Ionic Volume Research Articles

Experimental investigation of effective parameters on signal enhancement in spark assisted laser induced breakdown spectroscopy

A combination of electrical spark and laser induced breakdown spectroscopy (LIBS), which is called spark assisted LIBS (SA-LIBS), has shown its capability in plasma spectral emission enhancement. The aim of this paper is a detailed study of plasma emission to determine the effect of plasma and experimental parameters on increasing the spectral signal. An enhancement ratio of SA-LIBS spectral lines compared with LIBS is theoretically introduced. The parameters affecting the spectral enhancement ratio including ablated mass, plasma temperature, the lifetime of neutral and ionic spectral lines, plasma volume, and electron density are experimentally investigated and discussed. By substitution of the effective parameters, the theoretical spectral enhancement ratio is calculated and compared with the experimental one. Two samples of granite as a dielectric and aluminum as a metal at different laser pulse energies are studied. There is a good agreement between the calculated and the experimental enhancement ratio.

Sacrificial mortars for surface desalination

Four absorbent mortars were designed in this study and used as sacrificial desalinating media. The mortars comprised lime, sepiolite, nanosilica (72/3/25 by weight) and three admixtures (H2O2 and two commercial aerators) and had a liquid/solid ratio of 0.9, a mean porosity of 40% and a mean pore size of 0.8–0.7 μm. These mortars were applied three times to ashlars exhibiting surface saline efflorescence on a church at Talamanca del Jarama, a town in the Spanish province of Madrid. The salts impregnating the wall were characterised with XRD, FTIR and Micro-Raman spectroscopy. The ion concentrations in the ashlars was studied with ion chromatography at 0.5 cm, 1.5 cm and 3.0 cm from the surface after each application and the inner and outer surfaces of the mortars were analysed with Micro-Raman spectroscopy to determine the desalinating efficacy of the mortars.The mortars designed mobilised and absorbed the soluble salts in the ashlars; as a rule, elimination was most effective in anions with a smaller ionic volume and therefore greater ionic mobility and when the salt concentration was high and superficially located. Three years after application of the desalinating mortars, the salt concentration in the ashlars treated was 50% lower than prior to treatment.

Thermochemical Properties of the Dissolution of Rubidium d-Gluconate Rb[d-C6H11O7]2(s) in Aqueous Solutions

A novel coordination compound rubidium d-gluconate Rb[d-C6H11O7](s) has been synthesized and characterized by chemical analysis, elemental analysis, and X-ray diffraction. Single-crystal X-ray analysis reveals that the crystal is monoclinic with space group P21 and Z = 2. Also, the d-gluconate anion in Rb[d-C6H11O7](s) has a bent-chain conformation, in which the carbon atoms of the anion form two approximate planes. The compound exhibits an obvious chelation of the d-gluconate anions to the rubidum(I) cation and the cation is seven-coordinated to all seven oxygen atoms. The lattice potential energy and ionic volume of the anion d-\( {\text{C}}_{ 6} {\text{H}}_{ 1 1} {\text{O}}_{7}^{ - } \) were obtained to be UPOT = 484.23 kJ·mol−1 and V− = 0.2004 nm3 from crystallographic data. Molar enthalpies of dissolution of Rb[d-C6H11O7](s) in double-distilled water at various molalities were measured by use of an isoperibol solution–reaction calorimeter at T = 298.15 K. According to Pitzer’s electrolyte solution model, the molar enthalpy of dissolution of the title compound at infinite dilution was determined to be \( \Delta_{\text{s}} H_{\text{m}}^{\infty } = (29.76 \pm 0.72){\text{ kJ}}{\cdot}{\text{mol}}^{ - 1} \). The values of the apparent relative molar enthalpies (\( ^{\phi } L_{{}} \)) of the title compound and relative partial molar enthalpies (\( \bar{L}_{2} \) and \( \bar{L}_{1} \)) of the solute and the solvent at different concentrations were derived from the experimental enthalpies of dissolution of the compound. Furthermore, the molar enthalpy of hydration of the anion d-\( {\text{C}}_{ 6} {\text{H}}_{ 1 1} {\text{O}}_{7}^{ - } \) was calculated to be ΔH− = − (166.4 ± 2.7) kJ·mol−1 by use of a thermochemical cycle.

