Lipophilic Surfactant Research Articles

A microfluidic study to investigate the effect of magnetic iron core-carbon shell nanoparticles on displacement mechanisms of crude oil for chemical enhanced oil recovery

The main objective of this work is to evaluate the effect of the simultaneous use of a surfactant mixture and magnetic iron core-carbon shell nanoparticles on oil recovery via a microfluidic study based on the rock-on-a-chip technology. The surfactant solution used for all experiments was prepared based on a field formulation and consisted of a mixture of a hydrophilic and a lipophilic surfactant. Magnetic iron core-carbon shell nanoparticles with a mean particle size of 60 nm and a surface area of 123 m2 g−1 were employed. The displacement experiments consisted of waterflooding, surfactant flooding and nanoparticle-surfactant flooding and were performed using PDMS (polydimethylsiloxane)-glass microdevices type random network. The characteristics and design of the microfluidic device allowed to emulate a mixed wettability of a porous medium. Then, the oil was displaced by injecting the solution at a constant injection rate, until steady-state conditions were obtained. Furthermore, the effect of three injection rates corresponding to 0.1 ft day−1, 1 ft day−1, and 10 ft day−1 was investigated. The increase in the injection rate favored the oil recovery percentage. In addition, for all injection rates, the oil recovery decreased in the following order: nanoparticle-surfactant flooding > surfactant flooding > waterflooding. The nanoparticle-surfactant system at the injection rate of 1.9 μL min−1 presented the highest oil recovery (i.e., 84%). Likewise, nanoparticle-surfactant flooding showed a more stable displacement front and consequently, the highest capillary number among the injection fluids. Oil recovery by waterflooding was the lowest among the evaluated systems due to the viscous fingering phenomena under different injection rates. In addition, it can be observed that for all injection rates, the presence of the surfactant mixture and nanoparticles reduce the viscous fingering effect. The results can be used to visually and quantitatively analyze the role of the simultaneous use of nanoparticles with surfactants in enhanced oil recovery processes.

Comparison of Nanoparticle and Surfactant Oil/Water-Emulsion Separation Kinetics

Summary Experimental observations, during oil–production operations, regarding the formation of oil/water emulsions stabilized by nanoparticles and surfactants, are presented. Similarities and differences between the two types of emulsions are discussed on the basis of acquired separation profiles, as well as respective fluid interfacial properties. A state–of–the–art portable dispersion–characterization rig (PDCR) was used to run the experiments, and a surveillance camera was deployed to monitor the emulsion separation kinetics. Commercial–grade mineral oil and distilled water were used as the test fluids. Silica nanoparticles of different wettabilities, as well as surfactants with different hydrophilic-lipophilic balance (HLB) values, were deployed to investigate commonalities/differences between the surfactant– and nanoparticle–stabilized emulsions under ambient–temperature and –pressure conditions. Separation profiles were analyzed, and similar behaviors between the corresponding surfactant and nanoparticle emulsions were observed for the 25%–water–cut case. For higher water cuts, however, the surfactant–stabilized emulsions were tighter than their nanoparticle counterparts, displaying much lower separation rates. In the most severe cases, the surfactants totally inhibited the oil–creaming process and oil remained trapped in the emulsion for several hours. Multiple emulsions (O/W/O) were observed in certain cases [for hydrophilic nanoparticles and lipophilic surfactants (Span® 80)]. On the basis of the aforementioned experimental observations, the presence of surfactants caused more–severe problems for the oil/water–separation process than did the presence of an equal concentration of nanoparticles. Pendant–drop measurements indicated that the surfactants significantly lowered the interfacial tension (IFT) between the oil and water, whereas the nanoparticles did not. Finally, a literature model was used to predict separation profiles for the oil/water dispersions and evaluated by comparing the predictions with the acquired experimental data. Current research sets the benchmark for more–thorough investigations aimed at providing guidelines for a more efficient operation of separators that handle surfactant– or nanoparticle–stabilized emulsions and a better understanding of the related phenomena.

Structuring of water-in-oil emulsions using controlled aggregation of polysaccharide in aqueous phases

The influence of high methoxy pectin, kappa-carrageenan (kC) and starch on the rheological and microstructural properties of structured Water-in-Oil emulsions was examined. An acidic aqueous phase (pH 3.5) was prepared by dispersing 2 wt % of polysaccharides in buffer solution (10 mM Citrate, 100 mM NaCl), while the oil phase consisted of lipophilic nonionic surfactant (8 wt % polyglycerol polyricinoleate) in Soybean oil. These phases were emulsified to create 40 wt % Water-in-Oil emulsions, and were either characterized before or after heat treatment at 90 °C for 30 min. It was observed that the shear viscosity and shear modulus of heated emulsions were higher than for unheated systems, which can be attributed to heating induced gelation process in polysaccharide molecules primarily, as well as influence on the overall rheology of W/O emulsions. The shear viscosity and shear modulus of kC in aqueous solutions, as well as in emulsions, were higher than the other polysaccharide systems, which may be due to formation of larger junction zones in kc emulsions. This work's insights may contribute in fabrication of reduced fat margarine and spreads.

