Quantitative detection of Amino Acid, Organic Acid and Sugar using an Electrode-separated Piezoelectric Quartz Crystal

Abstract

An electrode-separated piezoelectric quartz crystal (electrode-separated PQC) is constructed with no electrode attached to either side of the quartz plate, but electrodes are separately inserted in the electrolyte solution on both sides of the quartz plate, and are connected to an oscillator. The frequency shifts due to the solution properties and the mass change on the quartz plate is just the same as for a normal piezoelectric quartz crystal (normal PQC) having two electrodes. The electrode-separated PQC will be more useful than the normal PQC because it can be made smaller, higher frequency, and then cheaper. Amino acid, organic acid and sugar are important substances in the alcoholic beverage made by fermentation, such as sake. The Amino acids were determined using electrode-separated PQC coated with chitosan in copper (II) solution. Formation of complex with chitosan on the quartz plate, Cu(II) and amino acid in the sample solution induced the frequency shift of PQC. On the other hand, using non-coated electrode-separated PQC, concentration of organic acid and sugar in the liquid were determined, because the frequency of the crystal filled with the liquid containing organic acid and sugar was shifted with the viscosity and conductivity, respectively.