The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater
The sulfonephthalein indicator meta-Cresol Purple (mCP) is well suited to direct spectrophotometric pH measurements throughout the oceanic water column. In prior work the molar absorbance and proton exchange characteristics of purified mCP were characterized over a wide range of salinities and tempe...
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Digital Commons @ University of South Florida
2013
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Online Access: | https://digitalcommons.usf.edu/msc_facpub/1773 https://doi.org/10.1016/j.marchem.2013.09.003 |
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ftunisfloridatam:oai:digitalcommons.usf.edu:msc_facpub-2624 2023-05-15T17:51:42+02:00 The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater Soli, Alan L. Pav, Brody J. Byrne, Robert H. 2013-01-01T08:00:00Z https://digitalcommons.usf.edu/msc_facpub/1773 https://doi.org/10.1016/j.marchem.2013.09.003 unknown Digital Commons @ University of South Florida https://digitalcommons.usf.edu/msc_facpub/1773 https://doi.org/10.1016/j.marchem.2013.09.003 Marine Science Faculty Publications Sea water pH Ocean acidification meta-Cresol Purple Pressure effects Spectrophotometric techniques Life Sciences article 2013 ftunisfloridatam https://doi.org/10.1016/j.marchem.2013.09.003 2022-01-20T18:40:25Z The sulfonephthalein indicator meta-Cresol Purple (mCP) is well suited to direct spectrophotometric pH measurements throughout the oceanic water column. In prior work the molar absorbance and proton exchange characteristics of purified mCP were characterized over a wide range of salinities and temperatures, allowing use of the indicator over a broad range of oceanic conditions in the surface ocean. Modern spectrophotometric instrumentation allows direct in situ measurements of seawater pH at depths that create substantial pressure-dependent changes in the physical chemical behavior of mCP. In order to allow use of purified mCP for quantitative pH measurements over essentially the full range of ocean depths, prior calibrations of mCP for measurements of seawater pH were extended to include pressures up to 827 bar. Using purified mCP, seawater pH is measured using the equation pHT=−logK2e2+logR−e11−R⋅e3e2 where e1=−0.007762+4.5174×10–5T+1.7×10–6Pe3/e2=−0.020813+2.60262×10–4T+1.0436×10–4S–35+4.6×10–6P–logK2e2=a+b/T+clnT−dT−0.05645/T×P and a = 246.64209 + 0.315971S + 2.8855 × 10− 4S2 b = 7229.23864 − 7.098137S − 0.057034S2 c = 44.493382 − 0.052711S d = 0.0781344. = 246.64209 + 0.315971S + 2.8855 × 10− 4S2 = 7229.23864 − 7.098137S − 0.057034S2 = 44.493382 − 0.052711S = 0.0781344. P and T are gauge pressure (bar) and Kelvin temperature, and the coefficients a, b and c are salinity dependent coefficients determined in previous work. The influence of pressure on the properties of mCP is sufficient to cause easily measureable effects at depths less than 100 m. Article in Journal/Newspaper Ocean acidification Digital Commons University of South Florida (USF) Marine Chemistry 157 162 169 |
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Open Polar |
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Digital Commons University of South Florida (USF) |
op_collection_id |
ftunisfloridatam |
language |
unknown |
topic |
Sea water pH Ocean acidification meta-Cresol Purple Pressure effects Spectrophotometric techniques Life Sciences |
spellingShingle |
Sea water pH Ocean acidification meta-Cresol Purple Pressure effects Spectrophotometric techniques Life Sciences Soli, Alan L. Pav, Brody J. Byrne, Robert H. The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater |
topic_facet |
Sea water pH Ocean acidification meta-Cresol Purple Pressure effects Spectrophotometric techniques Life Sciences |
description |
The sulfonephthalein indicator meta-Cresol Purple (mCP) is well suited to direct spectrophotometric pH measurements throughout the oceanic water column. In prior work the molar absorbance and proton exchange characteristics of purified mCP were characterized over a wide range of salinities and temperatures, allowing use of the indicator over a broad range of oceanic conditions in the surface ocean. Modern spectrophotometric instrumentation allows direct in situ measurements of seawater pH at depths that create substantial pressure-dependent changes in the physical chemical behavior of mCP. In order to allow use of purified mCP for quantitative pH measurements over essentially the full range of ocean depths, prior calibrations of mCP for measurements of seawater pH were extended to include pressures up to 827 bar. Using purified mCP, seawater pH is measured using the equation pHT=−logK2e2+logR−e11−R⋅e3e2 where e1=−0.007762+4.5174×10–5T+1.7×10–6Pe3/e2=−0.020813+2.60262×10–4T+1.0436×10–4S–35+4.6×10–6P–logK2e2=a+b/T+clnT−dT−0.05645/T×P and a = 246.64209 + 0.315971S + 2.8855 × 10− 4S2 b = 7229.23864 − 7.098137S − 0.057034S2 c = 44.493382 − 0.052711S d = 0.0781344. = 246.64209 + 0.315971S + 2.8855 × 10− 4S2 = 7229.23864 − 7.098137S − 0.057034S2 = 44.493382 − 0.052711S = 0.0781344. P and T are gauge pressure (bar) and Kelvin temperature, and the coefficients a, b and c are salinity dependent coefficients determined in previous work. The influence of pressure on the properties of mCP is sufficient to cause easily measureable effects at depths less than 100 m. |
format |
Article in Journal/Newspaper |
author |
Soli, Alan L. Pav, Brody J. Byrne, Robert H. |
author_facet |
Soli, Alan L. Pav, Brody J. Byrne, Robert H. |
author_sort |
Soli, Alan L. |
title |
The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater |
title_short |
The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater |
title_full |
The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater |
title_fullStr |
The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater |
title_full_unstemmed |
The Effect of Pressure on Meta-Cresol Purple Protonation and Absorbance Characteristics for Spectrophotometric pH Measurements in Seawater |
title_sort |
effect of pressure on meta-cresol purple protonation and absorbance characteristics for spectrophotometric ph measurements in seawater |
publisher |
Digital Commons @ University of South Florida |
publishDate |
2013 |
url |
https://digitalcommons.usf.edu/msc_facpub/1773 https://doi.org/10.1016/j.marchem.2013.09.003 |
genre |
Ocean acidification |
genre_facet |
Ocean acidification |
op_source |
Marine Science Faculty Publications |
op_relation |
https://digitalcommons.usf.edu/msc_facpub/1773 https://doi.org/10.1016/j.marchem.2013.09.003 |
op_doi |
https://doi.org/10.1016/j.marchem.2013.09.003 |
container_title |
Marine Chemistry |
container_volume |
157 |
container_start_page |
162 |
op_container_end_page |
169 |
_version_ |
1766158931441221632 |