Surface-Enhance Raman Spectroscopy Detection of Thiabendazole in Frozen Food Products: The Case of Blueberries and Their Extracts

Abstract

To improve the control and detection methods of thiabendazole (TBZ), a fungicide and parasiticide often used in food products, we investigated the performance of the SERS technique applied to frozen blueberry fruits available on the market. TBZ-treated fruit extracts provided a multiplexed SERS feature, where the SERS bands of TBZ could be distinctly recorded among the characteristic anthocyanidins from blueberries. Quantitative SERS of TBZ in a concentration range from 20 µM to 0.2 µM has been achieved in solutions. However, quantitative multiplexed SERS is challenging due to the gradually increasing spectral background of polyphenols from extracts, which covers the TBZ signal with increasing concentration. The strategy proposed here was to employ food bentonite to filter a substantial amount of flavonoids to allow a higher SERS signal-to-background recording and TBZ recognition. Using bentonite, the LOD for SERS analysis of blueberry extracts provided a detection limit of 0.09 µM. From the relative intensity of the specific SERS bands as a function of concentration, we estimated the detection capability of TBZ to be 0.0001 mg/kg in blueberry extracts, which is two orders of magnitude lower than the maximum allowed by current regulations.

Identification of the Beverage Sotol Adulterated with Ethylene Glycol Using UV-Vis Spectroscopy and Artificial Neural Networks

“…The main advantage of this analytic technique is its high sensitivity and resolution, which depend on the type of detector incorporated into the gas chromatograph equipment, allowing in some cases the identification of substances with concentrations as low as 1 × 10 −12 g. However, there are also other non-destructive techniques that could be considered for the same purpose [11]. These techniques include (a) infrared spectroscopy (analysis of the interaction of infrared light with molecules) [12], (b) Raman spectroscopy (analysis of the inelastic scattering of photons by matter after laser excitation) [13], (c) fluorescence spectroscopy (analysis of the light emissions which take place after the excitation of the electrons in a material) [14], (d) an electronic tongue (this is a multisensor system based on various sensor arrays with limited selectivity and allowing for advanced mathematical data analysis) [15], (e) nuclear magnetic resonance spectroscopy (analysis of the molecular structure of a material by observing and measuring the interaction of nuclear spins when placed in a powerful magnetic field) [16], (f) an electronic nose (captures the fingerprints of volatile organic compounds present in an alcoholic beverage sample using an array of semi-selective sensors) [17], (g) a colorimetric sensor array (produces a chemical interaction between the active center and analyte, which results in chemo-responsive changes in color) [18], (h) a combination of sensors (involves a data fusion approach with various sensors to acquire an optimal response) [19] and UV-Vis spectroscopy [20], which is the selected analytical technique carried out in the present work.…”