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

¹ Institute for Nuclear Problems of Belarusian State University, 220030, Bobruyskaya Str., 11, Minsk, Belarus
² Chemistry Faculty, Department of Analytical Chemistry, Belarusian State University, Leningradskaya Str., 14, 220050, Minsk, Belarus
³ All-Russian Scientific Research Institute of the Brewing, Non-Alcoholic and Wine Industry – Branch of the V.M. Gorbatov Federal Scientific Center of Food Systems of RAS, 119021, Rossolimo Str., 17, Moscow, Russia
⁴ Charles University, Faculty of Science, Department of Analytical Chemistry, Hlavova Str., 2030/8, 128 40, Prague 2, Czech Republic
⁵ JS “Mosazervinzavod”, 115088, Yuzhnoportovaya Str., 30, Moscow, Russia
⁶ Republican Centre for Hygiene, Epidemiology and Public Health, 220099, Kazintsa Str., 50, Minsk, Belarus
⁷ General Directorate of Customs, Customs Technical Laboratory, Budějovická Str., 7, 140 96, Prague 4, Czech Republic
⁸ Inonu University, Faculty of Engineering, Department of Food Engineering, 44280, Malatya, Turkey
⁹ Cukurova University, Faculty of Agriculture, Department of Food Engineering, 01330, Adana, Turkey

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.