m-Aminophenylarsonic Acid as a Reagent for the Extraction Preconcentration of Phenol

The azocoupling reaction of phenol with the diazonium salt of m-aminophenylarsonic acid was used for the determination of phenol in water at a level of maximum permissible concentrations. The resulting compound is stable in a wide pH range, which made it possible to develop a procedure for the determination of phenol with the preconcentration of the azo compound by extraction to isobutanol at pH 2 and subsequent back extraction to the aqueous phase at pH 10. The high concentration coefficient of phenol (65) provides for determination of phenol down to 0.9 g/L.     

Use of Silica Gel Chemically Modified with Mercapto Groups for the Extraction, Preconcentration, and Spectroscopic Determination of Palladium

Silica gel chemically modified with mercaptopropyl groups is proposed for the extraction and preconcentration of palladium. This silica gel extracts palladium(II) at an acidity from 6M HCl to pH 4 with distribution ratios at a level of n× 10⁴ g/cm³. Hyphenated procedures for the adsorption–photometric determination of palladium with detection limits of 0.1 g/0.1 g of the adsorbent have been developed. The procedure includes the adsorption preconcentration of palladium, elution by hot (50 ± 5°C) 8% thiourea in 1M HCl, and atomic absorption determination of palladium in the eluate (detection limit is 0.05 g/mL). The procedures were applied to the determination of palladium in standard reference samples of copper–nickel ore and copper concentrate.     

By-Product of the Red Ginseng Manufacturing Process as Potential Material for Use as Cosmetics: Chemical Profiling and In Vitro Antioxidant and Whitening Activities

Red ginseng (RG), which is obtained from heated Panax ginseng and is produced by steaming followed by drying, is a valuable herb in Asian countries. Steamed ginseng dew (SGD) is a by-product produced in processing red ginseng. In the present study, phytochemical profiling of extracts of red ginseng and steamed ginseng dew was carried out using gas chromatography-mass spectrometry (GC-MS) and rapid resolution liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (RRLC-Q-TOF-MS) analysis. Additionally, antioxidant activities (DPPH, ·OH, and ABTS scavenging ability) and whitening activities (tyrosinase and elastase inhibitory activity) were analyzed. Phytochemical profiling revealed the presence of 66 and 28 compounds that were non-saponin components in chloroform extracts of red ginseng and steamed ginseng dew (RG-CE and SGD-CE), respectively. Meanwhile, there were 20 ginsenosides identified in n-butanol extracts of red ginseng and steamed ginseng dew (RG-NBE and SGD-NBE). By comparing the different polar extracts of red ginseng and steamed ginseng dew, it was found that the ethyl acetate extract of red ginseng (RG-EAE) had the best antioxidant capacity and whitening effect, the water extract of steamed ginseng dew (SGD-WE) had stronger antioxidant capacity, and the SGD-NBE and SGD-CE had a better whitening effect. This study shows that RG and SGD have tremendous potential to be used in the cosmetic industries.     

Microemulsions as reaction media for the synthesis of Pt nanoparticles

For the synthesis of Pt nanoparticles we used water-in-oil droplet microemulsions as templates. The focus was on the correlation between the size of the microemulsion droplets and that of the resulting Pt particles. To study this correlation in a systematic way, all particles were synthesized at the water emulsification failure boundaries where the microemulsion droplets are spherical and where their size can easily be tuned by the amount of added water. The metallic particles were synthesized by mixing two microemulsions one of which contains the metal salt H(2)PtCl(6) and the other the reducing agent NaBH(4). The size and structure of the microemulsion droplets was studied via small-angle X-ray scattering, while the Pt particles were characterized by high-resolution transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy and selected area electron diffraction. The clear correlation between droplet and particle size was further supported by accompanying Monte Carlo simulations.     

Determination of Methylphosphonic Acid and Its Esters as Chemical Markers of Organophosphorus Chemical Warfare Agents

The feasibility of isolation and quantitative determination by gas chromatography of methylphosphonic acid and its mono- and dialkyl etsers, which originate from destruction of organophosphorus chemical warfare agents and have been detected in bitumen-salt compounds is examined.     

