RESUMO
Colloidal suspensions of oxocarbon-encapsulated gold nanoparticles have been synthesized in a one-step procedure by pulsed-laser ablation (PLA) at 532 nm of a solid gold target placed in aqueous solution containing CO2 absorbers, but without any stabilizing agent. Multi-wavelength surface enhanced Raman spectroscopy allows the identification of adsorbed amorphous carbon and graphite, Au-carbonyl, Au coordinated CO2-derived bicarbonates/carbonates and hydroxyl groups around the AuNPs core. Scanning electron microscopy, energy dispersive x-ray analysis and high resolution transmission electron microscopy highlight the organic shell structure around the crystalline metal core. The stability of the colloidal solution of nanocomposites (NCs) seems to be driven by solvation forces and is achieved only in neutral or basic pH using monovalent hydroxide counter-ions (NaOH, KOH). The NCs are characterized by a blue shift of the localized surface plasmon resonance (LSPR) band typical of metal-ligand stabilization by terminal π-back bonding, attributed to a core charging effect caused by Au-carbonyls. Total organic carbon measurements detect the final content of organic carbon in the colloidal solution of NCs that is about six times higher than the value of the water solution used to perform PLA. The colloidal dispersions of NCs are stable for months and are applied as analytical probes in amino glycoside antibiotic LSPR based sensing.
RESUMO
The selective determination of norfloxacin in mixtures with other fluorquinolones was achieved by synchronous scanning solid surface room-temperature phosphorimetry (SSRTP) and Th(NO(3))(4) as selective phosphorescence inducer. The method also allowed the determination of levofloxacin in a sequential way. The optimization of experimental conditions was made through an univariate approach, in order to find the best conditions for norfloxacin phosphorescence, followed by a 2(3) factorial design in order to verify interaction among relevant variables, to check robustness for each variable and to perform final adjustment of parameters. Absolute limit of detection (ALOD) for norfloxacin was 12ng with a linear signal response extending up to 400ng. Under the same experimental conditions set for norfloxacin, the ALOD for levofloxacin was 13ng with linear signal response up to 450ng. Accuracy of the method, using Th (IV) as selective phosphorescence inducer, was evaluated through the analysis of commercial and simulated pharmaceutical formulations with recoveries between 94.4 and 101% for norfloxacin and 95.9 and 103.8% for levofloxacin. The use of Cd (II), a traditional phosphorescence inducer for fluorquinolones, did not allow selective determination of norfloxacin. Further studies indicated the potential application of the method in urine samples.
Assuntos
Medições Luminescentes/métodos , Tálio/química , Animais , Anti-Infecciosos Urinários/análise , Humanos , Levofloxacino , Norfloxacino/análise , Ofloxacino/análiseRESUMO
An analytical method based on solid surface room temperature phosphorescence (SSRTP) for the determination of rescinamine was developed. Signal enhancements were obtained by heavy atom effect, use of surfactant agent and use of basic medium. Alternatively, an ultraviolet treatment of the analyte was tried in order to induce a phoshor with higher phosphorescence quantum efficiency. A limit of detection of 2.70 ng and linear dynamic range of 2 orders of magnitude were achieved in paper substrate treated for background reduction. A study was performed to verify potential interferences of several pharmacological active ingredients that could be associated with rescinamine in a pharmaceutical preparation. The method was tested by analyzing rescinamine in three different laboratory-made tablets.