Application of potentiometric method using a cell without liquid junction to underway pH measurements in surface seawater

This study evaluated a method to carry out underway pH measurements of surface seawater by means of a cell without liquid junction using glass electrodes for hydrogen and sodium ions as follows:The Pitzer method was used as the theoretical basis for the calibration of the above cell and calculations of the pH in total hydrogen concentration scale. It was shown that abovementioned cell has long-term stability and can be calibrated only once a day. A buffer solution, TRIS–HCl–TRIS–NaCl–H2O, is recommended for calibration. This approach has been applied to a cruise in the Sea of Okhotsk on the R/V Akademik M.A.Lavrentyev during September and October 2007.