Electrochemical oxidation of Paracetamol (PAR), Acetylsalicylic acid (ASA) and Caffeine (CAF) was investigated employing square wave stripping voltammetry (SWSV) using screen–printed carbon electrodes (SPCE). Determinations were performed in 0.1 mol L−1 BR buffer (pH 2.0) without accumulation step. SWV were obtained by scanning the potential from 0.00 to 1.40 V employing a scan increment of 4 mV, pulse amplitude 25 mV and frequency of 25 Hz. PAR, ASA and CAF presents oxidation signals at 0.45, 1.03 and 1.32 V. The detection limits were 1.2, 1.7 and 1.7 mg L−1, respectively. The method was applied in the PAR‐ASA‐CAF determination on pharmaceutical formulations.

For the determination of progesterone (P4) electroanalytical studies were performed using mercury electrode (HMDE) and screen-printed boron-doped diamond electrode (BDD-SPE). The effects of pH, supporting electrolyte, accumulation potential and time (E acc , t acc ) were studied in both systems. The optimum conditions were: i) HMDE: pH 7,0; E acc : À 0,1 V and t acc : 40 s, ii) BDD-SPE: 0,5 mol L À 1 H 2 SO 4 ; E acc : 0,0 V and t acc : 120 s. Under these conditions, the detection limit was 3.1 μg L À 1 for HMDE and 45.6 μg L À 1 for BDD-SPE. Both methods were validated and applied in the P4 determination on pharmaceutical formulations and milk samples.