Novel use of calmagite as a fast and easy colorimetric anion chemosensor and solid-state sensor for carbonate ion in running water

This experiment studies the use of an available azo dye, calmagite (CAL), for the recognition of carbonate ion in running water. The linear range of carbonate, derived from the results of this simple, selective, sensitive and rapid determination, was 1.2 × 10−8–5.4 × 10−6 mol L−1 with the detection limit of 1.6 × 10−8 mol L−1. In the examined cases, the coexisting cation, anions and weak acids (NO3−, NO2−, SO42−, SO32−, HSO3−, OAc−, I−, Br−, F−, Cl−, SCN−, CO32−, HCO3−, H2PO4−, HPO42−, Cit3−), (Ascorbate, K+, Na+, Mg2+ <6.9 × 10−4 mol L−1) did not restrict the analysis by causing interference. The recoveries which were in the range of 97.3–101.4% established the evidence of the validity of the method for real water samples. The obtained results manifested good proof of the accuracy of the method to be comparable with acid-base titration. In general, the method was cost-effective and fast, with the uncomplicated operation, which made the receptor suitable for rapid detection of carbonate ion in freshwater in the field. On the other hand, having regard to the modifications calmagite made in the filter paper strips, this chemosensor revealed the great potential to be applied as a carbonate solid-state colorimetric indicator.