{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:27:11Z","timestamp":1760236031373,"version":"build-2065373602"},"reference-count":25,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2021,10,21]],"date-time":"2021-10-21T00:00:00Z","timestamp":1634774400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["SFRH\/BD\/144962\/2019","UIDB\/50016\/2020"],"award-info":[{"award-number":["SFRH\/BD\/144962\/2019","UIDB\/50016\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>In this work, the design of a microfluidic paper-based analytical device (\u03bcPAD) for the quantification of nitrate in urine samples was described. Nitrate monitoring is highly relevant due to its association to some diseases and health conditions. The nitrate determination was achieved by combining the selectivity of the nitrate reductase enzymatic reaction with the colorimetric detection of nitrite by the well-known Griess reagent. For the optimization of the nitrate determination \u03bcPAD, several variables associated with the design and construction of the device were studied. Furthermore, the interference of the urine matrix was evaluated, and stability studies were performed, under different conditions. The developed \u03bcPAD enabled us to obtain a limit of detection of 0.04 mM, a limit of quantification of 0.14 mM and a dynamic concentration range of 0.14\u20131.0 mM. The designed \u03bcPAD proved to be stable for 24 h when stored at room temperature in air or vacuum atmosphere, and 60 days when stored in vacuum at \u221220 \u00b0C. The accuracy of the nitrate \u03bcPAD measurements was confirmed by analyzing four certified samples (prepared in synthetic urine) and performing recovery studies using urine samples.<\/jats:p>","DOI":"10.3390\/molecules26216355","type":"journal-article","created":{"date-parts":[[2021,10,21]],"date-time":"2021-10-21T23:27:39Z","timestamp":1634858859000},"page":"6355","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Design and Functionalization of a \u00b5PAD for the Enzymatic Determination of Nitrate in Urine"],"prefix":"10.3390","volume":"26","author":[{"given":"Francisca T. S. M.","family":"Ferreira","sequence":"first","affiliation":[{"name":"CBQF\u2014Centro de Biotecnologia e Qu\u00edmica Fina\u2014Laborat\u00f3rio Associado, Escola Superior de Biotecnologia, Universidade Cat\u00f3lica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7745-1860","authenticated-orcid":false,"given":"Raquel B. R.","family":"Mesquita","sequence":"additional","affiliation":[{"name":"CBQF\u2014Centro de Biotecnologia e Qu\u00edmica Fina\u2014Laborat\u00f3rio Associado, Escola Superior de Biotecnologia, Universidade Cat\u00f3lica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal"}]},{"given":"Ant\u00f3nio O. S. S.","family":"Rangel","sequence":"additional","affiliation":[{"name":"CBQF\u2014Centro de Biotecnologia e Qu\u00edmica Fina\u2014Laborat\u00f3rio Associado, Escola Superior de Biotecnologia, Universidade Cat\u00f3lica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,21]]},"reference":[{"key":"ref_1","unstructured":"(2021, September 13). Healthline Nitrites in Urine: Causes, Symptoms, and Treatments. 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