Use of Molecular Imprinted Polymers for the Separation and Preconcentration of Organic Compounds

Data on the use of molecular imprinted polymers for the separation and preconcentration of organic substances in chemical analysis are summarized. The main approaches and methods used in the synthesis of these polymers are considered. The development of combined and hybrid methods of analysis with the use of these adsorbents is discussed.     

Preconcentration of Volatile Hydrocarbons as Air Pollutants by C-18 Bonded Silica used for Solid Phase Extraction

ABSTRACT

C₁₈-Silica used for Solid-Phase Extraction exhibits the same degree of adsorption of volatile hydrocarbons as compared to conventional Tenax adsorbent. The vapor pressure of the hydrocarbons and the velocity of the air sample through the sorbent are dominants of the preconcentration. Recovery of 80% for n-hexane and 98% for p-xylene at a concentration of 10 mg.m^?3 was obtained at 10 ml.g^?.min^? velocity.

C₁₈Bond Elut cartridges have been successfully used for quantitative determination of hydrocarbons as air pollutants by gas chromatography. The detection limit for p-xylene using preconcentration from 1 L air sample and a S/N ratio of 5 was 0.1 mg.m^?3. After regeneration of C₁₈Bond Elut cartridges by washing with acetonitrile and diethyl ether and drying at 85°C/15 min, their preconcentration potential remain acceptable upon reusing at least three times.     

Simultaneous Preconcentration of Triazole Fungicide Residues Using In-Situ Coacervative Extraction Based on a Double-Solvent Supramolecular System Prior to High Performance Liquid Chromatographic Analysis

An in situ coacervative extraction (IS-CAE) based on a double-solvent supramolecular system coupled to liquid–liquid microextraction is investigated for extraction and enrichment of triazole fungicides. The formation of a double-solvent supramolecular system was generated by in situ formation and used as an extraction solvent for the coacervative extraction method. No disperser solvent was required. This new double-solvent supramolecular system has a higher extraction ability than any of its components alone. The different factors that could affect the extraction capability were studied and optimized, including the type of double extractant and its volume, salt addition, vortex time, and centrifugation time. Under optimum extraction conditions, this method provides high enrichment factors (EFs) of 73–318 with low limits of detection (LODs) of 0.3–1 μg L⁻¹ and limits of quantitation (LOQs) of 1–3 μg L⁻¹. In addition, the proposed method was prosperously applied for the determination of triazole fungicides in water, fruit juice, and soy milk samples.     

Magnetic Sorbent with a Mesoporous Shell for the Simultaneous Preconcentration of Ecotoxicants of Different Nature

A magnetic sorbent with a multilayer shell of the composition Fe₃O₄@TEOS@CTAB@TEOS + MPTEOS designed for the simultaneous or sequential preconcentration of components of various nature is obtained. The conditions of microwave synthesis and modification of a new magnetic sorption material are described; its composition and particle sizes are characterized. The sorption capacity of the sorbent is provided by creating a mesoporous silica layer filled with cetyltrimethylammonium bromide (CTAB) micelles and additionally modified with an S-containing polymer (MPTEOS) on the surface of the magnetic carrier. The properties of the obtained material with respect to the regulated substances from two groups of priority pollutants are studied: phenols of various structures and heavy metals. The main sorption characteristics (effect of pH, phase contact time, nature of eluent, V: m, salt background) are studied and the conditions for extracting ecotoxicants at their concentration in the solution at a level of μg/L are optimized. The data obtained under the conditions of separate and simultaneous extraction of analytes of different nature confirmed a possibility of the quantitative determination of various types of natural water pollutants at the levels significantly lower than the MPC using a single sorption material. In using HPLC methods and electrothermal atomic absorption spectrometry, a complete analysis of a single sample takes 40?50 min and of a series of samples, 2–3 h. Such characteristics, combined with the simplicity of material preparation make it promising for routine analytical studies.     

