Perspectives on using ethanol as an internal standard for the quantification of volatile compounds in alcoholic products by headspace SPME–GC/FID without sample preparation

Abstract

For the first time, the beneficial “Ethanol as Internal Standard (IS)” method developed for the analysis of alcoholic products was tested in headspace mode of solid-phase microextraction gas chromatography with flame ionization detector (SPME-GC/FID) and compared with the traditional IS method. The extraction and separation conditions were optimized for the analysis of 10 volatile congeners prescribed in European legislation: acetaldehyde, methyl acetate, ethyl acetate, methanol, butan-2-ol, propan-1-ol, 2-methylpropan-1-ol (isobutanol), butan-1-ol, 1,1-diethoxyethane (acetal), and 3-methylbutan-1-ol (isoamylol). To evaluate the accuracy of the compared methods, three real alcoholic product samples with ethanol content of 20%, 40%, and 80% v/v were spiked with gravimetrically prepared standard solutions to calculate recoveries. The obtained data indicates that the suggested method can be employed as a robust and accurate tool for SPME analysis of alcoholic products with low ethanol content, such as wines. It was also observed that an increase in ethanol content in the matrix affects the accuracy of the “Ethanol as IS” method, potentially due to non-linearity of analyte extraction. However, in the case of wine sample, the “Ethanol as IS” method showed significantly better results compared to the traditional approach. The precision of the suggested method, evaluated using relative standard deviations (RSD) of obtained concentrations was found to be comparable to that of the traditional method. Graphical abstract: [Figure not available: see fulltext.].