Substances In Aqueous Solutions Research Articles

AN ARRAY OF ENZYME BIOSENSORS FOR THE DETERMINATION OF CONCENTRATIONS OF NEUROTRANSMITTERS AND METABOLITES

The purpose of this work was to test the possibility of creating an array of enzyme biosensors for the simultaneous determination of six substances in aqueous solutions. Enzymes, selective for glutamate, glucose, choline, acetylcholine, lactate and pyruvate, were immobilized on the surfaces of amperometric transducers. The influence of pH, ionic strength and buffer capacity of the solution on the response of biosensors was studied; the conditions of simultaneous operation of all bioselective elements were optimized. High selectivity of biosensors and absence of influence of interfering substances on their work was found. The created array of biosensors had good reproducibility of responses and storage stability. The use of identical transducers and similar conditions of immobilization of enzymes make the biosensor array promising for mass production. The biosensor array is suitable for simultaneous, rapid and simple determination of substances in aqueous samples.

INVESTIGATION OF SURFACTANTS APPLICABLE IN WELL DRILLING

Background The relevance of the study is due to the need to improve the performance properties of surfactants used in drilling technology to reduce interfacial tension and negative effects on the natural reservoir properties of the formation. Aims and Objectives: o investigation of surfactants used in the construction of wells; o substantiation of the choice of the method of determining the surface tension at the boundaries «liquid - liquid», «liquid - air»; o investigation of surface activity of various substances in aqueous solutions at the border with air and purified kerosene; estimation of efficiency of addition of phosphates in water solutions of surfactants. Results o Analysis of surfactants showed that anionic surfactants effectively reduce the surface tension on the boundary of the media (due to high surface activity), have a flocculating ability, however, non-ionic surfactants in contact with oil are demulsifying and desalting, have a low adsorbability on clays, carbonate rocks, sandstones.

Real-time microwave sensor system for detection of polluting substances in pure water.

In the present work, a real-time coaxial sensor for detecting foreign substances in aqueous solutions was developed and tested. This tool, based on a coaxial propagation line for determining the electromagnetic parameters of materials, was updated into a liquid permittivity monitoring sensor of continuous flow. A few solutions of different nature were tested, and while adding a liquid or electrolyte substance, named "pollutant," variations in the base solution were documented. Ethanol and water mixtures were used as reference, while the ability of the system to detect emulsions (such as oil in water solutions) was also evaluated. The system shows great potential for the quantification and qualification of liquid mixtures, having a threshold of reduced volume/volume fractions of foreign substances or pollutants, a property which is shown to be extremely useful in an analogue of high glycaemia (diabetes disease)-thus, opening the possibilities of monitoring biological liquids.

The novel technique of vapor pressure analysis to monitor the enzymatic degradation of PHB by HPLC chromatography

A novel method was introduced for the quantitative determination of substances in aqueous solutions by using the evaporative light scattering (ELS) detector of a high performance liquid chromatograph (HPLC). The principle of the measurement is the different equilibrium vapor pressure of the solvent and the analyte resulting in decreasing evaporation rate, larger droplets and stronger signal with increasing concentration. The new technique based on vapor pressure analysis was validated with traditional UV-Vis detection carried out with a diode array detector (DAD). The new technique was used for monitoring the concentration of solutions obtained during the enzymatic degradation of poly(3-hydroxybutyrate) yielding the 3-hydroxybutyrate monomer as the product. The accuracy of the measurement allowed the determination of degradation kinetics as well. The results obtained with the two techniques showed excellent agreement at small concentrations. Deviations at larger concentrations were explained with the non-linear correlation between analyte concentration and detector signal and the linear regression used for calibration. Mathematical analysis of the method made possible the determination of the evaporation enthalpy of the analyte as well. The new approach is especially suitable for the quantitative analysis of compounds, which do not absorb in the detection range of the DAD detector or if their characteristic absorbance is close to the lower end of its wavelength range.

