Nonaqueous capillary electrophoretic behavior of 2-aryl propionic acids in the presence of an achiral ionic liquid. A chemometric approach

Ionic liquids (ILs) appear really attractive as electrolyte additives in nonaqueous capillary electrophoresis (NACE). These salts may offer new possibilities of interactions to modulate analyte effective mobilities. The presence of 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM NTf2) in acetonitrile/alcohol background electrolytes (BGEs) was investigated in this work. The aim of this study was to elucidate the influence of the IL concentration on the electrophoretic behavior of four arylpropionic acids and to identify the interactions between the analytes and the IL cation. The influence on mobility of the IL concentration, the nature and the proportion of the organic solvents, and the concentration of the ionic components of the BGE was first studied by a univariate approach. A four-factor D-optimal experimental design was then applied to provide a deeper insight into analyte interaction with IL cation present both free in BGE and adsorbed onto the capillary wall.     

A novel microfluidic flow-injection analysis device with fluorescence detection for cation sensing. Application to potassium

A microfabricated device has been developed for fluorimetric detection of potassium ions without previous separation. It is based on use of a fluorescent molecular sensor, calix–bodipy, specially designed to be sensitive to and selective for the target ion. The device is essentially made of a Y-shape microchannel moulded in PDMS fixed on a glass substrate. A passive mixer is used for mixing the reactant and the analyte. The optical detection arrangement uses two optical fibres, one for excitation by a light-emitting diode, the other for collection of the fluorescence. This system enabled the flow-injection analysis of the concentration of potassium ions in aqueous solutions with a detection limit of 0.5 mmol L⁻¹ and without interference with sodium ions. A calibration plot was constructed using potassium standard solutions in the range 0–16 mmol L⁻¹, and was used for the determination of the potassium content of a pharmaceutical pill. Figure Photography of the microfluidic channel showing the ridges in the PDMS substrate at the top of the channel     

New advances in countercurrent chromatography and centrifugal partition chromatography: focus on coupling strategy

Countercurrent chromatography (CCC) is an attractive separation method because the analytes are partitioned between two immiscible liquid phases avoiding problems related to solid stationary phase. In recent years, this technique has made great progress in separation power and detection potential. This review describes coupling strategies involving high speed CCC (HSCCC) or centrifugal partition chromatography (CPC). It includes on-line extraction–isolation, hyphenation with mass spectrometry (MS) and nuclear magnetic resonance (NMR) detectors, multidimensional CCC (MDCCC), two-dimensional CCC (2D-CCC), on-line coupling with liquid chromatography (LC), and biological tests, and innovative off-line developments. The basic principles of each method are presented and applications are summarized.     

Star-shaped triazine–thiophene conjugated systems

Star-shaped molecules consisting of short-chain oligothiophenes attached onto an electron acceptor triazine core have been synthesized. Results of the analysis of the electronic properties of these compounds by UV–vis spectroscopy and cyclic voltammetry are used to discuss the impact of the electron-withdrawing node on the properties of the compounds. The electrochemical oxidation of some of these systems into the corresponding electroactive polymers is briefly discussed.     

A new route towards fluorescent organic nanoparticles with red-shifted emission and increased colloidal stability

Suzuki–Miyaura cross-coupling reaction with a new boron reagent has been used to conveniently and efficiently synthetize a dipolar chromophore having an elongated π-conjugated system (i.e., bithiophene based), which displays a red-shifted emission while maintaining fluorescence. Bright orange emitting FONs made from this ‘naked’ dipole have been easily prepared and studied. Very interestingly, these FONs with red-shifted emission combine markedly enhanced colloidal and structural stability in water with giant one- and two-photon brightness. As such, they hold promises as fluorescent probes for bioimaging.     

In situ speciation of trace Fe(II) and Fe(III) in atmospheric waters by the FZ method coupled to GFAAS analysis

Two procedures to characterise atmospheres in piggeries are presented. The first allows delocalised sensorial analysis by trapping volatiles from pig shed emissions in a lipid phase. followed by laboratory analysis of their odour characteristics. The second procedure provides instrumental odour signatures of atmospheres. The volatile compounds are concentrated by solid-phase microextraction (SPME). and analysed directly by mass spectrometry without a chromatographic step (SPME-MS). The information supplied by the two analysis methods proved rich and consistent for the 42 piggeries analysed. In addition. the odour signatures allowed a good estimation of the key dimensions of the odour of the lipid phases. This result indicates that SPME-MS is a promising instrumental method to estimate the degree of odour nuisance in livestock buildings.     

Off-axis metallic diffractive lens for terahertz beams

A diffractive optical element for off-axis focusing of terahertz radiation is presented. It was designed in a nonparaxial regime and manufactured in a metal slab by laser cutting of curved stripes. The optical function of the structure includes focusing and deflecting the illuminating beam of a chosen frequency in a particular place. Therefore, the element acts as both a spatial and a spectral filter; hence it is especially suitable for separating the terahertz signal from a broadband thermal load in passive detection devices. The experimental evaluation of the proposed diffractive lens by means of time-domain spectroscopy is presented and discussed.