posted on 2020-03-05, 16:50authored byPitchnaree Kraikaew, Stéphane Jeanneret, Yoshiki Soda, Thomas Cherubini, Eric Bakker
Potentiometric
pH probes remain the gold standard for the detection
of pH but are not sufficiently sensitive to reliably detect ocean
acidification at adequate frequency. Here, potentiometric probes are
made dramatically more sensitive by placing a capacitive electronic
component in series to the pH probe while imposing a constant potential
over the measurement circuit. Each sample change now triggers a capacitive
current transient that is easily identified between the two equilibrium
states, and is integrated to reveal the accumulated charge. This affords
dramatically higher precision than with traditional potentiometric
probes. pH changes down to 0.001 pH units are easily distinguished
in buffer and seawater samples, at a precision (standard deviation)
of 28 μpH and 67 μpH, respectively, orders of magnitude
better than what is possible with potentiometric pH probes.