Hydrogel-Based Sensors for Ethanol Detection in Alcoholic Beverages

Abstract

A fast and reliable determination of the ethanol concentration is essential in the analysis of alcoholic beverages. However, different factors like pH value or salt concentration can influence the ethanol measurement. Furthermore, analytical figures of merit for the alcohol sensor, such as limit of detection, sensitivity and measurement uncertainty, are necessary for the application. In this paper, a detailed sensor characterization of a novel sensor based on ethanol-sensitive poly acrylamide hydrogels will be presented. The resulting swelling pressure of the hydrogel was transformed via a piezoresistive pressure sensor into a measurable output voltage. These kinds of sensors can be used over a large measuring range, up to 50 vol% ethanol and more, with a high sensitivity. In the range from pH 7.4 to 4, the pH value had no influence on the sensor signal. Higher salt concentrations can slightly influence the measurement. The detection limit amounts to 0.06–0.65 vol% ethanol. The concentration of a vodka sample was determined with a sufficient measuring uncertainty.

NiO Grained-Flowers and Nanoparticles for Ethanol Sensing

“…The overall response of two morphologies of NiO under investigation is excellent, with low operational temperature and linear response vs. gas concentration in the 100-700 ppm range. In detail, the grained-flower display an optimal temperature of 200 • C and 250 • C, respectively, i.e., below or equal to the temperatures reported for ethanol sensing by other NiO morphologies [13], though with a better Ra/Rg ratio. In Figure 3a,b, the response vs. temperature is reported for 2 concentrations, i.e., 150 ppm and 200 ppm.…”

“…Ethanol as a volatile organic compound (VOC) requires accurate and fast sensing since it is pivotal in monitoring chemical reactions, breath analysis, food control, and biomedical productions. Therefore, several types of sensors have been developed based on metal oxides, conducting polymers carbon nanostructured materials, and porous materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Among metal oxides, NiO is a p-type semiconductor with a wide band gap (3.0-4.0 eV) [15][16][17] and supercapacitor properties extensively applied in electrochemical devices, lithium ion batteries, and dye-sensitized photocathodes [18].…”

Enzyme-Functionalized Piezoresistive Hydrogel Biosensors for the Detection of Urea

“…To show the application potential and for the determination of important sensor properties, hydrogel-based piezoresistive urea biosensors were constructed and measured. The construction corresponds to that described in previous studies [9,10,20]. At first, the repeatability of a hydrogel-based urea sensor was tested via cyclic changes of the urea concentration between 0 mmol/L and 20 mmol/L urea (Figure 8).…”

“…After wire bonding to connect the sensor chip with the circuit board, connector cables were soldered to the readout unit (Fluke 45, Glottertal, Germany). By using cyanoacrylate and two-component epoxy resin, an inlet and outlet hose for the measuring solutions were fixed on the resulting urea biosensor [9,10,20].…”

“…The deformation of the piezoresistors within the bending plate leads to a change in resistance that will be transformed via a Wheatstone bridge circuit into a measurable output voltage [6]. Based on this principle, hydrogel-based sensors for the detection of the pH value [7], temperature [8] or organic solvents like ethanol [9,10] could be realized.…”