Phase Behavior of Ascorbyl Palmitate Coagels Loaded with Oligonucleotides as a New Carrier for Vaccine Adjuvants

AbstractIn this work, the phase behavior variations of an ascorbyl palmitate (Asc16) system in aqueous solution were analyzed when immunologically active hydrophilic compounds (CpG and OVA) were introduced. This study was carried out through optical polarizing microscopy (OPM) and differential scanning calorimetry (DSC) at different temperatures and over a broad range of concentrations. The combination of both techniques allowed the determination of a complete phase diagram which was compared with those built for Asc16‐water system and it was demonstrated that fixed concentrations of hydrophilic compounds (300 and 24 µg/g for CpG‐ODN and OVA respectively) generate two lamellar liquid crystals, a cubic liquid crystal phase, and also other aggregates. However, no changes were observed in the phase diagram in terms of formation of new mesophases. The aqueous phase behavior was also studied as a function of surfactant and temperature. DSC and Fourier transform infrared spectroscopy (FT‐IR) measurements show differences in the free water and mainly in the secondary hydration layer, which confirm that the studied compounds are situated in the aqueous domain. The construction and analysis of Asc16 phase diagrams with a fixed concentration of CpG‐ODN/OVA allows the comprehension of Asc16 phase behavior and could be easily adapted to other concentrations. Moreover, these findings could be extrapolated to other hydrophilic substances in aqueous solution introduced in liquid crystal phases since they follow a similar behavior as those reported in the literature.

Arrhenius Kinetics As a Bioactivity Assessment Criterion for Drug Substances and Excipients

Arrhenius kinetic principles, in particular, E a values, were used to assess the biological activity of drug substances in aqueous solutions with different D/H ratios. The obtained activation energies indicated that deuterium-depleted solutions had lower toxicity and biological activity.

Removal of Iron Colloid Substances from Aqueous Solutions Using Pulsed Corona Discharge

Pulsed electric discharge has been used for the removal of iron colloid substances from aqueous solutions. The residual concentration of organic substances in aqueous solution depends on the pulse repetition rate. The maximum decrease in organic substances concentration was observed at the pulse repetition rate of 800 pps. Comparison of the results obtained for iron colloid solutions containing humic substances and solutions of humic subtances with no colloids shows that the highest removal efficiency of organic substances was obtained when no iron and silicon ions were present in the solution. The results of our experiments suggest that pulsed electric discharge treatment for the removal of organic substances from natural waters is more efficient at an after-treatment stage, after precipitation of colloid substances.

Large-scale synthesis of size-controllable silver nanoplates and their application in detecting strong oxidants in aqueous solutions

A scalable approach for preparation of Ag nanoplates in one-step is reported. Well-defined Ag nanoplates were obtained by reducing silver nitrate with hydrazine hydrate in the presence of insoluble silver salt, such as AgSCN, AgCl, AgBr, AgI, Ag2CO3, Ag2SO3, and Ag2C2O4. The size of Ag nanoplates can be well controlled by simply adjusting the ratio of Ag seeds to the amount of AgNO3. The exclusive formation of Ag nanoplates was due to the homogeneous nucleation of Ag nanoparticles is avoided in the presence of a small amount of counterions of insoluble silver salts, and large-scale synthesis with a yield ca.75 times higher than the record was achieved. In addition, a detecting strategy toward oxidizing substances in aqueous solutions was summarized based on the change of the surface plasma absorption via the size variation of the Ag nanoplates. This detecting method combines the advantages of generality, rapidity, simplicity, as well as a low detection limit and a wide linear response range.

