Sorption-spectrophotometric determination of bismuth ion (III) using immobilised xylenol orange on modified polyacrylonitrile

This study presents a new sorption-spectrophotometric method for determining bismuth (III) ions using a new adsorbent for PPM-1 fibre immobilised with xylenol orange. The complex exhibited a maximum reflectance at 550 nm and absorption at 530 nm, indicating stable formation. The method demonstrated high sensitivity with a detection limit of 0.1 mu g/mL and high selectivity, minimising interference from other metal ions. Optimal pH for complex formation was 1.37, with faster response and higher sensitivity in the immobilised state (detection limit 0.12 mu g/mL, formation time 10 minutes). The complex adhered to the Bouguer-Lambert-Beer law within 3-42 mu g/25 mL. Interferences from Cu2+, Ag+, Pd2+, and Fe3+ were reduced when the reagent was immobilised. Conductometric analysis confirmed the stable formation of the complex. Validation using model mixtures and pharmaceutical preparations showed accurate bismuth determination with an error margin of 0.005. For example, a mixture containing 25 mu g of bismuth with zinc and cadmium yielded 25.20 mu g, and De-nol had a found content of 49.50 mu g for 50.00 mu g added. IR spectroscopy confirmed complex formation with significant shifts in absorption bands. SEM and EDS analysis validated the reagent's effective immobilisation and interaction with bismuth ions. The method provides a rapid, accurate, and environmentally friendly approach for bismuth analysis, demonstrating high reproducibility, sensitivity, and selectivity, suitable for environmental monitoring and pharmaceutical quality control.