Evaluation of headspace solid-phase microextraction for the analysis of volatile carbonyl compounds in spirits and alcoholic beverages

A method was developed for the determination of C1-C6 carbonyl compounds in alcoholic solutions using pentafluorobenzoxymation followed by headspace sampling solid-phase microextraction and subsequent analysis by GC with electron-capture detection. Experimental conditions-alcohol content, exposure time, temperature and sample agitation were optimised. In this method, a spirit or distilled alcoholic beverage is first adjusted to 20% (v/v) alcohol. Detection limits for particular aldehydes and ketone varied from 0.05 to 0.5 microg/l and relative standard deviation was between 2.3 and 20%. Generally, the method showed good linearity for the tested concentration range 8 microg/l-0.32 mg/l with regression coefficients ranging between 0.9434 and 0.9983. The method was applied to the analysis of real alcoholic beverages (vodkas).     

A fluorescent chemical sensor for ethanol determination in alcoholic beverages

A sensor for ethanol is described that is based on the fluorescent probe 5,10,15,20-tetraphenyl porphyrin (TPP). Response is based on the quenching of the fluorescence of TPP by ethanol as a result of electrostatic attraction. The sensor linearly responds to ethanol in the concentration range from 1 to 75 vol.% and was applied to the determination of ethanol in various kinds of wines and whisky.     

Development of a dynamic headspace solid-phase microextraction procedure coupled to GC-qMSD for evaluation the chemical profile in alcoholic beverages

In the present study, a simple and sensitive methodology based on dynamic headspace solid-phase microextraction (HS-SPME) followed by thermal desorption gas chromatography with quadrupole mass detection (GC-qMSD), was developed and optimized for the determination of volatile (VOCs) and semi-volatile (SVOCs) compounds from different alcoholic beverages: wine, beer and whisky. Key experimental factors influencing the equilibrium of the VOCs and SVOCs between the sample and the SPME fibre, as the type of fibre coating, extraction time and temperature, sample stirring and ionic strength, were optimized. The performance of five commercially available SPME fibres was evaluated and compared, namely polydimethylsiloxane (PDMS, 100 μm); polyacrylate (PA, 85 μm); polydimethylsiloxane/divinylbenzene (PDMS/DVB, 65 μm); carboxen™/polydimethylsiloxane (CAR/PDMS, 75 μm) and the divinylbenzene/carboxen on polydimethylsiloxane (DVB/CAR/PDMS, 50/30 μm) (StableFlex).An objective comparison among different alcoholic beverages has been established in terms of qualitative and semi-quantitative differences on volatile and semi-volatile compounds. These compounds belong to several chemical families, including higher alcohols, ethyl esters, fatty acids, higher alcohol acetates, isoamyl esters, carbonyl compounds, furanic compounds, terpenoids, C13-norisoprenoids and volatile phenols. The optimized extraction conditions and GC-qMSD, lead to the successful identification of 44 compounds in white wines, 64 in beers and 104 in whiskys. Some of these compounds were found in all of the examined beverage samples.The main components of the HS-SPME found in white wines were ethyl octanoate (46.9%), ethyl decanoate (30.3%), ethyl 9-decenoate (10.7%), ethyl hexanoate (3.1%), and isoamyl octanoate (2.7%). As for beers, the major compounds were isoamyl alcohol (11.5%), ethyl octanoate (9.1%), isoamyl acetate (8.2%), 2-ethyl-1-hexanol (5.9%), and octanoic acid (5.5%). Ethyl decanoate (58.0%), ethyl octanoate (15.1%), ethyl dodecanoate (13.9%) followed by 3-methyl-1-butanol (1.8%) and isoamyl acetate (1.4%) were found to be the major VOCs in whisky samples.     

Chromatographic and electrophoretic approaches for the analysis of protein quality of soy beverages

Furosine, generated by acid hydrolysis of fructosyllysine, an early Maillard reaction product, is a highly valuable indicator of food quality and, more specifically, of food protein quality. Ion pair RP-HPLC and CZE techniques were employed to determine furosine content in beverages based on soymilk (n = 15) and cow's milk supplemented with soy isoflavones (n = 1). The levels of furosine found in the samples ranged from 25.55 +/- 0.18 to 170.72 +/- 10.4 mg/100 g of protein by HPLC and from 28.67 +/- 1.84 to 161.25 +/- 5.78 mg/100 g of protein by CZE. Results obtained by both analytical techniques do not differ significantly (p > 0.05), confirming their feasibility for furosine analysis in soy-based products.     

A comparative study of the ability of different solvents and adsorbents to extract aroma compounds from alcoholic beverages

Seven liquid solvent systems--dichloromethane, dichloromethane-pentane (1:1), freon 113, diethyl ether-pentane (1:1 and 1:9), ethyl acetate-pentane (with and without an additional salting-out effect) (1:3 and 1:20), and seven solid-phase extraction (SPE) systems (Amberlite XAD-2, 4, 7, and 16; Porapak Q; C8; and C18)--are comparatively studied. The distribution coefficients between the extraction system and a hydroalcoholic solution (12% v/v in ethanol, pH = 3.2) of 14 selected volatile compounds belonging to different chemical families and polarities are calculated. The results are processed by factor analysis and cluster analysis, and the following conclusions are reached. First, the efficiency of extraction decreases in this order: polymeric sorbents > silica-based sorbents > liquid-liquid systems with salting-out effect approximately dichloromethane > rest of liquid solvents. Second, the addition of salt mainly increases the recovery of compounds with Lewis acid properties. Third, the efficiency of the extraction of a liquid solvent depends not only on its polarity but also on its solubility in water. Fourth, in regards to the selectivity of the SPE systems, Porapak Q is the best to extract nonpolar compounds, Amberlite XAD 4 and 16 provide the least selective extraction profiles, and C8 and C18 have a special ability to extract compounds with a Br?nstedt-Lowry character. Results indicate that in all cases liquid solvents can be replaced satisfactorily by SPE systems.     