Formulation, clinical and histopathological assessment of microemulsion based hydrogel for UV protection of skin

The aim of this study was to prepare a microemulsion based hydrogel containing sesame oil and evaluate its topical application in preventing the harmful effects of UV radiation on the guinea pig's skin using histopathologic and clinical findings. Sesame oil with high antioxidant content and unique chemical and physiological properties is a suitable candidate for the evolution of UV protection on skin. Applying this natural oil in microemulsion formulation containing particles with nanometer size can enhance its efficacy. To prepare a stable microemulsion, it is necessary to select the appropriate surfactants. In this study, first the best combination of hydrophilic surfactant of Tween 80 with various lipophilic surfactants such as Span 20, Span 80 and Span 85 at different surfactant ratios was examined. The microemulsion formulations were assessed for particle size, zeta potential, polydispersity index, refractive index, electrical conductivity, pH value and stability. Results showed that among various samples, microemulsion containing a mixture of Tween 80 and Span 80 with the surfactant ratio of 9:1 was the best sample in terms of stability over time (six months). This sample had a lower particle size of 26.09 nm with a narrow particle size distribution. For topical application, the microemulsion based hydrogel was prepared with 0.6% Carbomer 940 as a gelling agent. The pH value and viscosity of gel formulation were 6.6 and 12.90 Pa.s, respectively, which is appropriate for topical applications. A slight enhancement of particle size inside hydrogel structure was observed after six months of the gel preparation. The clinical evolutions of formulation on guinea pig's skin were included skin scaling, skin irregularity, erythema, skin hyperpigmentation, and edema. Epidermal hyperkeratosis, hyperpigmentation, exocytosis, acanthosis, chromatin discoloration in nucleus of epidermal squamous cells, perifolliculitis, dermal vascular hyperemia, edema and dermal thickness, infiltration of plasma cell lymphocytes and eosinophils into dermis were observed for histopathological investigations. Based on clinical and histopathological examinations, topical application of microemulsion-based hydrogel of sesame oil can effectively prevent skin damage induced by UV radiation and is therefore suitable for skin products.

Synthesis of Redox-Light Responsive Alginate Nano Hydrogel to Produce Smart Textile

Nowadays, with improvements in technology, smart materials have gained much attention. The objective of the present study is to prepare light-reduction/oxidation responsive alginate nano hydrogels and finishing cotton fabric by these smart hydrogels to produce smart textile. Alginate nano hydrogels were prepared by the reverse emulsification-diffusion method in a water in oil system by using alginate solution as a model polymer and water phase, normal hexane as an oil phase, span 80 as a lipophilic surfactant, Iron (II)-chloride as a cross-linker and light-redox sensitive agent and sodium lactate as a reducing agent. Alginate nano hydrogels were characterized by fourier transform infrared (FTIR), scanning electron microscopy (SEM) methods and the synthesis of alginate nano hydrogels was confirmed. In the next step, cotton fabrics were finished by these smart hydrogels. Scanning electron microscopy and FTIR test confirmed the presence of alginate nano hydrogels on the fabric. Water retention capacity (WRC) and antibacterial properties were evaluated and the results exhibited the improvement of WRC and antibacterial activity against gram-positive and gram-negative bacteria. These kinds of alginate nano hydrogels made the fabric responsive to light stimuli. In order to evaluate this responsivity, a drug model (folic acid) was loaded in the structure of nano hydrogels by sonification, the rate of release by radiation of ultraviolet light was studied by spectroscopy, and the results proved the light responsivity of these nano hydrogels.

Confined Complexation Reaction of Metal Ions with a Lipophilic Surfactant at the Water/Air Interface: A New Understanding Based on Surface Experiments and Molecular Dynamics Simulations.

