Non-Destructive and Non-Invasive Measurement of Ethanol and Toxic Alcohol Strengths in Beverages and Spirits Using Portable Raman Spectroscopy

Abstract

The measurement of ethanol and toxic alcohol (methanol and isopropanol) strengths in beverages and spirits is crucial for health reasons but also for the identification of adulterated products. Many methodologies have been reported in the literature, based mainly on chromatographic and on spectroscopic techniques. Chromatographic techniques are laborious and time-consuming, while spectroscopic techniques are rapid and need no special sample pretreatment. All techniques were only applied to off-line or at-line manner. In the present work, Raman spectroscopy was used for fast and non-destructive measurements. A “through the container” method was developed for a non-invasive analysis, i.e., analysis without unsealing the bottles. This method, coupled with a miniature portable Raman, can serve for in-line measurements in a production line. The optimum laser focus for maximum spirit signal and minimum glass-wall signal was investigated. Calibration curves for the alcohols of interest were constructed and validated. The limits of detections were calculated and proved to be lower than the legitimate values. The influences of the liquor color and the bottle color, shape, and thickness were checked. Twenty-eight alcoholic products were studied. The concentrations found were compared against the nominal values (from the bottle labels).

Handheld Methanol Detector for Beverage Analysis: Interlaboratory Validation

“…Most importantly, this performance is comparable to gold-standard GC (e.g., reproducibility of up to 11.3% 30 ) or other analytical detection methods (e.g., portable Raman spectroscopy with repeatability of up to 10% 31 ), despite a more compact and inexpensive design (Table 1). Since the detector is handheld and battery-driven (Figure 1), methanol concentration can be monitored accurately on-site even during distillation, as demonstrated already with an early prototype of this device.…”

Handheld methanol detector for beverage analysis: interlaboratory validation

“…, portable Raman spectroscopy with repeatability of up to 10% (ref. 31)), despite a more compact and inexpensive design (Table 1). Since the detector is handheld and battery-driven (Fig.…”

Metal–Phenolic Film Coated Quartz Crystal Microbalance as a Selective Sensor for Methanol Detection in Alcoholic Beverages

“…The tremendous progress of engineering sciences allows the launch of innovative methods for methanol screening in alcoholic products [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Some of them rely on enzymatic, colorimetric and spectroscopic quantification [ 11 , 12 , 13 ], chiral nematic liquid crystals [ 14 ], handheld metal oxide microsensors [ 7 ], resistive sensors [ 15 , 16 , 17 ], metal–organic frameworks [ 18 ], immunosensors [ 19 ] or optical and microwave-based sensors [ 20 , 21 ].…”

“…The tremendous progress of engineering sciences allows the launch of innovative methods for methanol screening in alcoholic products [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Some of them rely on enzymatic, colorimetric and spectroscopic quantification [ 11 , 12 , 13 ], chiral nematic liquid crystals [ 14 ], handheld metal oxide microsensors [ 7 ], resistive sensors [ 15 , 16 , 17 ], metal–organic frameworks [ 18 ], immunosensors [ 19 ] or optical and microwave-based sensors [ 20 , 21 ]. Despite the valuable contribution of each of the mentioned strategies, a few shortcomings would impede their practical implementability.…”

“…However, the slow recovery of the detector’s baseline [ 7 ] and the color/light intensity-related sensor signal [ 14 ] limit the efficiency of these apparatuses or make them unusable by people with color blindness. Finally, the inclusion of spectroscopy measurements and different chemical or biological agents [ 11 , 12 , 13 , 19 ] implies cost ineffectiveness and applicability of the particular assays mostly to laboratory conditions.…”