A Rapid Method for Determination of Ethanol in Alcoholic Beverages Using Capillary Gas Chromatography
MEI-LING WANG1, YOUK-MENG CHOONG2*, NAN-WEI SU3 AND MIN-HSIUNG LEE3
1. Department of Food Health, Chia-Nan University of Pharmacy and Science. 60, Al-jen Road. Sect. 1,
Pau-an, Jen-teh Hsiang, Tainan Hsien 717, Taiwan, R.O.C.
2. Department of Food Science and Technology, Tajen Institute of Technology, 20, Wei-shinn Rd., Yan-puu hsiang,
Pintung Hsien 907, Taiwan, R.O.C.
3. Department of Agricultural Chemistry, National Taiwan University, 1,sec. 4, Roosevelt Road., Taipei 106, Taiwan, R.O.C
(Received: May 16, 2002; Accepted: September 30, 2002)
ABSTRACT
A simple and rapid method was developed to determine ethanol content in alcoholic beverages using megapore polar column (CPWax 58 CB, 30 m x 0.53 mm) with direct injection gas chromatography. Contrary to packed GLC method, distillation and/or stepwise dilution of samples were not necessary by the method developed in this study. Ethanol in sample was injected directly into GC for analysis, after adding suitable amount of internal standard, acetonitrile solution. Using this method, less than 8 min was required to obtain result since sample reparation, and the limit of quantitation (LOQ) was about 0.5 µg/mL. Recovery studies were performed using 0.5 mL of red wine and whisky. Each was spiked with ethanol at 50 and 100 mg, respectively. The recoveries were found in the range of 99~104% and 99~101%, respectively. The coefficients of variation were less than 3.4%. Comparisons of the AOAC method (AOAC 969.12 and 920.57) with current method showed no significant difference. These results suggested that precision of direct injection GC method was higher than that of AOAC methods. Several commercial alcohol beverages, including distilled and nondistilled spirits, were analyzed by the current method. The ethanol content of distilled and non-distilled spirit were found as: 165.2 ± 4.9~415.7 ± 17.6 and 28.2 ± 0.8~141.2 ± 4.9 mg/mL, respectively. Using this GC method, we could change the concentration in gravimetric percentage (%, w/v) to volumetric percentage (%, v/v) by the equation (%, w/v) = 0.814 (%, v/v) with linear coefficient R2, higher than 0.999.
Key words: alcoholic beverages, ethanol, direct injection gas chromatography, quantitative analyses.