Development of an Ionic Quartz Crystal Microbalance (QCM) Sensors for the Detection of Na+ and K+ in Human Urine

Abstract

In this study, we developed a quartz crystal microbalance (QCM) ionic sensor that can determine Na+ and K+ in human urine by the immobilization of crown ether as an ionic selector on a QCM electrode. In detail, –COOH was first introduced onto the QCM electrode surface by electrochemical copolymerization of thiophene and 3-thiopheneacetic acid, and then crown ether was introduced as an ionic selector onto the –COOH-modified QCM electrode by amide bond reaction. The prepared QCM ionic sensor was evaluated by FT-IR spectroscopy, SEM, contact angle, and cyclic voltammetry to confirm its successful fabrication. A prepared QCM ionic sensor with 4′-aminobenzo18-crown-6 adsorbed at 0.344 μg to K+ cation in this experiment. The Na+ cation was 0.360 mg in a human urine sample with a prepared QCM ionic sensor with 4′-aminobenzo-15-crown-5 and the K+ cation in a real human urine sample was 0.280 mg with a QCM ionic sensor with 4-aminobenzo18-crown-6, respectively. According to these results, the prepared QCM ionic sensor could be used to detection of sodium and potassium concentrations in human urine samples.