Evaluation of a nafion coated glassy carbon electrode for determination of paraquat by differential pulse voltammetry

Journal of the Brazilian Chemical Society

Ulisses M. F. De Oliveira¹  Jaim Lichtig¹  Jorge C. Masini¹ 

[1] ,Universidade de São Paulo Instituto de Química São Paulo SP ,Brazil

关键词: paraquat determination;    river water;    urine;    modified electrode;    voltammetry;    ion exchange;   

DOI  :  10.1590/S0103-50532004000500020

来源: SciELO

【 摘 要 】

This paper presents an evaluation of a Nafion coated glassy carbon electrode for determination of paraquat in river water and urine by differential pulse voltammetry. The film was formed applying 4 µL of a 1% (m/v) Nafion solution, which was evaporated under an infrared light. The maximum signal to noise ratio was obtained using a 40 mmol L-1 Britton-Robinson buffer at pH 12 as supporting electrolyte. For an accumulation time of 5.0 min in open circuit, the limit of detection was 0.7 µg L-1, while the quantification limit was 1.0 µg L-1, with a linear dynamic range up to 12 µg L-1. In these conditions, a sequence of ten experiments lead to a relative standard deviation of peak current of 2.2% for a 10 µg L-1 paraquat solution. Ion pair formation in solution was the major factor of error in analysis. Despite the film to avoid adsorption of anionic species at the electrode surface, paraquat suffers strong association in solution with humic substances, proteins, clays, anionic surfactants, etc. These interactions decrease the accumulation of paraquat in the Nafion film and, as a consequence, the magnitude of the reduction peak, requiring that quantifications have to be made by standard addition. Recoveries between 87 and 106% were obtained for river waters and urine samples spiked with 1.0 and 3.0 µg L-1 paraquat.

【 授权许可】

CC BY   
 All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License