{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T16:57:04Z","timestamp":1790614624985,"version":"4.1.0"},"reference-count":167,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T00:00:00Z","timestamp":1790380800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100007636","name":"German Federal Environmental Foundation","doi-asserted-by":"publisher","award":["35811-01"],"award-info":[{"award-number":["35811-01"]}],"id":[{"id":"10.13039\/100007636","id-type":"DOI","asserted-by":"publisher"}]},{"award":["35811-01"],"award-info":[{"award-number":["35811-01"]}],"id":[{"id":"https:\/\/ror.org\/05pmq5w14","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Photometric methods are essential in analytical chemistry for environmental, biological, and industrial monitoring. Conventional spectrometers rely on deuterium or tungsten lamps, which are bulky, energy-intensive, and costly to maintain. Advances in light emitting diode (LED) technology have enabled compact, energy-efficient, and cost-effective alternatives for portable and decentralized chemical analysis. This review provides an application-oriented synthesis of recent developments in LED-based photometry, systematically comparing major analytical fields to identify common design strategies, recurring performance limitations, and emerging trends. Representative applications include environmental monitoring, point-of-care diagnostics, food quality control, industrial process analysis, and STEM education. Design-related aspects, including optical layouts, detector selection, wavelength matching, and calibration strategies, are discussed where they influence analytical performance and practical implementation. Recent innovations, such as multi-wavelength LEDs, 3D-printed housings, and microcontroller-based systems, have further expanded the accessibility and adaptability of LED-based photometers. Across the reviewed studies, progress has been driven primarily by translating established photometric methods into compact, application-specific platforms rather than by developing new analytical assays. Despite these advances, challenges remain regarding sensitivity, calibration robustness, validation, and methodological standardization. By identifying cross-cutting challenges and successful implementation strategies, this review provides guidance for the future development of robust, low-cost, and reliable LED-based photometric systems for decentralized chemical analysis.<\/jats:p>","DOI":"10.3390\/s26196109","type":"journal-article","created":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T15:57:57Z","timestamp":1790611077000},"page":"6109","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["LED-Based Photometric Systems for Decentralized Chemical Analysis: Applications, Design Considerations, and Practical Limitations"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-2047-0184","authenticated-orcid":false,"given":"Elisa Jekel","family":"K\u00f6nnel","sequence":"first","affiliation":[{"name":"Department of Mechanical and Process Engineering, Division of Bioprocess Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7674-0967","authenticated-orcid":false,"given":"Roland","family":"Ulber","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Process Engineering, Division of Bioprocess Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8396-5881","authenticated-orcid":false,"given":"Lena","family":"Geuer","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Process Engineering, Division of Bioprocess Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"585","DOI":"10.1080\/00032717308058708","article-title":"Light Emitting Diodes and Phototransistors in Photometric Modules","volume":"6","author":"Flaschka","year":"1973","journal-title":"Anal. 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