DEVELOPMENT OF A HYBRID SORPTION–SPECTROSCOPIC SYSTEM BASED ON NITROSO-N-SALT IMMOBILIZED ON SILK FIBROIN FOR THE DETERMINATION OF Co(II) IONS

In this study, a hybrid sorption–spectroscopic system based on Nitroso-N-salt immobilized on a silk fibroin matrix was developed
for the determination of Co(II) ions. The immobilization process was optimized by investigating the effects of pH, contact time,
and reagent concentration on the analytical performance of the system. Spectrophotometric analysis showed that the maximum
absorption wavelength of Nitroso-N-salt was 368 nm, while the Co(II)–Nitroso-N-salt complex exhibited a maximum absorption
at 445 nm. The optimal immobilization pH ranged from 6.5 to 7.0. The immobilization efficiency reached 94%, whereas the
recovery value was 99%. Raman spectroscopy and X-ray fluorescence (XRF) analyses confirmed the successful immobilization of
Nitroso-N-salt on the silk fibroin matrix and the formation of a stable complex with Co(II) ions. The obtained results demonstrate
that the proposed hybrid system is a promising analytical material for the selective and sensitive determination of Co(II) ions in
aqueous media