Carbon black nanoparticles modified with palladium nanoparticles (Pd/CB) were prepared using a facile methodology. Stirring CB in an aqueous solution of palladium chloride was found to result in the spontaneous formation of Pd nanoparticles on the CB surface. The Pd/CB composite demonstrated high electrocatalytic activity towards hydrazine oxidation, with good stability and reproducibility. Three linear dynamic ranges of hydrazine determination were found between 5 mu M and 50 mM. The limit of detection (LOD) for hydrazine was found to be 8.8 mu M (based on 3 sigma). The sensitivity of unmodified CB to trace metal impurities present in certain common electrolytes is also noted.