Understanding the fundamentals of confined chemical reaction was an important subject in various heterogeneous physicochemical processes. Here, we investigated the orientation behavior of an amphiphilic ligand, the tri- n-octylphosphine oxide (TOPO), in a compressed monolayer at the air/water interface and its impact on the complexation reactivity of TOPO molecules with chromate ions at the interface. The analysis of sum frequency generation and polarization modulation infrared reflection absorption spectroscopy experiments combined with surface pressure measurements reveals a significant dependence of the adsorption rate and saturated concentration of chromate ions on the orientation of TOPO molecules during the increase of the surface pressure. In parallel, the analysis of molecular dynamics simulations indicates that the interaction energy between TOPO molecules and chromate ions is strongly sensitive to the orientation of TOPO molecules confined at the water/air interface. The present work provides a novel insight into the unique chemical reactivity of molecules in a confined microenvironment, and it provides a basis for further progresses in improving chemical reactivity and selectivity of molecules in a confined environment by regulating confinement of molecules.

Breaking of Water-in-Crude Oil Emulsions. 8. Demulsifier Performance at Optimum Formulation Is Significantly Improved by a Small Aromatic Content of the Oil

Asphaltenes tend to aggregate in different structures depending on the aromatic content of the oil phase. The different aggregates adsorb at the interface as some kind of lipophilic surfactant, whi...

Inter-Correlation among the Hydrophilic–Lipophilic Balance, Surfactant System, Viscosity, Particle Size, and Stability of Candelilla Wax-Based Dispersions

Owing to a decrease in mineral oil resources, it is crucial to develop packaging materials based on renewable resources. Hence, a water vapor-barrier coating is developed as a natural wax-based dispersion. This dispersion should be stable over the storage time. In this study, the physical stability of a wax-based melt dispersion was analyzed (24 h and 21 days after production), and instability phenomena such as agglomeration, coalescence, and flotation were identified. Furthermore, the inter-correlations among the particle size, viscosity of the continuous phase, physical stability, surfactant chemistry, and hydrophilic–lipophilic balance value were characterized. Particle sizes were described by volume/surface mean d3,2, volume moment mean d4,3, and number mean d1,0 diameter, as well as the span of the volume and number distribution. Stability was characterized by the flotation rate, emulsion stability index, and Turbiscan stability index. Coalescence and agglomeration were not observed after the solidification of the wax particles. A significant correlation was observed for the emulsion stability index, with d3,2, and for flotation rate, with d1,0, d4,3, and viscosity as well, with d1,0, d3,2. Surfactants with hydrophilic–lipophilic balance values of 11–13.5 seem to be the most suitable for stabilizing candelilla wax-in-water suspensions. Particles were smaller, and wax suspensions were better stabilized using Tween 20 and Span 20, compared with Tween 80 and Span 80.

Partition Coefficient and Glutathione Penetration of Topical Antiaging:Preformulation Study

Glutathione (GSH) is a broad antioxidant of the thiol-tripeptide group, highly hydrophilic, which has limitation for topical preparations. A lipophilic surfactant is an alternative method to enhance the glutathione partition. The purpose of this study was to determine the apparent partition coefficient (APC log) of glutathione; glutathione with additional surfactant at different HLB value of HLB 4.3; 5.5; 7; 11 and selected HLB was studied for penetration. The study was conducted by dissolving glutathione in water plus various HLB surfactants. Determination method of partition coefficient was done by shake flash method. The penetration test was conducted using the parameter of decreasing Matrix Metalloproteinase-1 expression on the balb-c male skin. The results can be used as a reference for topical glutathione formulations as these results are preformulation study.

Phase inversion of emulsions stabilized by lipophilic surfactants and SiO2 nanoparticles

This paper investigates the effects of the SiO2 nanoparticle mass concentration (w/v %) and oleic acid imidazoline mass fraction (w/w %) on the property of the emulsion stabilized jointly by SiO2 and oleic acid imidazoline, with SiO2 nanoparticles initially dispersed in different phases. In the experiment, the SiO2 nanoparticle mass concentration in the aqueous or oil phases is fixed, and the surfactant mass fraction in oil is gradually increased, changing the emulsion from oil-in-water into water-in-oil. Moreover, in these cases, the required oil-soluble surfactant mass fraction for phase inversion is relatively low, with solid nanoparticles initially dispersed in water. Then, the surfactant mass fraction in oil is kept constant, and the emulsion type is changed from the water-in-oil into the oil-in-water by raising up the SiO2 mass concentration in water or oil. Furthermore, under these conditions the solid nanoparticle mass concentration is higher with solid nanoparticles primarily dispersed in water than that in the case of solid nanoparticles initially placed in oil. The mechanism behind the emulsion type transition is analyzed by measuring the emulsion droplet size and rheological property of different emulsion systems. It is concluded that the difference regarding the initial dispersion medium of the solid nanoparticle affects the adsorption proportion of the solid nanoparticle and oleic acid imidazoline, the adsorption morphology, and the overall wettability of the interfacial stabilizer, which consequently impacts the property of the emulsion.

