Xerogels Modified with 4-(2-Pyridylazo)-Resorcinol and Cetylpyridinium Chloride: Determination of Zinc in Solutions by Solid-Phase Spectrophotometry

Silicon dioxide-based xerogels modified with 4-(2-pyridylazo)-resorcinol (PAR) and cetylpyridinium chloride (CP) were synthesized. The concentration of PAR and CP in the hydrolyzed mixture in the ranges (0.6–3.10) × 10^–3 and (5–12) × 10^–3 M, respectively, does not affect the rate of gel formation as well as the specific surface area and average pore diameter of xerogels obtained upon drying in a microwave oven with a power of 600 Wt. It was found that the retention of PAR can be significantly improved in the presence of CP. Reactions of zinc with modified xerogels were studied by solid-phase spectrophotometry at different concentrations of PAR and CP, pH of the solution, and equilibrium time. A procedure was developed for determining 0.1–4.5 mg/L zinc in solutions by solid-phase spectrophotometry. Results of determining zinc in acid soil extracts and milk ash are given.