Single-Laboratory Validation of a Gas Chromatographic Method of Direct Determination of Volatile Compounds in Spirit Drinks: Need for an Improved Interlaboratory Study

Abstract

Background: The quality and safety control of an alcoholic drink is mainly the establishment of its chemical content, particularly the quantity of volatile compounds. Objective: A single-laboratory validation of a gas chromatographic method of direct determination of volatile compounds in spirit drinks was conducted. The discussed method applies ethanol, the major volatile component of an alcoholic beverage, as an internal standard. Possible algorithms of method validation based on interlaboratory study were proposed and described. Methods: Seven standard solutions of the following volatile compounds were prepared gravimetrically in 40% (v/v) water–ethanol solution: acetaldehyde, methyl acetate,ethyl acetate, methanol, 2-propanol, 1-propanol, isobutanol, 1-butanol, and isoamylol. Each sample wasmeasured with the proposed method 30 times in repeatability conditions. Results: Flame ionization detector response was linearly correlated with assigned concentrations at a range of 2 to5000 mg/L of absolute alcohol (AA) with coefficients of determination (R2)more than 0.995 for all analyzed components. Repeatability (RSDr ≤ 4.5%; RSDr ≤ 2.0%), reproducibility (RSDR ≤ 5.0%; RSDR ≤ 2.0%), and trueness (relative bias ≤ 2.6%; relative bias ≤ 1.4%) were obtained for low (10–25 mg/L AA for methanol and 2–10 for othervolatiles) and high (25–5000 mg/L AA for methanol and 10–5000 for other volatiles) ranges of concentrations, correspondingly. Conclusions: The method increases the reliability of measurements and eliminates manual proceduresof internal standard addition into both calibrationstandard solutions and spirit drinks.

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

“…SS‐2 and SS‐3 as the most diluted samples exhibited slightly worse results. We already observed this phenomenon during our previous works with FID . The reason for the worse biases could consist in chemical transformations of the reactive acetaldehyde and esters or in the evaporation.…”

“…We already observed this phenomenon during our previous works with FID. 10,11 The reason for the worse biases could consist in chemical transformations of the reactive acetaldehyde and esters or in the evaporation. Nevertheless, the results are still acceptable, and the described method can be undoubtedly regarded as true.…”

“…This paper is a further development of our previously published method, which employs ethanol as an IS during direct determination of volatile compounds in ethanol‐containing products with GC‐FID . This method was first described in the publications, where it was shown that employing ethanol as an IS creates great perspectives for this method in analysis of alcoholic beverages and products of their origin.…”

“…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.…”

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

“…This paper is a logical continuation of a single-laboratory validation of the "Ethanol as Internal Standard" method [1]. The latter was already proved to be accurate and precise during single-laboratory experiment [2] and interlaboratory approbation within 3 laboratories [3].…”