Solid State Sensor for Simultaneous Measurement of Total Alkalinity and pH of Seawater

Ellen M. Briggs, Sergio Sandoval, Ahmet Erten, Yuichiro Takeshita, Andrew C. Kummel, Todd R. Martz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


A novel design is demonstrated for a solid state, reagent-less sensor capable of rapid and simultaneous measurement of pH and Total Alkalinity (AT) using ion sensitive field effect transistor (ISFET) technology to provide a simplified means of characterization of the aqueous carbon dioxide system through measurement of two "master variables": pH and AT. ISFET-based pH sensors that achieve 0.001 precision are widely used in various oceanographic applications. A modified ISFET is demonstrated to perform a nanoliter-scale acid-base titration of AT in under 40 s. This method of measuring AT, a Coulometric Diffusion Titration, involves electrolytic generation of titrant, H+, through the electrolysis of water on the surface of the chip via a microfabricated electrode eliminating the requirement of external reagents. Characterization has been performed in seawater as well as titrating individual components (i.e., OH-, HCO3-, CO32-, B(OH)4-, PO43-) of seawater AT. The seawater measurements are consistent with the design in reaching the benchmark goal of 0.5% precision in AT over the range of seawater AT of ∼2200-2500 μmol kg-1 which demonstrates great potential for autonomous sensing.

Original languageEnglish
Pages (from-to)1302-1309
Number of pages8
JournalACS Sensors
Issue number9
Publication statusPublished - 22 Sept 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.


This work was supported by grant NSF OCE Award 1155122. This material is also based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144086. The authors wish to acknowledge Bob Carlson and Jim Connery from Honeywell for kindly providing expert guidance during the development of this sensor. We also thank crew and scientists on GO-SHIP cruise I09N for assisting with collecting seawater for preliminary sensor assessment and two anonymous reviewers for their insightful comments.

FundersFunder number
National Science Foundation1155122


    • ISFET
    • pH
    • seawater
    • sensor
    • total alkalinity


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