Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures

Abstract Accurate pH measurements in polar waters and sea ice brines require pH indicator dyes characterized at near-zero and below-zero temperatures and high salinities. We present experimentally determined physical and chemical characteristics of purified meta-Cresol Purple (mCP) pH indicator dye...

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Autores principales:	Socratis Loucaides, Victoire M. C. Rèrolle, Stathys Papadimitriou, Hilary Kennedy, Matthew C. Mowlem, Andrew G. Dickson, Martha Gledhill, Eric P. Achterberg
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/b223db7be91a4039879f39e94bf14857
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spelling	oai:doaj.org-article:b223db7be91a4039879f39e94bf148572021-12-02T11:40:13ZCharacterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures10.1038/s41598-017-02624-02045-2322https://doaj.org/article/b223db7be91a4039879f39e94bf148572017-05-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-02624-0https://doaj.org/toc/2045-2322Abstract Accurate pH measurements in polar waters and sea ice brines require pH indicator dyes characterized at near-zero and below-zero temperatures and high salinities. We present experimentally determined physical and chemical characteristics of purified meta-Cresol Purple (mCP) pH indicator dye suitable for pH measurements in seawater and conservative seawater-derived brines at salinities (S) between 35 and 100 and temperatures (T) between their freezing point and 298.15 K (25 °C). Within this temperature and salinity range, using purified mCP and a novel thermostated spectrophotometric device, the pH on the total scale (pHT) can be calculated from direct measurements of the absorbance ratio R of the dye in natural samples as $${\boldsymbol{p}}{{\boldsymbol{H}}}_{{\boldsymbol{T}}}{\boldsymbol{=}}{\boldsymbol{-}}{\bf{log}}({{\boldsymbol{k}}}_{{\bf{2}}}^{{\boldsymbol{T}}}{{\boldsymbol{e}}}_{{\bf{2}}}){\boldsymbol{+}}\,{\bf{log}}(\frac{{\boldsymbol{R}}{\boldsymbol{-}}{{\boldsymbol{e}}}_{{\bf{1}}}}{{\bf{1}}{\boldsymbol{-}}{\boldsymbol{R}}\frac{{{\boldsymbol{e}}}_{{\bf{3}}}}{{{\boldsymbol{e}}}_{{\bf{2}}}}})$$ p H T = − log ( k 2 T e 2 ) + log ( R − e 1 1 − R e 3 e 2 ) Based on the mCP characterization in these extended conditions, the temperature and salinity dependence of the molar absorptivity ratios and − $${\bf{log}}({{\boldsymbol{k}}}_{{\bf{2}}}^{{\boldsymbol{T}}}{{\boldsymbol{e}}}_{{\bf{2}}})$$ log ( k 2 T e 2 ) of purified mCP is described by the following functions: e 1 = −0.004363 + 3.598 × 10−5 T, e 3/e 2 = −0.016224 + 2.42851 × 10−4 T + 5.05663 × 10−5(S − 35), and − $${\bf{log}}({{\boldsymbol{k}}}_{{\bf{2}}}^{{\boldsymbol{T}}}{{\boldsymbol{e}}}_{{\bf{2}}})$$ log ( k 2 T e 2 ) = −319.8369 + 0.688159 S −0.00018374 S 2 + (10508.724 − 32.9599 S + 0.059082S 2) T−1 + (55.54253 − 0.101639 S) ln T −0.08112151T. This work takes the characterisation of mCP beyond the currently available ranges of 278.15 K ≤ T ≤ 308.15 K and 20 ≤ S ≤ 40 in natural seawater, thereby allowing high quality pHT measurements in polar systems.Socratis LoucaidesVictoire M. C. RèrolleStathys PapadimitriouHilary KennedyMatthew C. MowlemAndrew G. DicksonMartha GledhillEric P. AchterbergNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-11 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Socratis Loucaides Victoire M. C. Rèrolle Stathys Papadimitriou Hilary Kennedy Matthew C. Mowlem Andrew G. Dickson Martha Gledhill Eric P. Achterberg Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
description	Abstract Accurate pH measurements in polar waters and sea ice brines require pH indicator dyes characterized at near-zero and below-zero temperatures and high salinities. We present experimentally determined physical and chemical characteristics of purified meta-Cresol Purple (mCP) pH indicator dye suitable for pH measurements in seawater and conservative seawater-derived brines at salinities (S) between 35 and 100 and temperatures (T) between their freezing point and 298.15 K (25 °C). Within this temperature and salinity range, using purified mCP and a novel thermostated spectrophotometric device, the pH on the total scale (pHT) can be calculated from direct measurements of the absorbance ratio R of the dye in natural samples as $${\boldsymbol{p}}{{\boldsymbol{H}}}_{{\boldsymbol{T}}}{\boldsymbol{=}}{\boldsymbol{-}}{\bf{log}}({{\boldsymbol{k}}}_{{\bf{2}}}^{{\boldsymbol{T}}}{{\boldsymbol{e}}}_{{\bf{2}}}){\boldsymbol{+}}\,{\bf{log}}(\frac{{\boldsymbol{R}}{\boldsymbol{-}}{{\boldsymbol{e}}}_{{\bf{1}}}}{{\bf{1}}{\boldsymbol{-}}{\boldsymbol{R}}\frac{{{\boldsymbol{e}}}_{{\bf{3}}}}{{{\boldsymbol{e}}}_{{\bf{2}}}}})$$ p H T = − log ( k 2 T e 2 ) + log ( R − e 1 1 − R e 3 e 2 ) Based on the mCP characterization in these extended conditions, the temperature and salinity dependence of the molar absorptivity ratios and − $${\bf{log}}({{\boldsymbol{k}}}_{{\bf{2}}}^{{\boldsymbol{T}}}{{\boldsymbol{e}}}_{{\bf{2}}})$$ log ( k 2 T e 2 ) of purified mCP is described by the following functions: e 1 = −0.004363 + 3.598 × 10−5 T, e 3/e 2 = −0.016224 + 2.42851 × 10−4 T + 5.05663 × 10−5(S − 35), and − $${\bf{log}}({{\boldsymbol{k}}}_{{\bf{2}}}^{{\boldsymbol{T}}}{{\boldsymbol{e}}}_{{\bf{2}}})$$ log ( k 2 T e 2 ) = −319.8369 + 0.688159 S −0.00018374 S 2 + (10508.724 − 32.9599 S + 0.059082S 2) T−1 + (55.54253 − 0.101639 S) ln T −0.08112151T. This work takes the characterisation of mCP beyond the currently available ranges of 278.15 K ≤ T ≤ 308.15 K and 20 ≤ S ≤ 40 in natural seawater, thereby allowing high quality pHT measurements in polar systems.
format	article
author	Socratis Loucaides Victoire M. C. Rèrolle Stathys Papadimitriou Hilary Kennedy Matthew C. Mowlem Andrew G. Dickson Martha Gledhill Eric P. Achterberg
author_facet	Socratis Loucaides Victoire M. C. Rèrolle Stathys Papadimitriou Hilary Kennedy Matthew C. Mowlem Andrew G. Dickson Martha Gledhill Eric P. Achterberg
author_sort	Socratis Loucaides
title	Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
title_short	Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
title_full	Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
title_fullStr	Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
title_full_unstemmed	Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
title_sort	characterization of meta-cresol purple for spectrophotometric ph measurements in saline and hypersaline media at sub-zero temperatures
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/b223db7be91a4039879f39e94bf14857
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Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures

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