The TC values of the eight peaks in PCA. The absolute value standing for the scattering degree to a certain PC is indicated with “-” standing for the direction. The sum of absolute values of peaks shows the significance of difference. Therefore, the rank of eight peaks was 4212 (TC=47.33), 1866 (TC=28.79), 2212 (TC=23.02), 2661(TC=19.9), 4284 (TC=17.88), 2863 (TC=14.67), 5909 (TC=6.41), and 5341 (TC=6.1). SC: single contribution, SC= loading value ×contribution of PC×100, (PC1=52%, PC2=15%, PC3=12%); TC: the sum of absolute value from SC.