A novel development of bromocresol green as a dual-analyte colorimetric chemosensor: Detection and determination of mercury (II) and cyanide ions in water media with analytical applications

Anions play important role in chemical, biological and environmental processes. An important aspect of modern chemistry is the utilization of hydrogen bonding in the development of receptors for recognition of anions [1]. Although cation receptors have been studied for more than four decades but the development of anion receptors received less attention. During last thirty years, many organic based synthetic anion receptors have been reported [2-4]. During last thirty years, many organic based synthetic anion receptors have been reported [5-7]. These anion receptors are rather difficult to synthesize or are expensive instruments for detections. Taking this dilemma into consideration recently, we have undertaken an extensive research program to explore bromo pyrogallol red (BPR) as an easily available dye demonstrated a high chromogenic receptor for cations and anions [8, 9]. In this work, the behavior of bromocresol green (BCG), an easily available dye has been studied for the first time in chromogenic sensing of CNˉ as an anionic species and for Hg2+ as a cationic species in H2O media. Initial experiments aimed at the optimization of concentration of cyanide led us to treat aqueous solution of CNˉ with BCG-Hg formed in solution. Spectrophotometric monitoring of the changes revealed that the peak at 620 nm decreased instantaneously with concomitant color change, because CNˉ is a strong p-acceptor. In order to support the above hypothesis, the process was repeated using scaled up quantities which unequivocally establish the proposed mechanism. The detection limit of the new chromogenic probe was measured to be 0.1 µmol L-1 which is much lower than most recently reported chromogenic probes for cyanide determination. The sensitivity is close to the maximum permissive level in drinking water, which is 1.9 µmol L-1 according to the World Health Organization (WHO). It can be used as a convenient and effective method to detect cyanide in aqueous media. Therefore the cyanide detection method described here should have potential application as a new family of probes for detecting cyanide in aqueous solution. The analytical utility of the method for the analysis of cyanide ions in human serum, tap and mineral water samples was demonstrated and the results were compared successfully with the conventional reference method. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of cyanide in a variety of samples e.g. fresh and drinking water.