Water-soluble polymers for binding hydrophobic biologically active compounds

Water-soluble neutral and charged copolymers of cholesterol methacrylate with 2-deoxy2-methacrylamido-D-glucose and methyl sulfate salt of N,N,N-trimethyl(aminoethyl methacrylate) and β-cyclodextrin-containing polymers of different compositions were synthesized. The interactions of the “dark” and luminescence-labeled copolymers with models of lowmolecular-weight hydrophobic compounds (cholesterol and acridine orange) and of highmolecular-weight biologically active compounds containing hydrophobic fragments with bovine serum albumin were studied by the method of polarized luminescence. Cholesteroland β-cyclodextrin-containing polymers actively bind these compounds by inclusion them into hydrophobic domains or due to the formation of host–guest complexes. The variation of the polymer structure makes it possible to control the degree of binding. The synthesized polymers are promising carriers of hydrophobic substances and can further serve as a basis for manufacturing systems for control of the level of hydrophobic substances in aqueous solutions and biological liquids.

Application of experimental design approach for optimization of the photocatalytic degradation of humic substances in aqueous solution using immobilized ZnO nanoparticles

Degradation of humic substances in water is important due to its adverse effects on the environment and human health. The aim of this study was modeling and investigating the degradation of humic substances in water using immobilized ZnO as a catalyst. ZnO nanoparticles were synthesized through simple coprecipitation (CPT) method and immobilized on glass plates. The immobilized ZnO nanocatalyst was characterized through scanning electron microscopy (SEM) and X-ray diffraction (XRD). Response surface methodology (RSM) and central composite design (CCD) were used to create an experimental design for humic degradation and color removal efficiency. The most important parameters including initial concentration, pH, and contact time were optimized. The optimum conditions were initial concentration of 7.68 mg/l, pH of 4.42, and contact time of about 125.6 minutes. Under optimal conditions, maximum humic substances and color removal of about 100 and 82.37% were obtained, respectively. These results illustrate that an immobilized form of ZnO can be used as an efficient nanocatalyst for effective degradation of humic substances in water.

Degradation of organic substances in aqueous solutions under the action of pulsed high-voltage discharges

Pollution of water with highly toxic durable organic substances leads to irreversible environmental changes. Physicochemical and biological methods of water treatment are being developed for controlling such pollution. Oxidation of aromatic and aliphatic organic substances in water by pulsed high-voltage discharges was studied. A decrease in the chemical oxygen demand was noted. The efficiency of the removal of organic substances from the solutions being treated was evaluated.

Photocatalytic degradation of humic substances in aqueous solution using Cu-doped ZnO nanoparticles under natural sunlight irradiation.

In this study, Cu-doped ZnO nanoparticles were investigated as an efficient synthesized catalyst for photodegradation of humic substances in aqueous solution under natural sunlight irradiation. Cu-doped ZnO nanocatalyst was prepared through mild hydrothermal method and was characterized using FT-IR, powder XRD and SEM techniques. The effect of operating parameters such as doping ratio, initial pH, catalyst dosage, initial concentrations of humic substances and sunlight illuminance were studied on humic substances degradation efficiency. The results of characterization analyses of samples confirmed the proper synthesis of Cu-doped ZnO nanocatalyst. The experimental results indicated the highest degradation efficiency of HS (99.2%) observed using 1.5% Cu-doped ZnO nanoparticles at reaction time of 120 min. Photocatalytic degradation efficiency of HS in a neutral and acidic pH was much higher than that at alkaline pH. Photocatalytic degradation of HS was enhanced with increasing the catalyst dosage and sunlight illuminance, while increasing the initial HS concentration led to decrease in the degradation efficiency of HS. Conclusively, Cu-doped ZnO nanoparticles can be used as a promising and efficient catalyst for degradation of HS under natural sunlight irradiation.