The long term stability of silica nanoparticle gels in waters of different ionic compositions and pH values

The use of silica nanoparticles for grouting underground tunnels offers an environmentally friendly option compared to organic grouting materials. Silica sols are commercially available and when mixed with an accelerator (salt) they form gels in a predetermined time. While much research has been focused on the practical implementation of silica sols in grouting as well as on the development of physical parameters such as viscosity and strength development, little is known about the long term stability of the resultant silica gels. When placed in rock fractures, parameters such as pH and ionic composition of groundwater may affect the long term stability and functionality of the gels.In this article we use a newly designed test equipment to simulate the behaviour of silica gels when water passes through the gel structure for up to 488 days. The pH and ionic composition of the water is varied to simulate environments that can be experienced by gels used for grouting applications. Results in the form of ionic composition, volume, and pH of leached water were used to evaluate and predict the lifetime of silica gels. The overall results show that several factors such as water flow and the nature of salt, so called accelerator used for gelling have significant effect on the gel life time. Furthermore, it is shown that the accelerator ions leach from the gels; however, the extent to which they are released from the gel depends upon the salt type. From these results we have predicted the lifetime of the 100 mL gels used in our experiments by using a simple numerical model. The predictions show that the total dissolution time for 100 mL gels are up to hundreds of years.

A simple, rapid and green ultrasound assisted and ionic liquid dispersive microextraction procedure for the determination of tin in foods employing ETAAS

This paper proposes a simple, rapid and green ultrasound assisted and ionic liquid dispersive microextraction procedure using pyrocatechol violet (PV) as complexing reagent and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide [C6MIM][Tf2N] as ionic liquid for the detection of tin employing electrothermal atomic absorption spectrometry (ETAAS). The optimization step was performed using a two-level full factorial design involving the following factors: pH of the working media, amount reagents, ionic liquid volume and extraction time and the chemometric response was tin recovery. The procedure allowed the determination of tin with limits of detection and quantification of 3.4 and 11.3 ng L−1, respectively. The relative standard deviation was 4.5% for a tin solution of 0.50 µg L−1. The validation method was confirmed by analysis of rice flour certified reference material. The method was applied for the quantification of tin in several food samples. The concentration range found varied from 0.10 to 1.50 µg g−1.

Graphene-modified Monolithic Capillary Column for the Microextraction of Trace Benzodiazepines in Biological Samples

ABSTRACTA graphene monolithic column was fabricated in a capillary using π-electron-rich poly(N-vinylcarbazole-divinylbenzene) as the supporter through in situ one-step polymerization for the enrichment of trace benzodiazepines in biological samples. This new three-dimensional monolith showed uniformity and a continuous column bed; more importantly, it retained the unique properties of graphene that are typically associated with individual graphene sheets. Based on the large delocalized π-electron system, graphene forms π–π stacking interactions with benzodiazepines and benzene rings of poly(N-vinylcarbazole-divinylbenzene), which not only enhance the extraction performance for benzodiazepines compared to the neat polymer but also provide chemical stability of the graphene monolith. Moreover, several factors likely to affect the extraction, including ionic strength, sample pH, sample volume, and eluant volume were studied in detail. The optimized method gave a linear range of 0.005–1 ng mL−1, and detection limits of 1.12–2.35 ng L−1. Finally, the graphene monolith was successfully applied to the separation and enrichment of benzodiazepines from urine and hair samples coupled with high-performance liquid chromatography–mass spectrometry. The recoveries were in the range of 78.6–85.6% for urine and 87.2–94.3% for hair with relative standard deviations of 3.4–6.9 and 2.9–8.3%, respectively.

