{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T08:57:25Z","timestamp":1774601845637,"version":"3.50.1"},"reference-count":41,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2022,10,18]],"date-time":"2022-10-18T00:00:00Z","timestamp":1666051200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Montana Space Grant Consortium (NASA, NNX15AJ19H)","award":["NA21OAR0210489"],"award-info":[{"award-number":["NA21OAR0210489"]}]},{"name":"Flathead Valley Community College Foundation","award":["NA21OAR0210489"],"award-info":[{"award-number":["NA21OAR0210489"]}]},{"name":"NOAA SBIR","award":["NA21OAR0210489"],"award-info":[{"award-number":["NA21OAR0210489"]}]},{"name":"Sunburst Sensors, LLC.","award":["NA21OAR0210489"],"award-info":[{"award-number":["NA21OAR0210489"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Ocean Acidification (OA) is negatively affecting the physiological processes of marine organisms, altering biogeochemical cycles, and changing chemical equilibria throughout the world\u2019s oceans. It is difficult to measure pH broadly, in large part because accurate pH measurement technology is expensive, bulky, and requires technical training. Here, we present the development and evaluation of a hand-held, affordable, field-durable, and easy-to-use pH instrument, named the pHyter, which is controlled through a smartphone app. We determine the accuracy of pH measurements using the pHyter by comparison with benchtop spectrophotometric seawater pH measurements, measurement of a certified pH standard, and comparison with a proven in situ instrument, the iSAMI-pH. These results show a pHyter pH measurement accuracy of \u00b10.046 pH or better, which is on par with interlaboratory seawater pH measurement comparison experiments. We also demonstrate the pHyter\u2019s ability to conduct both temporal and spatial studies of coastal ecosystems by presenting data from a coral reef and a bay, in which the pHyter was used from a kayak. These studies showcase the instrument\u2019s portability, applicability, and potential to be used for community science, STEM education, and outreach, with the goal of empowering people around the world to measure pH in their own backyards.<\/jats:p>","DOI":"10.3390\/s22207924","type":"journal-article","created":{"date-parts":[[2022,10,19]],"date-time":"2022-10-19T00:58:51Z","timestamp":1666141131000},"page":"7924","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Measuring Protons with Photons: A Hand-Held, Spectrophotometric pH Analyzer for Ocean Acidification Research, Community Science and Education"],"prefix":"10.3390","volume":"22","author":[{"given":"William","family":"Pardis","sequence":"first","affiliation":[{"name":"Flathead Valley Community College, Kalispell, MT 59901, USA"},{"name":"Woods Hole Oceanographic Institution, Applied Ocean Physics and Engineering, Woods Hole, MA 02543, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8771-7191","authenticated-orcid":false,"given":"Kalina C.","family":"Grabb","sequence":"additional","affiliation":[{"name":"Massachusetts Institute of Technology\/Woods Hole Oceanographic Institution Joint Program in Oceanography\/Applied Ocean Science & Engineering, Woods Hole, MA 02543, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1969-6709","authenticated-orcid":false,"given":"Michael D.","family":"DeGrandpre","sequence":"additional","affiliation":[{"name":"Sunburst Sensors LLC, Missoula, MT 59802, USA"},{"name":"Department of Chemistry and Biochemistry, College of Humanities and Sciences, University of Montana, Missoula, MT 59812, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6495-4274","authenticated-orcid":false,"given":"Reggie","family":"Spaulding","sequence":"additional","affiliation":[{"name":"Sunburst Sensors LLC, Missoula, MT 59802, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"James","family":"Beck","sequence":"additional","affiliation":[{"name":"Sunburst Sensors LLC, Missoula, MT 59802, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6155-4846","authenticated-orcid":false,"given":"Jonathan A.","family":"Pfeifer","sequence":"additional","affiliation":[{"name":"Flathead Valley Community College, Kalispell, MT 59901, USA"},{"name":"Massachusetts Institute of Technology\/Woods Hole Oceanographic Institution Joint Program in Oceanography\/Applied Ocean Science & Engineering, Woods Hole, MA 02543, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David M.","family":"Long","sequence":"additional","affiliation":[{"name":"Flathead Valley Community College, Kalispell, MT 59901, USA"},{"name":"Department of Chemistry and Biochemistry, College of Science and Mathematics, California Polytechnic State University, San Louis Obispo, CA 93407, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,18]]},"reference":[{"key":"ref_1","unstructured":"Keeling, R.F., and Keeling, C.D. 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