The use of a finite mixture distribution model in bottled water characterisation and authentication with stable hydrogen, oxygen and carbon isotopes - Case study from Slovenia

This study investigates the comparison of the stable isotopic composition of oxygen (delta(18)O), hydrogen (delta(2)H) and carbon in dissolved inorganic carbon (delta(13)C(DIC)) in domestic and foreign bottled waters randomly collected from the Slovene market. Empirical distributions of delta(2)H, delta(18)O and delta(13)C(DIC) were examined. Mathematical models of unimodal and polymodal probability density functions were applied for their description. A normal (Gaussian) finite mixture model as a representation of the polymodal empirical distribution of delta(13)C(DIC) was used as a classification tool. Finally, based on the classification, descriptive statistics of delta(2)H, delta(18)O and delta(13)C(DIC) for different groups are calculated. Components of the normal finite mixture model of delta(13)C(DIC) represent four groups of bottled water; a group of artificial sparkling bottled water, two groups of still and flavoured bottled water and a group of bottled water originating from deeper aquifers. Corresponding values of delta(2)H and delta(18)O show that only the group of bottled water originating from deeper aquifers has a distinct stable isotopic composition, where the others have similar empirical distributions. The proposed model showed that delta(13)C(DIC) for bottled water can be used as a strong discrimination parameter for the classification of bottled water and it can be applied as an authentication tool. (C) 2010 Elsevier B.V. All rights reserved.