Classification of honey samples produced in urban areas of the city of Vienna employing comprehensive two-dimensional gas chromatography-mass spectrometry

In this work, comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-QMS) was employed for the elucidation of the volatilome of honey locally produced in the twenty-three different districts of the city of Vienna (Austria) for their compositional differentiation and geographical classification. Solid-phase microextraction employing a divinylbenzene/Carboxen/polydimethylsiloxane coated fiber was used for the extraction and preconcentration of the different volatile organic compounds. For sample preparation, five grams of honey diluted with water saturated with NaCl was incubated for 5 min at 40 °C, followed by 45 min of extraction under stirring at 250 rpm. A total of 361 compounds were identified in the examined honey samples and were further treated with unsupervised and supervised chemometric tools. Hierarchical clustering analysis revealed that the samples from Vienna city center and its immediate surroundings tend to group together, while those from the outer, greener districts form a separate, distinct cluster. Finally, orthogonal partial least squares discriminant analysis suggested differentiation on the basis of the geographical origin with an explained total variance of 65.1%. OPLS-DA revealed a clear separation trend between the two predefined groups and identified volatile features associated with the observed differentiation.