Characterisation of whiskies by GC-MS and ICP-MS and their chemometric classification

Viski je destilirana alkoholna pijača iz žita, ki vsebuje veliko spojin in ionov, katerih koncentracija se razlikuje glede na uporabljene sestavine in postopek proizvodnje. Viskiji so zaradi svoje cene pogosto tarča ponarejevalcev. Da zaščitimo potrošnike, njihovo pristnost preverjamo z različnimi instrumentalnimi tehnikami, podprtimi s kemometrično obdelavo podatkov. Največ raziskav je bilo narejenih na področju preverjanja pristnosti škotskih viskijev, medtem ko so viskiji drugih regij slabše raziskani. V 43 trgovsko dosegljivih viskijih s Škotske, Irske, Združenih držav Amerike in Kanade smo netarčno določevali različne skupine spojin in kovin. S plinsko kromatografijo smo določevali lahkohlapne komponente (višji alkoholi in estri) in težjehlapne komponente (težjehlapni alkoholi, kisline in monosaharidi). Vsebnost kovin smo določili z masnim spektrometrom z induktivno sklopljeno plazmo (ICP MS). Posamezne delne faze uporabljenih analiznih postopkov smo optimirali tako, da smo dobili čim višje izkoristke posameznih preiskovanih komponent in čim boljšo ločljivost njihovih kromatografskih vrhov. S kemometrično obdelavo rezultatov, pridobljenih s kemijskimi analizami, smo vzorce grupirali po vrsti in regiji, pri čemer smo uporabili linearno diskriminantno analizo (LDA), dobljene modele pa navzkrižno validirali. V vzorcih viskijev smo analizirali vsebnosti 32 kovin, 6 lahkohlapnih komponent in 107 težjehlapnih komponent, od katerih smo uspešno določili in kemometrično obdelali 7 kovin, 6 lahkohlapnih komponent in 69 težjehlapnih komponent. Z linearno diskriminantno analizo smo razvili modele, ki omogočajo ločitev viskijev po vrsti in regiji. Razviti modeli dajejo pri navzkrižni validaciji napako pod 10 %. Whisky is a distilled alcoholic beverage made from cereal grains. It contains many compounds and ions that are present in different concentrations, depending on used ingredients and production process. Whiskies are interesting for counterfeiting because of their relatively high retail price. For consumer protection authenticity of whisky is checked with various instrumental techniques and chemometric analysis. Most studies have been focused on the authenticity of Scotch whisky, while whiskies from other regions were less researched. We have performed non-targeted analyses of various compounds and metals in 43 commercially available whiskies from Scotland, Ireland, United States of America and Canada. To determine volatile compounds (higher alcohols and esters) and less or non-volatile compounds (less volatile alcohols, acids and monosaccharides) gas chromatography was used. The concentration of metals was determined by inductively coupled plasma mass spectrometry (ICP-MS). All steps of analytical procedures we used were optimised in order to increase yields of investigated compounds and to increase resolution of chromatographic peaks. Obtained results were used in chemometric data analysis to group samples by type and region. We performed linear discriminant analysis (LDA) and obtained models were cross validated. We were analysing 32 metals, 6 volatile compounds and 107 less or non-volatile compounds in whisky samples. We have successfully determined 7 metals, 6 volatile compounds and 69 less or non-volatile compounds. Using linear discriminant analysis, we have developed models that allow separation of whiskies by type and region. Cross-validation error of developed models was under 10 %.