*2.17. Statistical Analysis*

All analyses were performed in triplicates. The results are presented as mean ± standard deviation. Significant differences between data obtained for tested samples were assessed using Tukey's test (*p* = 0.05) or Student's *t*-test (*p* = 0.01). The correlations between the results were expressed by the Pearson correlation coefficient. Principal component analysis (PCA) and cluster analysis were carried out to group the test samples according to the parameters tested. All calculations were performed using Statistica 13.1 software (StatSoft, Inc., Tulsa, OK, USA).
