Electrochemical detection of benzo(a)pyrene in acetonitrile–water binary medium

• Acetonitrile–water was selected as a medium to oxidize BaP;
• The oxidation potential was negatively shifted 180 mV compared to that in acetonitrile;
• The oxidation current was 22 times greater compared to that in acetonitrile;
• Acetonitrile–water binary medium was applied for sensitive and selective detection of BaP.

Electrochemical oxidation of adsorbed benzo(a)pyrene (BaP) on the glassy carbon electrode (GCE) was explored in acetonitrile–water. When the GCE was incubated in 100 nM BaP acetonitrile–water (Vwater:Vacetonitrile=1:1) for 10 min at open circuit, and then transferred into blank acetonitrile–water (Vwater:Vacetonitrile=1:1, pH= 0.70) for differential pulse voltammetry measurement, a distinct oxidation peak at 0.98 V (vs. Ag/AgCl) was observed. The peak potential was about 180 mV lower than that in acetonitrile. Importantly, the peak current was more than 22 times greater. The effects of water on BaP preconcentration on the electrode and electrochemical oxidation were revealed, respectively. Based on the results, an electrochemical assay for BaP detection was developed. The GCE was respectively incubated in acetonitrile–water (Vwater:Vacetonitrile=1:1)with BaP concentration ranged from 0 nM to 1000 nM, and then transferred into the corresponding blank acetonitrile–water (pH= 0.70) for DPV measurements. When the BaP concentration was increased, an increased oxidative current at 0.98 V (vs. Ag/AgCl) was observed, and a detection limit of 0.67 nM was achieved. Because all other priority polycyclic aromatic hydrocarbons could not be electrochemically oxidized at 0.98 V, the electrochemical assay showed very high selectivity to BaP. Finally, the developed electrochemical assay was successfully applied to determination of BaP in a series of real world samples, such as drinking water, tap water, lake water and river water.

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