Fast, Economic, and Improved Nanostructured Polymeric pH Sensor for Agrifood Analysis

Abstract

In the present work, a novel and economical pH sensor has been improved through the application of the conducting polymers poly(3,4-ethylendioxythiphene) and poly(sodium 4-styrene sulphonate). Sinusoidal voltages were applied to electrodeposit the different polymers studied for different periods (10, 15, and 20 min) on the electrode surface. The presence of polyaniline and its reversible redox structure have been corroborated by cyclic voltammetry. The working range has been increased from 3–8 to 2–12, obtaining adequate sensibility and linearity. This new sensor presented satisfactory repeatability, reproducibility (RSD < 5%), AND reversibility (pH range 2–12), and excellent selectivity towards H+ in the presence of diverse interferents in agrifood samples. Finally, the sensor was used to measure the pH in several real samples, whose pH values ranged from 2.23 to 11.5, obtaining excellent results. In addition, the values found were very similar to those reported by the gold technique (pH meter), with an error of less than 10% for most of the samples analyzed. In addition, a preliminary survey about measurements in a continuous flow, using a 3D homemade microfluidic cell, was performed with promising results.