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

Abstract

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 λ_max = 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 (t_exp = 1.2–1.5) was lower than the critical (t_exp = 2.78) at 95 % probability (n = 5). The stoichiometry and mechanism of formation of the cyano adduct were assigned and addressed.