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

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 was measured 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 to 5000 mg/L of absolute alcohol (AA) with coefficients of determination (R-2) more than 0.995 for all analyzed components. Repeatability (RSDr <= 4.5%; RSDr <= 2.0%), reproducibility (RSDr <= 5.0%; RSDr 5 2.0%), and trueness (relative bias <= 2.6%; relative bias 51.4%) were obtained for low (10-25 mg/L AA for methanol and 2-10 for other volatiles) 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 procedures of internal standard addition into both calibration standard solutions and spirit drinks.