Separation and determination of homogenous fatty alcohol ethoxylates by liquid chromatography with mulitstage mass spectrometry

Alcohol ethoxylates (AEs) are a significant component of a stream of surfactants directed to the aquatic environment. The aim of this work was the investigation of the dependence of the analytical signals of homogeneous AE homologues on liquid chromatography with tandem mass spectrometry conditions, as well as the separation of AEs from the water matrix and, on this basis, the development of an analytical procedure suitable for the determination of AEs in environmental samples. Homogeneous homologues containing dodecyl moiety and 2–9 oxyethylene subunits were investigated. The analytical signals of the investigated homologues were optimized in terms of concentration of ammonium acetate in the mobile phase (optimum 5 mM) and a column temperature (optimum 35°C) of the liquid chromatography with tandem mass spectrometry system. A separation of AEs from the water matrix by liquid–liquid extraction (ethyl acetate, chloroform) or solid‐phase extraction (C₁₈, styrene divinylbenzene, H‐RX) was investigated. In a model investigation, the best recoveries (>90%) were obtained with a styrene divinylbenzene cartridge eluted with a 1:1 mixture of chloroform and methanol. However, much worse recoveries were obtained from the river water sample. Better results were obtained for liquid–liquid extraction with ethyl acetate. Recoveries of 62–80% were obtained for homologues having 4–9 oxyethylene subunits, at the lowest spike.     

A Microfluidic Co-Flow Route for Human Serum Albumin-Drug–Nanoparticle Assembly

Nanoparticles are widely studied as carrier vehicles in biological systems because their size readily allows access through cellular membranes. Moreover, they have the potential to carry cargo molecules and as such, these factors make them especially attractive for intravenous drug delivery purposes. Interest in protein-based nanoparticles has recently gained attraction due to particle biocompatibility and lack of toxicity. However, the production of homogeneous protein nanoparticles with high encapsulation efficiencies, without the need for additional cross-linking or further engineering of the molecule, remains challenging. Herein, we present a microfluidic 3D co-flow device to generate human serum albumin/celastrol nanoparticles by co-flowing an aqueous protein solution with celastrol in ethanol. This microscale co-flow method resulted in the formation of nanoparticles with a homogeneous size distribution and an average size, which could be tuned from ≈100 nm to 1 μm by modulating the flow rates used. We show that the high stability of the particles stems from the covalent cross-linking of the naturally present cysteine residues within the particles formed during the assembly step. By choosing optimal flow rates during synthesis an encapsulation efficiency of 75±24 % was achieved. Finally, we show that this approach achieves significantly enhanced solubility of celastrol in the aqueous phase and, crucially, reduced cellular toxicity.     

Isotachophoretic determination of carboxylic acids in biodegradation samples

In the current study a method of isotachophoretic separation of selected carboxylic acids was developed. The method was used for the determination of carboxylated oligo(ethylene glycol)s and their degradation products in biodegradation tests of PEG 250 DA [a mixture of dicarboxylated oligo(ethylene glycol)s]. Two tests were performed in the studies: the Organization for Economic Cooperation and Development (OECD) screening test and the river water die-away test. Both the biodegradation tests proved relatively fast biodegradation of the studied compounds. In the OECD screening test the biodegradation was faster than in the river water die-away test which can be ascribed to a higher concentration of bacteria in the biodegradation liquor. The minimal sample pretreatment and relatively low cost of analysis by the isotachophoretic method used here make it a good alternative to existing methods of carboxylic acids analysis.     

An adaptive critic neural network for motion control of a wheeled mobile robot

In this paper, we propose a new application of the adaptive critic methodology for the feedback control of wheeled mobile robots, based on a critic signal provided by a neural network (NN). The adaptive critic architecture uses a high-level supervisory NN adaptive critic element (ACE), to generate the reinforcement signal to optimise the associative search element (ASE), which is applied to approximate the non-linear functions of the mobile robot. The proposed tracking controller is derived from Lyapunov stability theory and can guarantee tracking performance and stability. A series of computer simulations have been used to emulate the performance of the proposed solution for a wheeled mobile robot.     

Catalysis of hydrosilylation. XV. A poly(phosphino-organosiloxanyl)silicate-supported rhodium(I) catalyst for gas-phase hydrosilylation of acetylene

Wilkinson's complex [RhCl(PPh₃)₃], anchored to phosphino-organosiloxane macromolecules grafted onto chrysotile asbestos, appeared to be an unusually effective and selective catalyst for the synthesis of vinylsilanes via gas-phase hydrosilylation of acetylene, particularly by methyldichlorosilane in a continuous-flow microreactor as well as in a laboratory reactor. Catalytic and kinetic parameters show an advantage for the catalyst based on the chrysotile-polyorganosiloxane support (catalyst CHR–Rh) over the phosphinated silica (catalyst A).     

