Copure ^® PSA sorbent is similar to NH2 sorbent, offering both normal phase and anion exchange retention mechanisms. Owing to the existence of primary and secondary amino groups (with pKa values 10.1 and 10.9, respectively), PSA has higher ion exchange capabilities and strong hydrogen bonding. Additionally, PSA is able to form chelate complexes with some metal ions and thus can be used to enrich them.