This study attempted to apply a rapid method for the determination of methanol,
acetaldehyde and ethyl acetate in wine spirits, brandies and grape marc spirits, using
Fourier Transform Infrared – Attenuated Total Reflectance (ATR) Spectroscopy

Anjos, O.

Caldeira, I.

Repositório Científico do Instituto Politécnico de Castelo Branco

APPLICATION OF FTIR-ATR SPECTROSCOPY FOR THE QUALITY CONTROL OF 
WINE SPIRITS, BRANDIES AND GRAPE MARC SPIRITS  
 
Ofélia Anjos1,Ilda Caldeira2  
 
1
 Polytechnique Instituto of Castelo Branco (IPCB), Castelo Branco, Portugal, 
ofelia@ipcb.pt 
2Instituto Nacional de Investigação Agrária e Veterinária I.P (INIAV), Dois Portos, 
Portugal, ilda.caldeira@iniav.pt 
 
This study attempted to apply a rapid method for the determination of methanol, 
acetaldehyde and ethyl acetate in wine spirits, brandies and grape marc spirits, using 
Fourier Transform Infrared – Attenuated Total Reflectance (ATR) Spectroscopy. 
The current quality control of the brandies includes the use of several analytical methods 
that are time consuming and sometimes they employ very expensive chemicals. In order 
to solve this problem it is possible use some different analytical techniques, namely the 
Fourier transform infrared (FTIR) spectroscopy with ATR. 
76 samples of wine spirits, brandies and grape marc spirits were analyzed by CG-FID 
according to the method validated by Luis et al (2011). GC-FID analysis was carried out 
using an Focus GC gas chromatograph (Thermo Scientific, USA) equipped with a flame 
ionization detector-FID (250ºC) and a fused silica capillary column of polyethylene glycol 
(DB-WAX, JW Scientific, Folsom, CA, USA), 60 m length, 0.32 mm i.d., 0.25 µm film 
thickness with the conditions described by Luis et al (2011). 
Duplicate spectra per sample were obtained with 32 scans per spectrum at a spectral 
resolution of 4 cm-1. The calibration model were developed by PLS-R using the Bruker 
OPUS Quant software by comparing the analytical results of methanol, acetaldehyde and 
ethyl acetate with the FTIR–ATR spectra, first in all spectral region (4000 cm-1 to 400-1) 
and after by selection of the better corresponding spectral zone and the better 
preprocessing method. The model was calculated to a maximum rank of 5 and the results 
of cross-validation were evaluated by the coefficient of determination (r2), root mean 
square error of cross-validation (RMSECV) mean square error of prediction (RMSEP) and 
residual prediction deviation (RPD). 
The average ATR-FTIR spectrum of the all wine spirits, brandies and grape marc spirits 
show representative peaks at 2968 cm-1 and 2906 cm-1 which is due to C–H stretch. 
Absorption peak at 1632 cm-1 is associated to –OH deformation and C–OH peak at 1452 
cm-1. The peaks, present at 1084 cm-1 and 1045 cm-1, are attributed to the C–O stretch. 
Since the major components absorption analyzed the partial least squares regression was 
done in the selected region of 3000 to 2800 cm-1 and 2000 to 1000 cm-1 and the selected 
models were first derivative + multiplicative scatter correction and second derivative. 
The calibration statistic obtained for methanol, acetaldehyde and ethyl acetate were 
obtained by PLS-R modelling with high coefficients of determination of the cross-validation 
(R2= 0.9659 to R2=0, 7957; RPD=6,9 to RPD=2,5). The external validation was made also 
with promising results. The values of RMSECV and RMSEP was similar of the obtained 
for the laboratorial analytical methods develop with GC-FID. 
The results show that FTIR-ATR could be a good technique to screening the methanol, 
acetaldehyde and ethyl acetate concentration in brandies sample. The more robust 
calibration model was found for methanol concentration. 
 