Dissipative Particle Dynamics Study of Interfacial Properties and the Effects of Nonionic Surfactants on Hydrocarbon/Water Microemulsions

The aim of this work was to apply dissipative particle dynamics (DPD) mesoscopic simulations to study the interfacial orientation and the effect of the nonionic surfactant, hexaethylene glycol monododecyl ether (C₁₂E₆), on different (oil (dodecane)/water) microemulsion systems. The Hildebrand-solubility-parameter model and Flory–Huggins/Hansen-solubility-parameter (FH/HSP) model were combined to evaluate the DPD interaction parameter (a_ij) where the solubility parameters (δ_i) as DPD input parameters were preliminary validated by all-atom molecular dynamics (MD) results and experimental data. The interfacial property dependence of dodecane/water/C₁₂E₆ system on the oil/water (o/w) ratio and on the concentration of surfactant and orientation at the interface were investigated. It was found that the surfactant addition reduced the IFT of o/w interfaces and this reduction was more efficient for water-in-oil microemulsions (o/w ≤ 1).     

三正辛胺萃淋树脂的合成及对银分离富集的研究

报道了Levextrel型三正辛胺（TOA）萃淋树脂的合成方法及对银分离富集的研究，用新合成的萃淋树脂，铅锌冶炼矿渣中的银在1mol/L的盐酸介质中定量吸附后可用0．25mol/L NH4Cl-0.5mol/L硫脲洗脱，以火焰原子吸收光谱法测定，其回收率为99．4％－104．3％。此树脂对浓度低至0．5μg/mL的银亦可富集和定量回收，并有较长的使用寿命。     

Chemical Variability and Pharmacological Potential of Propolis as a Source for the Development of New Pharmaceutical Products

This review aims to analyze propolis as a potential raw material for the development and manufacture of new health-promoting products. Many scientific publications were retrieved from the Scopus, PubMed, and Google Scholar databases via searching the word "propolis". The different extraction procedures, key biologically active compounds, biological properties, and therapeutic potential of propolis were analyzed. It was concluded that propolis possesses a variety of biological properties because of a very complex chemical composition that mainly depends on the plant species visited by bees and species of bees. Numerous studies found versatile pharmacological activities of propolis: antimicrobial, antifungal, antiviral, antioxidant, anticancer, anti-inflammatory, immunomodulatory, etc. In this review, the composition and biological activities of propolis are presented from a point of view of the origin and standardization of propolis for the purpose of the development of new pharmaceutical products on its base. It was revealed that some types of propolis, especially European propolis, contain flavonoids and phenolic acids, which could be markers for the standardization and quality evaluation of propolis and its preparations. One more focus of this paper was the overview of microorganisms’ sensitivity to propolis for further development of antimicrobial and antioxidant products for the treatment of various infectious diseases with an emphasis on the illnesses of the oral cavity. It was established that the antimicrobial activity of different types of propolis is quite significant, especially to Gram-negative bacteria and lipophilic viruses. The present study could be also of interest to the pharmaceutical industry as a review for the appropriate design of standardized propolis preparations such as mouthwashes, toothpastes, oral drops, sprays, creams, ointments, suppositories, tablets, and capsules, etc. Moreover, propolis could be regarded as a source for the isolation of biologically active substances. Furthermore, this review can facilitate partially overcoming the problem of the standardization of propolis preparations, which is a principal obstacle to the broader use of propolis in the pharmaceutical industry. Finally, this study could be of interest in the area of the food industry for the development of nutritionally well-balanced products. The results of this review indicate that propolis deserves to be better studied for its promising therapeutic effects from the point of view of the connection of its chemical composition with the locality of its collection, vegetation, appropriate extraction methods, and standardization.     

