Solid Phase Extraction of Molybdenum on Modified Octadecyl Silica Sorbents in the Presence of Cationic Surfactants and on Silica-Based Anionic Exchanger and its Determination by Inductively Coupled Plasma Emission Spectrometry

Molybdenum was separated and preconcentrated as molybdate on microcolumns of octadecyl silica sorbents and silica-based strongly basic anion exchanger prior to its determination by ICP-AES. With octadecyl silica Separon SGX C18 and Separon SGX RPS, the retention of 0.01–0.4µg·mL^–1 Mo from 50–1000mL sample solutions was quantitative in the presence of the cationic surfactants carbethoxypentadecyltrimethylammonium bromide (Septonex^®), dodecylbenzyldimethylammonium bromide (Ajatin^®) or tetradecylbenzyldimethylammonium chloride (Zephyramine^®) at pH 6–8. 96% ethanol was the most suitable eluent of the molybdate/surfactant associate. For the strongly basic anion exchanger Separon SGX AX, the optimal conditions for sorption of 5–20µg Mo from 50–250mL sample solutions were at pH 2 in the presence of 0.05M ascorbic acid and ammonium citrate. 3M HNO₃ was a satisfactory eluent in this case. Organic solvents and excess of acids were removed by evaporation prior to the determination of Mo by ICP-AES in eluates. Both procedures can be used for the determination of ion-level molybdenum in waters.     

Novel nonionic polymerisable surfactants based on sulfoxides. 1. Monomer synthesis and general surfactant behaviour

The synthesis, surface activity, and micellisation of a series of new nonionic polymerisable surfactants, often referred to as surfmers, are described. These monomers bear terminal vinyl groups or acrylic esters, and the nonionic sulfoxide moiety. Compared to many other nonionic hydrophilic fragments, the sulfoxide group behaves as a strongly hydrophilic fragment of small volume, that can balance up to an acryloyloxyundecyl hydrophobic chain. The incorporation of the polar acrylate moiety at the end of the hydrophobic chain seems to confer surfactant properties similar to the ones of bola amphiphiles to the monomers. Received: 22 March 2001 Accepted: 11 August 2001     

Fluorescence study of the core/shell interface in polyelectrolyte micelles. Binding of fluorescent surfactants in the interfacial region

Properties of the interfacial region between the nonpolar core and the polar shell in polystyreneblock-poly (methacrylic acid) micelles were studied by fluorescence techniques using 5-(N-octadecanoyl) aminofluorescein (OAF) as a probe for microfluidity and local pH. The block copolymer used was tagged between blocks by one 9, 10-diphenylanthracene (DPA) group, which allowed us to study binding of OAF at the interface by means of nonradiative energy transfer between DPA and OAF. A shift in the pK _a of OAF and appreciable changes in anisotropy and quenching efficiency due to immobilization of the fluorophore head-group in hydrophobic poly(methacrylic acid) domains were observed after binding of the probe at the interface.     

Molecular simulations of self-assembly processes of amphiphiles in dilute solutions: the challenge for quantitative modelling

We report on two recent developments in molecular simulations of self-assembly processes of amphiphilic solutions. We focus on the determination of micelle formation of ionic surfactants which exhibit the archetype of self-assembling compounds in solution. The first approach is centred on the challenge in predicting micellisation properties through explicit solvent molecular dynamics simulations. Even with a coarse-grained (CG) approach and the use of highly optimised software packages run on graphics processing unit hardware, it remains in many cases computationally infeasible to directly extract the critical micelle concentration (cmc). However, combined with a recently presented theoretical mean-field model this task becomes resolved. An alternative approach to study self-assembly is through implicit solvent modelling of the surfactants. Here we review some latest results and present new ones regarding capabilities of such a modelling approach in determining the cmc, and the aggregate structures in the dilute regime, that is currently not accessible through explicit solvent simulations, neither through atomistic nor through CG approaches. A special focus is put on surfactant concentration effects and surfactant correlations quantified by scattering intensities that are compared to recently published small-angle X-ray scattering data.     

