Reversed-phase HPLC (RP-HPLC) is now well establrshed as a technique for rsolanon, analysts, and structural elucrdatron of peptrdes and proteins (1,2) Its use m protem rsolatron and purificatron may have reached a peak owing to recent developments m high efficiency ron-exchange and hydrophobic-mteraction supports, which are now capable of equivalent levels of resolution to RP-HPLC without concomrtant risk of denaturatron and loss of brologrcal actrvtty. Nevertheless, there are many appllcatrons in which denaturatron may be unimportant and high concentrattons of organic modifier can be tolerated (e.g., purity analyses, structural studies, and micropreparative purification prior to mrcrosequencing) It is a widely used tool m biotechnology for process momtoring, purity studies, and stability determmatrons