A note on nonassociated plastic flow rules

The analytical properties of the constitutive equations in plasticity with a nonassociated flow rule are investigated. Under the assumption of small deformations the directional stiffness (and compliance) rule is considered and the relevant spectral properties of the tangent stiffness tensor are assessed. It is shown that the directional stiffness may be larger than the elastic. It may also be negative in the case of a formally perfectly plastic material and so the nonassociative flow rule represents (spurious) softening in terms of an associated flow rule. The issue of uniqueness at finite strains is briefly addressed, whereby use is made of the tangent stiffness tensor relating the velocity gradient to the first Piola-Kirchhoff stress rate. The relevant spectral properties, which generalise those from the small deformation case, are found explicit. A sufficient condition for uniqueness is given in terms of a critical (upper bound) value of the hardening modulus.     

Deposition of droplets from turbulent stream

A model of particle deposition from a turbulent stream is presented. It is based on the modified stopping distance concept which allows for the difference between particle and eddy diffusivities, recognizing that the particle has equal probability to move toward the wall or back into the turbulent core. The theory is tested against the data which cover a wide range of droplet size and duct Reynolds number for different surface configuration. A quite satisfactory agreement has been found in all examined cases.     

A Review of Infrared Spectra from Wood and Wood Components Following Treatment with Liquid Ammonia and Solvated Electrons in Liquid Ammonia

ABSTRACT

The chemical changes that occur in wood and wood components (cellulose, holocellulose and lignin) following treatment with liquid ammonia and solvated electrons (e^? _s,) in liquid ammonia have been investigated using FTIR spectroscopy.

When ammonia penetrates into a wood structure, all carboxylate groups will react with ammonia to form ammonium salts, aldehydic and ketonic groups will follow a similar reaction to produce imines, and ester groups will react to forni amides.

After treatment with (e^? _s) in liquid ammonia, wood samples show diminished absorption around 15 13 cm^?1, a position corresponding to aromatic groups, and diminished absorption peaks associated with aldehydic, ketonic, and ester groups.

The overall changes in the IR spectra of cellulose in liquid ammonia and (e^? _s) in liquid ammonia are not dramatic. The IR spectra of the isolated holocellulose after treatment with (e^? _s) in liquid ammonia have intensities and band shape similar to those of cellulose. The isolated lignin behaves in a manner similar to wood, in that the liquid ammonia causes some decrease in the intensities of absorptions associated with C-O and C=O bands, and increase in strength of the amide functional group at 1600 cm^?1. The resulting extracts of wood, following treatment with (e^? _s) in liquid ammonia, appear to loose their “aromaticity”.

Because wood has long been used, and still is used extensively as an important constructional material, the changes in mechanical characteristics caused by the action of various reducing agents appears to have been an important area of scientific interest. The following review focuses on the chemical changes in the functional groups of the surface moieties of wood when treated with a reducing agent, such as (e^? _s + NH_3liq), using infrared spectroscopy.     

The determination of traces of thiocyanate and copper(II) ions by cathodic stripping voltammetry

Cathodic stripping methods are described for the determination of traces of thiocyanate ions down to 2 × 10^-8 mol l^-1 and Cu(II) ions down to 1 × 10^-8 mol l^-1. The method involves electrolytic accumulation of copper(I) thiocyanate on the surface of a hanging mercury drop electrode followed by stripping of the deposit during the cathodic scan. For the determination of thiocyanate, a copper amalgam electrode can be used. Examples of application of the method for the determination of traces of thiocyanate in common salts, in saliva and urine as well as for the determination of copper(II) ions in tap water are described.     

Diffraction methods analysis of the approximation of the real glass structure

X-ray and electron diffraction methods are discussed and the results of an analysis of glass structure are reported.Experimental methods were employed to analyse the structures of a series of complex oxide glasses of the type:

$\text{SiO}{}_2\text{(～72\%)+}\text{Na}{}_2\text{O}\text{(～14\%)+}\text{CaO}\text{(～8\%) +}\text{MgO}\text{(～4\%)+R}{}_2\text{O}{}_3\text{(～2\%)}$

.In calculating the structural parameters of the real glass structure the assumed effective molecule was approximated which included from two (SiO₂) to five (SiO₂Na₂OCaOMgO) groups of various atoms. The structural parameters obtained allowed the real internal structure to be established and were employed in the construction of a space model of the glass.The most probable structural models are presented, obtained by successive approximation with individual oxide groups added one after another. The models' structural and physicochemical parameters were chosen to be consistent with those of the nodal model which is near to the real glass structure. The parameters required to construct the nodal model in question were established by analysing radial distribution functions and by the differentiation of the adequate radial distribution functions by subtraction and successively approximating the effective molecule including the oxide groups (SiO₂, Na₂O, CaO and MgO) added one after another.An aperiodic model of a nodal lattice is presented in a scheme, stressing the structural parameters and local orderings in groups describing the internal structure of complex oxide glasses. Also, an approximate nodal space model of great importance for the construction of a structural model of glass is presented and discussed with regard to its utility and accuracy in the determination of its parameters.