Limonene and Related Compounds as Potential Skin Penetration Promoters

Abstract

A transdermal therapeutic system can be developed by promoting the skin permeability of drugs with some materials. In this study, the promoting effect of terpenes present in essential oils on the percutaneous absorption of indomethacin from alcoholic hydrogels was investigated in rats in vivo. The enhancing activity of terpenes was expressed quantitatively as a quadratic function of lipophilicities of the terpenes, measured as a lipophilic index. Further increase in the significant level was observed when the molecular weight of terpenes was included in this function as the second factor. The synergism of ethanol with d-limonene, selected from among the other terpenes, on the promoting activity was statistically investigated. It was evident that both d-limonene and ethanol were important factors for promoting the percutaneous absorption of indomethacin. A significant synergism of d-limonene with ethanol was also observed. As a possible mechanism for enhancement action of d-limonene and ethanol, it was considered that, at first, d-limonene penetrates into the skin under coexistence with ethanol and may change the barrier structure of the stratum corneum. The transfer of ethanol to the skin is thereby enhanced under the coexistence with d-limonene in the skin. Thus, the permeation of indomethacin can be promoted due to its affinity with ethanol.     

Comparative sorption of citrus flavor compounds by low density polyethylene

Mixtures of seven characteristic flavor solutes commonly found in orange juice were studied for their interaction with low-density polyethylene (LDPE) from aqueous solutions at 20°C. Precautions were taken to avoid thermal and chemical degradation of the flavor solutes and degradation components were not found by HPLC analysis. Hydrocarbon monoterpenes showed 30–40% sorption by the LDPE over a 25-day period. Oxygenated monoterpenes showed ca. 10% sorption in the same time period. Further study of one of the hydrocarbon terpenes (d-limonene) showed both adsorption (surface attraction) and absorption (matrix dissolution), while its analogous oxygenated terpene (I-carvone) displayed predominantly adsorption. These findings are useful for deciding proper compensations for changes in flavor profiles in packaged orange juices in contact with LDPE. They also illustrate the importance of learning the nature of polymer-flavour interactions between foods and packaging materials.     

A study of the absorption of fruit juice volatiles by the sealant layer in flexible packaging containers (the effect of package on quality of fruit juice,part IV)

Various experimental packaging containers were tested for their tendency to absorb fruit juice volatiles in the innermost heat-sealing layer. Analysis of head-space gas by GLC and sensory evaluations were carried out in order to evaluate the effect of each type of sealant. Coextrusion sealants (thin low-density polyethylene, LDPE), a sealant containing the orange essence powdered with cyclo-dextrin (CD), and polyethylene-terephthalate (PET) or polyacrylonitrile (PAN), synthetic resisns with high transition temperatures (T_g) were prepared. Coextrusion or CD-containing sealants as compared with LDPE, reduced the sorption of d-Limonene from Mandarin orange [Citrum unshiu Marc.] juice by 15–20% but did not show effective results in sensory evaluations. On the other hand PET or PAN sealants showed no sorption at all. Similar results were obtained with 'citrus mix' model essence. However, LDPE also did not show volatile sorption in the case of 'soft fruit mix' model essence. It is difficult to prevent sorption of the volatiles of citrus fruit juices if the sealants are of the coextrusion type or CD-containing LDPE type. Sorption can be controlled most effectively when the sealats are PET or PAN.     

ISM-S Sorbent: Properties and Tests in a Sorption Process for Treatment of Water from Accumulating Basin of the Mayak Production Association To Remove 90Sr

ISM-S hydrated oxide sorbent, showing the most promise for strontium sorption, and its analog ISM-SP were studied under static and dynamic conditions. The optimal pH ranges for sorption (pH 6-10) and desorption (pH < 1.2) of strontium, the total exchange capacities for strontium of various forms of the sorbent, and the dependences of the degree of strontium sorption on concentrations of supporting electrolytes were determined. The limiting stage of sorption, rate constants of ion exchange, diffusion coefficients, and calculated and experimental exchange half-times were determined in kinetic experiments. Based on these data, the optimal productive capacity of the ion-exchange apparatus was suggested: up to 30 and up to 25 column volumes per hour with ISM-SP and ISM-S, respectively. Rig trials of a sorption process for treatment of water from accumulating basin to remove ^{9 0}Sr were performed. The working installation included a mechanical filter and two series-connected sorption columns (h : d = 10 : 1) packed with ISM-SP (V = 3.5 l). In the course of the tests, more than 7 m³ of the surface layers of radioactively contaminated water with the initial ⁹⁰Sr activity of about 3.0 × 10^{- 8} Ci l^{- 1} and total hardness of 4.5-5.4 mg-equiv l^{- 1} was treated, with the ⁹⁰Sr content being reduced to the level of 10UVwater according to NRB-99 (UV, interference level; NRB, radiation safety regulations valid in Russia).     

