Solvent Action Research Articles

Stochastic Nature and Intramolecular Coupling in Optical Response Profiles: Critical Analysis through Semiclassical Models.

We have studied the nonlinear absorptive and dispersive responses considering a molecular system consisting of two-levels, where aspects of the vibrational internal structure and intramolecular coupling are inserted, in addition to the considerations of interaction with the thermal reservoir. The Born-Oppenheimer electronic energy curve for this molecular model consists of two-intercrossing harmonic oscillator potentials with minima displaced in energy and nuclear coordinate. The results obtained show how these optical responses are sensitive to explicit considerations of both intramolecular coupling and the presence of the solvent through their stochastic interaction. Our study shows that the permanent dipoles of the system and the transition dipoles induced by electromagnetic field effects represent critical quantities for the analysis. The solvent action in our model is treated through the natural Bohr frequency shift to a time-dependent function, with explicit manifestations in its comparison as if the upper state were broadened. Significant variations in the nonlinear optical properties for cases of perturbative and saturative treatments, relaxation times, and optical propagation, mainly due to changes in the probe and pump intensities, are studied. Our studies relating the intramolecular effects with those generated by the presence of the solvent and its stochastic interaction with the solute of study, have allowed not only to analyze the influence of these in the profile of the optical responses, but they could also provide some insights into the analysis and characterization of molecular systems through nonlinear optical properties.

The importance of surface tension in endodontic irrigation: A review study

The surface tension of irrigants determines their ability to penetrate dentinal tubules and access the apical third of root canals. It is defined as an affinity for a liquid's surface area to decline in the case of surface tension between molecules. Irrigating the canal wall is vital for dissolving organic tissues and disinfecting dentin and its tubules in root canal preparation. Even with super elastic rotary preparation, untouched spaces are a typical issue during root canal instrumentation. As a result, the antimicrobial activity and solvent action in these areas is essential to the disinfection of root canals. The ability to diagnose irrigants quickly and treat them successfully depends on a thorough discernment of their surface tension. In this study, surface tension involved in endodontic solutions was examined for etiological factors, features, and possible consequences. The relevant studies were found by searching online databases. We identified 30 articles using the hand search method and summarized the critical factors of each study. It was found that low surface tension agents would penetrate tubules more acceptable and that surface tensions estimated at various temperatures and concentrations affected canal cleaning.

Non-Negligible Modulation Role of the Solvent in the Asymmetric Growth of α-Resorcinol

It is accepted that the asymmetric growth of α-resorcinol is an intrinsic property and the solvent only plays a secondary role. Therefore, this work combines single-crystal growth experiments and molecular dynamics simulations to quantify the non-negligible modulation role of the solvent in the asymmetric growth of α-resorcinol. According to the experimental results, the growth rate ratio of α-resorcinol in water is the largest, followed by that in ethyl acetate, and ethanol had the least influence. The (01̅1̅) face along the polar −c axis is a hydroxyl-rich surface, and the capability of hydrogen bond formation determines the magnitude of the growth rate. However, the (011) face along the polar +c axis is a hydrogen-rich surface, and the growth rate mainly depends on the molecular structure of the crystalline surface and the steric hindrance between molecules. In general, the molecular arrangement of α-resorcinol along both ends of the polar c-axis makes the solvent exhibit significant modulation differences in the asymmetric growth, which are entirely attributed to the mechanisms of solvent action on the specific crystalline surface. This work will further enrich the asymmetric growth mechanism of α-resorcinol in solution and potentially provide some guidance for the selection of the solvent for other organic polar crystals.

