Abstract: Trace amount of cobalt in molecular sieve was determined by simple differentialoscillographic voltammtry in Co-PAR system (PAR= 4-(2-pyridylazo) resorcinol).Resultsshowed that in a solution of 0.2 mol/L HAc-0.2 mol/L NaAc-2.5 ?10^-5 mol/L PAR (pH=4.7) cobalt was able to cause a sharp incision on the cathodeic branch of the oscillogram at -1.68 V(vs.SCE).The method is simple, rapid and has less interferences than spectropho-tometry.

Key words: cobalt, trace determination, oscilloanalysis, PAR, molecular sieve