AMPEROMETRIC DETECTION AFTER HPLC SEPARATION OF SELECTED POLYPEPTIDESAND PROTEINS AT AN ELECTRODE MODIFIED BY MIXED-VALENT RUTHENIUM OXIDECROSS-LINKED WITH CYANIDE

An indicator electrode, in which a film containing Ru oxides with cyan o-crosslinks comprised the active surface, was used in an amperometric detector for ion-exchange and reverse-phase high-performance liquid c hromatography (HPLC). The latter used a C-18 column and an eluent of 0 .04 M citric acid, 0.1 M KH2PO4, 0.1% trifluoroacetic acid, and 20-80% acetonitrile. Oxytocin, isotocin, vasopressin, tocinoic acid. myoglob in, and ribonuclease A were separated and determined with detection li mits at the 1-3 pmol level. The response to ribonuclease A, as a typic al example, was linear over the range of 0.050-2.5 muM, with a slope o f 15 nA/muM at 0.94 V (vs. Ag/AgCl). A single preparation of the elect rode was generally stable for 3 weeks, as long as the analyte concentr ations were below 10 muM.