Online pH monitoring based on a wireless electrodeless quartz crystal microbalance with dissipation

Abstract

Online real-time detection is crucial for biochemical and healthcare monitoring. Methods that could conduct the measurements in low-volume analytes are essentially required. A wireless electrodeless quartz crystal microbalance with dissipation (WE-QCM-D) based sensor was proposed to realize real-time pH monitoring in low-volume solutions. The WE-QCM-D pH sensor was fabricated by coating with a pH-sensitive poly (hydroxyethyl methacrylate-co-methacrylic acid) (poly (HEMA-co-MAA)) film and observed the dynamic pH variation in the range from 4 to 9. The sensitivity of the WE-QCM-D pH sensor nearby the pKa was 1.47 V/pH and the maximum response time was around 80 s. The pH sensor performed well in synthetic urines with a measurement deviation less than 1% compared with that measured by a pH meter and reversible responses has been achieved when 140μl buffer solutions at pH 4.18, 5.6 and 7.62 were loaded on the quartz disc that was located in a glass vial. The results indicated that the WE-QCM-D pH sensor could be potentially used for online low volume detections.