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Therefore, monitoring this inorganic form of nitrogen is essential for any water quality management structure. This research was conducted to develop a novel Nitrate Portable Measurement System (NPMS) to monitor nitrate concentrations in water samples. NPMS is a reagent-free ultraviolet system developed using low-cost electronic components. Its operation principle is based on the Beer\u2013Lambert law for measuring nitrate concentrations in water samples through light absorption in the spectral range of 295\u2013315 nm. The system is equipped with a ready-to-use ultraviolet sensor, light emission diode (LED), op-amp, microcontroller, liquid crystal display, quartz cuvette, temperature sensor, and battery. All the components are assembled in a 3D-printed enclosure box, which allows a very compact self-contained equipment with high portability, enabling field and near-real-time measurements. The proposed methodology and the developed instrument were used to analyze multiple nitrate standard solutions. The performance was evaluated in comparison to the Nicolet Evolution 300, a classical UV\u2013Vis spectrophotometer. The results demonstrate a strong correlation between the retrieved measurements by both instruments within the investigated spectral band and for concentrations above 5 mg NO3\u2212\/L.<\/jats:p>","DOI":"10.3390\/s24165367","type":"journal-article","created":{"date-parts":[[2024,8,20]],"date-time":"2024-08-20T06:07:35Z","timestamp":1724134055000},"page":"5367","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["The Development of a Novel Nitrate Portable Measurement System Based on a UV Paired Diode\u2013Photodiode"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3537-9271","authenticated-orcid":false,"given":"Samuel","family":"Fernandes","sequence":"first","affiliation":[{"name":"Department of Mechatronics Engineering, School of Science and Technology, Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"},{"name":"Instrumentation and Control Laboratory (ICL), Insititute of Earth Sciences (ICT), Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8026-1988","authenticated-orcid":false,"given":"Mouhaydine","family":"Tlem\u00e7ani","sequence":"additional","affiliation":[{"name":"Department of Mechatronics Engineering, School of Science and Technology, Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"},{"name":"Instrumentation and Control Laboratory (ICL), Insititute of Earth Sciences (ICT), Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2334-4055","authenticated-orcid":false,"given":"Daniele","family":"Bortoli","sequence":"additional","affiliation":[{"name":"Instrumentation and Control Laboratory (ICL), Insititute of Earth Sciences (ICT), Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"},{"name":"Physics Department, School of Science and Technology (ECT), Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"},{"name":"Earth Remote Sensing Laboratory (EaRSLab), Institute of Earth Sciences (ICT), Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3147-4511","authenticated-orcid":false,"given":"Manuel","family":"Feliciano","sequence":"additional","affiliation":[{"name":"Centro de Investiga\u00e7\u00e3o de Montanha (CIMO), Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"},{"name":"Laborat\u00f3rio Associado para a Sustentabilidade e Tecnologia em Regi\u00f5es de Montanha (SusTEC), Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"}]},{"given":"Maria Elmina","family":"Lopes","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry, School of Science and Technology (ECT), Universidade de \u00c9vora, 7000-671 \u00c9vora, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,8,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/j.watres.2004.07.026","article-title":"Non-agricultural sources of groundwater nitrate: A review and case study","volume":"39","author":"Wakida","year":"2005","journal-title":"Water Res."},{"key":"ref_2","first-page":"1163","article-title":"Nitrates, agriculture and environment","volume":"79","author":"Puttanna","year":"2000","journal-title":"Curr. 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