The optimised pH range was wider than the typical grayscale-based image analysis and was successful for a wide pH range of 2–12 measurements. The QR codes attached to the strips enable tracking to obtain the location from which a leakage was detected and this is done with the use of Google analytics which can tell real-time users from the website and their locations. The digital images obtained with the μPADs were analysed using the CIEL*a*b* colour system. The colour change was also validated using both spectroscopy and optical microscope. The study has exhaustively demonstrated that the combination of digital image analysis and a microfluidic paper-based analytical device (μPADs) are highly effective for both quantitative and qualitative analysis, and thus useful for the detection of household water leaks.
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    Development of paper-based microfluidic strips for quantification of ammonia
    (2019) Nxumalo, Nonhlazeko Loveday; Mdluli, Phumlane S.; Madikizela, Lawrence Mzukisi
    Water is one of the most valuable and crucial of life and therefore accurate monitoring and assessment of water resources for sustainability is imperative. Conventional water investigation includes manual gathering of tests, their transportation and resulting examination in the research center. This is time and labour-intensive, costly and requires exceptionally qualified personnel. Sovereign of this procedure empowers more continuous examination, sparing time and cash for analysts, ventures and administering bodies. Consequently, there is requirement for advancement of minimal effort ecological microfluidic paper-based expository gadget that is fundamental for compelling administration of our profitable water assets. This will address the huge and growing demand for low-cost ammonia sensors as legislation becomes more stringent and as more frequent monitoring becomes essential for legislative compliance. Subsequently, this thesis reports on the development of a low-cost, colorimetric, wax- printed microfluidic paper-based analytical device (µPAD) to detect ammonia in industrial wastewaters. Microfluidic innovation was utilized to facilitate the examination of analytes on the colorimetric explanatory techniques onto a convenient detecting gadget. This therefore empowers the blending of little volumes of analytes with synthetic reagents to form a coloured/hued product in the sight of the analyte of interest. The µPAD fabricated was an oval shaped pattern which was designed on Corel draw software. The hydrophilic segments were made by printing a chromatographic paper with hydrophobic paper sizing agents utilizing a standard Xerox wax printer (Xerox colorqube 8570). The quantification of ammonia in wastewater was performed on the µPADs using two typical colorimetric methods namely, Nessler reagent and Salicylate. The reaction of ammonia with the Nessler reagent resulted in a brown or intense yellow colour whereas with the salicylate method, the final colour was green. For both methods, the colour intensity increased proportionally with the analyte concentration, and all images of the μPADs were captured and colorimetrically analyzed with ImageJ software for quantification. The analytical performances of the µPAD were linear from 0 to 5 mg L-1 with a limit of detection of 3.37 mg L-1 and 3.20 mg L-1 for the Nessler vii reagent and salicylate methods respectively. The validity and accuracy of aforementioned methods was supported by the standard UV Visible spectrophotometric method and applied to the measurement of wastewater effluent samples. Wastewater samples were analyzed and the results obtained were similar to those obtained with a spectrophotometric method, demonstrating that the µPAD is suitable to determine ammonia in wastewater.