There were eight main peaks in XOS sample in its HPLC-UV
chromatograms. The peak 2 to peak 6 were confirmed to be X2–X6
by comparing their retention times with the XOS standards.
However, there were three unknown peaks in 13.1 min (peak 8),
14.5 min (peak 7) and 21.8 min (peak 1) (Fig. 2B, under gradient
elution), and their structure needed to be illustrated further by
LC–MS analysis.