Enzymatic-spectrophotometric determination of paraquat in urine samples: A method based on its toxic mechanism

Abstract

Paraquat is a broad-spectrum contact herbicide that has been encountered worldwide in several cases of accidental, homicidal, and suicidal poisonings. The pulmonary toxicity of this compound is related to the depletion of NADPH in the pneumocytes, which is continuously consumed by the reduction/oxidation of paraquat and reductase enzyme systems in the presence of O₂ (redox cycling). Based on this mechanism, an enzymatic-spectrophotometric method was developed for the determination of paraquat in urine samples. The velocity of NADPH consumption was monitored at 340 nm, every 10 s during 15 min. The velocity of NADPH oxidation correlated with the paraquat levels found in samples. The enzymatic-spectrophotometric method showed to be sensitive, making possible the detection of paraquat in urine samples at concentrations as low as 0.05 mg/L.

Keywords::

• Paraquat
• urine samples
• enzymatic–spectrophotometric method
• redox cycling

Acknowledgements

The authors thank Dr Radi Gebara Neto from Hospital Regional do Vale do Ribeira (Pariquera, São Paulo, Brazil) for the collaboration of collecting urine sample from an intoxicated patient.

Declaration of interest

Financial supports from FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo, grant no. 05/51592-9) and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) are gratefully acknowledged. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.