Measuring Protons with Photons: A Hand-Held, Spectrophotometric pH Analyzer for Ocean Acidification Research, Community Science and Education

• Published in: Sensors
• Main Authors: William Pardis, Kalina C. Grabb, Michael D. DeGrandpre, Reggie Spaulding, James Beck, Jonathan A. Pfeifer, David M. Long
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: chemical sensor; coastal ocean monitoring; science education; colorimetric pH measurement; meta-cresol purple; Chemical technology; TP1-1185; Kayak; Ocean acidification
• Online Access: https://doi.org/10.3390/s22207924; https://doaj.org/article/8d14ae1d1f0a44449fd464e3087f3183

Ocean Acidification (OA) is negatively affecting the physiological processes of marine organisms, altering biogeochemical cycles, and changing chemical equilibria throughout the world’s 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 ±0.046 pH or better, which is on par with interlaboratory seawater pH measurement comparison experiments. We also demonstrate the pHyter’s 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’s 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.