Miniaturized dual-wavelength β-correction spectrophotometric probe for sensitive detection of cyanide in water via formation of cyano dithizone adduct.

Cyanide toxicity in water significantly threatens public health and the environment. To address this, a miniaturized simple, low-cost, selective and sensitive direct dual wave β-correction spectrophotometric probe has been established for cyanide detection in water. The dual-wavelength β-correction spectrophotometry enhances the selectivity and sensitivity of the probe in the presence of interfering species. The assay relies a highly selective nucleophilic addition of cyanide ions to dithizone (H2Dz) as chromogenic reagent in aqueous media of pH 6.8-7.2, forming a red-colored cyano H2Dz adduct. The electronic spectrum of the formed adduct displays a sharp absorption peak at λmax = 480 nm, enabling precise colorimetric detection. The molar absorptivity and Sandell's sensitivity index for the cyano H2Dz adduct with and without β-correction spectrophotometry were 5.62 × 103, and 1.79 × 103 L mol-1 cm-1, and 0.002 and 0.0033 µg cm-2, respectively. Beer's law and Ringbom's plots are valid in the range 0.01-5.0 and 0.06-2.0 µg mL-1 CN- concentration, respectively. The limits of detection (LOD) and quantification (LOQ) improved from 1.03 × 10-1 and 3.13 × 10-1 μg/mL using ordinary spectrophotometry to 2.8 × 10-2 and 8.7 × 10-2 μg mL-1 employing β-correction spectrophotometry. The probe offers rapid response, good anti-interference ability, reproducibility, and cost-effectiveness. The probe was successfully applied for detection of trace levels of cyanide ions in water with good repeatability. It has been also validated in water samples with good recoveries (99.2 ± 5.02 %). The experimental Student t test (texp = 1.2-1.5) was lower than the critical (texp = 2.78) at 95 % probability (n = 5). The stoichiometry and mechanism of formation of the cyano adduct were assigned and addressed.