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91.
Laura Rubio María Leticia Oca Luis Sarabia Inmaculada García María Cruz Ortiz 《Journal of Chemometrics》2016,30(2):58-69
Internal standards can be added at different stages of an analytical procedure. When they are added at the beginning of a multiresidue method and their behavior is not exactly the same as that of the analytes, the intended correction for small variations within the analytical process could not be achieved. Because of this, in the present work, the use of d ‐optimal designs together with desirability functions is proposed to state the experimental response under study. The overall desirability function used relates two analytical criteria: to assess a similar chemical behavior of each analyte in relation to its internal standard and to avoid a significant reduction of the absolute peak area of the internal standards. This strategy has been applied to the analysis of the effect of four factors related to the extraction and purification steps of six tranquillizers and a β‐blocker from pig muscle analyzed by liquid chromatography–tandem mass spectrometry. The effect of those factors has been evaluated by means of an ad hoc d ‐optimal design consisting of only 11 experiments. The resulting levels of the four factors that enable to achieve the greatest overall desirability have also been compared with those obtained when either the standardized or absolute peak area has been considered as response. Differences in both the significant factors and their optimum levels have been observed. It is noticeable that the experimental effort necessary to study the effect of the factors has been reduced by more than 50% thanks to the d ‐optimal design. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
92.
A. Martínez-de la Cruz S. Obregón Alfaro S. M. G. Marcos Villarreal 《Research on Chemical Intermediates》2010,36(8):925-936
Nanoparticles of α-Bi2Mo3O12 were prepared by the Pechini method. The process of formation of the bismuth molybdate was followed by simultaneous thermogravimetric and differential thermal analysis (TGA/DTA). Different samples of α-Bi2Mo3O12 were obtained at 400, 450, and 500 °C, and characterized by X-ray powder diffraction (XRD), nitrogen physisorption (BET), and scanning electron microscopy (SEM). When observed by SEM, the morphology of the sample obtained at the lowest temperature consisted of semi-spherical particles with an average diameter of 150 nm. On the other hand, the highest calcination temperature led to the formation of sintered particles of 500–600 nm. The photocatalytic activity of α-Bi2Mo3O12 was tested by photodegradation of the organic dyes rhodamine B (rhB) and indigo carmine (IC) under visible-light irradiation. The bismuth molybdate nanoparticles were able to bleach aqueous solutions of both organic dyes. The sample obtained at 400 °C was the best photocatalyst with half-lives, t 1/2, of 108 and 154 min for rhB and IC, respectively. 相似文献
93.
Elena Chekmeneva José Manuel Díaz‐Cruz Cristina Ariño Miquel Esteban 《Electroanalysis》2010,22(2):177-184
The complexation of the natural antioxidants α‐lipoic acid (ALA) and its reduced form dihydrolipoic acid (DHLA) with Hg2+ was investigated by a recently proposed differential pulse voltammetric (DPV) method using the rotating Au‐disk electrode. Complexation processes are proposed from the multivariate curve resolution by alternating least squares (MCR‐ALS) analysis of DPV titration data. Main complexes were both 1 : 1 Hg : ALA and Hg : DHLA, although the formation of 1 : 2 complexes can be also deduced. ALA and DHLA show different Hg2+‐binding patterns at different pH. Voltammetric findings are completed with the data obtained by electrospray ionization mass‐spectrometry (ESI‐MS), especially in negative mode. 相似文献
94.
Aline Machado de Castro Kelly Cristina Nascimento Rodrigues Pedro Juliana Cunha da Cruz Marcela Costa Ferreira Selma Gomes Ferreira Leite Nei Pereira 《Applied biochemistry and biotechnology》2010,162(7):2111-2122
Sugarcane bagasse is an agroindustrial residue generated in large amounts in Brazil. This biomass can be used for the production
of cellulases, aiming at their use in second-generation processes for bioethanol production. Therefore, this work reports
the ability of a fungal strain, Trichoderma harzianum IOC-4038, to produce cellulases on a novel material, xylan free and cellulose rich, generated from sugarcane bagasse, named
partially delignified cellulignin. The extract produced by T. harzianum under submerged conditions reached 745, 97, and 559 U L−1 of β-glucosidase, FPase, and endoglucanase activities, respectively. The partial characterization of this enzyme complex
indicated, using a dual analysis, that the optimal pH values for the biocatalysis ranged from 4.9 to 5.2 and optimal temperatures
were between 47 and 54 °C, depending on the activity studied. Thermal stability analyses revealed no significant decrease
in activity at 37 °C during 23 h of incubation. When compared to model strains, Aspergillus niger ATCC-16404 and Trichoderma reesei RutC30, T. harzianum fermentation was faster and its extract showed a better balanced enzyme complex, with adequate characteristics for its application
in simultaneous saccharification and fermentation processes. 相似文献
95.
J. Canotilho R. A. E. Castro M. T. S. Rosado S. C. C. Nunes M. S. C. Cruz J. S. Redinha 《Journal of Thermal Analysis and Calorimetry》2010,99(2):423-429
The growth of atenolol, pindolol and betaxolol hydrochloride from melt was investigated by differential scanning calorimetry
(DSC) and polarized light thermal microscopy (PLTM). Phase transitions occurring on cooling and subsequent reheating runs
performed between −160 °C and a temperature above the respective melting points were studied by DSC. The thermal cycles were
also followed by PLTM. Details about the dynamic of the crystallization front taken from microscopic observations are given.
