Raman and 31P nmr characterization of the pH dependence of aqueous phosphates: An undergraduate experiment

CHED 363

Joseph Jabbour, Drew Dolino, Sam Simmons, Michelle A. Steiger, and Thomas B. Malloy Jr., malloyt@stthom.edu. Department of Chemistry, University of St. Thomas, 3800 Montrose Blvd, Houston, TX 77450
We have measured the phosphorus chemical shifts of aqueous phosphates and corresponding Raman spectra over the range of pH from 1-14 for solutions with a constant total phosphate concentration. These data were obtained with instrumentation appropriate for undergraduate laboratory experiments; an Anasazi Eft60 FTNMR and a Delta Nu Advantage 200 Raman spectrometer with 632.8 nm excitation. The changes as the pH is varied are compared to the expected appearance and disappearance of species based on known pKa values.