Synthesis and Surface Activity of Heterogemini Imidazolium Surfactants

A series of heterogemini imidazolium surfactants with two-methylene spacer groups ([C_m-2-C_nim]Br_{2, m, n}=8, 10, 12, 14, 16; m≠n) have been synthesized and characterized by 1H NMR and ESI-MS spectroscopy. The effects of various reaction parameters, including stoichiometry, reaction temperature and time, were investigated. In addition, the surface activity study about heterogemini imidazolium surfactants was carried out and the influences of dissymmetric degree on the surface properties were also discussed.     

The Petroleum Industry Surfactants Synthesized from Fish Oils

Biodegradable surfactants for the petroleum industry have been synthesized by the sulfurization of fish oils. A qualitative composition analysis of surfactants was conducted by FTIR spectroscopy that showed the presence of sulfonic acid groups in the samples. Previously, several samples of the technical fish oils (fish processing waste) have been studied with regard to their use for the synthesis of biodegradable surfactants. It has been shown by gas–liquid chromatography, FTIR spectroscopy, high-performance liquid chromatography, and mass spectrometry method that samples under study contain a large amount of saturated and nonsaturated fatty acids with hydrocarbon radicals comprising from 16 to 22 carbon atoms. The results reveal that the concentration of oleic acid approaches to 15 wt%. Fish oils with a high content of free fatty acids were used as the basis for the synthesis of technical, environmentally friendly surfactants that can be applied in the petroleum industry.     

Morphological and mechanical behavior of montmorillonite grafted block copolymer brushes

Here we report the phase behavior of a family of montmorillonite (MMT) block copolymer brushes (MBBs), a novel class of polymer nanocomposites. MBBs are comprised of discrete MMT platelets encapsulated with block copolymer brushes. These MBBs were synthesized via surface-initiated atom transfer radical polymerization using halogenated alkylammonium surfactants to localize initiation sites on the clay surfaces. Two styreninc MBB systems—poly(styrene-b-n-butyl acrylate) and poly(styrene-b-t-butyl acrylate)—were prepared varying the composition and total 80–250 kDa. MBB materials were compared with their non-clay bulk block copolymer counterparts via electron microscopy and a host of mechanical tests in both the solid and melt states. Notably, MBBs have similar melt-state rheological properties compared to neat block copolymers and are thus amenable to current processing techniques. MBBs were found to self-assemble into single grain morphologies across incredibly large areas (>3 μm) which resulted in extremely well-ordered, defect-free lamellar structures with applications in microelectronics. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 353–361     

Novel cationic coating agent for protein separation by capillary electrophoresis†

A novel positively charged surfactant N‐dodecyl‐N,N‐dimethyl‐(1,2‐propandiol) ammonium chloride was used for the dynamic coating of the inner wall of a silica capillary. This paper covers the evaluation of dynamic coating and study of the influence of the analysis conditions for the magnitude and direction of electroosmotic flow as well as for the effective and selective separation of chosen proteins (ribonuclease A, cytochrome c, lysozyme, and myoglobin). The concentration of 0.1 mM of N‐dodecyl‐N,N‐dimethyl‐(1,2‐propandiol) ammonium chloride enabled the reversal of the electro‐osmotic flow, however, to separate basic as well as neutral proteins the higher concentration of the studied surfactant was necessary. The final conditions for the separation of studied proteins were set at 100 mM sodium acetate pH 5.5 with 10.0 mM of the studied surfactant. The results were also compared with those of two commercially available cationic surfactants, cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide. Additionally, the developed method for protein separation was applied for the determination of lysozyme in a cheese sample. The limits of detection and quantification of lysozyme were 0.9 and 3.0 mg/L, respectively. The mean concentration of lysozyme found in the cheese sample was 167.3 ± 10.3 mg/kg.