Abstract
In this study, an effective method for accurately detecting Pb(II) concentration was developed by coupling square wave anodic stripping voltammetry (SWASV) with support vector regression (SVR) based on a bismuth-film modified electrode. The interference of different Cu2+ contents on the SWASV signals of Pb2+ was investigated, and a nonlinear relationship between Pb2+ concentration and the peak currents of Pb2+ and Cu2+ was determined. Thus, an SVR model with two inputs (i.e., peak currents of Pb2+ and Cu2+) and one output (i.e., Pb2+ concentration) was trained to quantify the above nonlinear relationship. The SWASV measurement conditions and the SVR parameters were optimized. In addition, the SVR mode, multiple linear regression model, and direct calibration mode were compared to verify the detection performance by using the determination coefficient (R2) and root-mean-square error (RMSE). Results showed that the SVR model with R2 and RMSE of the test dataset of 0.9942 and 1.1204 μg/L, respectively, had better detection accuracy than other models. Lastly, real soil samples were applied to validate the practicality and accuracy of the developed method for the detection of Pb2+ with approximately equal detection results to the atomic absorption spectroscopy method and a satisfactory average recovery rate of 98.70%. This paper provided a new method for accurately detecting the concentration of heavy metals (HMs) under the interference of non-target HMs for environmental monitoring.
Highlights
A large amount of lead ions have accumulated in soil in recent decades due to improper agricultural management, such as excessive usage of fertilizers, pesticides and sewage water irrigation [1], and the addition of wine vinasse [2,3]
To ensure the electrochemical activity of the glassy carbon electrode (GCE) used in the subsequent work, the electrochemical property of this GCE was investigated via cyclic voltammetry (CV) by using [Fe(CN)6]3−/4− as the redox probe
The results showed that the relative standard error (RSD) values of the above ions were all less than 10%, as shown in Figure S2 (Supplementary Information)
Summary
A large amount of lead ions have accumulated in soil in recent decades due to improper agricultural management, such as excessive usage of fertilizers, pesticides and sewage water irrigation [1], and the addition of wine vinasse [2,3]. The interference law of Cu2+ content on the stripping peak current of Pb2+ could be investigated through statistical analysis by adding different concentrations of Cu2+. The support vector regression (SVR) was chosen to characterize the above nonlinear relationship to establish a quantitative model for accurate detection of Pb2+ concentration. In this study, the radial basis function was selected as the SVR kernel function to interpret the nonlinear relationship between the stripping peak currents of Pb2+ and Cu2+ and Pb2+ concentration. To avoid the limitations of complex CMEs, a bismuth film-modified glassy carbon electrode (Bi/GCE) was used to perform the SWASV measurement in this study due to the many advantages of bismuth, such as wide potential window, low toxicity, and ability to reduce the activation energy of Pb2+ [27,28,29]. Real soil samples were collected to verify the feasibility and practicality of the proposed method
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