In order to determine lead in propolis samples, a pre-treatment step was necessary to stabilize the surface of the modified electrode before each measurement. This step involved cyclic voltammograms from −1.40 V to 0.20 V with a scan rate of 0.100 V s−1 in pH 4.5 acetate buffer solution. SWASV measurementswere carried out in pH4.5 acetate buffer solution containing 1000 μg L−1 of Bi(III). The experiments were performed with an in situ deposited bismuth film on MWCNT/DMF/NA/GC (BiFE) with a deposition time of 120 s at −1.40 V, under conditions of forced convection (stirring). Then, the stirring was stopped and after 10 s the voltammogram was recorded in square-wave voltammetric mode between −1.40 and 0.20 V. Other experimental parameters were: step potential, ΔEs=2 mV; frequency, f=25 Hz and amplitude of the square wave, ΔEsw=40 mV. After a series of measurements, the bismuth film and the residual metals were removed by applying 0.20 V during 30 s under stirring conditions. All themeasurementswere carried out at room temperature in non-deaerated solutions.