Laser cleaning of works of art: evaluation of the thermal stress induced by Er:YAG laser

The Er:YAG laser has proven particularly efficient in cleaning procedures of works of art. The removal of the superficial deposits is achieved through melting, thermal decomposition and evaporation. However, the energy absorbed by vibrational modes is dissipated as heat, increasing the temperature of the surface coating that could cause damage on the object. The aim of this study was to evaluate the temperature increase induced by a Er:YAG MonaLaser (LLC., Orlando, FL, USA). To that purpose, we designed a dedicated device to perform the tests in an inert atmosphere or with a wetting agent, to measure the radiant energy per laser pulse. Tests were carried out both on graphite, which absorbs IR radiation and showed a very intense flash emission, and on different kind of samples representative of materials with different levels of conductivity and thermal diffusivity. Results obtained showed that the temperature increase in the irradiated surface depends on the substrate but never causes the damage of the organic and inorganic material. The use of a solvent as wetting agent has been also tested.     

Quantification of p-cresol sulphate in human plasma by selected reaction monitoring

Chronic renal failure patients accumulate in the blood molecules that are normally excreted into the urine. p-Cresol Sulphate (pCS), the most representative retained toxin, shows a high level of toxicity. Therefore, its quantification could represent a prediction factor to determine the risk of endothelial dysfunction and cardiovascular complication and response to the haemodialysis treatment. The aim of this study was to evaluate the suitability of the multiple reaction monitoring (MRM) technique in order to improve the sensibility, the selectivity and the timing of pCS detection in a small amount of plasma. Deproteinized plasma of uremic patients was concentrated and dissolved in liquid chromatography (LC) mobile phase solution. pCS was quantified by LC coupled to tandem mass spectrometry (LC-MS/MS) on a triple-quadrupole mass spectrometer. Selective and sensitive detection of pCS was achieved by selecting the specific parent ion and monitoring two specific fragment ions. The MRM assay was carried out using the following transitions: m/z 187?→?80.00 and m/z 187?→?107.00. A good linearity was observed for each calibration curve. The intra-day and inter-day results showed a good precision and repeatability. The percentage recoveries indicate an optimal selectivity of the analytical method. The MRM assay to quantify pCS in a small amount of human plasma is rapid, highly sensitive, selective and with a good repeatability.     

Determination of perfluorinated compounds in mollusks by matrix solid-phase dispersion and liquid chromatography–tandem mass spectrometry

Perfluorinated compounds (PFCs) have been used for over 40 years in different commercial and industrial applications mainly as surfactants and surface protectors and have become an important class of marine emerging pollutants. This study presents the development and validation of a new analytical method to determine the simultaneous presence of eight PFCs in different kinds of mollusks using matrix solid-phase dispersion (MSPD) followed by liquid chromatography–tandem mass spectrometry (LC-MS/MS). Simplicity of the analytical procedure, low volume of solvent and quantity of sample required, low global price, and integration of extraction and clean-up into a single step, are the most important advantages of the developed methodology. Solvent, solid support (dispersing agent), clean-up sorbent, and their amounts were optimized by means of an experimental design. In the final method, 0.5 g of sample are dispersed with 0.2 g of diatomaceous earth and transferred into a polypropylene syringe containing 4 g of silica as clean-up sorbent. Then, analytes are eluted with 20 mL of acetonitrile. The extract is finally concentrated to a final volume of 0.5 mL in methanol, avoiding extract dryness in order to prevent evaporation losses and injected in the LC-MS/MS. The combination of this MSPD protocol with LC-MS/MS afforded detection limits from 0.05 to 0.3 ng g⁻¹. Also, a good linearity was established for the eight PFCs in the range from limit of quantification (LOQ) to 500 ng mL⁻¹ with R ² > 0.9917. The recovery of the method was studied with three types of spiked mollusk and was in the 64–126% range. Moreover, a mussel sample was spiked and aged for more than 1 month and analyzed by the developed method and a reference method, ion-pair extraction, for comparison, producing both methods statistically equal concentration values. The method was finally applied to the determination of PFCs in different kinds of mollusks revealing concentrations up to 8.3 ng g⁻¹ for perfluoroundecanoic acid.     

Determination of terbuthylazine and desethylterbuthylazine in human urine and hair samples by eletrospray ionization-liquid chromatography/triple quadrupole mass spectrometry

Terbuthylazine (TBA) is a widely applied herbicide and an environmental contaminant. Following its use, humans, such as agricultural workers and rural residents, may be exposed. An isotope-dilution liquid chromatography coupled to electrospray-tandem mass spectrometry method for the determination of TBA, and its metabolite desethylterbuthylazine (DET) in human urine and hair was developed and validated. Under the optimised conditions, analytes were extracted from urine using a solid phase cartridge or from hair by sonication in methanol. Analytes were separated using a C18 reversed-phase chromatographic column and quantified, after positive ionization using a heated electrospray source, by a triple quadrupole mass detector in the selected reaction monitoring mode. Validation showed linear dynamic ranges up to 100 μg/L or 5.00 ng/mg hair, inter- and intra-run precisions <7%, and accuracies within 12% of spiked concentrations. Limits of quantification were 0.25 μg/L in urine and 0.01 ng/mg hair for both TBA and DET. Matrix effect evaluation showed that the isotope dilution approach allowed for the control of bias sources. TBA and DET were determined in specimens of agriculture workers exposed to TBA using the validated method. Hair samples contained TBA levels in the low nanogram per milligram range, and urine samples contained DET levels in the low microgram per liter range. Conversely, TBA levels in urine samples and DET levels in hair samples were always below the limit of quantification.     

