The use of buffers to measure the pH of seawater

Frank J. Millero, Jia Zhong Zhang, Sarah Fiol, Sara Sotolongo, Rabindra N. Roy, Kitack Lee, Sanjay Mane

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


The pH of seawater can be measured in the field using potentiometric and spectrophotometric methods. The use of pH standards or buffers is an important aspect of the calibration of both methods in a laboratory on a common concentration scale. The buffers can also be used to monitor the performance of pH meter and spectrophotometer during a cruise. A procedure is described for the determination of the pH of seawater, where the proton concentration is expressed as moles kg-H2O-1 using seawater buffers. The buffers are prepared in synthetic seawater in the laboratory by the methods outlined by Bates and coworkers. We have prepared four buffers (Bis, Tris, Morpholine and 2-Aminopyridine) that cover a pH range from 6.8 to 8.8. The emf values of the buffers were measured with a H2, Pt/AgCl, Ag electrode system after their preparation and bottling for use at sea. The measured emf values were found to be in good agreement (±0.05 mV) with the original measurements of Bates and coworkers from 0 to 45°C. The measured pH of these buffers are in good agreement (±0.001 pH units) with the values calculated from the equations of Dickson on the total pH scale based on Bates et al. Studies are underway to access the long term stability of these buffers. We have also used these buffers to calibrate systems used to make potentiometric and spectrophotometric measurements of pH on seawater relative to the H2, Pt/Ag, AgCl electrode from 5 to 45°C.

Original languageEnglish (US)
Pages (from-to)143-152
Number of pages10
JournalMarine Chemistry
Issue number2-4
StatePublished - Dec 1993

ASJC Scopus subject areas

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology


Dive into the research topics of 'The use of buffers to measure the pH of seawater'. Together they form a unique fingerprint.

Cite this