entire sequence. The RSDs of the peak areas and retention times of all peaks in base peak chromatograms (positive and negative mode) were calculated. More than 90% of RSDs were less than 30% for QC samples in negative mode and positive mode. Therefore, the repeatability and stability of global experimental performances were high and acceptable. Furthermore, the cluster of QC samples in the PCA scores plot also demonstrated satisfactory stability and repeatability of the metabolic profiling method (Fig. 3).