Modelling of Migration from Printing Inks on Paper Packaging

The migration model of contaminants from inks on paper packaging to food is developed based on the penetration of ink in paper and Fick's diffusion. The printed paper is divided as ink layer and paper layer. The mass transfer coefficient h_m and partition coefficient K_F,P in the interface between paper and food are considered in the model. The model equation is solved, and the migration expression is obtained by using the method of separation of variables. The fitting method is used between the model and the migration experimental data to obtain the diffusion coefficients and mass transfer coefficients for dibutyl phthalate (DBP) and acetyl tributyl citrate (ATBC). It is found that there exist linear relationships between ln(D_P) and 1/T, and also between ln(h_m) and 1/T for DBP and ATBC. The migrations of DBP in the paper sample 2402 at different temperatures and of ATBC in the paper sample 2401 at 50°C are predicted by using the model, and a good agreement is obtained between the model predictions and the migration experimental data. Copyright © 2014 John Wiley & Sons, Ltd.     

Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions

Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH_PZC and pH_PZNPC to be 3.4 ± 0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu²⁺ and Ni²⁺ uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu²⁺ and Ni²⁺ could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive ΔG° values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (ΔH°) for Ni²⁺ and Cu²⁺ were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of ΔS° indicate low randomness at the solid/solution interface during the uptake of both Cu²⁺ and Ni²⁺ by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.     

A new recycling system for expanded polystyrene using a natural solvent. Part 2. Development of a prototype production system

A prototype production system for recycling expanded polystyrene (EPS), which uses an orange oil, d-limonene, as the EPS shrinking agent, has been developed. This system consists of an apparatus to dissolve EPS and a recycling plant to separate the limonene solution. The recycling plant can mass reproduce polystyrene with the same mechanical properties as new polystyrene. The recycled polystyrene can be used for packaging a 28 inch TV set. © 1998 John Wiley & Sons, Ltd.     

A new recycling system for expanded polystyrene using a natural solvent. Part 1. A new recycling technique

A new recycling technique has been developed which uses a natural solvent, d limonene, to shrink expanded polystyrene (EPS). d-Limonene is a natural vegetable oil which is extracted from the rinds of citrus fruits and is a good solvent of EPS. Limonene has almost the same solubility as toluene at room temperature. This technique reduces the volume of EPS to about 1/20th of the original. Contracted EPS is recyclable with almost no molecular weight degradation because d-limonene acts as an antioxidant of polystyrene during the heating process. © 1998 John Wiley & Sons, Ltd.     

Sorption behavior of nano-TiO2 for the removal of selenium ions from aqueous solution

Titanium dioxide nanoparticles were employed for the sorption of selenium ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption was found to be fast, and to reach equilibrium basically within 5.0 min. The sorption has been optimized with respect to the pH, maximum sorption has been achieved from solution of pH 2–6. Sorbed Se(IV) and Se(VI) were desorbed with 2.0 mL 0.1 mol L⁻¹ NaOH. The kinetics and thermodynamics of the sorption of Se(IV) onto Nano-TiO₂ have been studied. The kinetic experimental data properly correlate with the second-order kinetic model (k₂ = 0.69 g mg⁻¹ min⁻¹, 293 K). The overall rate process appears to be influenced by both boundary layer diffusion and intraparticle diffusion. The sorption data could be well interpreted by the Langmuir sorption isotherm. The mean energy of adsorption (14.46 kJ mol⁻¹) was calculated from the Dubinin–Radushkevich (D–R) adsorption isotherm at room temperature. The thermodynamic parameters for the sorption were also determined, and the ΔH⁰ and ΔG⁰ values indicate exothermic behavior.     

Adaptive Neuro-Fuzzy inference system analysis on sorption studies of strontium and cesium cations onto a novel impregnated nano-zeolite

