title: Construction and evaluation of a potassium-selective tube-mounted membrane electrode.
abstract: A simple procedure for the rapid construction of inexpensive potassium-selective electrodes with valinomycin-based PVC membranes is described. Potassium-selective membranes were formed on the end of Parafilm- or Tygon-covered glass tubes by dipping the tubes into a mixture of PVC, valinomycin, and dioctyl sebacate dissolved in tetrahydrofuran. Small internal Ag/AgCl reference electrodes were made with silver wire and placed inside the tubes with AgCl-saturated potassium chloride solution. This procedure yields tube-mounted membrane electrodes that perform as well as commercially available potassium-selective electrodes in terms of their response characteristics and practical applications with soil extracts. Moreover, it facilitates the evaluation of membranes with different compositions, for making ion-selective electrodes.
authors.affiliation: Department of Agronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Farrell
authors.forename: A D
authors.initials: AD
authors.lastname: Scott