Application of Graphene as a Sorbent for Simultaneous Preconcentration and Determination of Trace Amounts of Cobalt and Nickel in Environmental Water and Vegetable Samples

A new method using a column packed with graphene as adsorbent was developed for the preconcentration of trace amounts of cobalt (Co) and nickel (Ni) prior to their determinations by flame atomic absorption spectrometry. Several factors influencing the extraction efficiency of Co and Ni and their subsequent determinations, such as pH, amounts of the chelating agent, flow rates of sample and eluent solution, eluent type and its volume, breakthrough volume, and adsorption capacity were established. Under the optimum conditions, the calibration graphs were linear in the range of 4.0‐200.0 μg L^?1 and 5.0‐200.0 μg L^?1 with detection limits of 0.36 μg L^?1 and 0.51 μg L^?1 for Co and Ni, respectively. Good relative standard deviations for ten determinations of 100.0 μg L^?1 of Co and Ni were 3.2 and 3.6%, respectively. The results for determination of Co and Ni in tap water, river water, sea water, vegetable and spiked samples have demonstrated the accuracy and applicability of the proposed method. To validate the proposed method, three certified reference materials of environment water (GSBZ 50030‐94 and GSB 07‐1186‐2000) and tomato leaf (GSBZ 51001‐94) were analyzed, and the determined values were in good agreement with the certified values.     

Selection of Conditions for Chromatomembrane Gas Extraction at Its Combination with the Gas-Adsorption Preconcentration of Analytes

Optimal conditions (temperature, porous structure and configuration of mass exchange layer in the chromatomembrane cell, and also the direction of water sample and extractant gas flows through it) for the chromatomembrane gas extraction of volatile organic compounds from aqueous solutions in combination with the gas-adsorption preconcentration of the analytes are selected. An analysis scheme based on a combination of these methods and a two-step thermal desorption of analytes ensures the shortening of the preconcentration time by several times compared to the schemes involving traditional bubbling. Metrological characteristics are given and the accuracy of the developed scheme of analysis is proved.     

Simultaneous Electroanalysis of Hypochlorite and H2O2: Use of I−/I2 as a Probing Potential Buffer

Sodium hypochlorite (NaClO) and hydrogen peroxide (H₂O₂) have been simultaneously analyzed, for the first time, using a simple and rapid potentiometric method. The present method shows a high sensitivity, selectivity and satisfactory reproducibility. Pt electrode was used as an indicator electrode and the I₂/I^? redox couple was used as a probing potential buffer. The large difference in the rates of the oxidation of I^? by the two oxidizing agents, that is, the oxidation of I^? by NaClO is by several orders of magnitude faster than that by H₂O₂, enabled the selective analysis of these two species. Based on such a large difference in the rates, a momentary potential response corresponding to the oxidation of I^? by NaClO and another quite slow one by H₂O₂ could be obtained. Factors affecting the selectivity as well as the sensitivity, such as the concentrations of molybdate (used as catalyst for the oxidation of I^? by H₂O₂), H⁺, I₂, and I^? in the potential buffer were examined. The expected Nernstian responses were obtained over a considerable range of the concentrations of the two oxidizing agents with slopes of 30.5 and 29.9 mV for NaClO and H₂O₂, respectively (in a close agreement with the theoretical value, that is, 29.6 mV) and with a detection limit in the submicromolar range (0.2 μM).     

Use of Optically Transparent Membranes for Preconcentration and Direct Phosphorimetric Determination of Pharmaceutical Flumequine

A preconcentration membrane for the retention and phosphorimetric determination of flumequine is proposed. The membrane has a circular zone adhering to the surface of a polyester strip, which constitutes the preconcentration area where the analyte is retained by absorption from a solution that contains it. The phosphorescence intensity emitted by the flumequine can be measured directly in the solid phase, at λ_exc = 358 nm and λ_em = 459 nm. The variables that influence the construction of the membrane have been studied, along with the experimental variables related to the fixation process of the analyte in the membrane. The calibration graph was linear over the range 0.1–2.0 mg/L with a detection limit of 0.03 mg/L and a precision of 0.5%. The method was applied to samples of human urine and cow's milk, with recovery percentages ranging between 100.0 and 102.8%.