Quantification of Full Range Ethanol Concentrations by using pH Sensor

Abstract

A differential pH measurement device was used to achieve operation conditions of alcohol dehydrogenase reaction. Optimum operating conditions were temperature of 30°C, 10 µl of alcohol dehydrogenase enzyme volume (with a final activity of 563.75 units ml-1) per 50 µl of sample, NAD + concentration of 0.05 mM and 20 mM glycine-pyrophosphate buffer solution of pH 9.1. In this method a range of ethanol concentrations from 0 -99,985 %, which means 0.000001714 -17.14 M, were used. The maximum obtained change in pH, delta pH, was (-33) mpH. A calibration curve of logarithmic values of ethanol concentrations against change in pH for standard ethanol samples was done. Since this calibration curve is a linear with a correlation coefficient (R) of 0.998, this calibration curve can be used in quantification of ethanol concentration. End point of equilibrium concentrations of reactants and products of ethanol oxidation reaction was measured within spectrophotometer. The results indicated 100 seconds of process time is required to reach the end point for all ethanol standard samples. This required time was satisfied with results of measuring change in pH within differential pH analyzer system.

Characterization of an hrp-aox-polyaniline-graphite composite biosensor

“…Those measurements were based on the depletion of dissolved oxygen upon exposure to ethanol solution (0.15 -0.75 mM). Al-Mhanna and Hueber [36] reported an economic system that worked with one enzyme in a differential pH measurement device for alcohol oxidase and -nicotinamide adenine dinucleotide (NADH + ) reaction and obtained a logarithmic curve for ethanol concentrations against change in pH for standard samples. These authors described an inverse correlation between the signal response and the analyte concentration for the indirect detection measurements working with a wide range of ethanol standard concentration solutions (17.14 μM -17.14 M).…”