Use of Silica with Immobilized 2-Nitrozo-1-Naphthol-4-Sulfonic Acid for the Sorption–Photometric Determination of Palladium

Silica modified with 2-nitroso-1-naphthol-4-sulfonic acid (NNS), quantitatively extracting palladium(II) from solutions in the pH range 1–8, is proposed for the preconcentration and photometric determination of palladium(II) in the adsorbent phase. In the sorption of palladium(II) from solutions with pH 1–3, complex compounds of the stoichiometry Pd : NNS = 1 : 2 were formed on the adsorbent surface. They has intense lilac color and a maximum in diffuse reflectance spectrum at 550 nm. A procedure is developed for sorption–photometric determination of palladium in the version of diffuse reflectance spectroscopy with a limit of detection 0.03 µg per 0.1 g of the sorbent. The analytical range is 0.1–10 µg/0.1 g. The procedure was tested in the determination of palladium in wastewater and water extract from the soil.