Structure investigation of the recovered zinc sulfide from fulfilled electron-excited phosphorus

Some investigation results of recovered zinc sulfide from electron-excited phosphorus of fulfilled television picture tubes and computer monitors is shown in the article. The purpose of investigation is determination of modification type of crystal structure, investigation of some its characteristics and behavior of recovered zinc sulfide. For this purpose the crystalline precipitate of recovered zinc sulfide obtained from electron-excited phosphorus solutions in an aqueous solution of hydrochloric acid by deposition method. The processes of dehydration and crystallization are investigated by thermographic, differential - thermal, chemical and X-ray diffraction analysis methods. It is possible to determine the type of structural modifications of recovered zinc sulfide and also explore the behavior of recovered substances in aqueous solutions. Complex of physical and chemical properties of recovered zinc sulfide can be used as semiconducting compound. Zinc sulfide recovery from electron-excited phosphorus of fulfilled television picture tubes and computer monitors from aqueous solutions by precipitation allow to establish basic patterns of behavior in these solutions, to identify the sphalerite modification of zinc sulfide.

Adsorptive removal of fluoride from aqueous solution by a PES/LDH blend flat-sheet membrane

Adsorption of fluoride by PES/LDH (layered double hydroxide) blend flat-sheet membrane was investigated. The SEM, AFM, and fluoride adsorption capacity of the membrane were evaluated. The addition of LDH led to a significant enhancement in the adsorption capacity of the membrane. The batch adsorption experiments demonstrated that the membrane effectively removed fluoride in a wide pH ranging from 2–10. The adsorption equilibrium could be established in 30 min, and the maximum adsorption capacity was 2.63 mg/g. The pseudo-second-order kinetics was observed for the adsorption process which followed the Langmuir-type adsorption isotherm. The membrane can be regenerated with 0.1 M NaOH. This work provides a new method to the adsorptive removal of hazardous substance in aqueous solutions.

Surface Enhanced Raman Spectroscopy on Silver Nanoparticles

The main purpose of this study is to detect dif- ferent ecologically harmful substances in aqueous solutions using surface enhanced Raman spectroscopy (SERS) as a tool. Therefore, assigning the vibrational modes is essential to identify the substances. SERS using silver nanoparticles was used to obtain reproducible intense signals for detection of molecules in aqueous solutions. The study extends the use of thiol layers for attracting molecules onto the silver surface. Optimization for SERS measurements during scanning was made by scanning different points per line and different lines per image. The dependence of SERS intensity on scan speed had been demonstrated using descriptive figures. The spectra in pure solid forms and aqueous solutions of the carbamezapine (CBZ) sample helped for assigning which band belongs to which bond in the compound.

A strategy to estimate the intrinsic flux of a poorly water soluble substance for comparison with its release from lipid-core nanocapsules

In studies on the release of drugs, antioxidants, vitamins, etc., from submicrometric particles, the released portion cannot be separated from that which remains entrapped in the carrier using conventional filtration methods due to the membrane cut-off. Thus, other methods, for example, ultrafiltration–centrifugation or dialysis with dialysis bags, which enable this separation are used. However, as the substances vehiculated in colloidal aqueous solutions are usually poorly water soluble substances, it is not easy to obtain their intrinsic flux (J0) value in aqueous solution. In this context, our objective was to develop a strategy to obtain the J0 value of a poorly water soluble substance dialysate from an aqueous solution aiming to compare it with its apparent flux (Japp) from an aqueous colloidal system allowing the evaluation of the effect of nanoencapsulation on the release rate of a lipophilic substance. Different hydroethanolic solutions of a poorly water soluble substance (benzophenone-3 (BZ3)) were dialyzed against hydroethanolic media using dynamic dialysis with bags. The Japp value of BZ3 in each system was plotted as a function of the proportion of organic solvent and the exponential mathematical equation of this relation was used to calculate the J0 value of the substance in aqueous solution. BZ3-loaded lipid-core nanocapsule suspensions (BZ3-LNC) were used as a model for colloidal nanocarriers. The Japp value obtained for the release from the BZ3-LNC suspension was around 14-fold lower than the J0 value, indicating that the encapsulation of BZ3 into the LNC system was able to slows its diffusion. The strategy developed allows the use of the J0 values of poorly water soluble substances in aqueous solutions to verify whether the nanoencapsulation can prolong, for example, the substance delivery on the biological environment.

