A New Solid Sorbent System for Rapid Monitoring of Paraquat and Diquat

A new solid sorbent system is developed for the monitoring of paraquat and diquat in the environment. The reagent system for the indicator tube consists of glucose and sodium hydroxide impregnated over silica gel and a humectant calcium chloride. This reagent system has also been used for the preparation of reagent paper. Glucose is used here as a very good reducing agent for the reduction of paraquat/diquat in an alkaline medium to give a stable blue coloured free radical ion. After exposing the indicator tubes and test paper to paraquat and diquat for a constant time, the blue colour developed could be compared with those obtained from standards. Alternatively the coloured compound was extracted in water and measured at 600 nm. The lower limit of detection is 0.1 μgm−3 and 0.5 μgm−3 of paraquat and diquat, respectively, for the reagent papers and indicator tubes. The lower limit of determination by spectrophotometric procedure is 0.5 μgm−3 and 1 μgm−1 of air for paraquat and diquat respectively. The preparation of indicator tubes, test papers and their applications for the detection and determination of paraquat and diquat in air, biological and food samples is described in this paper.