Crystal structure and chemical thermodynamic properties of potassium d-gluconate K(d-C6H11O7)(s)

An important coordination compound potassium d-gluconate K[d-C6H11O7](s) has been synthesized by liquid phase method. The chemical component and crystal structure of the important compound are characterized by chemical analysis, elemental analysis, and X-ray crystallography. Single-crystal X-ray analysis reveals that the compound exhibits the chelate property of d-gluconate anions to K+ cations, a six-membered chelate ring is formed by the coordination of K+ with O2 of carboxylate and O4 of hydroxyl in a d-gluconate, and one cation is coordinated to six d-gluconate anions. The lattice potential energy and ionic volume of the anion [d-C6H11O7]− are obtained from crystallographic data. In accordance with Hess’ law, a reasonable thermochemical cycle is designed according to the practical synthesis reaction of the compound and the standard molar enthalpy of formation of the compound is calculated to be −(1754.17 ± 0.19) kJ mol−1 as an important physical quantity in chemical thermodynamics by an isoperibol solution–reaction calorimeter. Molar enthalpies of dissolution of the compound at various molalities are measured at T = 298.15 K in the double-distilled water. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the title compound at infinite dilution is calculated to be \(\Delta_{\text{s}} H_{\text{m}}^{\infty }\) = (27.92 ± 0.21) kJ mol−1. In terms of the above value, the standard molar enthalpy of formation of the anion [d-C6H11O7]− in the aqueous solution is determined to be = −(1473.87 ± 0.28) kJ mol−1. The values of relative apparent molar enthalpies (Φ L) and relative partial molar enthalpies of the solvent (\(\bar{L}_{1}\)) and the compound (\(\bar{L}_{2}\)) at different concentrations m/(mol kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound.

Ion association at discretely-charged dielectric interfaces: Giant charge inversion.

Giant charge reversal has been identified for the first time by Monte Carlo simulation for a discretely charged surface in contact with a trivalent electrolyte solution. It takes place regardless of the surface charge density under study and the monovalent salt. In stark contrast to earlier predictions based on the 2-dimensional Wigner crystal model to describe strong correlation of counterions at the macroion surface, we find that giant charge reversal reflects an intricate interplay of ionic volume effects, electrostatic correlations, surface charge heterogeneity, and the dielectric response of the confined fluids. While the novel phenomenon is yet to be confirmed with experiment, the simulation results appear in excellent agreement with a wide range of existing observations in the subregime of charge inversion. Our findings may have far-reaching implications to understanding complex electrochemical phenomena entailing ionic fluids under dielectric confinements.

High throughput sequencing of RNA transcriptomes in Ruditapes philippinarum identifies genes involved in osmotic stress response

Ruditapes philippinarum, is an economically important marine bivalve species. The ability to cope with low salinity stress is quite important for the survival of aquatic species under natural conditions. In this study, the transcriptional response of the Manila clam to low salinity stress was characterized using RNA sequencing. The transcriptomes of a low salinity-treatment group (FRp1, FRp2), which survived under low salinity stress, and control group (SRp1, SRp2), which was not subjected to low salinity stress, were sequenced with the Illumina HiSeq platform. A total of 196,578 unigenes were generated. GO and KEGG analyses revealed that signal transduction, immune response, cellular component organization or biogenesis, and energy production processes were the most highly enriched pathways among the genes that were differentially expressed under low salinity stress. All these pathways could be assigned to the following biological functions in the low salinity tolerant Manila clam: signal response to low salinity stress, antioxidant response, intracellular free amino acid transport and metabolism, energy production and conversion, cell signaling pathways, and regulation of ionic content and cell volume. In summary, this is the first study using high-throughput sequencing to identify gene targets that could explain osmotic regulation mechanisms under salinity stress in R. philippinarum.

