An Integrated Screen-Printed Potentiometric Strip for Determination of Ca2+ in Seawater

The detection of Ca2+ in seawater is of critical importance to understand the growth of marine organisms and the circulation of the ocean ecosystem. This paper reports an integrated screen-printed potentiometric strip based on an all-solid-state Ca2+-selective polymeric membrane indicator electrode and an all-solid-state reference electrode for determination of Ca2+ in seawater, for which the conductive carbon ink-based substrate was pretreated by the physical and electrochemical methods. The proposed pretreatment procedures are found to improve the electro-transfer kinetics, decrease the electron-transfer resistances and increase the double layer capacitance of the screen-printed carbon electrode, which are favorable for constructing the all-solid-state Ca2+-ISEs without the additional materials as solid contacts. The proposed screen-printed potentiometric strip shows a stable linear potential response in the range of 1.0 x 10(-5) - 0.1 M with a slope of 26.7 +/- 1.3 mV/dec (n = 3) in the presence of 0.5 M NaCl. Additionally, the prepared potentiometric strip was used to investigate the vertical distributions of Ca2+ in seawater, and the results are consistent with those by inductively coupled plasma-optical emission spectrometry. This work indicates that the proposed potentiometric strip can be used as an alternative tool for on-site and rapid detection of Ca2+ for marine monitoring. (C) 2019 The Electrochemical Society.