Determining trace amounts of zinc in environmental and biological samples using solid-phase spectrophotometry

An eco-friendly analytical system utilizing solid-phase spectrophotometry is established for zinc quantification in environmental and biological samples. This method involves sorption of Zn²⁺ as 4-(2-amino-3-hydroxypyridine-4-yl-azo)1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (AHDDO) onto Dowex 1-X8 type anion-exchange resin. The influence of various analytical factors like sample volumes, quantity of AHDDO and pH of the aqueous solution was examined. Direct absorbance assessments of the gel, contained within a 1.0 mm cuvette, were recorded at wavelengths of 640 and 795 nm. The calculated molar extinction coefficients were 3.91 × 10⁷ for 500 mL and 9.78 × 10⁷ L mol^-1 cm^-1 for 1000 mL. A linear calibration curve was obtained within the range 20-2250 ng mL^-1 with RSD of >2.55 (<i>n</i> = 10). Employing 50 mg ion-exchange material, the quantification and detection limits were 50 and 15 ng mL^-1 for 500 mL sample and 20 and 6.0 ng mL^-1 for 1000 mL sample, respectively. Expanding the volume of the sample may improve sensitivity. The presence of other examined anions and cations showed no notable interference in the quantification of Zn²⁺. The suggested SPS system was utilized for assessing Zn²⁺ in environmental and biological specimens. The outcomes were evaluated against those acquired through FAAS, confirming the method's validity.