In vitro study of the effect of three commercial solvents on gutta-percha cones used for the cold and thermoplastic technique

The sample consisted of 80 gutta-percha cones No. 80 Endomedic and F3 ProTaper Universal. The cones were divided into 4 groups (n = 20) according to the type of solvent, and each one was divided into two subgroups (n = 10) according to the exposure time (5 min and 10 min). The cones were immersed in the respective solvent for 5 or 10 minutes. Then, they were washed with 5 ml of alcohol for 5 minutes and rinsed with water. Finally, after drying at room temperature for one hour, the solvent action was recorded in grams (g) of weight loss. The results were analyzed and compared using Tukey's test (p<0.05). The Endomedic cone exposed for 5 min to eucalyptol obtained the lowest average weight (0.0625 ± 0.0009 g), followed by Lemongrass oil (0.0629 ± 0.0003 g) and orange oil (0.0629 ± 0.0010 g), although not a significant difference (p > 0.05) was found between each one. The experimental solvent of Lemongrass, eucalyptol and orange oil presented a similar solvent effect on the guta-percha cone for cold and thermoplastic technique. At a clinical level, the three solvents studied could be used in endodontic retreatment as alternative solutions with a similar solvent effect.

Hydrogel from all in all lignocellulosic sisal fibers macromolecular components

The heterogeneous structure of lignocellulosic biomass makes it difficult to dissolve its main components (cellulose, hemicelluloses, and lignin) by solvent action with the aim of further applying the mixture of the biological macromolecules generated in the solvent medium. In the present study, the dissolution efficiency (DE) of lignocellulosic sisal fibers in the lithium chloride/dimethylacetamide solvent system (LiCl/DMAc) was evaluated for further application in the formation of hydrogels. Catalytic amounts of trifluoroacetic acid (TFA) were used in some experiments, which increased the DE from 40% to 90%. The regeneration of the solutions, either previously filtered or not, led to hydrogels based on sisal lignocellulosic biomass. In brief, the properties of the hydrogels were influenced by the content of the lignocellulosic components in the hydrogels, present both in the dissolved fraction and in the incorporated undissolved fraction (when nonfiltered solutions were used). Hydrogels presented water absorption up to 7479% and resorption content in the lyophilized hydrogel up to 2133%. Extracts obtained from preselected hydrogels exhibited cell viability up to 127% compared to the control group when in contact with fibroblast cultures, exhibiting their noncytotoxic properties. This attribute increased the range of possible applications of these hydrogels, ranging from agriculture to biocompatible materials.

Effect of solvation on the synthesis of MOF-based microrobots and their targeted-therapy applications

Five different morphologies of MOFs were generated on the microrobot surface under the solvent action, and the MOF-based microrobots obtained by screening had good biocompatibility, high drug loading capacity and targeted delivery capability.

Quantifying solvent action in oil paint using portable laser speckle imaging

The exposure of oil paintings to organic solvents for varnish removal or to water for the removal of surface dirt can affect the chemical and physical properties of oil paint in an undesired way. Solvents can temporarily plasticise and swell the polymerised oil paint binding medium, enhancing both the thermal mobility and mechanical displacement of pigments embedded in this film. The enhancement of these microscopic motions can affect both the chemical and physical stability of the object as a whole. In order to minimise solvent exposure during cleaning, an analytical method that can quantitatively measure the microscopic motions induced by solvent uptake, is required first. In this study, we use Fourier Transform Laser Speckle Imaging (FT-LSI) and a newly developed portable FT-LSI setup as highly resolved motion detection instruments. We employ FT-LSI to probe pigment motion, with high spatiotemporal resolution, as a proxy for the destabilising effects of cleaning solvents. In this way, we can study solvent diffusion and evaporation rates and the total solvent retention time. In addition, qualitative spatial information on the spreading and homogeneity of the applied solvent is obtained. We study mobility in paint films caused by air humidity, spreading of solvents as a result of several cleaning methods and the protective capabilities of varnish. Our results show that FT-LSI is a powerful technique for the study of solvent penetration during oil paint cleaning and has a high potential for future use in the conservation studio.

