Capillary electrophoresis for the analysis of paralytic shellfish poisoning toxins in shellfish: Comparison of detection methods

Paralytic shellfish toxins (PSTs) are produced by marine and freshwater microalgae and accumulate in shellfish including mussels, oysters, and scallops, causing possible fatalities when inadvertently consumed. Monitoring of PST content of shellfish is therefore important for food safety, with currently approved methods based on HPLC, using pre‐ or postcolumn oxidation for fluorescence detection (HPLC‐FLD). CE is an attractive alternative for screening and detection of PSTs as it is compatible with miniaturization and could be implemented in portable instrumentation for on‐site monitoring. In this study, CE methods were developed for C⁴D, FLD, UV absorption detection, and MS—making this first report of C⁴D and FLD for PSTs detection. Because most oxidized toxins are neutral, MEKC was used in combination with FLD. The developed CZE‐UV and CZE‐C⁴D methods provide better resolution, selectivity, and separation efficiency compared to CZE‐MS and MEKC‐FLD. The sensitivity of the CZE‐C⁴D and MEKC‐FLD methods was superior to UV and MS, with LOD values ranging from 140 to 715 ng/mL for CZE‐C⁴D and 60.9 to 104 ng/mL for MEKC‐FLD. With the regulatory limit for shellfish samples of 800 ng/mL, the CZE‐C⁴D and MEKC‐FLD methods were evaluated for the screening and detection of PSTs in shellfish samples. While the CZE‐C⁴D method suffered from significant interferences from the shellfish matrix, MEKC‐FLD was successfully used for PST screening of a periodate‐oxidized mussel sample, with results confirmed by HPLC‐FLD. This confirms the potential of MEKC‐FLD for screening of PSTs in shellfish samples.     

A double discharge high power TEA CO2 laser

A double discharge TEA CO₂ laser of simple design has been tested. The linearly polarized beam delivers a total energy of 14 Joules in 25 ns. The influence of the different gas mixtures on the problem of arcing, delay between pumping and lasing, and evolution of the light pulse, has been investigated. Using 0.1% xylene in the gas mixture, 200 Joules per liter were fed in the glow discharge without arcing. The maximum efficiency is 6.5%.

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Résumé Le comportement d'un laser CO₂TEA à deux décharges est étudié. Il délivre des impulsions de lumière polarisée d'une énergie de 14 Joules et durant 25 ns. L'influence de la composition du mélange gazeux sur des phénomènes tels que l'arcage, le dálai entre le pompage et l'émission lumineuse ainsi que sur la forme de l'impulsion, a été étudiée. L'introduction de 0.1% de xylène dans le mélange gazeux a permis de dissiper une énergie de 200 Joules par litre de décharge sans produire d'arc. Le rendement maximum a été de 6.5%.

     

Thermal, pressure and light switchable spin-crossover materials

This article reviews the most relevant chemical and structural aspects that influence the spin-crossover phenomenon (SCO). Special attention is focussed on the recent development of SCO coordination polymers. The different approaches currently being explored in order to achieve multifunctionality in SCO materials are discussed.     

Stabilized two-dimensional vector solitons

In this Letter, we introduce the concept of stabilized vector solitons as nonlinear waves constructed by the addition of mutually incoherent fractions of Townes solitons that are stabilized under the effect of a periodic modulation of the nonlinearity. We analyze the stability of these new kinds of structures and describe their behavior and formation in Manakov-like interactions. Potential applications of our results in Bose-Einstein condensation and nonlinear optics are also discussed.     

Bromine catalyzed conversion of S-tert-butyl groups into versatile and, for self-assembly processes accessible, acetyl-protected thiols

The facile and efficient conversion of a tert-butyl protecting group to an acetyl protecting group for thiols by catalytic amounts of bromine in acetyl chloride and the presence of acetic acid has been developed. The fairly mild reaction conditions are of particular interest for new protecting group strategies for sulfur functionalised target structures.     

Impregnated active carbons to control atmospheric emissions. 2. Influence of the raw material on the porous texture

The preparation of impregnated active carbons was optimized, in order to use them as catalysts for the deep oxidation of volatile organic compounds on atmospheric emissions. When impregnation is performed on the raw material or after activation, the influence of raw material on the texture and on the catalyst dispersion is already well studied. This paper aims to analyze the influence of raw material when the impregnation step is performed after the carbonization of different carbon precursors, as yet knowledge is very scarce. Olive stones, pinewood sawdust, nut shells, and almond shells were used as raw materials. In order to evaluate the influence of impregnation methodology of CoO, Co(3)O(4), and CrO(3) on the catalyst dispersion in the porous carbon texture, the impregnation step was made after activation and between carbonization and activation. On the first sequence, for all the raw materials, the impregnated oxides must be deposited on the internal surface, blocking part of the initial porous texture. When the impregnation step is conducted after carbonization, metal species act as catalysts during the activation step. The textures developed strongly depend either on the raw material or on the chemical state and distribution of the catalyst in the carbonized material. Olive stones and sawdust carbons stay with a microporous texture with very narrow pores where catalysts are not deposited. In nut shell and almond shell carbons, metal species are dispersed in the largest micropores and in a well-developed mesoporous texture.     

Molecular damage in bi-isonicotinic acid adsorbed on rutile TiO2(1 1 0)

Here we present the characteristic signatures in X-ray absorption and photoemission spectroscopy for molecular damage in adsorbed monolayers of bi-isonicotinic acid on a rutile TiO₂(1 1 0) surface. Bi-isonicotinic acid is the anchor ligand through which many important inorganic complexes are bound to the surface of TiO₂ in dye-sensitized solar cells. The nature of the damage caused by excessive heating of the adsorbed monolayer is consistent with splitting the molecule into two adsorbed isonicotinic acid molecular fragments. The effect on the lowest unoccupied molecular orbitals (involved in electron transfer in the molecule) can be understood in terms of the adsorption geometry of the reaction products and their nearest neighbor interactions.