Flow injection amperometric determination of isoniazid using a screen-printed carbon electrode modified with silver hexacyanoferrates nanoparticles

A rapid and simple method was developed for isoniazid (INZ) determination by flow injection analysis (FIA) using a screen-printed carbon electrode (SPCE) modified with silver hexacyanoferrates (NPAg-HCF) as amperometric detector. Dodecanethiol-stabilized silver nanoparticles were prepared by biphasic method and applied as modifier in a screen-printed electrode, used as precursors for the electrochemical hexacyanoferrates preparation (NPAg-HCF). The electrochemical behavior of both silver nanoparticles and silver hexacyanoferrates was evaluated by cyclic voltammetry in the presence of potassium or silver ions and was verified a strong dependence with the nature of the cations in the voltammetric profile. A catalytic response of the SPCE/NPAg-HCF electrode was observed for INZ determination confirmed by the increase int the current of the Ag3K[FeII(CN)6]/Ag3[FeIII(CN)6] redox couple at the electrode surface, proportionally to the INZ concentration. The device was evaluated as an amperometric sensor in an FIA system. Using the best operation conditions assigned as: potential applied of +0.45 V, pH 3.0, flow rate of 2.9 mL min−1, sample volume of 200 μL, and analytical path of 30 cm, it was possible to construct a linear calibration curve from 5.0 × 10−6 to 5.0 × 10−4 mol L−1 with a limit of detection of 2.6 μmol L−1. Recoveries values obtained for INZ provided mean values ranging from 99.0 to 102%, and an analytical frequency of 24 injections per hour was achieved. The method was successfully applied for the determination of INZ in simulated human urine samples with good agreement between the added and recovery values.