Multi-site phase transfer catalyzed radical polymerization of methyl methacrylate in mixed aqueous\u2013organic medium: a kinetic study

This work establishes the kinetics of radical polymerization of methyl methacrylate in an aqueous–organic two-phase system using 1,4-bis (triethylmethylammonium) benzene dichloride (TEMABDC) as multi-site phase transfer catalyst and potassium peroxydisulphate (K2S2O8) as water-soluble initiator at 60 ± 1 °C under nitrogen atmosphere. The role of concentrations of monomer, initiator, catalyst, acid and ionic strength, temperature and volume fraction of aqueous phase on the rate of polymerization (Rp) was investigated. The rate of polymerization (Rp); Rp α [MMA]0.64, [TEMABDC]1.24 and [K2S2O8]1.50. The rate of polymerization increases with an increase in the concentration of monomer, initiator, catalyst and temperature. A generalized reaction model was developed to explain the phase transfer catalyzed polymerization reaction. Based on the kinetic results, radical mechanism has been derived. The activation energy and other thermodynamic parameters were calculated. The FT-IR spectroscopy validates a band of 1732 cm−1 of ester group of the obtained polymer. The viscosity average molecular weight of the PMMA was found 1.6955 × 104 g/mol.

On the surface tension of room temperature ionic liquids

Following previous workers, the surface tension of room temperature ionic liquids (RTILs) is shown to depend reciprocally on the surface area of the void space in the RTILs. The void space in liquids in general and in RTILs in particular can be expressed in several manners. The fraction of free space in RTILs can be estimated well and most simply from their actual molar volumes and the ionic volumes of the constituting ions. The temperature dependence of the surface tension is explored and shown to be essentially independent on the natures of the RTILs.

Transferable ionic parameters for first-principles Poisson-Boltzmann solvation calculations: Neutral solutes in aqueous monovalent salt solutions.

Implicit solvation calculations based on a Stern-layer corrected size-modified Poisson-Boltzmann (SMPB) model are an effective approach to capture electrolytic effects in first-principles electronic structure calculations. For a given salt solution, they require a range of ion-specific parameters, which describe the size of the dissolved ions as well as thickness and shape of the Stern layer. Out of this defined parameter space, we show that the Stern layer thickness expressed in terms of the solute's electron density and the resulting ionic cavity volume completely determine ion effects on the stability of neutral solutes. Using the efficient SMPB functionality of the full-potential density-functional theory package FHI-aims, we derive optimized such Stern layer parameters for neutral solutes in various aqueous monovalent electrolytes. The parametrization protocol relies on fitting to reference Setschenow coefficients that describe solvation free energy changes with ionic strength at low to medium concentrations. The availability of such data for NaCl solutions yields a highly predictive SMPB model that allows to recover the measured Setschenow coefficients with an accuracy that is comparable to prevalent quantitative regression models. Correspondingly derived SMPB parameters for other salts suffer from a much scarcer experimental data base but lead to Stern layer properties that follow a physically reasonable trend with ionic hydration numbers.

Dispersive liquid-liquid microextraction for the determination of menthol residue in fish by GC–MS

Conventional dispersive liquid-liquid microextraction (DLLME) and low density solvent-based dispersive liquid-liquid microextraction (LDS-DLLME) were evaluated in the extraction of menthol (1R, 2S, 5R)-2-isopropyl-5-methylcyclohexanol from tilapia (Oreochromis niloticus) fillets. The nature of the extraction and disperser solvents underwent univariate analysis. The results indicated greater efficiency in the extraction of menthol when toluene was used as extraction solvent and acetone as the disperser solvent. Once the extraction and disperser solvents were set, the parameters: ionic strength and volumes of the extraction solvent and water were evaluated using the central composite design (CCD). The conditions determined as ideal were 0.1g of sodium sulfate, 100μL of toluene and 5mL of water. The enrichment factor of the LDS-DLLME technique was of 80 times, the limits of detection and quantification were of 0.0539 and 0.1190μgL−1, respectively. The methodology developed was applied to determine menthol residues in tilapia fillets killed at different times and at different anesthesia concentrations. The results showed that the time needed for the organism of the fish to completely eliminate the menthol was >24h. This methodology becomes promising for the obtaining of protocols which regulate the use of menthol as an anesthetic used in aquaculture.

New temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction method for the determination of glyphosate and aminomethylphosphonic acid in water samples

ABSTRACTA new analytical temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction (TA-IL-DLLME) method was developed for glyphosate and aminomethylphosphonic acid determination in water samples. Extracted analytes were derivatized using 9-fluoroenylmethylchloroformate and quantified by liquid chromatography with fluorescence detection. For the TA-IL-DLLME method, two strategies for phase solubilization were evaluated; in approach 1, the ionic liquid and aqueous matrix sample were mixed and then heated, while in approach 2, the aqueous sample was first heated and then the ionic liquid was injected. For both approaches, optimization included parameters that significantly affect extraction efficiency: ionic liquid type and volume, solubilization temperature and time, cooling and centrifugation time. Among the evaluated ionic liquids, 1-decyl-3-methylimidazolium tetrafluoroborate showed the best performance for TA-IL-DLLME and was selected for the two solubilization approaches; with approach 2, slightly better results were obtained. Thus, sample analyses were performed using a procedure based on approach 2. An important matrix effect, attributed to the presence of salts and metals in real water samples was observed. Sample acidification before derivatization allowed this problem to diminish, with recoveries ranging from 75 and 99%, and enrichment factors between 57 and 76 for target analytes.

Crystal structure and thermodynamic properties of sodium d-gluconate Na[d-C6H11O7](s)

The sodium d-gluconate Na[d-C6H11O7](s) has been synthesized and characterized by elemental analysis and X-ray crystallography. X-ray single-crystal analysis reveals that the compound exhibits an obvious chelate property of d-gluconate anions to sodium cation, and the latter is coordinated to six d-gluconate anions. The lattice potential energy of the compound and ionic volume of the d-gluconate anion are obtained from crystallographic data. In accordance with law of Hess, a reasonable thermochemical cycle is designed and the standard molar enthalpy of formation of the compound Na[d-C6H11O7](s) is determined to be −(1472.68 ± 0.48) kJ mol−1 by use of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of Na[d-C6H11O7](s) at various molalities are measured at T = 298.15 K in the double-distilled water. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the title compound at infinite dilution is determined to be (23.783 ± 0.128) kJ mol−1.

Application of ionic liquid-based ultrasonic-assisted microextraction coupled with HPLC for determination of citalopram and nortriptyline in human plasma

ABSTRACTIn this paper, an effective and environmentally friendly method of ultrasound-assisted ionic liquid-based dispersive liquid–liquid microextraction (UA-IL-DLLME) combined with high-performance liquid chromatography (HPLC)–photodiode array detector was applied for extraction and determination of two antidepressant drugs citalopram hydrobromide and nortriptyline hydrochloride from human plasma samples. Several important parameters affect the steps and efficiency of extraction, some of which are sample solution’s pH, type and volume of ionic liquid, ultrasonic time, centrifuging time and rate, and the ionic strength of solution. Optimum conditions were obtained at pH = 11, 1-octyl-3-methyl imidazolium hexafluorophosphate for ionic liquid, 55 µL for ionic liquid volume, 4 min for ultrasonic time, 5 min and 3,500 rpm for centrifuging time and rotation’s speed, due to ionic strength by the addition of NaCl 1%. Under optimized conditions, the linearity was obtained in the range of 0.02–2,000 µg/L, with correlation coefficients higher than 0.995. The limits of detection were 10 µg/L for citalopram and 6 µg/L for nortriptyline. Preconcentration factors were 920 for citalopram and 800 for nortriptyline. The present method of UA-IL-DLLME combined with HPLC was successfully used for the determination of citalopram and nortriptyline drugs in real samples of human plasma.

Absolute ion hydration enthalpies and the role of volume within hydration thermodynamics

This paper reports that various thermodynamic properties in aqueous media for certain individual ions and for compounds are linear functions of the inverse cube root of the solid respective ionic and compound solid state volumes, Vm−1/3.