Sulfidization mechanism in malachite flotation: A heterogeneous solid-liquid reaction that yields CuxSy phases grown on malachite

Sulfidizationfollowed byxanthateflotation is an effective technique to recover copper oxide minerals. However, the sulfidization mechanism of malachite has not been determined. In this work, the sulfidization mechanism was investigated by microflotation, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), electron probe X-ray microanalysis (EPMA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The flotation results showed that sulfide ions at an appropriate concentration could activate malachite flotation while excess sulfide ions could depress this. The depression of malachite flotation by excess sulfide ions was attributed to the residual sulfide species in the liquid. FESEM–EDS showed that sulfidization product grown on the malachite surface was heterogeneously distributed, which was consistent with the EPMA results. The XRD results for the sulfidized malachite samples showed that the amount of sulfidization product was insufficient for detection under flotation-related conditions. By the selective solvent action of sulfuric acid, the sulfidization product was extracted from the sulfidized malachite. The XRD results for the extracts indicated that the sulfidization product comprised djurleite (Cu31S16) and anilite (Cu7S4), which both were compounds of the chalcocite group (Cu2−xS), suggesting transformation of solid Cu2(OH)2CO3 to Cu2−xS on the malachite surfaces during sulfidization. Moreover, the XPS results were consistent with the XRD results. These results demonstrated that sulfidization of malachite is a phase-transition process driven by the solubility difference between Cu2(OH)2CO3 and Cu2−xS. In this case, Cu2−xS phases formation on malachite involves heterogeneous nucleation and growth, and sulfide ions act as a reductant and sulfidizing agent in malachite sulfidization. The copper sulfide grown on malachite radically changed the surface properties of malachite particles, rendering malachite amenable to xanthate flotation. Based on these findings, we present a new formula for malachite sulfidization and a schematic diagram of the sulfidized malachite particle.

Sulfidization mechanism in the flotation of cerussite: A heterogeneous solid-liquid reaction that yields PbCO3/PbS core-shell particles

Sulfidizationfollowed byxanthateflotation is an extensively used method for recovering the lead oxide minerals. However, there is a debate about the sulfidization mechanism of cerussite. In this work, the sulfidization mechanism was investigated using optical microscopy (OM), scanning electron microscopy and energy dispersive spectrometry (SEM-EDS), atomic force microscopy (AFM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The OM, SEM-EDS and AFM results indicated that many microspheres grew on the cerussite particle surfaces to form a high-density sulfidization product layer after sulfidization, which changed the color, optic character, electrical conductivity and surface morphology of cerussite particles. The XRD results for the sulfidized cerussite samples showed that the sulfidization product layer was too thin to be detected. By the selective solvent action of acetic acid, the sulfidization product was extractedfrom the sulfidized cerussite particles. The XRD pattern interpreted that the sulfidization product were galena (PbS) phase, which provided the strongest proof for the generation of PbS on the cerussite surfaces. Moreover, the crystallite size of PbS calculated by the Scherer formula was in nanoscale. The EPMA analysis showed that the oxygen element was localized in the interior section, whereas the sulphur element was occurred in the outer surfaces of the particle. The aforementioned results demonstrated that after cerussite sulfidization, the mineral particles have a lead carbonate (PbCO3) core and a lead sulfide (PbS) shell. These findings also demonstrated that the sulfidization reaction is a heterogeneous reaction of solid phase (cerussite particles) with an aqueous solution (sodium sulfide solution) in which the solid reaction product adheres to the cerussite surface. From another point of view, the sulfidization process is a crystallization process including the heterogeneous nucleation and growth of PbS.

