Abstract
The article presents naked-eye methods for fast, sensitive, and selective detection of isopentylamine and cadaverine vapours based on 4-N,N-dioctylamino-4′-dicyanovinylazobenzene (CR-528) and 4-N,N-dioctylamino-2′-nitro-4′-dicyanovinylazobenzene (CR-555) dyes immobilized in ethylene-vinyl acetate copolymer (EVA). The reaction of CR-528/EVA and CR-555/EVA indicator layers with isopentylamine vapours caused a vivid colour change from pink/purple to yellow/orange-yellow. Additionally, CR-555/EVA showed colour changes upon exposure to cadaverine. The colour changes were analysed by ultraviolet–visible (UV/VIS) molecular absorption spectroscopy for amine quantification, and the method was partially validated for the detection limit, sensitivity, and linear concentration range. The lowest detection limits were reached with CR-555/EVA indicator layers (0.41 ppm for isopentylamine and 1.80 ppm for cadaverine). The indicator layers based on EVA and dicyanovinyl azobenzene dyes complement the existing library of colorimetric probes for the detection of biogenic amines and show great potential for food quality control.
Highlights
Sensors are devices that obtain a physical quantity and convert it into an analytical signal
We have previously reported on the synthesis of two new azobenzene dyes, 4-N,N-dioctylamino-40 dicyanovinylazobenzene (CR-528) and 4-N,N-dioctylamino-20 -nitro-40 -dicyanovinylazobenzene (CR-555), and their detection of biogenic amines in ethanol solution, which exhibited significant colour changes from pink/purple to pale yellow/orange-yellow [33]
Partial method validation was performed by determining the LOD, linear concentration range, confidence intervals, and sensitivity
Summary
Sensors are devices that obtain a physical quantity and convert it into an analytical signal (i.e., mechanical, optical, or electrical). Azobenzene, with two phenyl rings separated by an azo (–N=N–) bond, serves as the parent molecule for a broad class of aromatic azo compounds. Azobenzenes have found applications in the field of nonlinear optics [2], surface relief gratings [3], photo switching [4], optical data storage [5], photoprobes [6], and liquid crystal alignment [7].
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