Hg and Cu selective detection using a dual channel receptor based on thiopyrylium scaffoldings

2,4,6-Triphenylthiopyrylium functionalized with an aza-oxa-thia macrocycle is able to selectively recognize Hg²⁺ cation by a color change and Cu²⁺ cation by a remarkable significant emission enhancement.     

Euryjanicin A: a new cycloheptapeptide from the Caribbean marine sponge Prosuberites laughlini

A new proline-containing cycloheptapeptide, euryjanicin A (1), has been isolated from the marine sponge Prosuberites laughlini indigenous to Puerto Rico, and its structure established by an X-ray crystal structure determination. The absolute configuration of each amino acid residue was determined by Marfey’s method.     

Mixing chambers in flow analysis: A review

Inclusion of a mixing chamber in a flow system is critically rev—iewed in-relation to sample dilution, improvement of mixing conditions and exploitation of exponential concentration lessening. Analytical perspectives related to the use of a mixing chamber such as time-based flow analysis, flow titrations, and analyte separation/concentration are also discussed along with the examination of several ordinary manifold components that might act as mixing chambers. The possibility of using the mixing chamber in order to accommodate or to carry out the multiple steps inherent to the specific analytical procedure or, in other words, to behave as a mini-laboratory, is also highlighted. This aspect is foreseen as a logical evolution of the lab-on-a-valve and the flow-batch concepts. The article is published in the original.     

Nitrate reduction on Pt(1 1 1) surfaces modified by Bi adatoms

This work presents the effect of Bi modification of Pt(1 1 1) electrodes on the electroreduction of nitrate anions by using voltammetric and FTIR experiments. On Pt(1 1 1) nitrate consumption occurs at potentials lower than 0.35 V, but with Pt(1 1 1)/Bi this process is shifted to significantly higher potentials (0.6–0.7 V). In the latter surface N₂O was observed as the main product in solution. Different forms of adsorbed NO were detected on the adatom covered surfaces as well as on clean Pt(1 1 1).     

Unusual adsorption state of carbon monoxide on single-crystalline gold electrodes in alkaline media

We report an unusual and not previously reported adsorption state of CO on a Au(1 1 1) electrode and a hexagonally reconstructed Au(1 0 0) surface. Chemisorbed CO exhibits a reversible adsorption feature close to the onset of the oxidation of CO in solution. We suggest that the voltammetric feature is associated with the co-adsorption (and desorption) of OH^- from the alkaline solution at low potential.     

Practical guidelines for characterization of O‐diglycosyl flavonoid isomers by triple quadrupole MS and their applications for identification of some fruit juices flavonoids

Fifteen flavonoid O‐diglycosides with different interglycosidic linkage isomery and glycosylation position have been studied in order to analyze their fragmentation patterns. Initial separation was carried out using high performance liquid chromatography with diode array detection (HPLC/DAD) coupled to an electrospray ionization (ESI) interface and a triple quadrupole mass spectrometer. Some useful differences in their MS spectra have been found and discussed. As it has already been reported, [Y*]⁺/[Y₀]⁺ ratio for flavanones and [Y₁]⁺/[Y₀]⁺ ratio for other flavonoids is specific for each isomeric interglycosidic linkage. In this work it has also been observed that the abundance of these ions is dependent on the position of glycosylation. On the basis of these differences, systematic guidelines for our experimental conditions have been proposed for the differentiation of not only isomeric interglycosidic linkage but also glycosylation position using collision‐induced dissociation MS/MS (CID‐MS/MS) spectra in positive mode. These results have been successfully applied for the characterization of three diglycosyl flavonoids found in Citrus fruit juices and these conclusions have also been extrapolated for characterizing two triglycosides in the same fruits. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct characterization of aqueous extract of Hibiscus sabdariffa using HPLC with diode array detection coupled to ESI and ion trap MS

The phenolic fraction and other polar compounds of the Hibiscus sabdariffa were separated and identified by HPLC with diode array detection coupled to electrospray TOF and IT tandem MS (DAD‐HPLC‐ESI‐TOF‐MS and IT‐MS). The H. sabdariffa aqueous extract was filtered and directly injected into the LC system. The analysis of the compounds was carried out by RP HPLC coupled to DAD and TOF‐MS in order to obtain molecular formula and exact mass. Posterior analyses with IT‐MS were performed and the fragmentation pattern and confirmation of the structures were achieved. The H. sabdariffa samples were successfully analyzed in positive and negative ionization modes with two optimized linear gradients. In positive mode, the two most representative anthocyanins and other compounds were identified whereas the phenolic fraction, hydroxycitric acid and its lactone were identified using the negative ionization mode.     

Determination of tetracycline residues in soil by pressurized liquid extraction and liquid chromatography tandem mass spectrometry

An optimized extraction and cleanup method for the analysis of chlortetracycline (CTC), doxycycline (DC), oxytetracycline (OTC) and tetracycline (TC) in soil is presented. Soil extraction in a pressurized liquid extraction system, followed by extract clean up using solid-phase extraction (SPE) and tetracycline determination by liquid chromatography tandem mass spectrometry (LC-MS/MS) provided appropriate efficiency and reproducibility. Different dispersing agents and solvents for soil extraction and several SPE cartridges for cleanup were compared. The best extraction results were obtained using ethylenediamine tetraacetic acid-treated sand as dispersing agent, and water at 70 °C. The most effective cleanup was obtained using Strata-X^TM sorbent in combination with a strong anion exchange cartridge. Recoveries ranged from 71% to 96% and precision, as indicated by the relative standard deviations, was within the range of 8–15%. The limits of quantification (LOQs) by using LC-MS/MS, based on signal-to-noise ratio (S/N) of 10, ranged from 1 μg kg⁻¹ for TC to 5 μg kg⁻¹ for CTC. These results pointed out that this technique is appropriate to determine tetracyclines in soils. Analysis of 100 samples taken in the Valencian Community revealed that, in soil, up to 5 μg kg⁻¹ CTC, 15 μg kg⁻¹ OTC, 18 μg kg⁻¹ TC, and 12 μg kg⁻¹ DC could be detected. Detection of the analytes in several samples, which typify great part of the Spanish agricultural soils, should be outlined as most important result of this study. Electronic supplementary material  The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Common-path phase-shifting lensless holographic microscopy

We present an approach capable of high-NA imaging in a lensless digital in-line holographic microscopy layout even outside the Gabor's regime. The method is based on spatial multiplexing at the sample plane, allowing a common-path interferometric architecture, where two interferometric beams are generated by a spatial light modulator (SLM) prior to illuminating the sample. The SLM allows phase-shifting interferometry by phase modulation of the SLM diffracted beam. After proper digital processing, the complex amplitude distribution of the diffracted object wavefront is recovered and numerically propagated to image the sample. Experimental results are reported that validate the proposed method.     

Zero-lag long-range synchronization via dynamical relaying

We show that isochronous synchronization between two delay-coupled oscillators can be achieved by relaying the dynamics via a third mediating element, which surprisingly lags behind the synchronized outer elements. The zero-lag synchronization thus obtained is robust over a considerable parameter range. We substantiate our claims with experimental and numerical evidence of such synchronization solutions in a chain of three coupled semiconductor lasers with long interelement coupling delays. The generality of the mechanism is validated in a neuronal model with the same coupling architecture. Thus, our results show that zero-lag synchronized chaotic dynamical states can occur over long distances through relaying, without restriction by the amount of delay.