Effect of K+ Concentration on the Direct pH Measurement of Peat Matrix by Sb Electrode pH Sensor and Compensation Methods

Abstract

pH of the substrate for soilless cultures is crucial information. As comparison to laboratory analysis, direct pH measurement with an all-solid-state pH sensor is quicker, more cost-effective, and more accurate. There are a variety of impacting factors and measuring inaccuracies, though. Peat was utilized as the test item in order to examine the variables and regulations affecting the measurement error and minimize it. Using KCl solution, substrate specimens with various mass water contents (MWC) and K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> concentrations (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> ) were created. Using an alumina substrate, a Sb working electrode and an Ag/AgCl reference electrode were created to form an all-solid-state pH sensor. On the basis of the direct pH measurements of peat substrate, it was used to investigate the error patterns of MWC and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> . A statistical examination of the measured pH values revealed that MWC and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> clearly affected the pH of the peat’s direct measurement error. The greatest inaccuracy is 0.98 pH units when C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> is 0 M and MWC is 0.2, and it progressively declines as MWC is increased. The inaccuracy is 0.39 pH units when C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> is 0.1 M. From 0 to 0.1 M, the measurement error falls linearly as C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> is increased. A double compensation model of MWC and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K+</sub> was constructed using statistical analysis, and after compensation, the maximum error of the pH of peat substrate was decreased from 1.05 to 0.41. For the purpose of furthering the development of an all-solid-state pH sensor in practice, the work offers a theoretical and experimental foundation.