A smartphone-assisted hybrid sensor for simultaneous potentiometric and distance-based detection of electrolytes

Abstract

At home electrolyte analysis is of growing interest due to the importance for early diagnosis for various diseases. This work presents the first device that integrates a potentiometric ion-selective electrode (ISE) with distance-based colorimetric detection for the simultaneous analysis of K+ and Cl− ions at the point of care (POC). This hybrid sensing device was designed in a two-dimensional configuration using a plastic transparency sheet containing a stencil printed K+-ISE and a paper substrate for distance-based colorimetric detection of Cl−. K+ quantification was performed using a low-cost (<$25) lab-made Wi-Fi supported potentiometer with a custom smartphone application while Cl− ions were quantified with an instrument-free distance-based paper analytical device (dPAD). The total analysis time is 5 min once the sample is added. The K+-ISE showed a sensitivity of 55.89 ± 2.52 mV/decade from 0.1 to 100 mM with a limit of detection (LOD) of 0.01 mM. The linear working range for Cl− detection was 0.5–50 mM whereas the LOD was 0.16 ± 0.05 mM. The proof-of-concept application of the sensing hybrid device was demonstrated in human urine and artificial sweat samples containing K+ and Cl− ions at physiologically relevant ranges. The recoveries were found to be 88–108% for K+ and 90–104% for Cl−, showing the potential use of the proposed device for low-cost routine analysis of biological samples at POC.