Simultaneous Determination of Calcium (II) and Magnesium (II) by Dual-Calibrated Solid-State Potentiometric Sensors

Potentiometric sensing devices designed for at-home use enable real-time monitoring of personal health status. Nevertheless, inherent variations in the background matrix composition and pH of clinical urine samples can induce pronounced drift in the basic potential and response slope of potentiometric sensors, thereby severely compromising detection reliability and accuracy. Herein, a dual-calibrated solid-state potentiometric sensor based on polystyrene-Au nanocomposites was proposed for the simultaneous determination of Ca2+ and Mg2+ in urine, integrating five channels: a Ca2+ sensing channel, a Mg2+ sensing channel, a self-calibration channel, a pH channel and a reference channel. The self-calibration channel effectively eliminates nonspecific interference from the background matrix of urine samples by subtracting its potential response value from that of the corresponding sensing channels. The integrated pH channel compensates for pH-induced deviations in response slope via a pH-dependent linear calibration model. The sensor exhibited near-Nernstian behaviors toward both Ca2+ and Mg2+ across a linear range of 1.0 × 10−4 − 1.0 × 10−2 mol/L with limits of detection of 3.2 × 10−5 mol/L for Ca2+ and 2.1 × 10−5 mol/L for Mg2+. The dual-calibrated potential-concentration relationships were derived as ECa2+ (mV) = (−2.300pH + 39.34) × log[Ca2+] + 125.7 and EMg2+ (mV) = (−1.628pH + 34.97) × log[Mg2+] + 153.6. Benefiting from the high detection accuracy, excellent selectivity, satisfactory reproducibility and long-term stability, this sensor was successfully applied to the direct determination of Ca2+ and Mg2+ in artificial urine samples. This work provides an effective and accessible strategy for at-home urinary ion monitoring, and holds substantial promise for routine personal health management.