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61.
Sonia Herranz Markéta Bocková María Dolores Marazuela Ji?í Homola María Cruz Moreno-Bondi 《Analytical and bioanalytical chemistry》2010,398(6):2625-2634
A surface plasmon resonance (SPR) biosensor for the detection of microcystins (MCs) in drinking water has been developed.
Several assay formats have been evaluated. The selected format is based on a competitive inhibition assay, in which microcystin-LR
(MCLR) has been covalently immobilized onto the surface of an SPR chip functionalized with a self-assembled monolayer. The
influence of several factors affecting sensor performance, such as the nature and concentration of the antibody, the composition
of the carrier buffer, and the blocking and regeneration solutions, has been evaluated. The optimized SPR biosensor provides
an IC50 0.67 ± 0.09 μg L−1, a detection limit of 73 ± 8 ng L−1, and a dynamic range from 0.2 to 2.0 μg L−1 for MCLR. Cross-reactivity to other related MCs, such as microcystin-RR (88%) and microcystin-YR (94%), has also been measured.
The SPR biosensor can perform four simultaneous determinations in 60 min, and each SPR chip can be reused for at least 40
assay–regeneration cycles without significant binding capacity loss. The biosensor has been successfully applied to the direct
analysis of MCLR in drinking water samples, below the provisional guideline value of 1 μg L−1 established by the World Health Organization for drinking water. 相似文献
62.
Roberta Del Sole Anna Scardino Maria Rosaria Lazzoi Lucia Mergola Sonia Scorrano Giuseppe Vasapollo 《Mikrochimica acta》2013,180(15-16):1401-1409
A molecularly imprinted polymer (MIP) for the specific retention of neopterin has been developed. A set of 6 polymers was prepared by radical polymerization under different experimental condition using methacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinker, with the aim to understand their influence on the efficiency of the MIP. The performance of each MIP was tested in batch experiments via their binding capacity. The MIP prepared in the presence of nickel ions in dimethylsulfoxide-acetonitrile mixture (P4) exhibited the highest binding capacity for neopterin (260 μmol per gram of polymer). A selectivity study with two other pteridines demonstrated the polymer P4 also to possess the best selectivity. Figure
A molecularly imprinted polymer for the specific retention of neopterin was developed. A set of 6 polymers was prepared under different experimental condition. The performance of each MIP was tested through their binding capacity. The MIP P4 prepared in the presence of nickel ions exhibited the highest binding capacity 相似文献
63.
Ayesha Kausar Sonia ZulfiqarCafer T. Yavuz Muhammad Ilyas Sarwar 《Polymer Degradation and Stability》2011,96(7):1333-1341
A new generation of segmented thermoplastic poly(urethane-thiourea-imide)s (PUTIs) was synthesized via reaction of polyethylene glycol and thiourea-based prepolymer with dianhydride as chain extenders. NCO-terminated prepolymer was synthesized from a new diisocyanate, 3-(3-((4-isocyanatophenyl)carbamoyl)thioureido)phenyl-4-isocyanatophenylcarbamate (IPCT), as a hard segment and PEG forming soft segment. The starting materials and polymers were characterized by conventional methods and physical properties such as solubility, solution viscosity, molecular weight, thermal stability and thermal behavior were studied. PUTIs showed partially crystalline structures. Weight average molecular weights of PUTIs (GPC measurements) were in the range of 1,68,694-1,97,035. Moreover, thermogravimetric analysis indicated that poly(urethane-thiourea-imide)s were fairly stable above 500 °C having T10 of 521-543 °C. Investigation of the results authenticated the approach of introducing thiourea (using IPCT) and imide structure in polyurethanes for the improvement of thermal stability. In comparison to typical polyurethanes, these polymers exhibited better heat resistance, chemical resistance as well as processability. 相似文献
64.
Maria V. Encinas Carlos M. Previtali Sonia G. Bertolotti Miguel G. Neumann 《Photochemistry and photobiology》1995,62(1):65-70
Abstract—
The reactions of the excited states of safranine T with aliphatic amines have been studied in methanol and acetonitrile. Quenching of the singlet and triplet states occurs by different mechanisms. Whereas the former excited state is quenched by a charge-transfer mechanism, the triplet state is quenched through proton transfer from the excited dye to the amine. This process leads to the unprotonated form of the dye in the triplet state, which is later quenched by amines to form the corresponding semireduced species. The monoprotonated triplet also undergoes self-quenching in both solvents (k = 1.2 × 108 M -1 s-1 ). 相似文献
The reactions of the excited states of safranine T with aliphatic amines have been studied in methanol and acetonitrile. Quenching of the singlet and triplet states occurs by different mechanisms. Whereas the former excited state is quenched by a charge-transfer mechanism, the triplet state is quenched through proton transfer from the excited dye to the amine. This process leads to the unprotonated form of the dye in the triplet state, which is later quenched by amines to form the corresponding semireduced species. The monoprotonated triplet also undergoes self-quenching in both solvents (k = 1.2 × 10
65.
