Simultaneous determination of inorganic arsenic,antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of ⁷⁵As, ⁸²Se, ¹²¹Sb and ¹²⁵Te by ICP-MS for amounts less than 10?µg?L^?1. Internal standards such as ⁷²Ge and ²⁰⁹Bi were successfully used for the suppression of both influence of macro elements Na⁺, K⁺, Ca²⁺, Mg²⁺ or Al³⁺, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon? SGX C18, C8, CN, NH₂, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5?µg?L^?1) in the form of ion associates with cationic surfactants from 50–250?mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005?mol?L^?1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7?±?0.2 and the mixture of acetone with ethanol in ratio 1?:?1 in the presence of 0.1?mol?L^?1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon? SGX C18 and the above reagents were compared with the standard addition method.     

Spectral characterisation of new organic fluorescent dyes with an alkoxysilane moiety and their utilisation for the labelling of layered silicates

New fluorescence dyes with an alkoxysilane moiety were synthesised by the condensation of 3-(triethoxysilyl)-1-propanamine (3-aminopropyltriethoxysilane) with 4,10-benzothioxanthene-3,1′-dicarboxylic acid anhydride (BTXA) and N,N-dimethylaminonaphthalene-1,8-dicarboxylic acid anhydride (DMANA), which was accompanied by the formation of an imidic bridge. The compounds N-(3-(triethoxysilyl)propyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTX-S) and 4-(N′, N′-dimethyl)-N-(triethoxysilyl)propyl-1,8-naphthalene dicarboxylic acid imide (DMAN-S) were characterised by steady-state and time-resolved fluorescence spectroscopy in chloroform and ethanol. Both conjugates (BTX-S and DMAN-S) exhibited absorption and emission bands in the same region as the un-substituted BTXA and DMANA. An important Stokes shift was observed for DMAN-S in ethanol. A high fluorescence quantum yield was observed for BTX-S in both solvents and for DMAN-S in chloroform. In addition, the newly developed fluorescent silane dyes were covalently attached to the microscopic particles of layered silicates and on the surface of SiO₂ wafers as a proof of concept for fluorescence particle (surface) visualisation. The surface wafer modification was precisely characterised by X-ray photoelectron spectroscopy (XPS). Successful covalent linkage onto the particles of layered silicates was proved by confocal laser scanning microscopy technique.     

Synthesis and properties of macrocyclic diazene switch with binaphthalene unit attached via acrylamide linkers

2,2′-Diiodo-1,1′-binaphthalene undergoes a tandem Heck reaction with methyl acrylate to afford methyl 2-(7H-dibenzo[c,g]fluoren-7-ylidene)acetate. As a consequence, the target macrocyclic diazene with binaphthalene unit attached via acrylamide linker was prepared by the stepwise building of acrylamide at a binaphthalene moiety, including the Doebner modification of the Knoevenagel condensation, and completed by oxidative macrocyclisation of aniline end-groups. Despite being an equimolar mixture of monomer and dimer, it exhibited remarkable changes in CD spectra due to reversible (E/Z) isomerisation of N=N diazene bonds upon irradiation at 365/465 nm. Although the dimer isomerises from (E) to (Z) isomer 7.4 times faster than the monomer, the latter’s contribution to the change in ellipticity at 307 nm in the photostationary state is 2.4 times greater.     

“Heteroglycals” As New Potential Glycosidase Inhibitors. Synthetic Approaches From D-Arabinose

Within the frame of an ongoing project on glycosidase inhibitors, we have been interested in the synthesis of “heteroglycals”, namely, glycal analogues with sulfur or nitrogen in the ring. Glycals² are well known for their applications in sugar chemistry in particular for glycosyl transfer.³ They are also known as glycosidase inhibitors through a slow chemical reaction with the enzyme. Recently exo-glycals emerged as a new class of glycals⁴ which showed interesting features as glycosidase inhibitors but also as precursors of glycomimetics such as C-glycosides.⁵ We have undertaken investigations on related heteroglycals: such compounds are of interest because they combine a planar geometry at the anomeric center and a possible charge site - both elements known to be important to mimic the transition state of the enzymatic glycoside hydrolysis process.⁶     

Hydrothermal Degradation and Kinetic Studies of 1,3-Dihydroxy-2-Propanone and 2,3-Dihydroxypropanal

The equilibrium of 1,3-dihydroxy-2-propanone (dihydroxyacetone) and 2,3-dihydroxypropanal (glyceraldehyde) and their dehydration reaction to methylglyoxal has been studied in the range of 180 - 240 °C under hydrothermal reaction conditions. A reaction mechanism for the conversion of these C-3 compounds was formulated which allowed the calculation of the product yields. In the investigated temperature range both compounds produce a maximum of 30-40% of methylglyoxal.     