A sensitive method for the determination of nitroamines in alcoholic beverages

Summary Nitrosamines in alcoholic beverages and malted barley were analysed by adsorption from the gas phase onto a porous polymer trap of Chromosorb 104 and subsequent desorption of the trapped compounds directly to a gas chromatograph fitted with glass capillary column and alkali-FID. The detection limit for NDMA was 0.05 g/l in beer samples and 0.3 g/kg in malted barley.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Characterisation of aroma volatiles of indigenous alcoholic beverages: burukutu and pito

Pito and burukutu are indigenous alcoholic beverages in Nigeria, and are fermentation products of Sorghum bicolor and Sorghum vulgare. The production is similar to that of beer, which involves steeping, malting, mashing and fermenting. A total of 30 volatile organic compounds were identified by gas chromatography. These compounds can be broadly grouped into alkanols, phenols, acids, esters, ketones and aldehydes. Although few acids are present, they are dominant (30.887% and 27.669%) and followed by esters (26.467% and 27.442%) in pito and burukutu, respectively. Alkanols constitute the next dominant group after acids and esters; however, ethanol was not identified as a constituent. The health and social implication of the constituents are explained.     

Chromatographic determination of phthalic acid esters as an indicator of adulterated cognacs and cognac spirits

Based on the study performed, a conclusion was drawn that a system of procedures should be introduced into the practice of arbitration laboratories in order to identify the authenticity of cognacs and cognac spirits. These procedures were exemplified in the identification of diethyl phthalate in cognacs. Factors responsible for the falsely positive detection of diethyl phthalate in cognacs and cognac spirits were revealed. A substance that has a retention time equal to that of diethyl phthalate was identified as monoethyl succinate. As an example, recommendations were given for revealing adulterated cognac samples upon the detection of phthalic acid esters in them (including diethyl phthalate, which is a marker of denaturation). Sources of the contamination of test samples with diethyl phthalate were identified; an algorithm was developed for distinguishing between diethyl phthalate as an impurity component and diethyl phthalate added to an alcohol as a denaturation marker.     

HPLC/UV-spectrometric and electrochemical detection of lignin-decomposition products in alcoholic beverages

Summary The determination of compounds responsible for the flavour of alcoholic beverages, which were separated by HPLC-RP-chromatography, was performed with a combination of UV-diode-array and electrochemical detection. The recording and comparing of diode-array spectra on the rising and descending flanks of each peak was very suitable for identifying peak impurities. The selectivity of the detection depends strongly on the detection wavelength, detection potential and electrode material. For higher sensitivity the electrochemical detection is favoured. The lowest detection limit is 30 pg (absolute) for syringic acid.     

Investigation into the structural composition of hydroalcoholic solutions as basis for the development of multiple suppression pulse sequences for NMR measurement of alcoholic beverages

An eight‐fold suppression pulse sequence was recently developed to improve sensitivity in ¹H NMR measurements of alcoholic beverages [Magn. Res. Chem. 2011 (49): 734–739]. To ensure that only one combined hydroxyl peak from water and ethanol appears in the spectrum, adjustment to a certain range of ethanol concentrations was required. To explain this observation, the structure of water–ethanol solutions was studied. Hydroalcoholic solutions showed extreme behavior at 25% vol, 46% vol, and 83% vol ethanol according to ¹H NMR experiments. Near‐infrared spectroscopy confirmed the occurrence of four significant compounds (‘individual’ ethanol and water structures as well as two water–ethanol complexes of defined composition – 1 : 1 and 1 : 3). The successful multiple suppression can be achieved for every kind of alcoholic beverage with different alcoholic strengths, when the final ethanol concentration is adjusted to a range between 25% vol and 46% vol (e.g. using dilution or pure ethanol addition). In this optimum region, an individual ethanol peak was not detected, because the ‘individual’ water structure and the 1 : 1 ethanol–water complex predominate. The nature of molecular association in ethanol–water solutions is essential to elucidate NMR method development for measurement of alcoholic beverages. The presented approach can be used to optimize other NMR suppression protocols for binary water–organic solvent mixtures, where hydrogen bonding plays a dominant role. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of ethyl carbamate in alcoholic beverages: an interlaboratory study to compare HPLC-FLD with GC-MS methods

An international interlaboratory study on the determination of ethyl carbamate in alcoholic beverages by a new HPLC-FLD and by the official GC-MS methods is presented. The aim of this study was to improve the knowledge about precision and accuracy parameters of the new method and to compare the performance of both HPLC and GC methods. Five different samples representing table wines, fortified wines (red and white), distilled spirits, and wine spirits were available for analysis by each participant. Despite the low number of participants (6), the results obtained by the laboratories using the HPLC-FLD method are comparable to those obtained by GC-MS methods. The present study emphasizes the possibility to use, as routine, a much simpler analytical method than the current reference method by GC-MS for ethyl carbamate determination in alcoholic beverages.