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A combined experimental and computational study of the interactions of three sulfonamides--sulfadiazine, sulfamethazine, and sulfachloropyridazine--embedded into the cages of high silica zeolite Y is here proposed. For all host-guest systems, the close vicinity of aromatic rings with zeolite framework was evidenced by multidimensional and multinuclear ((1)H, (13)C, (29)Si) SS-NMR measurements. Host-guest and guest-guest interactions were also elucidated by in situ FTIR spectroscopy and confirmed by ab initio computational modeling. Single molecules of sulfamethazine and sulfachloropyridazine were stabilized inside the zeolite cage by the vicinity of methyl and amino groups, respectively. Sulfadiazine is present in both monomeric and dimeric forms. Multiple weak H-bonds and van der Waals type interactions between organic molecules and zeolite are responsible for the irreversible extraction from water of all the examined sulfa drugs.

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Fourier transform infrared spectroscopy (FT-IR), surface-enhanced Raman spectroscopy (SERS), and nuclear magnetic resonance (NMR) (1H, 13C, and 31P) have been applied to the study of fractions of humic acids in Irish peat. Owing to the high fluorescence of these materials, no Raman spectra have been obtained, up to now, for the characterization of humic acids. The SERS technique was employed for the first time in the study of these complex substances, demonstrating that very valuable information about the aromatic groups and the spacial conformation of these macromolecules in water solution can be obtained. The combined use of these techniques has evidenced an increase of oxygenated groups in those fractions containing humic acids with low molecular weight. The presence of a greater number of carboxylate and phenolic groups can explain the high concentration of metals and phosphate ions found in these fractions.

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