Pus solvents as new drugs with unique physical and chemical properti

The literature review shows that standards for the treatment of purulent diseases to date include antiseptic and disinfectants, but do not include agents that dilute and/or dissolve thick pus. It is shown that the pharmacodynamics of antiseptic and disinfectants consists in the local disinfecting effect of these agents. With local interaction with the surface of living and non-living tissues, these agents are able to sterilize it. It was found that for disinfection of the selected surfaces, these agents are used in solutions that contain these agents in concentrations that provide a denaturing effect. It is shown that denaturing action of antiseptic and disinfectants is a special case of dependence of local action of solutions of all medicines and chemical compounds on their concentration. The fact is that increasing the concentration of chemical compounds in solutions sooner or later turns that solutions into a liquid medium that is not compatible with life. Therefore, this liquid kills all cells of the micro-and macroworld. That is why the use of solutions with denaturing action provides a detrimental effect on the cells of all microorganisms and cells of the macroorganism. With local interaction with the tissues of the macroorganism, the drugs cause the following pharmacological effects: local sterilizing, irritating (local inflammatory) and cauterizing (necrotic) action. Thus solutions with denaturing concentration of one means increase the hardness, other means do not change the hardness, and the third means decrease the hardness of biological tissues, including purulent masses. From this it is concluded that today in the treatment of purulent diseases are used means, detrimental effect on all forms of life, and not means, unidirectionally acting on purulent masses. At the same time, it is shown that some of the modern antiseptic and disinfectants can change the properties of purulent masses in the right direction and optimize their removal by diluting and dissolving the thick pus. It is established that the leaders in the solvent action on thick and sticky pus are sodium bicarbonate solutions in combination with hydrogen peroxide. It is shown that solutions that effectively dissolve thick pus have special physical and chemical properties: all of them have moderate alkaline, temperature, boiling and osmotic activity. Preparations that most effectively dissolve thick pus and most quickly and completely remove it out of the purulent cavities, additionally contain carbon dioxide gas or oxygen gas under excessive pressure. In chronological order are recipes invented hygiene products with special physical and chemical properties, providing them with the ability to quickly and effectively liquefy, dissolve and remove the thick pus out of the purulent cavities. It is shown that a new group of hygiene products was discovered in Russia and was called Solvents of pus. The most effective and safe solvents of pus are warm (heated to a temperature of 42 C) solutions containing 24% sodium bicarbonate and 0.53% hydrogen peroxide.

Graphic vandalism: Multi-analytical evaluation of laser and chemical methods for the removal of spray paints

In this work, we propose the laser-based cleaning with a Q-switched Nd:YAG laser ( λ = 532 nm) not as a standalone methodology but rather in combination with chemical agents for the efficient removal vandal signs made with spray paints from marble substrates. The advantage of such approach is based on the preliminary removal of the superficial paint by pulsed laser radiation so as to minimize the risk of the further colorant diffusion in the stone, caused by the solvent-based cleaning that is performed in the second step. The outcome was demonstrated on the removal of five aerosol paints (red, blue, black, green and yellow by Montana Colors 94), whose typology was chosen in agreement with the widespread use of this brand. The influence of substrate characteristics on the cleaning performance, such as roughness, porosity, and ageing of the paint, was investigated on fresh and aged paints on sound marble as well as on fresh paints on aged marble. Fresh and aged paints were characterized in terms of mineralogy and chemistry using X-ray diffraction (XRD), X-ray fluorescence (XRF), Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS), Gas/Chromatography/Mass spectrometry (GC/MS). The efficiency for single cleaning step and when applied in sequence was evaluated by colorimetric measurements, optical microscopy on surface and in cross section, XRF and reflection Fourier Transform Infrared spectroscopy (FTIR). Invasiveness of laser cleaning on sound marble was evaluated by Laser Scanner microprofilometry. The results converge in indicating the combined approach as a promising method where the preliminary thinning of the paint layer with laser ablation and the subsequent solvent action proved more efficient than the standalone approaches. The dependence of cleaning efficiency on the paint composition and ageing, as well as on the porosity of the stone, is also discussed.

