DOI: https://doi.org/10.55373/mjchem.v25i5.51

Keywords: Soil phosphate; Co-C electrode; potentiometric method; spectrophotometric method; soil sample analysis

Abstract

Phosphorus is a nutrient in the soil that is used by plants to grow, so its presence needs to be known as basic information in land management. Phosphorus content analysis is usually carried out by measuring phosphate ions extracted from soil samples using spectrophotometric methods. This paper reports the results of the development of an alternative phosphate measurement method through the design of a cobalt-based potentiometric electrode capable of selectively detecting phosphate ions. The electrodes were made voltammetrically to reduce the cobalt ions in solution and attach them to the ends of the carbon rods. The cobalt thin layer on the carbon tip is an active part of the Co-C electrode in the process of potentiometric detection of phosphate ions. The results of the characterization of the electrode performance on the measurement of a series of standard phosphate solutions showed that this electrode had a sensitivity value of 28.01 mV/decade. Meanwhile, the selectivity coefficient for interfering ions (NO3-, NH4+, K+ and Cl-) is <1 which indicates that the interference of these ions does not significantly affect the measurement of the main ion. The electrode also has good precision by showing the value of variation coefficient < 5%. Compared with the spectrometric method in the measurement of agricultural soil samples at four locations, it was shown that the Co-C electrodes showed equivalent results, as evidenced by the correlation coefficient of 0.998. It can be stated that the Co-C electrode is very promising to be used as an alternative method of measuring phosphate.