title: Characterization of an ion sensitive field effect transistor and chloride ion selective electrodes for pH measurements in seawater.
abstract: Characterization of several potentiometric cells without a liquid junction has been carried out in universal buffer, aqueous HCl, and artificial seawater media. The electrodes studied include Ion Sensitive Field Effect Transistor (ISFET) pH electrodes, and Chloride-Ion Selective Electrodes (Cl-ISE) directly exposed to the solution. These electrodes were compared directly to the conventional hydrogen electrode and silver-silver chloride electrode in order to report the degree to which they obey ideal Nernstian laws. These data provide a foundation for operating the ISFET|Cl-ISE pair in seawater as a pH sensor. In order to obtain the highest quality pH measurements from this sensor, its response to changes in pH and salinity must be properly characterized. Our results indicate near-ideal Nernstian response for both electrodes over a wide range of pH (2-12) and Cl(-) molality (0.01-1). We conclude that the error due to sub-Nernstian response of the cell ISFET|seawater|Cl-ISE over the range of seawater pH and salinity is negligible (<0.0001 pH). The cross sensitivity of the Cl-ISE to Br(-) does not seem to be a significant source of error (<0.003 pH) in seawater media in the salinity range 20-35.
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Takeshita
authors.forename: Todd R
authors.initials: TR
authors.lastname: Martz
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Johnson
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Dickson
mesh_terms: D002712:Chlorides / Q000032:analysis*; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000032:analysis; D012623:Seawater / Q000737:chemistry*; D014173:Transistors, Electronic
chemical_list: D002712:Chlorides; D007477:Ions