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Keywords = meta-cresol purple

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13 pages, 1716 KiB  
Article
Measuring Protons with Photons: A Hand-Held, Spectrophotometric pH Analyzer for Ocean Acidification Research, Community Science and Education
by William Pardis, Kalina C. Grabb, Michael D. DeGrandpre, Reggie Spaulding, James Beck, Jonathan A. Pfeifer and David M. Long
Sensors 2022, 22(20), 7924; https://doi.org/10.3390/s22207924 - 18 Oct 2022
Cited by 5 | Viewed by 3658
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Ocean Sensors)
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14 pages, 2167 KiB  
Article
HPLC-DAD Purification and Characterization of Meta-Cresol-Purple for Spectrophotometric Seawater pH Measurements
by Paola Rivaro, Davide Vivado, Pierpaolo Falco and Carmela Ianni
Water 2021, 13(21), 3030; https://doi.org/10.3390/w13213030 - 28 Oct 2021
Cited by 3 | Viewed by 3275
Abstract
High-quality pH measurements are essential for observing ocean acidification and interpreting its chemical and ecological effects. Spectrophotometric measure is the preferred method for pH analysis of seawater because of its high reproducibility and excellent precision. Meta-cresol purple (mCP) is one of the most [...] Read more.
High-quality pH measurements are essential for observing ocean acidification and interpreting its chemical and ecological effects. Spectrophotometric measure is the preferred method for pH analysis of seawater because of its high reproducibility and excellent precision. Meta-cresol purple (mCP) is one of the most used indicator dyes for spectrophotometric pH determination. Impurities in indicator salts can significantly bias spectrophotometric pH determinations, and therefore the use of purified mCP is recommended. This work describes the use of a fast, simple, and green-friendly High-Performance-Liquid Chromatography (HPLC) procedure for purification of mCP dye solution. A C18 reversed phase column was used, and different compositions of the mobile phase were considered. The selected mobile phase was 85% Milli-Q water and 15% CH3CN pH 8.0 that allowed reasonable run time and a suitable purified mCP retention time (4.65 ± 0.005 min). Aliquots of purified mCP were mixed and evaporated by rotary evaporator that resulted in the fastest preconcentration procedure among those considered in this study. Purified mCP was used for measuring the pH in seawater samples collected in the Ross Sea (Antarctica) and the values ranged between 8.202 and 7.983, with the highest values at the surface. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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