European Journal of Chemistry

New chemometric strategies in the spectrophotometric determination of pKa

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Judith Amador-Hernandez
Alberto Rojas-Hernandez
Edith Madai Colunga-Urbina
Iliana Margarita De La Garza-Rodriguez
Miguel Velazquez-Manzanares
Luis Felipe Medina-Vallejo


In this work, principal component regression and partial least squares regression were used for the estimation of acid dissociation constants through UV-Vis spectrophotometric measurements, considering five well-known acid-base indicators as well as two herbicides as analytes. In each case, an acid-base titration was carried out. Then, the multivariate calibration model was constructed with a few absorption spectra of the series at extreme pH values, to which values of the dissociation fraction (α) of 1 or 0 were assigned, in the case of HA or Aspecies. After that, the prediction step consisted in the estimation of α for the rest of the series. Then, distribution diagrams were built up with α vs pH, to find α = 0.5 where pH = pKa. The results were compared with those obtained through multivariate curve resolution-alternating least squares and program stability quotients from absorbance data (SQUAD), which showed an excellent correspondence.

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How to Cite
Amador-Hernandez, J.; Rojas-Hernandez, A.; Colunga-Urbina, E. M.; De La Garza-Rodriguez, I. M.; Velazquez-Manzanares, M.; Medina-Vallejo, L. F. New Chemometric Strategies in the Spectrophotometric Determination of PKa. Eur. J. Chem. 2014, 5, 1-5.

Article Details

Author Biography

Iliana Margarita De La Garza-Rodriguez, Facultad de Ciencias Químicas, Universidad Autónoma de Coahuila, Blvd. V. Carranza s/n, 25280 Saltillo, Coahuila, México

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Supporting Agencies

Secretaría de Educación Pública (Project PIFI 2012) (Mexico) and Consejo Nacional de Ciencia y Tecnología (Project CB-2010/152918) (Mexico))
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