Aquaporin-4 in Astroglial Cells in the CNS and Supporting Cells of Sensory Organs-A Comparative Perspective.

The main water channel of the brain, aquaporin-4 (AQP4), is one of the classical water-specific aquaporins. It is expressed in many epithelial tissues in the basolateral membrane domain. It is present in the membranes of supporting cells in most sensory organs in a specifically adapted pattern: in the supporting cells of the olfactory mucosa, AQP4 occurs along the basolateral aspects, in mammalian retinal Müller cells it is highly polarized. In the cochlear epithelium of the inner ear, it is expressed basolaterally in some cells but strictly basally in others. Within the central nervous system, aquaporin-4 (AQP4) is expressed by cells of the astroglial family, more specifically, by astrocytes and ependymal cells. In the mammalian brain, AQP4 is located in high density in the membranes of astrocytic endfeet facing the pial surface and surrounding blood vessels. At these locations, AQP4 plays a role in the maintenance of ionic homeostasis and volume regulation. This highly polarized expression has not been observed in the brain of fish where astroglial cells have long processes and occur mostly as radial glial cells. In the brain of the zebrafish, AQP4 immunoreactivity is found along the radial extent of astroglial cells. This suggests that the polarized expression of AQP4 was not present at all stages of evolution. Thus, a polarized expression of AQP4 as part of a control mechanism for a stable ionic environment and water balanced occurred at several locations in supporting and glial cells during evolution. This initially basolateral membrane localization of AQP4 is shifted to highly polarized expression in astrocytic endfeet in the mammalian brain and serves as a part of the neurovascular unit to efficiently maintain homeostasis.

A New Volume-Based Approach for Predicting Thermophysical Behavior of Ionic Liquids and Ionic Liquid Crystals.

Volume-based prediction of melting points and other properties of ionic liquids (ILs) relies on empirical relations with volumes of ions in these low-melting organic salts. Here we report an accurate way to ionic volumes by Bader's partitioning of electron densities from X-ray diffraction obtained via a simple database approach. For a series of 1-tetradecyl-3-methylimidazolium salts, the volumes of different anions are found to correlate linearly with melting points; larger anions giving lower-melting ILs. The volume-based concept is transferred to ionic liquid crystals (ILs that adopt liquid crystalline mesophases, ILCs) for predicting the domain of their existence from the knowledge of their constituents. For 1-alkyl-3-methylimidazolium ILCs, linear correlations of ionic volumes with the occurrence of LC mesophase and its stability are revealed, thus paving the way to rational design of ILCs by combining suitably sized ions.

Crystal structure and thermochemical properties of potassium pyruvate C3H3O3K(s)

One important compound potassium pyruvate C3H3O3K(s) is synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. X-ray single-crystal structural analysis reveals that the compound is formed by one CH3COCOO− anion and one metal cation K+. An obvious feature of the crystal structure of the compound is the formation of the five-membered chelate ring, and it is good for the stability of the compound in structure. The lattice potential energy of the compound and ionic volume of the anion CH3COCOO− are obtained from crystallographic data. The lattice potential energy is determined to be: UPOT[C3H3O3K(s)] = 567.7 kJ mol−1. The V− (the volume of the anion CH3COCOO−) is estimated to be 0.088 nm3. Molar enthalpies of dissolution of the compound at various molalities in the double-distilled water are measured by use of an isoperibol solution-reaction calorimeter at 298.15 K. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of C3H3O3K(s) at infinite dilution is derived to be 22.9 kJ mol−1. The values of relative apparent molar enthalpies (ΦL), relative partial molar enthalpies (\( \bar{L}_{2} \)) of the compound, and relative partial molar enthalpies (\( \bar{L}_{1} \)) of the solvent (water) at different concentrations m/(mol kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound. Finally, the molar enthalpy of hydration of the anion CH3COCOO−(g) is calculated to be −227.8 kJ mol−1 by the design of the thermochemical cycle.