Flow-Injection Determination of Benzimidazole Fungicides in Natural Waters with Copper(II)-Hydrogen Peroxide Chemiluminescence

Abstract

A simple, sensitive, and rapid flow-injection method is reported for the determination of benzimidazole fungicides (BFs): fuberidazole, benomyl, and carbendazim. The method is based on enhancement of the chemiluminescence (CL) signal generated during the reaction of BFs with hydrogen peroxide and copper(II) in alkaline condition in the absence of luminescent reagents. Linear calibration graphs were obtained in the concentration range of 5–2000, 25–2000, and 25–5000 ng mL⁻¹ for fuberidazole, benomyl, and carbendazim, respectively. The relative standard deviations (n = 4) were in the range 1.2–2.6% with limits of detection (S/N = 3) 3 ng mL⁻¹ for fuberidazole, and 15 ng mL⁻¹ for benomyl and carbendazim. The proposed method allowed 120 injections h⁻¹. The effect of common anions, cations, and some pesticides on the determination of BFs was also examined. The method is applied to determine BFs in spiked natural water samples using Sep-Pak C₁₈ cartridges for solid phase extraction and preconcentration procedure. Recoveries were in the range of 94 ± 1 to 105 ± 1%. The CL mechanism is also discussed briefly.

Keywords:

• Benzimidazole fungicides
• Chemiluminescence
• Copper
• Flow injection
• Hydrogen peroxide

Acknowledgments

The authors are grateful to the Higher Education Commission, Pakistan, for financial support in the form of research project No. 639.

Notes

ELISA (enzyme-linked immuno-sorbent assay); HPLC-UV (high performance liquid chromatography-ultraviolet detector); HPLC-Flu (HPLC-fluorescence detector); FI-CL (flow injection-chemiluminescence).

Conditions: H₂O₂: 1 × 10⁻² M, Cu(II): 1 × 10⁻³ M, CO₃: 5 × 10⁻² M, BFs: 0.5 µg mL⁻¹ (60 µL injection), flow rate: 2.0 mL min⁻¹.

^a The correlation coefficient was calculated using 9 different concentration of each analyte.