Interlaboratory study of ethanol usage as an internal standard in direct determination of volatile compounds in alcoholic products

S Charapitsa,A Korban,L Sobolenko,I Shestakovich,J Vávra,T Cabaroglu,R Čabala,S Leschev,V Egorov,S Ondroušek,M Yilmaztekin,S Sytova,A Tolstouhova,R Busarova,M Zakharov,P Roca

doi:10.1051/bioconf/20191502030

Abstract

A collaborative interlaboratory study on the method of direct quantitation of volatile compounds in spirit drinks and alcoholic products was conducted. The discussed method applies ethanol, the major volatile component of an alcoholic product, as an internal standard. In this study 9 laboratories from 4 different countries were supplied with standard solutions for gas chromatographic measurements. Five aqueous ethanol 40% (v/v) standard solutions containing target compounds in concentrations ranging from 10 mg/L to 400 mg/L of absolute alcohol were prepared and sent to the participants for quantification of acetaldehyde, methyl acetate, ethyl acetate, methanol, 2-propanol, 1-propanol, 2-methyl-1-propanol, 1-butanol and 3-methyl-1-butanol. The interlaboratory study was evaluated according to the ISO 5725 standards and the Eurachem guide. The within-laboratory precision varied between 0.4% and 7.5% for all samples and compounds, showing a sufficiently high repeatability of the method. The between-laboratory precision was found to vary within a satisfactory range of 0.5% ÷ 10.0%. Precision of the method was well within the range predicted by the Horwitz equation for all analytes. The analysis of trueness showed that the bias of the method is insignificant at the significance level α = 5%. The determined concentrations of the analytes compared well to the gravimetrical values thus showing very satisfactory accuracy of the method. The results of the interlaboratory study confirmed that “Ethanol as Internal Standard” method is robust and reliable and can be used as a standard reference method for analysing volatile compounds in water-ethanol samples. The possibilities of method validation according to the previously obtained experimental data were shown.

Highlights

This paper is a logical continuation of a single-laboratory validation of the “Ethanol as Internal Standard” method [1]
The discussed method is applied for gas chromatographic (GC) direct quantification of volatile compounds in spirit drinks and other ethanol containing samples
Further we will use a more common ABV abbreviation during the description of analysed samples. The absence of these manual procedures leads to the fact that “Ethanol as Internal Standard (IS)” method is simpler, cheaper, more rapid and robust in comparison with currently used methods. These benefits originate from the fact that according to the abovementioned regulatory documents volatile compounds concentrations must be expressed in mass per litre of absolute alcohol units

Summary

Introduction

This paper is a logical continuation of a single-laboratory validation of the “Ethanol as Internal Standard” method [1]. The major difference between cited methods and the proposed one consists in employing ethanol, the main volatile organic component, as an IS. This uncommon approach allows to skip the necessity of IS compound addition into both calibration and test samples and the necessity of sample density and strength establishment. The absence of these manual procedures leads to the fact that “Ethanol as IS” method is simpler, cheaper, more rapid and robust in comparison with currently used methods These benefits originate from the fact that according to the abovementioned regulatory documents volatile compounds concentrations must be expressed in mass per litre of absolute alcohol units (mg/L AA, g/L AA etc.).

Methods

Results

Conclusion