Designing cost-effective optimal indicator displacement assay (IDA)-based sensor arrays for simultaneous quantification of sulfate and phosphate

A simple and efficient colorimetric sensor array for simultaneous quantifying of sulfate and phosphate anions in water samples was developed based on an indicator-displacement assay (IDA) and the PAN-Pb affinity pair. In this IDA-based sensor, a dye, PAN, was used as the indicator, and the selective detection of sulfate and phosphate was achieved based on the competition between the indicator and sulfate\ phosphate for binding with the Pb+2 metal ion. The competition of sulfate\ phosphate with PAN for Pb2+ resulted in an obvious color change of the solution from yellow to dark oranges. Based on the theory of simultaneous detection of analytes with non-selective responses, the presence of an array of sensors with at least two sensor units is unavoidable. Herein, different simple sensor arrays with a single indicator and receptor were designed. In the designed cost-effective sensor arrays, the difference in the concentration ratio of the probe composition in each sensor element is considered. These colorimetric sensor arrays recognize sulfate and phosphate over other interfering ions in natural waters, such as nitrite, nitrate, magnesium, potassium, calcium, and chloride. The designed sensor array allows the selective detection and quantification of sulfate and phosphate in real water samples without needing pre-treatment. The real sample recovery rate is between (96–104%) and (94–108%) for sulfate and phosphate, respectively.