In this research, a novel impregnated nano-zeolite (NAASMS-Z) was synthesized and characterized using different characterization techniques. Excellent properties, such as high specific surface area (~502.77 m²/g), low pore size (~8.92 Å) and the existence of numerous functional groups caused the efficient elimination of Sr²⁺ and Cs⁺ cations from aquatic systems. The sorption performance of the nano-particles was enhanced by impregnation up to 60% in the aquatic media. The kinetic study indicated that the elimination process of both the concerned cations is controlled by external film mass transfer through the boundary within the first 30 min then controlled by intra-particle diffusion. The sorption equilibrium data suggested that the sorption process occurs on the heterogeneous sorbent surface. Parameters affecting the elimination of Sr²⁺ and Cs⁺ from a single metal sorption system, such as pH, initial contaminant concentration (C_i) and contact time (t), were investigated and optimized. A predictive model based on an Adaptive Neuro-Fuzzy Inference system (ANFIS) analysis was applied to evaluate the experimental parameters affecting the elimination of Sr²⁺ and Cs⁺ cations from aquatic system. A Mamdani-type FIS was employed to justify a collection of 16 rules (If-Then format) by means of centroid membership functions. The suggested fuzzy model revealed high predictive concert with high correlation coefficient (R²) and satisfactory deviation from the experimental data, affirming its appropriateness to predict Sr²⁺ and Cs⁺ elimination efficacy from the studied system. Rooted in experimental data and statistical analysis, the synthetized material was effective for treating contaminated aquatic solutions containing Sr²⁺ and Cs⁺ cations.     

Modelling of oxygen diffusion through a model permeable package and simultaneous degradation of vitamin C in apple juice

The objective of this study was to apply the finite element method (FEM) to modelling the simultaneous oxygen diffusion and chemical reaction in a packaged liquid food. Cylindrical high-density polyethylene (HDPE) packages, top and bottom insulated, were designed to contain apple juice or water containing vitamin C. Oxygen consumption was monitored by a micro-oxygen electrode. A first-order chemical reaction and its reaction rate constant 7.3 ± 10^-3/min (in terms of O₂ consumption) was determined in apple juice with added vitamin C. The simultaneous permeation-diffusion reaction process was modelled by finite element block types developed by Swanson Analysis Systems. Inc. Houston, PA (Engineering Analysis Systems User's and Theoretical Manuals). Results indicate that the model generates acceptable predictions for a cylindrical, permeable package and a semi-infinite system (oxygen-saturated liquid surface).     

Describing non-Fickian water-vapour sorption in wood

Moisture transport and sorption in wood may not be accurately described by Fick's law of diffusion. The problem of making a model of non-Fickian behaviour (NFB) for wood is discussed. Some measurements in which NFB in wood is clearly seen are also reviewed. Four criteria, which must be satisfied by a model describing sorption in wood cell walls, are presented: (1) the model should not only describe the response to step changes in vapour pressure; (2) it should be able to predict sorption with more than one time scale; (3) the sorption rate should not depend on the thickness of the cell wall; (4) small rapid changes in vapour pressure should give slower fractional weight change than large rapid changes. A review of models of NFB in synthetic polymers indicates that there is presently no model of NFB which fulfills the above criteria. More measurements of the sorption behaviour of the cell wall are needed to construct such a model for wood. This model can then probably be used, together with a Fickian diffusion model, to model the sorption behaviour of whole wood.Nomenclature c concentration in a material kg m^–3 - D _c diffusivity with c as potential m² s^–1 - D _p diffusivity with p as potential kg/(m s Pa) - F flux kgm^–2–1 - p partial vapour pressure Pa - t time s - x distance m     

Mathematical model of heat and mass transfer processes in evaporative condensers

This study presents a new mathematical model of heat and mass transfer processes in evaporative condensers. The model consists of four ordinary differential equations with their boundary conditions and some associated algebraic equations. The model was formulated for steady-state heat and mass transfer conditions. A simulation computer program based on the model was written. It was devised for heat calculations in condensers built from bare tubes. The quality of the model was calculated by comparing the results obtained by running the program with experimental results achieved by other authors. The computed results show a good degree of conformity with experimental results. The differences are less than 20% (but in one case, 30%). The computer program may be used to determine heat performance of evaporative condensers of horizontal in-line and staggered bundle systems (if S_q > 2d_z).     

The mechanism and kinetics of growth of the superconducting compound Nb3Sn

A study has been made of the mechanism and kinetics of formation of Nb₃Sn from the elemental components. The Nb₃Sn forms partly by diffusion and partly by a solution/ deposition mechanism which depends on thermal gradient mass transfer. The effect of this is to modify the growth equation to x = kt ^0.36 over the temperature range 950 to 1150° C. The temperature dependence of these two processes, given by the difference between the activation energies for diffusion and solution, is –9.7 kcal/g atom (–0.42 eV/atom) so that the thickness of the Nb₃Sn layer produced in any given time decreases with increasing temperature.Various experimental factors are discussed in terms of their influence on the rate of growth of the layer.     

