As it is shown, the resulting calibration plot is linear over the 1–50 μg L−1 range for Pb(II). The slope of the Pb(II) curve on the BiFE correlation plotwas 0.135 μA L/μg−1. The calibration equation and the correlation coefficient for the linear fitting were Ip,n=(−0.021±0.034)+ (0.135±0.007) c*Pb, r=0.9963. The detection and quantification limits were 0.6 μg −1 and 1.84 μg L−1, estimated as 3 and 10 times Sy/x/slope, respectively [23]. Limit of detection obtained is lower than those found in the literature, i.e. 18 μg L−1 on μ-NP/BiFE and 29 μg L−1 on BiFE [24], 1.3 μg/L−1 on CNT screen-printed electrodes [21], comparable to others i.e. 0.95 μg L−1 on OMC-NA coated GCE [25], and also slightly higher than others [26]. The reproducibility of BiFE was evaluated by running 6 calibration curves obtained from 6 dispersions prepared in a similar way on different days. The repeatability was calculated as the percentage variation of slopes of 6 calibration curves obtained froma given dispersion. Then, the percent relative standard deviations were 7.4% and 7.0%, respectively. The sample throughput was 21 h−1. The results demonstrate that the BiFE shows a good performance. Statistical parameters are depicted in Table 1.