Voltammetric determination of salicylic acid and derivatives based on ferroceneboronic acid

Differential pulse voltammograms (DPV) of ferroceneboronic acid (FBA) were recorded on a glassy carbon (GC) electrode in the presence of salicylic acid (SA) and derivatives for the determination of SAs. The reduction peak in DPV for FBA was observed at +200 mV at pH 7.0 in the absence of SA. The reduction peak current was decreased in the presence of SA depending on the concentration, while a new reduction peak appeared at +50 mV. Similar DPV response was also observed for salicylamide, salicylalcohol, and salicylhydroxamic acid. The results were rationalized based on the formation of negatively charged boronate esters of FBA with SA and the derivatives. Thus, the reduction current of FBA in DPV depended on the concentration of SA and derivatives in the concentration range of 1-10 mM for salicylic acid salicylamide and salicylalcohol and of 0.1-1 mM for salicylhydroxamic acid.