Characteristics of a cobalt-based phosphate microelectrode for in situ monitoring of phosphate and its biological application

The in situ monitoring of phosphate has been of great importance in many environmental applications, particularly those involving biological treatment processes and eutrophication monitoring. A microelectrode with small tip size (∼10 μm) was fabricated with cobalt wire, characterized and evaluated for in situ and in vivo environmental analysis of phosphate in biological applications. The electrochemical performance of this cobalt-based microelectrode was fully examined for its characteristics, including detection limit, response time, selectivity, reproducibility, life time, interference with pH, ions and dissolved oxygen (DO), and the stirring effect. The microelectrode showed excellent selectivity for the ortho-phosphate ions (HPO42− and H2PO4−) in various environmental conditions. Alkalinity and DO were found to interfere with electrode response to phosphate. The phosphate microelectrode was also evaluated with scanning electron microscopy (SEM) and cyclic voltammetry (CV). The developed microelectrode was used for in situ monitoring of phosphate in microbial flocs. Well-defined phosphate profiles across the flocs were observed under anaerobic (phosphorus release) conditions. This full characterization and successful application showed that the cobalt-based phosphate microelectrodes can be a very useful tool for in situ measurement of phosphate in various environmental conditions, including within microbial flocs.