Removal of filling material in endodontic retreatment: a literature review

Removal of filling material from the root canal system is required when a previous endodontic treatment fails, what may result in the permanence of an unfavorable periapical condition. The intent is to completely remove the filling material from the root canal to achieve sufficient cleaning and shaping for successful retreatment. Objective: The aims of this article were to provide a systematic review of the different techniques of endodontic filling material associated or not with organic solvents and to analyze them critically in terms of advantages and disadvantages of each technique. Literature review: The descriptors used were “gutta-percha”, “obturation,” and “retreatment” in the following databases: PubMed, MEDLINE, Latin American and Caribbean Center on Health Sciences Information (Bireme), Latin-American and Caribbean Health Sciences (Lilacs), Brazilian Dentistry Bibliography (BBO), and Scientific Electronic Library Online (SciELO). Publications of in vitro/ex vivo and in vivo experiments without language restriction between the years 2010 and 2018 were selected. Conclusion: None of the techniques were capable of performing complete root canal cleaning, and the manual method was so effective as the automated method, although it requires longer working time. Furthermore, although this review confirmed that the solvent action did not allow a significant improvement in the removal of the filling material, ultrasound-activated irrigation proved to be an efficient adjunctive device as it could significantly reduce the volume of intracanal residuals.

Removal of obturation material in endodontic retreatment: a literature review

Introduction: Removal of filling material from the root canal system is required when a previous endodontic treatment fails, what may result in the permanence of an unfavorable periapical condition. The intent is to completely remove the filling material inside of the root canal to achieve sufficient cleaning and shaping for successful retreatment. Objective: The aims of this article were to provide asystematic review of the different techniques of endodontic filling material associated or not with organic solvents and to analyze them critically in terms of advantages and disadvantages of each technique. Literature review: The descriptors used were “guttapercha”, “obturation,” and “retreatment” in the following databases: PubMed, MEDLINE, Latin American and Caribbean Center on Health Sciences Information (Bireme), Latin-American and CaribbeanHealth Sciences (Lilacs), Brazilian Dentistry Bibliography (BBO), and Scientific Electronic Library Online (SciELO). Publications of in vitro/ ex vivo and in vivo experiments without language restriction between the years 2010 and 2018 were selected. Conclusion: None of the techniques were capable of performing complete root canal cleaning, and the manual method was so effective as the automated method, although it requires longer working time. Furthermore, although this review confirmed that the solvent action did not allow a significantimprovement in the removal of the filling material, ultrasoundactivated irrigation proved to be an efficient adjunctive device as it could significantly reduce the volume of intracanal residuals.

Investigation of different sodium hypochlorite volumes, concentrations and times of irrigation in endodontic therapy: a systematic review

Investigation of different sodium hypochlorite volumes, concentrations and times of irrigation in endodontic therapy: a systematic review

Self-assembly of mixed dodecylamine–dodecanol molecules at the air/water interface based on large-scale molecular dynamics

Dodecylamine (DDA)–alcohol mixtures have motivated great interest recently due to their superior performance in industrial processes compared with pure DDA. Self-assembly of surfactants at the air/water interface plays an important role in their surface properties. However, the self-assembly of mixed DDA–alcohol at an atomic level is still unknown. In this study, large-scale atomistic dynamic simulations of DDA–dodecanol (DOD) mixtures with different ratios were performed to clarify their molecular arrangement and explain the synergistic effect. The structural properties, such as molecular aggregation, orientation, angle distributions, and H bond distributions, of DDA–DOD mixtures were characterized in detail. Simulation results show considerable differences in the behavior of mixed DDA–DOD molecules with different ratios. The self-assembly of pure DDA molecules is not significant due to the strong electrostatic repulsion between head groups. The surface activity of pure DOD molecules is not strong due to their poor water solubility based on their fewer amounts of H-bonds with water. For mixed DDA–DOD, the addition of DOD does not directly affect the arrangement of DDA molecules; rather, DOD molecules insert between DDA molecules and form stable clusters at the air/water interface due to the van der Waals interactions between surfactant chains. Two main interaction patterns exist between DDA and DOD, including van der Waals interactions between the surfactant chains and H bonds between their head groups. DOD and DDA play an important role in forming the cluster and solvent action, respectively. The ratio of these two surfactants can affect the two above properties. This study provides a good strategy to investigate the self-assembly cluster of mixed surfactants and supports the experimental theory at the atomic level.

Free phenolic compounds extraction from Brazilian halophytes, soybean and rice bran by ultrasound-assisted and orbital shaker methods.

