The distilled spirits were obtained from small dis- tillery in Slovakia. A volume of 100 ml of diluted spirit sample (10times) plus 20 g NaCl was transferred into a 500 ml volumetric flask and the flask was vigorously shaken for 2 min at ambient temperature. Immediately af- ter shaking, an appropriate volume of headspace (10 ml) was taken through the microcolumn using a glass syringe with a glass plunger lauer (Poulten and Graf, Wertheim, Germany). The distance between the microcolumn and the surface of the liquid was about 1 cm. The loaded micro- column, with sorbed volatile compounds, was transferred into the GC inlet at the pressure of 20 kPa of carrier gas and the desorbed compounds were analysed.
Analyses were carried out on Shimadzu GC model 14A, modernized by Hrivňák in 2010. The outlet of the microcolumn afforded a tight connection with the capillary column. The fused silica capillary column DB-FFAP with parameters 60 m * 0,25 mm * 0,25 m (Supelco, Bellefon- te, Pennsylvania, USA) was used. The GC inlet tempera- ture was 230 °C and the detector temperature was 250 °C. The initial column temperature was maintained at 40 °C. Thermal desorption was performed at a pressure of 20 kPa min–1, then the pressure was increased to 60 kPa
and the column temperature was programmed at a rate of 3 °C min–1 up to 220 °C and maintained at 220 °C for
5 min. Helium was used as a carrier gas. Analysis of each spirits sample was repeated twice.
A computer program Class-VP 7.2 SP1 (Shimadzu, Columbia, Maryland, USA) was used for data acquisition. Chemicals
Methyl acetate, ethyl acetate, propanol, butanol, pen- tanol, hexanol, heptanol, octanol, 2-butanol, isobutanol, butyl acetate, amyl acetate, hexyl acetate, ethyl isovalerate, ethyl butyrate, isoamyl acetate were used like inside standards for qualitative interpretation and for created cali- bration rate.
Results and discussion
Aromatic compounds were analyzed by headspace solid phase microcolumn extraction gas chromatography. There were analyzed alcohols – propanol, butanol, 2-bu- tanol, isobutanol, hexanol, heptanol and octanol, esters – methyl acetate, ethyl acetate, propyl acetate, isobutyl ace- tate, ethyl butyrate, ethyl isovalerate, butyl acetate, iso- amyl acetate, amyl acetate and hexyl acetate. Fig. 1 shows a chromatogram of cherry spirit with aroma compounds which were analysed according to previous conditions.
ANALYSIS OF SPIRIT AROMA COMPOUNDS BY HEAD-SPACE SOLID-PHASE
MICROCOLUMN EXTRACTION
The identification of peaks was performed by analysing model mixtures which contain pure compounds.
The static headspace was preferred, because in a rela- tively short time the highest possible concentration of ana- lytes in the gas phase can be obtained. The limiting factor of the amount of an adsorbent in the microcolumn is the breakthrough volume of analytes and the aspirated volume of headspace. 2,5 mg of Tenax TA in the microcolumn was used and worked beyond the breakthrough volume of ethanol. In such condition, the compounds obtaining up to 3–4 carbon atoms are beyond their breakthrough volumes, therefore their peaks are lower and the ethanol peak narrower, but still can be used for analysis4.
Advantage of the method is the low dead volume of the microcolumn. The distance between the adsorbent and the head of a column in the inlet is only 10 mm (0.25 mm I.D.). This means that the microcolumn is practically a part of the capillary column and these results in obtaining of non-dispersed peaks even at the beginning of a chromato- gram (without cryofocusation or subambient temperatures)4.
Conclusion
A simple and inexpensive headspace method for analysis of aroma compounds of spirits was described. Sixteen volatile compounds (from acetaldehyde up to octanol) was analysed by microcolumn filled with 2,5 mg of Tenax TA. The microcolumn was thermally desorbed in the modified inlet of gas chromatograph (Shimadzu A14) during analysis, conditioning was not necessary between two analyses.
This project is co-financed by the Scientific Grant Agency of Ministry of Education of the Slovak Republic and Slovak Academy of Sciences VEGA (registration number 1/0096/11) and the Slovak Research and Development Agency (APVV - 0550-07). We would like to thank to Ing. Ján Hrivňák, CSc. for technical help. REFERENCES
1. Kobayashi M., Shimizu H., Shioya S.: J. Bios. Bio- engin. 106, 317 (2008).
2. Pinho O., Ferreira I., Santos L.: J. Chromatogr., A 1121, 145 (2006).
3. Veselý P., Lusk L., Basarova G., Seabrooks J., Ryder D.: J. Agric. Food Chem. 51, 6941 (2003).
4. Hrivňák J., Lakatošová J., Repka V., Kaňuchová Pátková J.: Chem. Listy 104 (S), 611 (2010).
5. Arthur C. L., Pawliszyn J.: Anal. Chem. 62, 2145 (1990).
6. Bigham J., Medlar J., Kabir A., Shende C., Alli A., Malik A.: Anal. Chem. 74, 752 (2002).
7. Lakatošová J., Hrivňák J., Kaňuchová Pátková J.: In: Proceedings (CD), 33rd World Congress of Vine and Wine and 8th General Assembly of the OIV, June 20 – 27 2010, Tbilisi, Georgia. p. P. II. 45-No 166.
8. Kružlicová D., Mocák J., Durčeková T., Hrivňák J., Pátková J..: In: Proceedings (CD), 30th World Con- gress of Vine and Wine and 5th General Assembly of the OIV, 10 -16 June 2007, Budapest, Hungary. p. S2- Po 19.
9. Hrivňák J., Šmogrovičová D., Lakatošová J., Nádaský P.: J. Inst. Brew. 116, 167 (2010).
10. Hrivňák J., Šmogrovičová D., Nádaský P., Lakatošová J.: Talanta 83, 294 (2010).
Fig. 1. Chromatogram of cherry spirit. Peaks: (1): methyl acetate, (2): ethyl acetate, (3):propanol, (4): 2-butanol, (5): ethyl butyrate, (6): ethyl isovalerate, (7): butyl acetate, (8): butanol, (9): amyl acetate, (10): isobutanol, (11): isoamyl acetate, (12): pentanol, (13): hexyl acetate, (14): hexanol, (15): heptanol, (16): octanol