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Investigations with human breath and cultures of oral bacteria have been performed to examine the analytical performance of the KAMINA gradient microarray based on a segmented metal oxide layer. Standard microarray chips with 38 segments, one chip equipped with platinum doped SnO2 and the other with WO3, were inspected. The results show that the gradient microarray is able to detect acetone and methyl-mercaptane as two model gases of medical relevance at lower ppm-levels in the presence of human breath. Even after consumption of smelly nutrition, acetone at lowest concentrations of some 10 ppm could be detected. A principal component analysis (PCA) of the signal patterns showed that both types of microarrays were able to discriminate between the model gases, ethanol and clean air. Moreover, the even more delicate distinction of different oral bacteria grown on an agar substrate proved to be feasible by the signal pattern analysis of their gaseous metabolites. The signal patterns obtained for mixed bacteria cultures even seem to allow assignment to and quantification of the main cultures of a mixture.