In several countries halophytes are commercially cultivated in low saline or even irrigated with seawater, as well as with saline aquaculture effluent, like a sea asparagus Sarcocornia ambigua, that show a biotechnological potential for bioactive compounds production. However, their recovery from matrix is sometimes inefficient because the lignocellulosic materials difficult the solvent action when drastic conditions are not applied. The ultrasound-assisted extraction (UAE) was optimized by a central composite rotational design for recovery free phenolic compounds (FPC) from the sea asparagus S. ambigua. Optimum conditions were validated and compared with orbital shaker extraction for S. ambigua, other Brazilian halophytes (Apium graveolens, Myrsine parvifolia, Paspalum vaginatum, and Schinus terebinthifolius), soybean and rice bran. Except for P. vaginatum, soybean and rice bran, UAE yielded 18-29% higher FPC than that of the orbital shaker. Besides this analytical performance UAE method optimized is faster than the orbital shaker, providing shorter exposure of the analyst to the extractor solvent and applicable in matrices with different compositions. It was also demonstrated that halophytes species showed to be good natural sources of FPC in a better way as soybean and rice bran. This work was the first to report FPC in M. parvifolia and P. vaginatum.

Synthesis and Characterization of a Butenafine Analogue

Aims: The study aims: (I) To synthesise N-(4-(tert-butyl) benzyl)-1-(4-tert-butyl) phenyl)-N-methyl methanaminium chloride, an analogue of butenafine from tertiary-butyl benzyl derivatives, (II) to compare the solvent actions of Tetrahydrofuran (THF), acetonitrile, methanol and 1,2-dichloroethane (DCE), and the reducing efficiencies of NaBH4 and sodium triacetoxyborohydride (STAB) during the synthesis.&#x0D; Study Design: The study involved laboratory experiments leading to the synthesis of the target compound by varying the non-aqueous solvents used, the reducing agent and the temperature of the operations. Silica chloride catalyst was used to speed up the reaction in one of the syntheses and in each synthesis, Thin Layer Chromatography was used to monitor the progress of the reaction. The time taken by each reaction and the yield were used as the basis for determining the solvent action and the reducing efficiency. &#x0D; Place and Duration of Study: M.Sc. Access controlled Teaching Laboratory, School of Chemistry, Newcastle University, New castle upon Tyne, United Kingdom from June to August 2012.&#x0D; Methodology: Reductive amination was carried out by reacting 4-tert-butylbenzaldehyde and 4-tert-butylbenzylamine, using the direct and then the indirect approaches. This was followed by methylation using the Eschweiler-Clarke reaction in each of the two approaches. The time taken by each reaction was monitored and the product of each approach was characterised by EIS-MS, 1H NMR, 13C NMR and FTIR.&#x0D; Results: 1,2-dichloroethane gave the best solvent action at 40°C (Yield: 75%) and NaBH4 gave the best-reducing action with silica chloride catalyst at 25°C (Yield: 50%). At the end of each synthesis, in all obtained products, 1H NMR spectrum gave a single peak of 18 hydrogen atoms at 1.3 -1.5 ppm for the existence of 6 methyl groups in the two tertiary-butyl substituents, the 13C NMR spectrum also showed a peak at 31-32 ppm for the six methyl carbon atoms in the two tertiary-butyl substituents, the FTIR spectrum showed a strong band at 2460 cm-1 for the presence of a tertiary ammonium ion and finally the EIS-MS gave a mass to charge ratio of 324.2693 as a confirmation of the relative molecular mass of the compound.&#x0D; Conclusion: The target compound can be synthesised by both direct and the indirect approaches of reductive amination in any of the solvents tested with/without a catalyst at room or elevated temperature using NaBH4 or STAB as a reducing agent but the best solvent action can be achieved with DCE at 40°C and the best-reducing action can be achieved with NaBH4 in the presence of silica chloride.

