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dc.contributor.author
Castells, Cecilia Beatriz Marta
dc.contributor.author
Ràfols, Clara
dc.contributor.author
Rosés, Martí
dc.contributor.author
Bosch, Elisabeth
dc.date.available
2020-01-21T20:26:58Z
dc.date.issued
2003-06
dc.identifier.citation
Castells, Cecilia Beatriz Marta; Ràfols, Clara; Rosés, Martí; Bosch, Elisabeth; Effect of temperature on pH measurements and acid-base equilibria in methanol-water mixtures; Elsevier Science; Journal of Chromatography - A; 1002; 1-2; 6-2003; 41-53
dc.identifier.issn
0021-9673
dc.identifier.uri
http://hdl.handle.net/11336/95471
dc.description.abstract
The knowledge of the acid-base equilibria in water-solvent mixtures of both common buffers and analytes is necessary in order to predict their retention as function of pH, solvent composition and temperature. This paper describes the effect of temperature on acid-base equilibria in methanol-water solvent mixtures commonly used as HPLC mobile phases. We measured the δ-correction parameter (δ=swpH-sspH=Ē j-log swγH0) between two pH scales: pH measured in the solvent concerned and referred to the same standard state, sspH, and the pH measured in that solvent mixture but referred to water as standard state, swpH, for several methanol compositions in the temperature range of 20-50°C. These determinations suggest that the δ-term depends only on composition of the mixture and on temperature. In water-rich mixtures, for which methanol is below 40% (w/w), δ-term seems to be independent of temperature, within the experimental uncertainties, whereas for methanol content larger than 50% (w/w) the δ-correction decreases as temperature increases. We have attributed this decrease to a large increase in the medium effect when mixtures have more than 50% methanol. The pKa of five weak electrolytes of different chemical nature in 50% methanol-water at 20-50°C are presented: the effect of temperature on pKa was large for amines, pyridine and phenol, but almost no dependence was found for benzoic acid. This indicates that buffers can play a critical role in affecting retention and selectivity in HPLC at temperatures far from 25°C, particularly for co-eluted solutes.
dc.format
application/pdf
dc.language.iso
eng
dc.publisher
Elsevier Science
dc.rights
info:eu-repo/semantics/openAccess
dc.rights.uri
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.subject
ACID-BASE EQUILIBRIA
dc.subject
METHANOL-WATER MIXTURES
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MOBILE PHASE COMPOSITION
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PH
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TEMPERATURE
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WEAK ELECTROLYTES
dc.subject.classification
Química Analítica
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Ciencias Químicas
dc.subject.classification
CIENCIAS NATURALES Y EXACTAS
dc.title
Effect of temperature on pH measurements and acid-base equilibria in methanol-water mixtures
dc.type
info:eu-repo/semantics/article
dc.type
info:ar-repo/semantics/artículo
dc.type
info:eu-repo/semantics/publishedVersion
dc.date.updated
2020-01-21T18:47:42Z
dc.journal.volume
1002
dc.journal.number
1-2
dc.journal.pagination
41-53
dc.journal.pais
Países Bajos
dc.journal.ciudad
Amsterdam
dc.description.fil
Fil: Castells, Cecilia Beatriz Marta. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; Argentina
dc.description.fil
Fil: Ràfols, Clara. Universidad de Barcelona; España
dc.description.fil
Fil: Rosés, Martí. Universidad de Barcelona; España
dc.description.fil
Fil: Bosch, Elisabeth. Universidad de Barcelona; España
dc.journal.title
Journal of Chromatography - A
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/url/https://www.sciencedirect.com/science/article/pii/S0021967303006447
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/doi/https://doi.org/10.1016/S0021-9673(03)00644-7
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