A Comparison of the Accuracy and Efficiency of Two Ionic Strength Adjustment Buffers in Measuring Potassium Using an Ion-Selective Electrode

Abstract

ABSTRACTIt is recommended to use ionic strength adjustment buffers to increase reading accuracy while measuring potassium (K+) concentrations in aqueous solutions by using ion-selective electrodes (ISEs). Three laboratory leachate column studies were conducted to evaluate the efficiency of two buffers, 2.5 M sodium perchlorate (NaClO4) and 2.5 M sodium chloride (NaCl), in measuring K+ concentrations in three media types (peat moss, Oxisols, and Mollisols soils). Three algae species, KCl, and KNO3 were applied to provide 112 and 336 kg K/ha. Leachate samples were collected to a total of 16 weeks and measured using a K-ISE. The K+ data from the three trials showed a highly significant (r ~ 0.99) correlation between the two buffers. T-Test results showed highly significant (P < 0.01) differences between unbuffered and the two buffered solutions. However, there were no significant differences between the two buffered solutions, under the peat moss, Oxisols, and Mollisols soils. The results suggest that the least expensive buffer of 2.5 M NaCl is as accurate as NaClO4 in such aqueous solutions.