Benzylium versus tropylium ion dichotomy: vibrational spectroscopy of gaseous C8H9+ ions

Definitely different: the path towards sorting out a long-standing dichotomy in carbocation chemistry is disclosed by infrared multiple photon dissociation spectroscopy of tropylium and benzylium isomers of C(8)H(9)(+) ions.     

Photo-controlled release of zinc metal ions by spiropyran receptors anchored to single-walled carbon nanotubes

Light controllable release of antinflammatory zinc ions by a smart multifunctional material composed of spiropyrans and single walled carbon nanotubes (SWNTs) is demonstrated. The exploitation of a number of complementary characterization techniques allows the investigation of both composition and performance of the multifunctional SP/SWNT nanomaterial developed. Moreover, its suitability for potential applications in bio-systems is suggested by the effective removal of the metal catalyst and the introduction of biocompatible linkers into the SP/SWNT material. The realization of potential photo controllable SP/SWNTs based drug delivery systems (DDSs) is envisaged, where nanotubes act as intracellular carriers of light modulated receptors for bioactive agents.     

Self-assembling endohedrally doped CdS nanoclusters: new porous solid phases of CdS

Hollow CdS nanoclusters were predicted to trap alkali metals and halogen atoms inside their cavity. Furthermore, electron affinities (EA) of endohedrally halogen doped clusters and ionization potentials (IE) of endohedrally alkali doped clusters were predicted to be very similar. This makes them suitable to build cluster-assembled materials, in the same vein as do related ZnO, ZnS and MgO nanoclusters, which yield porous solid materials. With this aim in mind, we have focused on the assembly of bare Cd(i)S(i) and endohedral K@Cd(i)S(i)-X@Cd(i)S(i) (i = 12, 16, X = Cl, Br) clusters in order to obtain solids with tailored semiconducting and structural properties. Since these hollow nanoclusters possess square and hexagonal faces, three different orientations have to be considered, namely, edge-to-edge (E-E), square-to-square (S-S) and hexagon-to-hexagon (H-H). These three orientations lead to distinct zeolite-like nanoporous bulk CdS solid phases denoted as SOD, LTA and FAU. These solids are low-density crystalline nanoporous materials that might be useful in a wide range of applications ranging from molecular sieves for heterogeneous catalysis to gas storage templates.     

New half sandwich Ru(II) coordination compounds for anticancer activity

With the aim of expanding the structure-activity relationship investigation, the series of Ru(II) half sandwich coordination compounds of the type [Ru([9]aneS3)(chel)(L)](n+) previously described by us (where [9]aneS3 is the neutral face-capping ligand 1,4,7-trithiacyclononane, chel is a neutral or anonic chelating ligand, L = Cl(-) or dmso-S, n = 0-2) was extended to 1,4,7-triazacyclononane ([9]aneN3). In addition, new neutral N-N, and anionic N-O and O-O chelating ligands, i.e. dach (trans-1,2-diaminocyclohexane), pic(-) (picolinate), and acac(-) (acetylacetonate), were investigated in combination with both [9]aneS3 and [9]aneN3. Overall, ten new half-sandwich complexes were prepared and fully characterized and their chemical behaviour in aqueous solution was established. The single-crystal X-ray structures of eight of them, including the versatile precursor [Ru([9]aneN3)(dmso-S)(2)Cl]Cl (9), were also determined. The results of in vitro antiproliferative tests performed on selected compounds against MDA-MB-231 human mammary carcinoma cells confirmed that, in this series, only compounds that hydrolyse the monodentate ligand at a reasonable rate show moderate activity, provided that the chelate ligand is a hydrogen bond donor.     

Tuning the Adsorption Properties of Isoreticular Pyrazolate-Based Metal-Organic Frameworks through Ligand Modification

Two isoreticular series of pyrazolate-based 3D open metal-organic frameworks, MBDP_X, adopting the NiBDP and ZnBDP structure types [H(2)BDP = 1,4-bis(1H-pyrazol-4-yl)benzene], were synthesized with the new tagged organic linkers H(2)BDP_X (X = -NO(2), -NH(2), -OH). All of the MBDP_X materials have been characterized through a combination of techniques. IR spectroscopy proved the effective presence of tags, while X-ray powder diffraction (XRPD) witnessed their isoreticular nature. Simultaneous TG/DSC analyses (STA) demonstrated their remarkable thermal stability, while variable-temperature XRPD experiments highlighted their high degree of flexibility related to guest-induced fit processes of the solvent molecules included in the channels. A structural isomer of the parent NiBDP was obtained with a sulfonate tagged ligand, H(2)BDP_SO(3)H. Structure solution from powder diffraction data collected at three different temperatures (room temperature, 90, and 250 °C) allowed the determination of its structure and the comprehension of its solvent-related flexible behavior. Finally, the potential application of the tagged MOFs in selective adsorption processes for gas separation and purification purposes was investigated by conventional single component adsorption isotherms, as well as by advanced experiments of pulse gas chromatography and breakthrough curve measurements. Noteworthy, the results show that functionalization does not improve the adsorption selectivity (partition coefficients) for the resolution of gas mixtures characterized by similar high quadrupole moments (e.g., CO(2)/C(2)H(2)); however, the resolution of gas mixtures containing molecules with highly differentiated polarities (i.e., N(2)/CO(2) or CH(4)/CO(2)) is highly improved.