Figure 2

Multivariate statistical analysis results. (a) PCA score plot of the analysis in ESI (+) mode. (PC1 covers 11.6% of the variables; PC2 covers 6.4% of the variables). (b) PCA score plot of the analysis in ESI (−) mode (PC1 covers 8.9% of the variables; PC2 covers 6.1% of the variables). (c) OPLS-DA score plot of the analysis in ESI (+) mode (R2X = 0.209, R2Y = 0.99, Q2 = 0.883). (d) OPLS-DA score plot of the analysis in ESI (−) mode (R2X = 0.183, R2Y = 0.984, Q2 = 0.833).