3.2. Repeatability, linearity and detection limit
Calibration data were obtained for paraquat solutions under optimum experimental conditions described above. Fig. 6 shows some of the typical SWASV voltammograms recorded on the Chit-CPE after being in contact with different paraquat concentrations for 180 s. A calibration graph was then constructed from the observed peak currents (Table 1). A linear fit was applied over the range of 1.5×10−9–1.0×0−5 mol L−1 with a correlation coefficient (R2) of 0.9826. The limit of detection (LOD) for PQ, based on a signal-to-noise ratio (S/N) of 3, was 2.67×10−10 mol L−1. The precision of this method was determined by the analysis standard solution at 1.0×0−5 mol L−1 and 5.0×10−8 mol L−1 of PQ for seven times continuously, and the relative standard deviation (RSD) was 5.2% and 6.02% for peak 2 respectively.