highly significantp = 4.5 × 10 −5
For the plastic bag-samples, a highly significant difference between the reference material and the two obtained samples (plastic bag-metal and plastic bag-no metal) was observed (1-way ANOVA, F = 12.9, p = 4.5 × 10 −5 ), while the means of the two plastic samples showed no significant difference (post-ANOVA Tukey-test, p adjusted = 0.11).