Electrochemical impedance spectroscopy measurements for determination of derivatized aldehydes in several matrices

A simple, selective and sensitive electrochemical method is described for the determination of different aldehydes at glassy carbon electrode using electrochemical impedance spectroscopy (EIS). The measurements were performed after their derivatization with 2,4-dinitrophenylhydrazine (DNPH) in acidic medium. The impedance measurements were investigated in the frequency range from 100 mHz to 100 kHz at a potential of 1.0 V versus Ag/AgCl. The Nyquist plots were modeled with a Randle's equivalent circuit. The charge transfer resistance was identified as the dependent parameter on relevant concentration of aldehydes (determined as their hydrazones). Under the optimized conditions, the linearity was established over the concentration range of 1000-0.05 μmol L^-1. The limits of detection (LODs) obtained were from 0.097 to 0.0109 μmol L^-1. Finally, the developed method has been applied to the determination of aldehydes in drinking water, orange juice and apple vinegar samples with relative standard deviations (RSDs) < 3.1% and acceptable recovery rate (around of 80%).