Synthesis and characterization of sol-gel silica films doped with size-selected gold nanoparticles.

Homogeneous nanocomposite silica films uniformly doped with size-selected gold nanoparticles (AuNPs) have been prepared by a combined use of colloidal chemistry and the sol-gel process. For this purpose, stable thiol-functionalized AuNPs (DDT-AuNPs) were first synthesized by a two-phase aqueous/organic system and, subsequently, dispersed in an acid-catalysed sol-gel silica solution. The microstructural morphology of the samples was investigated by x-ray diffraction and field emission scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) and UV-vis optical spectrophotometry were instead employed to investigate the elemental chemical behaviour and the evolution of the surface plasmon resonance (SPR) band of the AuNPs from their synthesis up to the formation of the Au-doped silica films. The results show that the size, shape and crystalline domains of the AuNPs remain unchanged during the entire preparation process, indicating that their aggregation or decomposition was prevented. XPS results show that the DDT-AuNPs lose the capping shells and oxidize themselves when dispersed in acid-catalysed sol-gel solutions, and that bare AuNPs are embedded in the SiO(2) films. A large broadening of the SPR band, observed for systems with DDT-AuNPs, suggests the presence of interface effects which cause a surface electron density lowering. Thiol chain detachment from the AuNPs determines an increase of the SPR peak intensity while the oxidation of the Au surfaces causes a red shift of its position. The latter is no longer observed in doped films, suggesting that no interfacial effects between bare AuNPs and the host medium are present.

On-line microdialysis-ion chromatographic determination of inorganic anions in olive-oil mill wastewater.

A fully automated method is presented for the determination of inorganic anions in olive-oil mill effluents using on-line dialysis-ion chromatography. The wastewater is first of all sonicated at room temperature to make it homogeneous, then diluted and microdialized. Most of the organic load of the effluents is removed in a few minutes without using reagents, while soluble anion quantitation remains unaffected. The clear solution is analyzed for the inorganic anions content by direct injection on to an ion chromatograph equipped with a conductivity detector. In the absence of standards, the separation efficiency of microdialysis has been investigated by spiking wastewater samples as well as standard oil emulsions with varying amounts of inorganic anions and subjecting them to microdialysis for different periods of time prior to performing instrumental analysis. Excellent spike recoveries and low relative standard deviations are obtained for all the anions if a 10 min microdialysis time is overcame. Chloride, nitrite, nitrate, phosphate and sulphate are not affected by the microdialysis procedure and their recovery is between 96 and 104% in wastewater as well as in standard oil emulsion. Calibration plots are linear over about two orders of magnitude. The dialysis membrane has been replaced after more than 100 analyses. The UV photolysis pre-treatment of the same sample evidences the different information that can be obtained by the two sample pre-treatment procedures.

Ion chromatographic determination of metals in biocompatibility testing.

The increasing numbers of materials used in surgical implants require a wide spectrum of tests to evaluate their biocompatibility. The release of metals is an important additional feature for determining the suitability for clinical applications of biomaterials such as ceramics and metals. Due to the difficulty of performing time-consuming experiments in vivo, one approach for rapidly determining the suitability of biomaterials and their interactions with the tissues with which they will come in contact is to perform in vitro tests, based on cell culture analysis, using solutions that reproduce the cleavage and binding capabilities of body fluids and tissues. The present work reports on the application of ion chromatography to the simultaneous determination of some metal ions in a few biologic media. Agar-Agar solution, "199 medium, " and betadine and Schiff's reagents were selected as some of the most representative biologic simulating solutions. A method is recommended for the pretreatment of the sample with minimal reagent addition since it is very rich in organic compounds and cannot be analyzed without pretreatment. The proposed procedure requires the sample to be subjected to oxidative UV photolysis for about 60 min in an UV digester at 85 degrees +/- 5 degrees C, followed by the ion chromatographic determination. Lead (II), cadmium (II), iron (III), copper (II), nickel (II), zinc (II), and cobalt (II) simultaneously were determined at microg/L levels.

LA-ICP-MS, IC and DPASV-DPCSV determination of metallic impurities in solar-grade silicon.

Stringent specifications are laid down for the silicon used for solar cells. The present work deals with the application of different techniques to the simultaneous determination of most common metallic impurities like iron, copper, nickel, zinc, lead and cadmium, in industrial process control. Laser ablation inductively coupled plasma mass spectrometry is quite expensive in apparatus, but it directly performs the analysis of solid silicon with very good sensitivity, even if coupled to considerable standard deviation, probably due to the material defects. Both ion chromatography and voltammetry need sample pre-treatment, but they are characterized by cheap and simple apparatus, suitable detection limits, good sensitivity and small standard deviation.

[Diagnostic imaging in the selection of candidates to orthotopic transplantation of the liver. Experience at a hospital lacking a transplantation department]. / Diagnostica per immagini nella selezione dei candidati al trapianto ortotopico del fegato. Esperienza in un ospedale non dotato di centro per trapianti.

We report the experience of our general hospital in selecting the patients for orthotopic liver transplantation (OLT). Fifty-one patients with cirrhosis were examined and 20 of them submitted to OLT from August, 1992, to November, 1995. For liver studies, the 20 transplant recipients were examined with US and plain and dynamic CT; 15/20 were submitted to CTAP, 10/20 to Lipiodol CT and 17/20 to angiography. The accuracy of these techniques in HCC detection was assessed by correlation with resected whole livers. The accuracy of duplex Doppler and color flow Doppler for portal and/or mesenteric vein thrombosis was evaluated by correlation with resected livers, CT and angiographic findings. Pathologic examinations diagnosed HCC in 5/20 transplant recipients: 2 lesions (1.5 cm and 2 cm; 2 cm and 3.5 cm) were found in 2 resected specimens (total hepatectomy) and 1 lesion was found in 3 cases (2.5 cm, 1.5 cm, 1 cm). The sensitivity of US, plain and dynamic CT in identifying HCC patients was 20%; US and CT specificity rates were 100% and 87%, respectively. CTAP sensitivity was 75% and the sensitivity of Lipiodol CT and angiography was 100%. Therefore, in our series, US was poorly sensitive in the detection of liver cancers, which may depend on the small number of patients, lesion size (< or = 3.5 cm) and the radiologists ignoring clinical and laboratory data on purpose. Nevertheless, the patients with a single HCC not exceeding 5 cm phi or with no more than 3 tumors, none of them exceeding 3 cm phi, are generally considered eligible for transplantation: therefore, our patients chosen for OLT on the basis of US and CT findings were actually eligible for transplantation in spite of US and CT false negative results. At US, the portal vein had an average caliber of 13.5 +/- 2.5 mm in 21/51 patients; the average caliber of the common hepatic artery was 6 +/- 1.5 mm in 49/51 patients; average spleen length was 174 +/- 38 mm. US showed ascites in 28/51 cases. In conclusion, considering also the long stand-by list for OLT, the first selection of transplant candidates could be performed with US and color flow Doppler, plain and dynamic CT. The patients who are ruled out as candidates for OLT on the basis of the findings of these imaging techniques and of clinical and laboratory findings are submitted to no further examination and referred to the transplantation unit. Otherwise, if conventional and color flow Doppler US and conventional CT are not enough to exclude a patient from OLT, the subject is submitted to more invasive (angiography, CTAP, Lipiodol CT) or less widespread (spiral CT, MRI) techniques.