Alegría Carrasco-Pancorbo Sonia Cortacero-Ramírez Alberto Fernández-Gutiérrez 《Talanta》2007,71(1):397-405
Two different families of compounds, i.e., phenolic and amino acids have been separated by capillary electrophoresis using a physically adsorbed polymer as capillary coating. The polymer used was N,N-dimethylacrylamide-ethylpyrrolidine methacrylate (DMA-EpyM) and it provided an stable coating by only flushing the capillary with a DMA-EpyM aqueous solution for 2 min between runs. The usefulness of this procedure has been demonstrated through the fast analysis of different families of solutes. Two different detection systems, diode-array detector and laser-induced fluorescence, have been used to determine phenolic acids and derivatized amino acids with fluorescein isothiocyanate, respectively. The main factors affecting reversal of electroosmotic flow (EOF) such as pH, type and concentration of buffer, and concentration and influence of organic solvents, as well as all the instrumental conditions were studied and optimized for both families of compounds. 相似文献
66.
67.
Fulvio Ratto Paolo Matteini Alberto Cini Sonia Centi Francesca Rossi Franco Fusi Roberto Pini 《Journal of nanoparticle research》2011,13(9):4337-4348
We investigate the photothermal conversion and transformation of gold nanoparticles with an initial dogbone shape after dispersion
in hydrated chitosan films, which is a representative model of biological tissue, and excitation by a CW diode laser for 1 min.
Gold nanodogbones are observed to undergo a distinct modification above a sharp threshold of ~11 W cm−2 and 110 °C. Surprisingly, the very same modification is achieved up to at least 36 W cm−2 and 250 °C. We use an analytical model derived from Gans theory to associate the change in color of the films with the change
in shape statistics of these gold nanoparticles. This model proves both convenient and dependable. We interpret the photothermal
transformation as a rearrangement of particles with a dogbone shape and an aspect ratio of 4.1 into rods with an aspect ratio
of 2.5, where material from the end lobes of the dogbones may relocate to the waists of the rods. In turn, additional transitions
to stable gold nanospheres may exhibit fairly slower kinetics. 相似文献
68.
Racemic 1-acetyl-2-methoxymethylferrocene, (±)-1 was subjected to asymmetric reduction with two different methodologies and complementary results were obtained. When the reduction of (±)-1 was carried out in the presence of CBS-oxazaborolidine catalyst and BH3·Me2S as the hydrogen source, both enantiomers of the substrate were converted with comparable reaction rates and selectivities. The corresponding diastereoisomeric ferrocenylalcohols 3a and 3b were obtained in a 1:1 ratio and >90% enantiomeric excess; this reaction profile being related with a parallel kinetic resolution with high ds1 and ds2 diastereofacial selectivities. On the contrary, the transfer hydrogenation of (±)-1 with HCOOH/triethylamine in the presence of (R,R)-Noyori’s catalyst proceeded via classical kinetic resolution, so that the formed (?)-3b or unreacted (+)-1 could be obtained in highly enantiopure form before or beyond 50% of the substrate conversion, respectively. Alcohol 3b with an (1Rp,S)- or (1Sp,R)-configuration is not easily accessible by the diastereoselective metallation/electrophilic quenching sequence routinely applied in the synthesis of planar chiral ferrocenes. As a result, the described procedures provide a valuable access to this useful starting material for the synthesis of homochiral related derivatives. 相似文献
69.
70.
Electrodes based on particulate carbon-epoxy or silicone composites have been formed and characterised using electrochemical methods, scanning electron microscopy and scanning electrochemical microscopy. These composites are rigid, exhibit high electrical conductivity and are stable in organic solvents for prolonged periods. The bulk resistance of the Araldite-M and Araldite-CW2215 based electrodes is low, 130+/-12 and 185+/-15 ohms, respectively. In contrast, the bulk resistance of the silicone based electrodes is 1480+/-112 ohms. The uncompensated resistance of electrochemical cells where the composites act as working electrodes is significantly larger than that expected on the basis of solution resistance alone, i.e., up to 7.5 kohms in the case of the silicone composites. These results are interpreted in terms of the presence of pores within the composite material. The response times of the composite electrodes to changes in the applied potential is between 3.1 and 7.2 ms which, although almost an order of magnitude longer than a comparable glassy carbon electrode, is sufficiently rapid to give useful voltammetric data for scan rates of several V s(-1). Close to ideal reversible cyclic voltammetry is observed for ferrocene under semi-infinite diffusion control for scan rates between 0.01 and 0.1 V s(-1) at the Araldite composites. In contrast, the large resistance associated with the silicone based materials causes quasi-reversible responses to be observed over this range of scan rate. Scan rate dependent cyclic voltammetry and time resolved chronoamperometry responses observed for ferrocene in solution are consistent with those expected for a random array of microelectrodes. Scanning electron microscopy and scanning electrochemical microscopy has been used to image the shape, size and electrochemical activity of the electroactive zones. In the case of Araldite-M, the quality of the electrode surface has been probed by comparing the rate of heterogeneous electron transfer at a composite microelectrode with that found for a carbon fibre electrode. The standard heterogeneous electron transfer rate constant, k degrees , is 6.0+/-0.1 x 10(-3) cm s(-1) for the composite compared to 1.5+/-0.1 x 10(-1) cm s(-1) for the carbon fibre electrode. While the smaller rate constant found for the composite suggests a less pristine surface, k degrees is sufficiently large to support reversible, electron transfer under typical electroanalytical conditions. These fundamental measurements will underpin the development of enzyme based biosensors for use in organic solvents. 相似文献