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

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.

Variability of internal standard method calibration factors estimated with a multifactorial Taguchi experiment in the analysis of alcoholic products by gas chromatography with flame ionization detection

“…where C st i and C st IS are concentrations of the i-th analyzed compound and IS, correspondingly; A st i and A st IS are the detector responses for the i-th analyzed compound and IS, correspondingly. In the case of using ethanol as an IS compound, its concentration in each and every prepared standard solution equals 789300 mg/L AA [13][14][15].…”

The Method for Direct Gas Chromatographic Determination of Acetaldehyde, Methanol, and Other Volatiles Using Ethanol as a Reference Substance: Application for a Wide Range of Alcoholic Beverages

“…• the developed method was validated in one laboratory (single-laboratory study) (Charapitsa et al 2019b); • the developed method was investigated in international interlaboratory study (in 9 laboratories from 4 countries) (Charapitsa et al 2019a); • the influence of matrix effects to the results, obtained for developed method, was estimated for 13 ethanol-containing matrices (absence of matrix effect was proved) (Charapitsa et al 2021). • the perspectives of ethanol usage as a reference substance for the quantification of volatile compounds in alcoholic products by GC-MS-developed method were investigated (Korban et al 2019(Korban et al , 2021.…”

“…The data, obtained in abovementioned single-laboratory (Charapitsa et al 2019b) and interlaboratory (Charapitsa et al 2019a) studies (the metrological characteristics of the method, such as repeatability, intermediate precision, reproducibility, trueness, uncertainty), was applicable to control the acceptability and trueness (according to the ISO 5725-6: 1994) of results of analysis of only model water-ethanol solutions. The results of estimation of metrological characteristics (relative standard deviation (RSD) of repeatability-RSD r ; RSD of intermediate precision-RSD I(TO) ; relative expanded uncertainty P = 95%, with coverage factor k = 2-U; limit of detection-LOD; and limit of quantitation-LOQ) of the developed method, obtained in singlelaboratory study (Charapitsa et al 2019b) for concentration range from 2.10 to 5000 mg (L AA) −1 , are presented in Table 1.…”

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

“…When using FID, a large area of ethanol signal did not cause any inconveniences in the calculations. Although its peak area was more than 100 000 times greater than that of the analysed volatiles, ethanol was successfully employed in direct quantification . A specific procedure should be employed for the MS.…”

“…Although its peak area was more than 100 000 times greater than that of the analysed volatiles, ethanol was successfully employed in direct quantification. [9][10][11][12][13][14] A specific procedure should be employed for the MS. Here, we had to tune the ethanol peak area within the linear dynamic range of the MS detector.…”