Sol-Gel Derived Potentiometric pH Sensors
A potentiometric sol-gel derived (xerogel) pH sensor based on covalently attached amine groups is described. The sensor consists of a Ag/AgCl electrode coated with a hybrid aminosilane/alkylsilane xerogel film. Various combinations of aminosilanes and alkylsilanes are evaluated for their potentiometric response to pH. The optimal sensor design is composed of (aminoethylaminomethyl)- phenethyltrimethoxysilane and methyltrimethoxysilane. Thissensorexhibitsnear-Nerstianresponse(-55mV·decade-1), responds rapidly (< or = 3 s) to changes in pH, and has H+ selectivity coefficients (log KpotH+,j) of -13 and -11 for interfering j cations Na+ and K+, respectively. In vitro platelet adhesion tests indicate that the xerogel coatings are more blood compatible than conventional poly(vinyl chloride) and poly(urethane) ion-selective electrode coatings.