A renewable liquid drop sensor for di- or trinitrophenol based on fluorescence quenching of 3,3′,5,5′-tetramethylbenzidine dihydrochloride

Abstract

A novel renewable liquid drop sensor is proposed for the execution of a sensitive, simple and rapid assay. The dynamically growing and falling drops are formed at the bottom tip of a silanized silica capillary tube connected to the end of a flow system. The feasibility of the proposed method was demonstrated by performing the fluorimetric determination of di- or trinitrophenol by using 3,3′,5,5′-tetramethylbenzidine dihydrochloride (TMB-d) as sensing reagent. The optimum analytical conditions were established. The sensor shows linear responses in the measuring ranges from 2.45 × 10⁻⁷ to 5.0 × 10⁻⁵ mol l⁻¹ 2,4-dinitrophenol and from 1.07 × 10⁻⁷ to 8.0 × 10⁻⁶ mol l⁻¹ 2,4,6-trinitrophenol, and has detection limits of 1.0 × 10⁻⁸ mol l⁻¹ for 2,4-dinitrophenol and 4.0 × 10⁻⁹ mol l⁻¹ for 2,4,6-trinitrophenol. The analysis is simple and rapid and consumes only micro-amounts of reagent and sample. The sensor was applied to the direct determination of 2,4-dinitrophenol in synthetic water samples and the indirect assay of quinine through quantitative precipitation with 2,4,6-trinitrophenol. The results were in good agreement with those obtained by another method.