Spectral Characterization of Fungal Metabolites in Aqueous Medium with Humus Substances

The work is targeted to confirm participation of microscopic fungi in transformation of humus substances in aquatic environments. The research is focused on the spectroscopic study of the collection of fungal strains with different pigmentation of mycelium. Spectral properties of fungal metabolites were measured and compared to that of natural aquatic nonliving organic matter and commercial humus substances in aqueous solutions. The experiments revealed that the effect of microscopic fungi growing in the culture medium with added humate appeared as changes in the humic-type fluorescence: its characteristics became more similar to that of nonliving organic matter in natural waters than to original humate preparation. The experiments demonstrated degradation of coal-originated humate due to microbial activity into compounds of smaller molecular size and increased heterogeneity. We resume that transformation of humus substances by fungal cultures can be monitored and characterized using spectral measurements.

The bioscope system—testing and validating a novel sensor for aqueous solutions

A novel device called the Bioscope System is investigated for feasibility as sensor for chemicals in aqueous solutions. Thereby a sample is examined by a pulsed voltage and electrical properties of that sample are measured. These electrical properties can be considered as a sum parameter of the sample in terms of conductivity and permittivity. It is demonstrated that the Bioscope System can indeed measure differences between different substances in aqueous solution and between different concentrations of the same substance in aqueous solution. A qualitative explanation is provided. Possible improvements of the system are suggested.

Determination of amino acids, vitamins, and drug substances in aqueous solutions using new potentiometric sensors with Donnan potential as analytical signal

Basic principles of a new potentiometric sensor are considered. Its analytical signal is the Donnan potential at the ion-exchange polymer/studied solution of electrolyte interface. Assessments of potential drops at individual interfaces are presented, same as estimates of diffusion potentials in the electrochemical circuit for measurement of the sensor response. It is shown that the overall contribution of the values of all potentials to EMF of the electrochemical circuit, except for the Donnan potential, at the ion-exchange polymer/studied solution interface are negligibly low as compared to the experimental values of the circuit EMF in the studied systems. Certain regularities of the Donnan potential formation are studied in the systems with the polymers of different structure and solutions containing inorganic ions and organic electrolytes in different ionic forms. The possibility is shown of using a sensor with such an analytical signal as the Donnan potential for assay of amino acids, vitamins, and drug substances in aqueous solutions. The sensor was used as a selective electrode for determination of lysine in aqueous solutions with neutral amino acids in the range of pH 5.0–7.0 and glycine in aqueous alkali solutions in the range of pH 9.00–11.00. The developed sensor is introduced as a cross-sensitive electrode into the array of multisensor systems for multicomponent quantitative analysis of the lysine monohydrochloride, thiamine chloride, novocaine hydrochloride, lidocaine hydrochloride solutions containing potassium and sodium chlorides. The measurement error of electrolytes in aqueous solutions did not exceed 10%.

Destruction of the Water Layer on a Hydrophobic Surface Induced by the Forced Approach of Hydrophilic and Hydrophobic Cations

Structural change of the water layers is the primary step for the direct interactions among the hydrated substances in aqueous solutions. We have studied how the water layers on a solid surface is destroyed by the approach of several hydrophilic and hydrophobic cations, which are used as model substances. The combined use of electrochemical system and IR spectroscopy enables the study of the destruction process of water layers during the close contact among them. We have observed for the first time that hydrophilic cations cause greater destruction of the interfacial water structure than hydrophobic cations. This result is ascribed to the different orientations of water molecules around the cations: H-bonds around hydrophilic cations expand toward the outer hydration shells, while they are closed inside the primary shell in the case of hydrophobic cations. These different orientations of water molecules cause different effects on the interfacial water structures.