Keywords: methanol, acetaldehyde, ethyl acetate; brandies, FTIR-ATR spectroscopy 
 
Luís A, Mota D, Anjos O, Caldeira I, 2011. Single-Laboratory Validation of Determination of 
Acetaldehyde, Ethyl Acetate, Methanol and Fusel Alcohols in Wine Spirits, Brandies and Grape 
Marc Spirits Using GC-FID. Ciência e técnica vitivinícola/journal of viticulture and enology. 26(2): 
69-76   


English

Application of FTIR-ATR Spectroscopy for the quality control of wine spirits, brandies and grape marc spirits

Caldeira, Ilda

Repositório do Instituto Politécnico de Castelo Branco

APPLICATION OF FTIR-ATR SPECTROSCOPY FOR THE QUALITY CONTROL OF WINE SPIRITS, BRANDIES AND GRAPE MARC SPIRITS   Ofélia Anjos1,Ilda Caldeira2   1 Polytechnique Instituto of Castelo Branco (IPCB), Castelo Branco, Portugal, ofelia@ipcb.pt 2Instituto Nacional de Investigação Agrária e Veterinária I.P (INIAV), Dois Portos, Portugal, ilda.caldeira@iniav.pt  This study attempted to apply a rapid method for the determination of methanol, acetaldehyde and ethyl acetate in wine spirits, brandies and grape marc spirits, using Fourier Transform Infrared – Attenuated Total Reflectance (ATR) Spectroscopy. The current quality control of the brandies includes the use of several analytical methods that are time consuming and sometimes they employ very expensive chemicals. In order to solve this problem it is possible use some different analytical techniques, namely the Fourier transform infrared (FTIR) spectroscopy with ATR. 76 samples of wine spirits, brandies and grape marc spirits were analyzed by CG-FID according to the method validated by Luis et al (2011). GC-FID analysis was carried out using an Focus GC gas chromatograph (Thermo Scientific, USA) equipped with a flame ionization detector-FID (250ºC) and a fused silica capillary column of polyethylene glycol (DB-WAX, JW Scientific, Folsom, CA, USA), 60 m length, 0.32 mm i.d., 0.25 µm film thickness with the conditions described by Luis et al (2011). Duplicate spectra per sample were obtained with 32 scans per spectrum at a spectral resolution of 4 cm-1. The calibration model were developed by PLS-R using the Bruker OPUS Quant software by comparing the analytical results of methanol, acetaldehyde and ethyl acetate with the FTIR–ATR spectra, first in all spectral region (4000 cm-1 to 400-1) and after by selection of the better corresponding spectral zone and the better preprocessing method. The model was calculated to a maximum rank of 5 and the results of cross-validation were evaluated by the coefficient of determination (r2), root mean square error of cross-validation (RMSECV) mean square error of prediction (RMSEP) and residual prediction deviation (RPD). The average ATR-FTIR spectrum of the all wine spirits, brandies and grape marc spirits show representative peaks at 2968 cm-1 and 2906 cm-1 which is due to C–H stretch. Absorption peak at 1632 cm-1 is associated to –OH deformation and C–OH peak at 1452 cm-1. The peaks, present at 1084 cm-1 and 1045 cm-1, are attributed to the C–O stretch. Since the major components absorption analyzed the partial least squares regression was done in the selected region of 3000 to 2800 cm-1 and 2000 to 1000 cm-1 and the selected models were first derivative + multiplicative scatter correction and second derivative. The calibration statistic obtained for methanol, acetaldehyde and ethyl acetate were obtained by PLS-R modelling with high coefficients of determination of the cross-validation (R2= 0.9659 to R2=0, 7957; RPD=6,9 to RPD=2,5). The external validation was made also with promising results. The values of RMSECV and RMSEP was similar of the obtained for the laboratorial analytical methods develop with GC-FID. The results show that FTIR-ATR could be a good technique to screening the methanol, acetaldehyde and ethyl acetate concentration in brandies sample. The more robust calibration model was found for methanol concentration.  Keywords: methanol, acetaldehyde, ethyl acetate; brandies, FTIR-ATR spectroscopy  Luís A, Mota D, Anjos O, Caldeira I, 2011. Single-Laboratory Validation of Determination of Acetaldehyde, Ethyl Acetate, Methanol and Fusel Alcohols in Wine Spirits, Brandies and Grape Marc Spirits Using GC-FID. Ciência e técnica vitivinícola/journal of viticulture and enology. 26(2): 69-76   

https://repositorio.ipcb.pt/bitstream/10400.11/1966/1/Anjos%20%20Caldeira%202013.pdf

Application of FTIR-ATR Spectroscopy for the quality control of wine spirits, brandies and grape marc spirits

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