Self-Calibrated Potentiometric Sensor Based on Polystyrene-Au Nanocomposites for Home Detection of Ca²⁺in Urine

Home detection of urine is of great significance for health assessment and long-term surveillance of some chronic diseases. However, the most reported sensors require complicated pretreatment of samples or operations, thus limiting their application in home detection. Herein, a self-calibrated potentiometric sensor based on polystyrene-Au nanocomposites has been developed for the determination of Ca2+, consisting of a sensing channel, a calibration channel and a reference channel. By transporting Ca2+ ionophore and ion exchanger into polystyrene nanoparticles, the sensing nanocomposites were synthesized with the functions of target recognition and ion-electron transduction. The construction of the sensor required the modification of the nanocomposites by only drop-casting, which greatly simplified the preparation process and thus increased the stability and reproducibility. Furthermore, the calibration channel provided the same basic potential as the sensing channel in real samples. By subtracting the potential value of calibration channel from that of sensing channel could eliminate the interference of background matrix on target response, thus improving the accuracy of the results in the actual urinalysis. The developed self-calibrated potentiometric sensor showed a near Nernstian response to Ca2+ in a range of $1.0\times 10$ -4 - $1.0\times 10$ -2 M with a slope of 26.3 ± 1.7 mV/decade and intercept of 126.2 ± 5.3 mV and the detection limit is $4.2\times 10$ -5 M. In the application to real urine samples, the results were in good agreement with those obtained by ICP-AES, suggesting this self-calibrated potentiometric Ca2+ in urine and long-term health monitoring.