Malachite green as a novel selective colorimetric and fluorescent chemosensor for recognition and determination of sulfite anion in DMSO/water media

As we all know, Sulfite is an important additive in many food products because it inhibits development of both enzymatic and non-enzymatic browning in a variety of processing and storage situations [1]. It is also a very effective microbial inhibitor in acid or acidified foods. Several methods have been reported for the measurement of sulfite, such as electrochemical detection, chemiluminescence detection and high-performance liquid chromatography followed by spectrophotometric or fluorometric detection [2]. These methods usually require, however, adding an oxidant or derivative reagent that react with sulfite. Moreover, these methods always have some limitations, for example derivatives are not very stable, selectivity is not high and the procedure is complicated and difficult to synthesize. Taking this dilemma into consideration recently, we have undertaken an extensive research program to explore easily available dye demonstrated a high chromogenic receptor for cations and anions [3, 4]. In this paper, Malachite green (MG) an available dye has been developed as novel and efficient colorimetric and fluorometric chemosensor for sulfite ions over wide range of anions such in DMSO/water media. The UV–Vis absorption and fluorescent emission titrations experiments have been employed to study the sensing process. MG displayed ability to detect of up to 0.05 and 0.06 µmol L-1for sulfite (SO32-) ion in DMSO/H2O (1:9 v/v) at media over a large number of other anions by absorption and fluorescent method respectively at pH 7.8. Results reveal that the fluorescence emissions of the dye were only ‘switched off ‘in the presence of sulfite ion. The dye also showed remarkable spectral shifts in visible region by adding the sulfite ion and process proceeded with distinct visual color changes. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of sulfite in a variety of real samples.

Colorimetric chemosensor, Florescent chemosensor, Naked-eye detection, Malachite green, sulfite,