Tetraphenylporphyrin Sensors with High Cross Sensitivity for “Electronic-Tongue” Analyzers

Tertaphenylporphyrin-based film sensors were prepared with anionic and cationic lipophilic ionic additives introduced into polyvinyl chloride membranes plasticized with various solvents. The data obtained with these sensors were used to calculate the parameters of the cross sensitivity of the sensors. A multisensor system of the electronic tongue type was developed on the basis of the sensors studied.     

A gel-based visual immunoassay for non-instrumental detection of chloramphenicol in food samples

A gel-based non-instrumental immuno-affinity assay was developed for the rapid screening of chloramphenicol (CAP) in food samples with the limit of detection (LOD) of 1 μg L⁻¹. The immuno-affinity test column (IATC) consisted of a test layer containing anti-CAP antibody coupled gel, and a control layer with anti-HRP antibody coupled gel. Based on the direct competitive immuno-reaction and the horseradish peroxidase enzymatic reaction, the test results could be evaluated visually. Basically, blue color development represented the negative results, while the absence of color development represented the positive results. In this study, CAP spiked samples of raw milk, pasteurized milk, UHT milk, skimmed milk powder, acacia honey, date honey, fish and shrimp were tested. Little or none sample pretreatment was required for this assay. The whole procedure was completed within 10 min. In conclusion, the gel-based immuno-affinity test is a simple, rapid, and promising on-site screening method for CAP residues in food samples, with no instrumental requirement.     

INDENTATION OF A RIGID CYLINDER WITH A ROUGH FLAT BASE INTO A THIN VISCOELASTIC LAYER

Journal of Applied Mechanics and Technical Physics - Interaction between a thin viscoelastic layer and a rigid cylinder whose contacting end surface is nominally flat but has a microrelief is...     

Fluorescent properties of aflatoxins in organized media based on surfactants,cyclodextrins, and calixresorcinarenes

Fluorescent properties aflatoxin B1 (AfB1) and its metabolites, aflatoxins B2, G1, and G2 in the presence of surfactants, cyclodextrins, and calix[4]resorcinarenes are studied. It is found that surfactants and cyclodextrins enhance the fluorescence of aflatoxins B1 and G1. Using the example of AfB1, it is shown that the fluorescence intensity in solution attains a maximum in the presence of 2-hydroxypropyl-β-cyclodextrin. The effects observed increase the sensitivity of the fluorimetric determination of AfB1: the detection limit in water is 3.1 × 10^?8 M and decreases to 2.1 × 10^?9 M in a solution of cyclodextrin.     

Novel gel-based rapid test for non-instrumental detection of ochratoxin A in beer

A rapid easy-to-use immunoassay was optimised for the non-instrumental detection of ochratoxin A (OTA) in beer. The analytical method involves preconcentration on the immunoaffinity layer inside a column followed by direct competitive ELISA detection in the same layer. The visual cut-off value, i.e. the lowest OTA concentration resulting in no colour development, was 0.2 μg L^-1. Assay validation was performed using samples spiked with OTA. Thirty-seven naturally contaminated samples were screened with the gel-based method developed and no false-negative results were obtained. The method described offers a simple, rapid and cost-effective screening tool, thus contributing to better health protection of consumers. Figure Gel-based immunoassay of spiked beer samples.     

Mechanisms of elastic energy dissipation in the transition layer between a coating and a substrate under contact interaction

A theoretical and experimental analysis of the influence of the dispersed transition layer between a coating and a substrate on the development of deformation structures near the interface has been performed as part of an interdisciplinary study of the deformation and fracture of coating-substrate compositions under contact interaction. Elastic energy transfer from an indenter was simulated using excitable cellular automata taking into account the self-organization of translations and rotations of the structure near the interface. The effect of the transition layer between the coating and the substrate on the development of deformation structures during contact interaction with the indenter in three-point bending was studied experimentally using a TOMSC television-optical measuring complex.     

Modeling of friction at different scale levels

We construct a model for studying the common influence of the imperfect elasticity of actual bodies, the microgeometry of their surfaces, and their adhesive interaction on the contact characteristics (the contact pressure distribution, the region of actual contact) and on the sliding friction force. The model is based on the solution of a plane contact problem of sliding of a rigid body with a regular relief on the boundary of a viscoelastic foundation with surface molecular attraction in the gap between the surfaces taken into account. We analyze the influence of the surface microgeometry parameters at different scale levels on the character of the surface interaction (the saturated or discrete contact) and the friction force for different sliding velocities of the contacting bodies.     

Luminescence properties of acridine dyes in micellar sodium dodecyl sulfate solutions containing thallium ions

The effect of external heavy Tl^I ion on the luminescence properties of Trypaflavine, Acridine Yellow, and Acridine Orange solubilized in sodium dodecyl sulfate micelles was studied. An increase in the concentration of thallium ions results in a decrease in the intensity of prompt fluorescence, an increase in the intensity of delayed fluorescence, the appearance of phosphorescence at 20 °C, and a shortening of the triplet state lifetime of the dyes. The effective and micellar Stern—Volmer constants of fluorescence quenching of the dyes by thallium ions were determined. The effective and micellar quenching rate constants of triplet states of the dyes by Tl(i) ions and lifetimes of the triplet states of the dyes in the absence of thallium ions were calculated on the basis of kinetic measurements.     

Erratum to: New-Generation Low-Toxic I–III–VI2 Quantum Dots in Chemical Analysis

Journal of Analytical Chemistry - An Erratum to this paper has been published: https://doi.org/10.1134/S1061934822350015     

New-Generation Low-Toxic I–III–VI2 Quantum Dots in Chemical Analysis

Journal of Analytical Chemistry - Luminescent quantum dots (QDs) of I–III–VI2 semiconductors present a new class of luminescence materials that combine unique optical and electronic...