Cleaning materials: A compositional multi-analytical characterization of commercial agar powders

Effectiveness and selectivity are the main requirements for a proper cleaning of artworks. The complexity of the soiling and the limits of traditional cleaning methods make it necessary to increase the knowledge on the chemical and physical mechanisms involved in cleaning methods Agar gels have been successfully used in the restoration practise, but it is not yet clarified if their cleaning capability is due only to the solvent action or also to the polysaccharide structure. A multi-analytical procedure including elemental analyses, vibrational spectroscopies, thermogravimetric analysis and pyrolysis-gas chromatography/mass spectrometry is proposed to characterize agar powders in terms of morphology, composition and thermal stability, and to differentiate agar products intended for different applications, i.e. conservation of Cultural Heritage, biology and food industry.The multi-analytical approach proposed allows differentiating agar samples with slight compositional differences. In particular, agar products can be rapidly differentiated by a semi-quantitative analysis of pyrolysis-gas chromatography/mass spectrometry data. The results presented show that agar powders used for cleaning treatments contain impurities probably derived from cellulosic residues.

Solid as solvent-Novel Spectrophotometric Analytical Method for Metronidazole Tablets using Solids (Eutectic Liquid of Phenol and Niacinamide) as Solubilizing Agents (Mixed Solvency Concept)

The researchers are doing much work to give eco-friendly solutions for the pollution and toxicity caused by most of the organic solvents. Maheshwari has given a nice concept, known as mixed-solvency concept by the application of which, innumerable solvent systems can be developed. Maheshwari is of the opinion that each substance possesses solubilizing power. He has given several eco-friendly methods in the area of drug estimations and formulations precluding the use of toxic organic solvents. The present research work also provides an eco-friendly method to estimate spectrophotometrically, the metronidazole drug in tablet formulations without the help of organic solvent. The present investigation is an attempt to show that solids can also be wisely used to act as solvent precluding the use of organic solvents. The main objective of the present study is to demonstrate the solvent action of solid. Solid excipients can nicely be employed as solubilizers in the development of pharmaceutical dosage forms in solution form of poorly soluble drugs (mixed solvency concept). Present study describes the application of solvent character of eutectic liquid consisting of phenol and niacinamide in 25:10 ratio (PNM 2510) on the weight basis for spectrophotometric estimation of metronidazole tablets. Solubility of metronidazole in distilled water was found to be 7.28 mg/ml at room temperature. More than 80 mg of metronidazole dissolves in 1 ml of PNM 2510. In the present investigation, PNM 2510 was utilized to extract out (dissolve) the drug from tablet powder of metronidazole tablets. Distilled water was used for dilution purpose. Absorbance was noted at 320 nm against reagent blank to calculate the amount of drug in the tablets. Proposed method is novel, eco-friendly, rapid, free from toxicity of organic solvent, accurate and reproducible. Recovery studies and statistical data proved the accuracy, reproducibility and precision of the proposed method. The presence of phenol, niacinamide and tablet excipients did not interfere in the spectrophotometric estimation of metronidazole at 320 nm. Phenol and niacinamide do not interfere above 300 nm in spectrophotometric analysis.

Study of the Raveling Resistance of Porous Asphalt Pavements Used in Sustainable Drainage Systems Affected by Hydrocarbon Spills

Permeable pavements are one of the most commonly-used sustainable drainage systems (SuDS) in urban areas for managing stormwater runoff problems. Porous asphalt is widely used in surface layers of permeable pavement systems, where it can suffer from accidental oil spills from vehicles. Oil spills affect bituminous mixes through the solvent action of the hydrocarbons on the bitumen, reducing the raveling resistance of asphalt pavements. In order to assess the raveling resistance in porous asphalt pavements, the Cantabro abrasion test was performed on 200 test samples after applying controlled oil spills. Three different types of binders were used: conventional bitumen, polymer-modified bitumen and special fuel-resistant bitumen. After analyzing the results, it was concluded that the most suitable bitumen to protect against oil leakages is the polymer-modified one, which is far better than the other two types of bitumen tested.