Hot melt granulation method for the preparation of floating matrix tablets of Tolperison Hydrochloride

Tolperisone HCl is a centrally muscles relaxant drug. It is a highly water-soluble drug. It has a biological half-life of 1.5–2.5 h. It has absorption window in the small intestine and unstable in intestinal pH 4 to 7. Gastroretentive drug delivery systems have shown to be of better significance in controlling release rate for drug having site specific absorption. The aim of the present investigation was to develop effervescent floating matrix tablets of Tolperisone Hydrochloride. Cetyl alcohol was selected to prepare hot melt granules (HMG) of Tolperisone HCl. Effervescent floating matrix tablet was prepared using cetyl alcohol as lipophilic surfactant and HPMC K100M as hydrophilic polymers. The HMG based floating matrix tablets were optimized by 32 full factorial design to study the effect of independent variables, i.e. amount of cetyl alcohol (X1) and amount of HPMC K100M (X2) on dependent variables like % swelling index (Y1), time required to 50% drug released(t50)(Y2) and time required for 90% drug release (t90)(Y3). From the regression analysis, it was observed that selected two independent variables show significant effect on response variables. From the results obtained, F10 formulation (58.10 mg of cetyl alcohol, 147.18 mg of HPMC K100M) was selected as optimized batch which showed optimum floating lag time (14 s), drug content (102.78 ± 2.15%), %swelling index (182.63 ± 2.15 at 12 h), t50 (310.2 min) and t90(649.8 min). Thus, the effervescent floating matrix tablets based on HMG is suitable to get site specific delivery and controlled release of Tolperisone HCl.

Coencapsulation of (-)-Epigallocatechin-3-gallate and Quercetin in Particle-Stabilized W/O/W Emulsion Gels: Controlled Release and Bioaccessibility.

Particle-stabilized W1/O/W2 emulsion gels were fabricated using a two-step procedure: ( i) a W1/O emulsion was formed containing saccharose (for osmotic stress balance) and gelatin (as a gelling agent) in the aqueous phase and polyglycerol polyricinoleate (a lipophilic surfactant) in the oil phase; ( ii) this W1/O emulsion was then homogenized with another water phase (W2) containing wheat gliadin nanoparticles (hydrophilic emulsifier). The gliadin nanoparticles in the external aqueous phase aggregated at pH 5.5, which led to the formation of particle-stabilized W1/O/W2 emulsion gels with good stability to phase separation. These emulsion gels were then used to coencapsulate a hydrophilic bioactive (epigallocatechin-3-gallate, EGCG) in the internal aqueous phase (encapsulation efficiency = 65.5%) and a hydrophobic bioactive (quercetin) in the oil phase (encapsulation efficiency = 97.2%). The emulsion gels improved EGCG chemical stability and quercetin solubility under simulated gastrointestinal conditions, which led to a 2- and 4-fold increase in their effective bioaccessibility, respectively.

Tayloring W/O/W emulsion composition for effective encapsulation: The role of PGPR in water transfer-induced swelling

The role of the lipophilic surfactant, polyglycerol polyricinoleate (PGPR) in water transfer in food-grade double emulsions was investigated, and related to physical emulsion stability. Double (W/O/W) emulsions were prepared with various PGPR concentrations (0.5–5.0 wt%) in the oil phase, at initial osmotic pressure differences of up to 1.1 MPa between the water phases. At high PGPR concentrations (>2 wt%), emulsions showed good physical stability, with encapsulation efficiency close to 100%. It was found that PGPR is involved in water transfer between the water phases through reverse micelle formation by PGPR molecules or hydrated monomers of PGPR, and this allows for controlled swelling. Emulsions that are initially of low viscosity (milk-like emulsions), obtain an apparent viscosity of up to 3 Pa·s, and this effect can be used to tune the emulsion properties to the targeted application, whithout the need to gel either the internal or external phase.

Development of a Novel Spontaneous Emulsification Method for Peptide Delivery Using Porous Silica Particles.

A new emulsification technique using porous silica particles was studied as a facile and instantaneous formation method for thermodynamically unstable emulsions. In this study, oil encapsulated in silica particles was released instantly upon the addition of a phosphate buffer, forming an oil-in-water (O/W) emulsion. Emulsion formation was inhibited or promoted using lipophilic or hydrophilic surfactant additives, respectively. We concluded that this phenomenon is affected by the wettability of the soybean oil on the silica surface, which is controlled by the surfactant. We prepared submicron size emulsions in a simple method involving the addition of the silica particles to an aqueous solution. This spontaneous emulsification technique could be applied to the formation of solid-in-oil-in-water (S/O/W) emulsions for oral delivery of hydrophilic peptide medicine.

