Chloride and pH Determination on a Wireless, Flexible Electrochemical Sensor Platform

Abstract

A stamp-sized, flexible, wireless, generic electrochemical sensor platform was demonstrated for use as a potentiometric pH and amperometric Cl <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> sensor. The platform combines flexible printed circuit technology with screen-printed electrodes, which enables cheap and easy quantification of biorelevant analytes in many different environments. pH sensors with graphene oxide as the recognition element was constructed on a ferrocyanide modified carbon electrode, to maintain a well-defined redox potential even at high alkalinity. A solid-state reference electrode based on a NaCl-doped polyvinyl butyral membrane ensured applicability towards sample matrices of unknown composition by remaining unsensitive (±7.1 mV) to external Cl <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> in the range pCl 0-3. The platform was able to linearly (-26.3 mV pH <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , r <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.99) quantify pH in the range of 2-9 with a maximum inter-sensor standard deviation of 0.43 pH units. Secondly, a Cl <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> sensor combining three unmodified Ag/AgCl electrodes with squarewave amperometry was designed, simulated and tested. A sensitivity of (-147.7 μA pCl <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , r <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.97) was obtained, with a maximum inter-sensor standard deviation of 0.27 pCl units in the range pCl 0-3.