Mass transfer study of an extractive electrochemical sulfide/sulfur reaction in a parallel plate reactor

Abstract

The mass‐transfer phenomenon between an aqueous‐organic phase and an electrode producing sulfur from sulfide ions in a parallel plate reactor is studied. A kinetic model of the electrochemical conversion and extraction process is developed and tested. Under steady‐state conditions, the electrochemical reaction rate at limiting operation, defined as K‘_m A (1 – θ) C_R/α, is equal to the extraction rate, defined as K‘_d A θ (C^sat _s/β ‐ C_s/β ) for this extractive electrochemical system. Experimental parameters include volume fraction (X_d ) and fluid velocity (Re‘). The mass transfer coefficients, K‘_m and K‘_d, were obtained as K‘_m = 7.044 × 100^–5 Re‘ ^? (1.073 + 0.575 X_d – X ² _d ) and K‘_d = 5.15 × 10^–4 Re‘ ^? X_d with a Reynolds number between 18～54 and volume fraction under 70% for this two‐phase solution.     

Sorption of Cs,Sr, U,and Pu radionuclides on natural and modified clays

The ability of natural and modified montmorillonite clays from Belgorod oblast to sorb Cs, Sr, U, and Pu radionuclides was studied. The clays were modified by treatment with metal (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe²⁺, Zn²⁺) chloride solutions or aqueous HCl. The natural and modified clays studied show high performance in sorption treatment of solutions to remove Cs radionuclides. The natural clay and the Na and Mg forms of clays show the best sorption characteristics with respect to Cs. The distribution coefficient K _d of ¹³⁷Cs in sorption on the above samples from a 0.1 M NaNO₃ solution is (1.1–1.4) × 10⁴ cm³ g⁻¹, which is 4–5 times higher compared to natural clinoptilolite. The Sr, U, and Pu radionuclides are sorbed on the examined clay samples to a considerably lesser extent. The K _d values in sorption of these radionuclides from tap water are lower by 2–3 orders of magnitude than in sorption of Cs. Addition of clay materials in the course of cementation of liquid radioactive wastes, including NPP bottom residues, allows the rate of radiocesium leaching from the hardened cement compounds to be decreased by a factor of 5–16. The most efficient sorption additive in cementation of NPP bottom residues is natural montmorillonite clay.     

Dynamic mechanical analysis and water sorption of some experimental elastomeric soft lining materials

This research was undertaken to develop a better understanding of the relationships among the compositions, structures and properties of denture soft liners. Five butadiene-styrene-acrylic elastomers were prepared. They were prepared using 50% of powdered prepolymerized butadiene-styrene polymer combined with 50% of a methacrylate monomer (HMA or EHMA) plus varying amounts of initiator and crosslinker. The mixtures were gelled and processed conventionally. Specimens were then committed to dynamic mechanical analysis and water sorption. Dynamic mechanical analysis was performed over the temperature range 5–95°C at the rate of 2.5°C/min using a Perkin Elmer DMA-7 with 3 mm flat tip probe at 1 Hz. Wet and dry values for storage modulus (E') and damping factor (tan ) were determined at 37°C. Water sorption of these butadiene styrene elastomer-acrylic systems from solutions of varying concentrations was measured in order to establish the role of osmotic pressure. Diffusion coefficient (D _d) was determined from the desorption values. The relatively lower values of D _d observed in most highly concentrated solutions particularly 1 m sodium chloride and glucose may be interpreted as related to reduced water sorption from these solutions. Increasing crosslinking increased the modulus and decreased water sorption. Using hydrophobic EHMA instead of HMA reduced water uptake, reduced dry modulus and reduced the decrease in modulus caused by water sorption. Dynamic moduli and water sorption generally exceeded those of the commercial materials studied. For all experimental materials, water uptake from saline and glucose solutions confirmed that the diffusion process is osmotically driven.     

Kinetic and thermodynamic studies for cesium removal from low-level liquid radioactive waste using impregnated polymeric material

A novel polymeric impregnated material was prepared by loading 4,4′(5′)di-t-butylbenzo-18-crown-6 (DtBB18C6) onto poly(acrylamide-acrylic acid-acrylonitrile)-N,N′-methylenediacrylamide [P(AM-AA-AN)-DAM]. The sorption of ¹³⁷Cs onto P(AM-AA-AN)-DAM/DtBB18C6 was studied using batch equilibrium technique with respect to the pH, contact time, and temperature. The applicability to treatment of low-level liquid radioactive waste was examined. The free energy (ΔG ⁰), enthalpy (ΔH ⁰), and entropy (ΔS ⁰) of the sorption were calculated. These parameters showed that the sorption of ¹³⁷Cs onto P(AM-AA-AN)-DAM/DtBB18C6 was spontaneous and endothermic in nature. The Lagergren first-order, pseudo-second-order, and homogeneous particle diffusion models were tested kinetically to describe the reaction mechanism. The experimental data were fitted well by the pseudo-second-order kinetic model.