Page 22 - Application Notebook - Solution for Food Development

Application Food and Beverages / GC-2010

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A Comparison Study of Different Capillary
Columns for Analysis of Alcohol Congeners
AD-0124Ph in Alcoholic Beverages

 Introduction

Alcoholic beverages contain a wide range of volatile components, primary of which are alcohols and short-chain aldehydes.
To ensure consistency in the quality and flavour of the finished products, distilleries and alcoholic beverage manufacturers
monitor the presence and relative levels of these compounds. Gas chromatography (GC) is usually the preferred technique
in analysing these compounds. Fifteen components as listed in Table 1 are monitored by ethanol distilleries and alcoholic
beverage manufacturers in the Philippines. The Association of Official Analytical Chemists (AOAC) and the Commission of
the European communities have published methods for the analysis of fusel oils, methanol, ethanol, aldehydes and higher
alcohols by GC in spirit drinks and distilled liquors [1~3]. The conventional GC methods for alcoholic beverage analysis are
based on packed column, because glass tubing material for the packed column is inert, rarely causes tailing or
decomposition of samples and minimizes interaction between the target component and the walls of the tube. However,
packed glass columns are prone to breakage and may cause adsorption of the more reactive components present in
alcoholic beverages. Most modern GC instruments are configured for capillary column use for the inherent advantages over
packed columns such as more efficient separation, narrower peaks and consequently, lower limits of detection. This
motivates an investigation into the potential of using capillary column in separating alcohols, aldehydes and other congeners
typically found in alcoholic beverages. In this study, four capillary columns are selected and their performance are compared
with packed column in terms of separation of all key components found in alcoholic beverages.

 Experimental Table 1: Alcohols, aldehydes and other compounds
monitored in local alcoholic beverages
Methods and Standard Preparation
Peak ID Component
Standard solutions containing varying amounts of alcohol 1 Acetaldehyde
congeners were prepared in accordance with in-house 2 Acetone
procedures. All solutions were diluted to volume with 40%
(v/v) ethanol in water. The linear velocity of He carrier gas 3 Ethyl acetate
of GC for each column was optimized to achieve the best 4 Acetal
separation. The injection and FID detection conditions 5 Methanol
were set according to the column supplier’s 6 Isopropanol
recommendation or in-house procedures. Four columns 7 N-propyl acetate
from different suppliers were employed and compared in 8 N-propanol
9
this work. The columns were chosen based on availability 10 N-butyl acetate
Isobutanol
and suitability of each column for alcohol congeners 11 Isoamyl acetate
separation as published in literature [4,5].
12 N-butanol
13 Isoamyl alcohol
Instrument, Columns and Analytical Conditions
13a Active amyl alcohol
GC : GC-2010 with FID 14 1-pentanol
Auto injector : AOC-5000 15 Furfural
Columns : Capillary columns are used as below:
 Results and Discussion
(1) CP-Wax 57 CB, 50 m L. x 0.25 mm I.D. x 0.20 µm δf (see
Table 3) The most popular packed column employed for alcohol
(2) Supelcowax 10, 60 m L. x 0.53 mm I.D. x 1.0 µm δf (see congeners analysis is the Carbopack B packed with 5% or
Table 4) 6.6% Carbowax 20M [6]. This column provides excellent
(3) SPB-20, 40 m L. x 0.25 mm I.D. x 1.0 µm δf (Table 5) peak shape for methanol, resolves methanol from ethanol
(4) Supel-Q PLOT, 30 m L. x 0.32 mm I.D. (Table 6) completely and separates two predominant fusel oils
namely active amyl alcohol and isoamyl alcohol (see
Figure 1 and Table 2).