Nuclear magnetic resonance pH effects

Nuclear magnetic resonance studies on meso-ionic l,2,4-triazol-3-ones (200) were used to examine their relationship to the alternative l,3,4-oxadiazol-2-imine structure (153). The effect of solvent polarity upon the ultraviolet spectrum of anhydro-3-hydroxy-1,4-diphenyl-1,2,4-triazolium hydroxide (200, R = = Ph, R = H) has been discussed... 

N. J. Greenfeld, M. Hussain and J. Lenard (1987). Effect of growth state and amines on cytoplasm and vacuolar pH, phosphate and polyphosphate levels in Saccharomyces cerevisiae a 31P nuclear magnetic resonance study. Biochim. Biophys. Acta, 926, 205-214. 

Y. C. Yang, M. Bestos and K. J. Chen (1993). Effect of osmotic stress and growth stage on cellular pH and polyphosphate metabolism in Neurospora crassa as studied by 31-P-nuclear magnetic resonance spectroscopy. Biochim. Biophys. Acta, 1179, 141-147. 

Panjwrmi, N., Hodgson, D.J., Sauve, S., Aubin, Y. (2010) Assessment of the effects of pH, formulation and deformulation on the conformation of interferon alpha-2 by NMR. J Pharm Sci, 99 (8), 3334-3342. Amezcua, C.A., Szabo, C.M. (2013) Assessment of higher order structure comparability in therapeutic proteins using nuclear magnetic resonance spectroscopy. J Pharm Sci, 102 (6), 1724—1733. 

If the objective is identification (qualitative analysis), it suffices to compare the spectrum of the analyte with that of a standard, both recorded in the same solvent and at an identical pH. This is not the main application of UV-Vis spectrophotometry as the best results in this context are provided by spectroscopic methods considered more effective for the study of the molecular structure of organic compounds (infrared, nuclear magnetic resonance, mass spectrometry, and X-ray diffraction). However, UV-Vis spectrophotometry is a source of relevant supplementary information that helps in the elucidation of molecular structures of drugs, impurities, metabolites, intermediate compounds of degradation, etc. 

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