Investigation for Phosphoric Acid in Soda using Raman Spectroscopy Measurements

  • Bethann Oberlander
  • Luke Bartlett


Certain circumstances prevent utilizing an acid-base titration for determining an acid’s concentration. Analyzing the contents of a pharmaceutical tablet intended for sale, or corrosive solutions used in electrochemical plating and finishing are both examples where detecting acid concentrations using an acid-base titration would be implausible. In this study, a Raman Spectrometer was utilized to determine the concentrations of phosphoric acid and dihydrogen phosphate ion within soda samples and external standards. The soda samples used in this study were Pepsi, Mountain Dew, and Sierra Mist. The external standards were formed through parallel dilutions of stock phosphoric acid samples with hydrochloric acid solution. The Raman Spectrometer results were then organized into a calibration model using Microsoft Excel, which provided a graphical representation of the relationship between the concentration of phosphoric acid present and the intensity of light scattered by the sample as it was tested. The represented relationship displays that while dihydrogen phosphate ion was detected in the Pepsi samples tested with the Raman Spectrometer, further testing may be required to validate these results.