Ultrasensitive Electrochemical Phosphate Detection by Pyridine–zinc(ii) Complex

Phosphorous is an important environmental health parameter as the availability of phosphorus within water systems plays an essential role in the prevalence of harmful algal blooms (cyanobacteria blooms). Currently, phosphates are detected using sensitive chromatographic and colorimetric techniques; however, major disadvantages stem from the lack of anion selectivity in samples with complex matrices, as well as the high cost of analysis. Electrochemical techniques utilizing self-assembled monolayers can provide a cheaper yet sensitive method of detection. This work explores the modification of a gold working electrode using pyridine–zinc(II) complexes. The implementation of self-assembled monolayers allows for an ultrasensitive and selective method of indirect detection of the H2PO4 − species, ranging in concentrations between 0.0 and 1.2 fmol/L phosphate. Electrochemical techniques such as cyclic voltammetry and square-wave voltammetry were explored for their phosphate-detection abilities, with detection limits of 4.0 × 10−16 and 9.0 × 10−17 mol/L H2PO4 −, respectively. X-ray photoelectron spectroscopy measurements were also taken to confirm the modification of the electrode. The selectivity of this sensor towards phosphate anions was successfully explored for this sensor in the presence of potential interfering agents (sulfate, chlorine, carbonate, fluoride, nitrite, and hypochlorite ions), and applicability of sensor was also explored through the detection of phosphate in a tap and lake water sample.