Determination of Methanol, Acetaldehyde, and Ethyl Acetate in Thousand Folds of Ethanol Sample by Headspace Gas Chromatography with Mass Spectrometry

Alcohol beverages have been widely consumed in several parts of the world. In this study, volatile organic compounds in alcoholic beverages including acetaldehyde, ethyl acetate, methanol, and higher ethanol were investigated and evaluated using a headspace gas chromatograph equipped with a mass spectrometer. This study evaluated the suitability of the chromatographic system, linearity, limit of detection, and limit of quantification, accuracy, and precision of the single and simultaneous determination of acetaldehyde, ethyl acetate, and methanol in thousand folds of ethanol. Results showed that the acetaldehyde concentration in local beer samples and local manual product liqueur samples ranged from 4.65 to 13.22 mg/L and from 5.55 to 75.96 mg/L, respectively, but in local industrial product liqueur samples, acetaldehyde was not detected. Methanol was only detected in a few local beer samples and locally manually produced liqueur samples within low concentrations. Ethyl acetate was only detected in all local beer samples, but it was not present in local industrial product liqueur samples.

Advanced GC-MS method for quality and safety control of alcoholic products

Recently developed and validated simple and reliable quantitative method employing ethanol as an internal standard (IS) for GC-MS quantification of volatile compounds in alcoholic products was applied to 36 samples including commercially available world-famous brand spirits from 18 countries and homemade distillates. The GC-MS analyses were performed simultaneously by the suggested approach and official IS method that is prescribed in the legislation of EU and USA. The independent samples t-test was employed to evaluate the statistical difference between the results of these two methods. The test revealed no difference in the results and their repeatability. The main benefits of the suggested method are the elimination of the necessity of manual IS addition and samples density measurement thus making it more economical and productive.

The perspectives of ethanol usage as an internal standard for the quantification of volatile compounds in alcoholic products by GC-MS

The potential use of ethanol as an internal standard (IS) for GC-MS analysis was studied. The paper describes the analysis of spirit drinks and other alcoholic products which consist of a mixture of water, ethanol, and volatile compounds. In the suggested method, ethanol was employed as an IS for the common procedure of volatile compounds quantification. A number of standard solutions of nine compounds with different concentrations was prepared in a water-ethanol matrix and measured with GC-MS in the SIM mode. Two possible approaches were suggested to avoid detector saturation during ethanol detection. The first one consisted in using less abundant m/z 47 as quantifiers. These ions mainly correspond to unfragmented heavy ethanol molecules containing one ¹³ C isotope. The second method consisted in reduction of the voltage of MS electron multiplier. The experiment also included the preparation and subsequent dilution of the standard solution and ethanol with water, which determined the linearity of the modified MS response relative to the ethanol content. Analysis of the obtained results revealed that volatile compounds can be successfully accurately determined with GC-MS by employing ethanol as an IS. Application of the suggested method is not limited to the reported volatile compounds and alcoholic products.

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

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.