Design of a new colorimetric chemosensor based on indicator displacement assay for rapid and selective detection of total phosphate

Abstract

The present study introduces a simple, rapid, and selective method for detecting and determining total phosphate anions (Pi) using an indicator displacement assay (IDA) approach. A simple probe of Yttrium: Eriochrome cyanine R (Y: ECR complex) was chosen to detect Pi. When phosphate anions were added to the Y: ECR complex solution, it caused a color change from purple to yellow, at an optimal pH of 7.00. As the concentration of Y³⁺ increased, the absorption intensity at 441 nm gradually decreased, while a new absorption peak appeared at 531 nm (Δλ = 90 nm). Then, adding phosphate anions to the resulting complex solution increased the absorption intensity at 531 nm and an increase at 441 nm. This significant change was due to the release of ECR and forming a more stable complex between the Pi and Y³⁺. A linear response (R² = 0.9924) was observed within the Pi concentration range of 2.27 to 39.3 μM, with a detection limit of 0.55 μM. A good relative standard deviation (RSD = 1.39 %) was achieved over 10 replicates under optimal conditions. The IDA-based chemosensor was successfully used to recover the total phosphate in water samples (94.25–99.60 %) and urine samples (97.80–103.60 %).