An explanation of the results on the basis of molecular supramolecular recognition is advanced. 相似文献
96.
Rocio Díez Azofra Luis A. Sarabia Maria Cruz Ortiz 《Analytical and bioanalytical chemistry》2010,396(2):923-935
The objective of this work is to optimize a solid-phase extraction procedure for the simultaneous determination of sulfadiazine,
sulfamerazine, and sulfamethazine in milk by fluorimetric detection. For this task, an alternative strategy is employed, which
allows one to reduce noticeably the number of experiments without losing the quality of the estimations. It consists of the
use of a D-optimal design together with PARAFAC decomposition for the calculation of the response in the experimental design.
Effects of amount of cartridge sorbent, kind of milk, volume of conditioning solutions, kind of wash and elution, and kind
of mixture of sulfonamides have been evaluated, for maximizing sulfonamide mean recovery and minimizing its standard deviation.
Since milk without sulfonamides may give some matrix effect over the fluorescence signal, its behavior has also been studied.
Optimal conditions have been selected where the ratio between sulfonamide recovery and milk without sulfonamides was the highest,
which are 500 mg of cartridge sorbent, acid wash, and elution and 3 mL of conditioning solutions. The type of milk and mixture
of sulfonamides not significant. This makes the procedure suitable for the combined determination of sulfadiazine, sulfamerazine,
and sulfamethazine in any kind of milk. Finally, an experimental procedure is proposed, obtaining a sulfonamide mean recovery
equal to 68.5% with values of standard deviation between 7 and 8 μg kg−1. 相似文献
97.
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
98.
WO3 nanoparticles were synthesized by the precipitation method varying the time employed in the formation of their precursor in aqueous media and the calcination temperature. The WO3 crystallization process and morphology of the synthesized samples were followed by the XRD, TEM and SEM techniques. The effects of the calcination temperature on the surface area and optical properties of the WO3 nanoparticles were also investigated. Nanoparticles with morphologies such as square and rectangular plates and ovoid forms were observed for the different experimental conditions. WO3 nanoparticles with different morphologies were tested for the photocatalytic degradation of organic dyes. In general, the photocatalysts showed a capacity to bleach the dye solution in the following sequence: indigo carmine (IC) > rhodamine B (rhB) > congo red (CR). The extent of mineralization was determined by means of total organic carbon (TOC) measurements, which showed a satisfactory TOC reduction (93%, within 75 h) only for IC. This value was even better than the one concerning the P-25 Degussa reference. 相似文献
99.
Ladie Kimberly De La Cruz Xiaoxiao Yang Anna Menshikh Maya Brewer Wen Lu Minjia Wang Siming Wang Xingyue Ji Alyssa Cachuela Haichun Yang David Gallo Chalet Tan Leo Otterbein Mark de Caestecker Binghe Wang 《Chemical science》2021,12(31):10649
Carbon monoxide as an endogenous signaling molecule exhibits pharmacological efficacy in various animal models of organ injury. To address the difficulty in using CO gas as a therapeutic agent for widespread applications, we are interested in developing CO prodrugs through bioreversible caging of CO in an organic compound. Specifically, we have explored the decarboxylation–decarbonylation chemistry of 1,2-dicarbonyl compounds. Examination and optimization of factors favorable for maximal CO release under physiological conditions led to organic CO prodrugs using non-calorific sweeteners as leaving groups attached to the 1,2-dicarbonyl core. Attaching a leaving group with appropriate properties promotes the desired hydrolysis–decarboxylation–decarbonylation sequence of reactions that leads to CO generation. One such CO prodrug was selected to recapitulate the anti-inflammatory effects of CO against LPS-induced TNF-α production in cell culture studies. Oral administration in mice elevated COHb levels to the safe and efficacious levels established in various preclinical and clinical studies. Furthermore, its pharmacological efficacy was demonstrated in mouse models of acute kidney injury. These studies demonstrate the potential of these prodrugs with benign carriers as orally active CO-based therapeutics. This represents the very first example of orally active organic CO prodrugs with a benign carrier that is an FDA-approved sweetener with demonstrated safety profiles in vivo.1,2-Dicarbonyl compounds with FDA-approved sweeteners as leaving groups deliver CO for protection against acute kidney injury in mice. 相似文献
100.
Villegas I. L. Cuadrado-Laborde C. Díez A. Cruz J. L. Martínez-Gámez M. A. Andrés M. V. 《Laser Physics》2011,21(9):1650-1655
We show an actively Q-switched ytterbium-doped strictly all-fiber laser. Cavity loss modulation is achieved in a tapered optical
fiber by core-to-cladding mode-coupling induced by travelling flexural acoustic waves. When the acoustical signal is switched-off,
the optical power losses within the cavity are reduced, and then a laser pulse is emitted. Trains of Q-switched pulses were
successfully obtained at repetition rates in the range 1–10 kHz, with pump powers between 59 and 88 mW, at the optical wavelength
of 1064.1 nm. Best results were for laser pulses of 118 mW peak power, 1.8 μs of time width, with a pump power of 79 mW, at
7 kHz repetition rate. 相似文献