Application of a new fluorescent Schiff base for determination of cadmium

Cadmium ion (Cd2+), known as highly toxic heavy metal ion, is frequently used in industrial and agricultural activities, which results in its widespread distribution in environment. Furthermore, its bioaccumulation in the food chain leads to its transportation into the human body, which may cause serious health hazards [1]. Cadmium toxicity is associated with several clinical complications: cancer, liver and kidney dysfunction, increased risk of bone fracture, hypertension, atherosclerosis and severe anemia. Current evidence suggests that exposure to cadmium induces genomic instability through complex and multifactorial mechanisms; there are no proven effective treatments for chronic cadmium intoxication [2]. As such, Cd2+ contamination has attracted significant attention because of its toxicity and accumulation in human tissues which led to increasing needs to determine even trace Cd2+ in a variety of matrices [3]. In this study, 1,5-bis(2-hydroxy-3-methoxybenzaldehyde) thiocarbohydrazone (BHMT) as a new and highly intensive fluorescent Schiff base has been introduced for monitoring cadmium ions in aqueous samples. It was synthesized by the reaction of 2-hydroxy-3-methoxy-benzaldehyde with thiocarbohydrazide and showed strong fluorescence at 502 nm under excitation wavelength of 380 nm. The synthesized compound was characterized using Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. It was found that the fluorescence intensity of BHMT decreased with increasing of Cd2+ concentrations which allows the spectrofluorimetric sensing of Cd2+. The effect of important parameters such as acidity or basicity of solution, BHMT concentration was studied and optimized. Under the established optimum conditions, the calibration graph was linear in the range of 10 to 200 ng mL−1 of Cd2+. The limit of detection for the target metal ion based on 3Sb/m definition was 2 ng mL−1. The developed method showed good reproducibility and adequate selectivity, and it was successfully applied to the determination of trace amounts of cadmium in water samples.