The results (Fig. 2) clearly show improved resolution and sharper peaks for the core–shell particle column compared to the fully-porous particle column, as evidenced by the ability of the core–shell particle column to resolve a trailing impurity from the main peak that is poorly resolved with the fully-porous particle column (arrows). In addition, it is also important to note that more peaks eluting before the main component were also better resolved on the Kinetex column, where differences in selectivity and narrower peak widths generated this result. A similarly improved ability to resolve closely related impurities from the main peak was generally observed for other oligonucleotide samples.