Blood Proteins Strongly Reduce the Mobility of Artificial Self‐Propelled Micromotors

Autonomous self‐propelled catalytic microjets are envisaged as an important technology in biomedical applications, including drug delivery, micro/nanosurgery, and active dynamic bioassays. The direct in vivo application of these microjets, specifically in blood, is however impeded by insufficient knowledge on the in vivo viability of the technique. This study highlights the effect of blood proteins on the viability of the microjets. The presence of blood proteins, including serum albumin and γ‐globulins at physiological concentrations, has been found to dramatically reduce the viability of the microjets. The reduction of viability has been measured in terms of a lower number of active microjets and a decrease in the velocity of propulsion. It is clear from this study that in order for microjets to function in biomedical applications, different modes of propulsion besides platinum‐catalyzed oxygen bubble ejection must be employed. These findings have serious implications for the biomedical applications of catalytic microjets.     

Gadolinium(III)‐Hydroxy Ladders Trapped in Succinate Frameworks with Optimized Magnetocaloric Effect

Two kinds of inorganic gadolinium(III)‐hydroxy “ladders”, [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd₂(OH)₂(suc)₂(H₂O)]_n ? 2n H₂O ( 1 ) and [Gd₆(OH)₈(suc)₅(H₂O)₂]_n ? 4n H₂O ( 2 ), respectively. Such coordination polymers could be regarded as alternating inorganic–organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg^?1 K^?1 for complex 1 and 48.0 J kg^?1 K^?1 for complex 2 . The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm^?3 K^?1 for complexes 1 and 2 , respectively.     

Nucleoside Analogues with a 1,3‐Diene?Fe(CO)3 Substructure: Stereoselective Synthesis,Configurational Assignment,and Apoptosis‐Inducing Activity

The synthesis and stereochemical assignment of two classes of iron‐containing nucleoside analogues, both of which contain a butadiene? Fe(CO)₃ substructure, is described. The first type of compounds are Fe(CO)₃‐complexed 3′‐alkenyl‐2′,3′‐dideoxy‐2′,3′‐dehydro nucleosides (2,5‐dihydrofuran derivatives), from which the second class of compounds is derived by formal replacement of the ring oxygen atom by a CH₂ group (carbocyclic nucleoside analogues). These compounds were prepared in a stereoselective manner through the metal‐assisted introduction of the nucleobase. Whilst the furanoid intermediates were prepared from carbohydrates (such as methyl‐glucopyranoside), the carbocyclic compounds were obtained by using an intramolecular Pauson–Khand reaction. Stereochemical assignments based on NMR and CD spectroscopy were confirmed by X‐ray structural analysis. Biological investigations revealed that several of the complexes exhibited pronounced apoptosis‐inducing properties (through an unusual caspase 3‐independent but ROS‐dependent pathway). Furthermore, some structure–activity relationships were identified, also as a precondition for the design and synthesis of fluorescent and biotin‐labeled conjugates.     

A Recyclable Trinuclear Bifunctional Catalyst Derived from a Tetraoxo Bis‐Zn(salphen) Metalloligand

A tetraoxo bis‐Zn(salphen) supramolecular host can bind various divalent metal salts, thereby providing access to trinuclear bifunctional systems that incorporate both Lewis acid sites and dynamically bound nucleophilic anions. The formation of these trinuclear species was investigated and their stability features were also determined. The application of these trinuclear complexes as bifunctional catalysts was evaluated in the formation of cyclic organic carbonates from epoxides and CO₂. The catalytic data, in combination with control experiments, clearly demonstrate that these trinuclear compounds show much higher recycling potential compared to various control compounds and they can be used in up to five cycles without an observable loss in activity. Furthermore, this new recyclable catalytic system does not require any additives and can be applied under solvent‐free conditions.     

Unusual Inherent Electrochemistry of Graphene Oxides Prepared Using Permanganate Oxidants

Graphene and graphene oxides are materials of significant interest in electrochemical devices such as supercapacitors, batteries, fuel cells, and sensors. Graphene oxides and reduced graphenes are typically prepared by oxidizing graphite in strong mineral acid mixtures with chlorate (Staudenmaier, Hofmann) or permanganate (Hummers, Tour) oxidants. Herein, we reveal that graphene oxides pose inherent electrochemistry, that is, they can be oxidized or reduced at relatively mild potentials (within the range ±1 V) that are lower than typical battery potentials. This inherent electrochemistry of graphene differs dramatically from that of the used oxidants. Graphene oxides prepared using chlorate exhibit chemically irreversible reductions, whereas graphene oxides prepared through permanganate‐based methods exhibit very unusual inherent chemically reversible electrochemistry of oxygen‐containing groups. Insight into the electrochemical behaviour was obtained through cyclic voltammetry, chronoamperometry, and X‐ray photoelectron spectroscopy experiments. Our findings are of extreme importance for the electrochemistry community as they reveal that electrode materials undergo cyclic changes in charge/discharge cycles, which has strong implications for energy‐storage and sensing devices.