Gas Chromatographic Determination of Ethanol in Wine: Collaborative Study

After a survey of laboratories using gas chromatographic procedures for wine alcohol analysis, 3 sets of columns and operating parameters were chosen on the basis of comparative reproducibility evaluations run in this laboratory. Fourteen collaborators participated in the study and were given their choice of any one of the 3 columns: (1) 1.8 m × 2 mm id glass, packed with 80-100 mesh Poropak QS; (2) 1.8 m × 2 mm id glass, packed with 0.2% Carbowax 1500 on 80-100 mesh Carbopack C; (3) 1.8 m × 6.35 mm copper, packed with 3% Carbowax 600 on 40-60 mesh Chromosorb T. Standards and samples were diluted 1:100 with 0.1% v/v n-butanol in water before analysis. Eight samples containing from 7.3 to 23.6% ethanol (v/v) were submitted as randomly coded duplicates along with a calibration standard and a practice sample. Two injections each of the diluted duplicates were made. On the basis of the reported results, 2 laboratories were rejected as outliers. The results of the remaining 12 collaborators showed an average reproducibility of 0.142 and a repeatability of 0.036. The method has been adopted official first action.