Simultaneous determination of catechins, rutin, and gallic acid in Cistus species extracts by HPLC with diode array detection

A simple high-performance liquid chromatography method using a diode array detector (DAD) is developed for the simultaneous analysis of five major catechins: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GCT), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), and the phenolic plant metabolites gallic acid (GA) and rutin (RT) in lyophilized extracts of Cistus species. The optimal analytical conditions are investigated to obtain the best resolution and the highest UV sensitivity for the quantitative detection of catechins. The optimized conditions (acetonitrile-phosphate buffer 50mM, pH 2.5, gradient elution system on a C(18) reversed-phase column with a flow rate of 1 mL/min and UV absorbance at 210 nm) allowed a specific and repeatable separation of the studied analytes to be achieved. All compounds are successfully separated within 32 min. Calibration curves are linear in the 2-50 microg/mL range for GCT, C, and EGCG and in the 5-50 microg/mL range for GA, EGC, EC, and RT. The limit of detection values ranged from 0.24 to 0.74 microg/mL. The limit of quantitation limit values ranged from 0.77 to 1.94 microg/mL. The validated method is applied to the determination of the specific phytochemical markers GA, GCT, C, and RT in Cistus incanus and Cistus monspeliensis lyophilised extracts. The recovery values ranged between 78.7% and 98.2%. The described HPLC method appears suitable for the differentiation and determination of the most common catechins together with the glycoside rutin and the phenolic compound gallic acid and can be considered an effective and alternative procedure for the analyses of this important class of natural compounds.     

Determination of Mercury by Anodic Stripping Voltammetry with a Gold Nanoparticle‐Modified Glassy Carbon Electrode

The aim of this work is the development of a procedure for the determination of aqueous Hg(II) by anodic stripping voltammetry at a gold nanoparticle‐modified glassy carbon electrode (AuNPs‐GCE). The signal of aqueous Hg(II) was measured in the square wave mode; the effect of potential scan parameters, deposition potential and deposition time on the analytical signal was examined. The supporting electrolyte was 0.06 M HCl. The repeatability, the linearity, the accuracy, the detection limit of the procedure and the interferences of other cations and of anions were evaluated. The performance of the AuNPs‐GCE was compared with those of a solid (SGE) and a film (FGE) gold electrode: the AuNPs‐GCE showed to provide lower detection limits and higher repeatability. The renewable surface permits to eliminate memory effects, to maintain a stable baseline and response, and to avoid frequent mechanical cleaning steps. The applicability of the AuNPs‐GCE for Hg(II) determination in drinking waters, sediments and pharmaceuticals was demonstrated.     

Proteome analysis of human dorsolateral prefrontal cortex using shotgun mass spectrometry

The prefrontal cortex executes important functions such as differentiation of conflicting thoughts, correct social behavior and personality expression, and is directly implicated in different neurodegenerative diseases. We performed a shotgun proteome analysis that included IEF fractionation, RP-LC, and MALDI-TOF/TOF mass spectrometric analysis of tryptic digests from a pool of seven human dorsolateral prefrontal cortex protein extracts. In this report, we present a catalog of 387 proteins expressed in these samples, identified by two or more peptides and high confidence search scores. These proteins are involved in different biological processes such as cell growth and/or maintenance, metabolism/energy pathways, cell communication/signal transduction, protein metabolism, transport, regulation of nucleobase, nucleoside, nucleotide and nucleic acid metabolism, and immune response. This analysis contributes to the knowledge of the human brain proteome by adding sample diversity and protein expression data from an alternative technical approach. It will also aid comparative studies of different brain areas and medical conditions, with future applications in basic and clinical research.     

Direct measurement of the double emittance minimum in the beam dynamics of the sparc high-brightness photoinjector

In this Letter we report the first experimental observation of the double emittance minimum effect in the beam dynamics of high-brightness electron beam generation by photoinjectors; this effect, as predicted by the theory, is crucial in achieving minimum emittance in photoinjectors aiming at producing electron beams for short wavelength single-pass free electron lasers. The experiment described in this Letter was performed at the SPARC photoinjector site, during the first stage of commissioning of the SPARC project. The experiment was made possible by a newly conceived device, called an emittance meter, which allows a detailed and unprecedented study of the emittance compensation process as the beam propagates along the beam pipe.     

Effective monoallylation of anilines catalyzed by supported KF

A mild and straightforward monoallylation procedure for different anilines is described using the efficient, inexpensive, noncorrosive, and environmentally friendly reagent KF-Celite. By using only a 1/1.2 stoichiometric ratio of electrophilic reagent to aniline, in very short reaction times, the monoallylated products are obtained in high isolated yields via this procedure, which works very effectively regardless of the electronic nature of the substituent on the ring, although electron withdrawing groups make the reactions go even faster.     

Determination of trapidil in human serum and urine by derivative UV spectrophotometry after selective solid-phase extraction

A novel analytical technique able to determine the anti-ischemic drug trapidil in human serum and urine is proposed. In order to achieve satisfactory sensitivity and selectivity, an extraction procedure was required to isolate the drug from complex matrixes such as serum and urine. A solid-phase extraction procedure was investigated to both increase the analyte concentration and eliminate the interfering molecules present in large amounts in both matrixes. Optimization of the extraction step was realized by selecting a new polymeric sorbent based on a surface-modified styrene–divinylbenzene polymer which provided fast and efficient drug extraction. Drug quantification was performed by using the third-order derivative spectra of the SPE eluates. Absorbance specific signals at ³D_335,316 and ³D₃₁₆ nm for urine and serum, respectively, were demonstrated to be directly proportional to drug concentration and barely affected by residual matrix interferences. Under the optimized experimental conditions the calibration plots were linear over the concentration range 0.2–50 μg mL⁻¹. The method was validated by analysis of a series of spiked samples. Accuracy (recovery of 95 and 94% for serum and urine, respectively) and precision (RSD below 4%) were good. Figure Assay of Trapidil in biological fluids by SPE and derivative spectrophotometry     

A multiplicity theorem for the Neumann p-Laplacian with an asymmetric nonsmooth potential

We consider a nonlinear Neumann problem driven by the p-Laplacian differential operator with a nonsmooth potential (hemivariational inequality). By combining variational with degree theoretic techniques, we prove a multiplicity theorem. In the process, we also prove a result of independent interest relating and local minimizers, of a nonsmooth locally Lipschitz functional.