Highly improved simultaneous herbicides determination in water samples by differential pulse voltammetry using boron-doped diamond electrode and solid phase extraction on cross-linked poly(vinylimidazole)

摘要

A highly sensitive method for the simultaneous determination of multiresidues of diuron (DI), 2,4-dichlorophenoxyacetic acid (2,4-D) and tebuthiuron (TB) using a cathodically pretreated boron-doped diamond electrode (BDDE) by differential pulse voltammetry (DPV) associated with solid phase extraction was developed. The method is based on preconcentration of 100.0 mL of multiresidues solution at pH 3.7 through 200 mg of poly(vinylimidazole-TRIM) packed into a cartridge. The elution was carried out with 5.0 mL of ethanol, which was then evaporated and the eluent was dissolved in 10.00mL of supporting electrolyte 0.1 mol L~(-1) H_2SO_4. The electroanalytical measurement was performed under optimized conditions of DPV (pulse amplitude of 108 mV, scan rate of 92 mV s~(-1) and pulse width of 2 ms) using the BDDE. The analytical curve for DI and 2,4-D presented linear range between 1.0-9.0 u,mol L~(-1), while the linear range for TB was found to be between 2.5-22.5 µmol L~(-1) .Unear correlation coefficients of 0.99 were obtained for all curves. Very low limits of detection have been achieved for DI, 2,4-D, and TB, 0.035 µmol L~(-1),0.12 µmol L~(-1), and 0.34 µmol L~(-1), respectively. The electrochemical determination of DI, 2,4-D and TB was not prone to interferences by other pesticides (ametryn, hexazinone, imazethapyr, glyphosate, imazethapyr and picoxystrobin) as well as by humic acid substance. The proposed method was applied for analyses of lake and well water samples by using addition/recovery tests, which yielded satisfactory recovery values (96-104%). These results attest the feasibility of method for herbicides determination in water samples. Additionally, the accuracy of method was confirmed by high performance liquid chromatography (HPLC-DAD) as reference method.