Dispersive liquid–liquid microextraction (DLLME) is one of the most promising methods of the microextraction preconcentration of organic compounds. This method is eco-friendly, simple, and universal; ...in comparison with conventional extraction, the consumption of the reagents and solvents, the time of extraction, and the cost of analysis in this method are reduced. For a short time from the moment of the appearance of DLLME in 2006, analysts developed numerous versions, differing by the method of dispersion, the nature of the extractant and by combinations with other methods of sample preparation and methods of the subsequent determination of the preconcentrated substances. The popularity of the method among the analysts is attested in a great number of reviews summarized in this publication.
Single-drop microextraction (SDME) and hollow-fiber membrane microextraction (HFME) belong to methods of the liquid-phase microextraction preconcentration of organic compounds. These methods are ...characterized by the low consumption of organic solvents, high preconcentration factors, simplicity, low cost, ease of combination with various chromatographic methods; processes of preconcentration and sample injection are combined in a single device. Since the emergence of SDME (1996) and HFME (1999), a large number of versions have been developed that differ in the preconcentration technique, nature of the extractants used, and combinations with methods for the subsequent determination of the preconcentrated substances. The popularity of these methods among the analysts is evidenced by many reviews that we have summarized in this publication.
Current research fields of metal-organic frameworks (MOFs), which are being developed in the last 5-10 years by Russian scientific institutions and universities, are generalized. The review ...encompasses the design, synthesis, topological description, and prediction of MOF properties, the development of methods for their chemical engineering and modification, their investigation by modern physicochemical techniques, and the creation of functional materials based on porous frameworks (heterogeneous catalysts, highly efficient and highly selective sorbents of the new generation, conducting materials, systems for the target drug delivery).
The possibility of combining solid-phase extraction of natural catecholamines (adrenaline, norepinephrine, and dopamine) on a microcolumn filled with hypercrosslinked polystyrene with their ...subsequent spectrophotometric or solid-phase spectroscopic determination in an eluate using gold nanorods or their nanocomposites with polyurethane foam has been investigated. The desorption of catecholamines from hypercrosslinked polystyrene by various eluents has been studied. It has been shown that the quantitative elution of all three catecholamines is achieved using 6 M acetic acid, which as an eluent is well combined with the proposed determination options. The features of a dynamic sorption extraction of catecholamines from urine and blood serum have been described. It allows you to reduce the influence of the matrix components and increase the analysis sensitivity by concentrating. The average concentration coefficient is 10–56 with sample volumes of 10–300 mL. The developed methods make it possible to determine catecholamines in urine at the level of their normal content.
The hydrolysis of substituted 3-(3-cyanothiophen-2-yl)imino-3
H
-furan-2-ones was studied. It was found that the reaction proceeds with the opening of the furan ring and the formation of the ...corresponding 4-oxo-2-(3-cyanothiophen-2-yl)aminobut-2-enoic acids. The antibacterial activity of the obtained compounds against
Staphylococcus aureus
,
Escherichia coli
and
Candida albicans
was studied.
Gold nanorods (AuNRs) stabilized by cetyltrimethylammonium bromide (CTAB) were synthesized and an interaction of catecholamines (CAs) with silver ions in the presence of the obtained AuNRs was ...studied. The reaction results into formation of core-shell Au@Ag nanorods (Au@AgNRs) and leads to a hypsochromic shift of the long-wave surface plasmon resonance (SPR) band in the absorption spectrum of AuNRs. The influence of a CA structure, excess of CTAB, interaction time, pH, concentration of AuNRs, silver ions and CAs on this interaction was studied. Based on correlation of the NRs spectral characteristics with the concentration of CAs, a method for spectrophotometric determination of dobutamine, epinephrine, norepinephrine and dopamine with detection limits 27, 18, 16 and 13 μg L−1, respectively, has been developed. The method can be applied to the analysis of medicines.
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•Formation of core-shell Au@Ag nanorods under influence of catecholamines was systematically studied.•Influence of different parameters during the synthesis was evaluated.•Characterization of synthesized Au@Ag nanorods was performed.•A method for simple spectrophotometric determination of catecholamines was developed.
Published data on various versions of the homogeneous liquid–liquid microextraction (HLLME) of organic compounds are generalized and systematized, and a classification of these versions is given. The ...main HLLME procedures are discussed. Examples of the application of HLLME to the separation of organic compounds in the analysis of environmental samples, food products, and biological fluids are given.
A method was proposed for the synthesis of substituted 2-(3-cyano-4,5,6,7-tetrahydrobenzo
b
thiophen-2-ylamino)-4-oxobut-2-enoates containing a nitrile substituent in the thiophene ring by reacting ...the corresponding 3-thienylimino-3
H
-furan-2-ones with primary alcohols. The antinociceptive activity and acute toxicity of the obtained compounds were investigated. It was found that the substituted esters have pronounced antinociceptive activity and low toxicity. According to the classification of toxicity of drugs, the obtained substituted of 2-(3-cyano-4,5,6,7-tetrahydrobenzo
b
thiophen-2-ylamino)-4-oxobut-2-enoates belong to the V class toxicity.
The use of hypercrosslinked polystyrene for the group sorption preconcentration of catecholamines is proposed. The conditions for the preconcentration of noradrenaline, adrenaline, and dopamine are ...optimized: a microcolumn (10 × 6 mm), mass of adsorbent 0.03 g, 25 mL of solution (pH ~ 8.5), and transmission rate of the solution 1.0 mL/min. Compounds were desorbed with 1 mL of 6 M acetic acid and determined in the eluate by reversed-phase HPLC with an amperometric detector (
E
= 0.8 V). Adsorption preconcentration ensures the reduction of the limits of detection for catecholamines by more than 20 times. The limits of detection were 0.7 ng/mL for dopamine and 1 ng/mL for noradrenaline and adrenaline. The procedure was applied to the analysis of model mixtures based on urine.
A possibility of using a monitor calibrator for the determination of luminescent compounds is shown on an example of quinine. The determination is based on the irradiation of a sample with broadband ...radiation in the visible and near UV spectral regions from a built-in source exciting phosphor molecules and the simultaneous registration of the radiation incident on the detector. Measurement conditions are selected. Quinine can be determined in the range of 60−750 µM, the limit of detection is 20 µM. The determination is not affected by common inorganic ions, as well as sweeteners and acidity regulators present in many beverages. The developed method of determination is applicable to the analysis of carbonated drinks and drugs. Compared to a traditional spectrofluorimeter, monitor calibrator is characterized by compactness, mobility, ability of detecting luminescence in cuvettes of various sizes and shapes, and lower cost.