Effect of Surfactant HLB Value on Settlement Stability of Magnetorheological Fluid

The hydrophilic-hydrophobic balance (HLB) of surfactants has a great influ-ence on surfactants. Among them, polyethylene glycol has an HLB value of 20 and is highly hydrophilic; oleic acid has an HLB value of 1, which is very lipophilic; and sodium dodecylbenzenesulfonate has an HLB value of 10.6 be-tween the two. This paper explores the use of these three surfactants with typi-cal HLB values to improve the performance of magnetorheological fluids, mainly to study its effect on the stability of magnetorheological fluids. Tests have shown that the use of lipophilic surfactants in oil-based magnetorheologi-cal fluids has better sedimentation stability than the use of hydrophilic surfac-tants.

Ultrafine coal flotation and dewatering: Selecting the surfactants of proper hydrophilic–lipophilic balance (HLB)

ABSTRACT Fine and ultrafine coal (−200 µm) enrichment and its further dewatering processes are more difficult than that of coarser sizes. Utilization of this size fraction, however, is inevitable owing to economic and environmental enforcements. Chemical reagents are widely used in fine coal dewatering to achieve lower cake moistures. Surfactants of the same structures are also used effectively in coal flotation within preparation and coal washing processes. These surfactants contain hydrophilic and lipophilic groups, the ratio of which is known as hydrophilic–lipophilic balance (HLB). Flotation separation efficiency and dewatering performance of hard bituminous coal slimes as well as water recovery characteristics and related entrainment degree during the flotation were investigated using eight various nonionic surfactants of different HLB values. The main motivation of the study is to suggest proper reagent properties by which highest efficiency in both flotation and dewatering can be achieved. This can result in significant economic advantages for industrial processes and also reduce the environmental disadvantages of using chemicals. The flotation separation efficiency of the most lipophilic surfactants (lower HLB) and conventional oily collectors were found to be the highest, while the surfactants with moderate HLB (~10) showed the best filtration performance.

Characterization of ternary compound viscosity reducer system on viscosity of viscous crude oil

ABSTRACTBased on the theory that viscous crude oil can form stable two-phase oil-water interfacial molecular membrane with surfactant, the oil-water interfacial activity and viscosity reduction of oil-water interface of viscous crude oil were studied for the ternary compound system, including anionic surfactant alpha olefin sulfonate (AOS), weak alkali Na2CO3 and four different kinds of nonionic surfactant emulsifying silicon oil (LKR-1023), lauryl diethanolamide (LDEA), isomeric alcohol ethoxylates (E-1306), and polyoxyethylene sorbitan monooleate (T-80). Results showed when lipophilic or hydrophilic nonionic surfactants were used separately in the same compound system. The viscosity of viscous crude oil could be reduced, but the viscosity reduction efficacy was not desirable. However, using LKR-1023, E-1306, and T-80 as nonionic surfactant with mass fraction 1.0%, the viscosity reduction rate of viscous crude oil reaches 98.92%, 98.29%, and 96.87%, respectively. With 1.4% of LDEA, the viscosity reduction rate of viscous crude oil can reach 98.89%. Through all different kinds of the nonionic surfactant tested, oil-in-water (O/W) emulsion under LDEA ternary compound system has been proved to be the most stable with no phase inversion. Therefore, it is promising to improve the viscosity reduction of the super viscous crude oil by selecting the proper surfactant and dosage.

A New Vaccine Delivery Vehicle and Adjuvant Candidate: Bordetella pertussis Inactivated Whole Cells Entrapped in Alginate Microspheres.

There is no doubt about the whole cell pertussis vaccine efficacy, but it is necessary to improve the vaccine quality specially to decrease its toxicity by obtaining good immunogenicity with low bacterial content. In this work, under optimum condition inactivated B. pertussis bacteria cells entrapped with alginate microparticles were fabricated and in vivo immunogenicity and ptency of new microparticle based vaccine were evaluated in mice. Microspheres loaded with inactive B. pertussis bacterium cells were prepared via an emulsification method and analyzed for morphology, size, polydispersity index, loading efficiency, loading capacity, release profile and in vivo potency. The inactivated bacterial suspension mixture prepared in this work was nontoxic and showed potent ED50 (1:333 of human dose) and preserved agglutinins 1, 2, 3. The optimum conditions for the preparation of microparticles were achieved at alginate concentration 3.8% (w/v), CaCl2 8% (w/v), PLL 0.1% (w/v), lipophilic surfactant 0.22 (%w/v), hydrophilic surfactant 3.6 (%w/v), cross linking time 3min, homogenization rate 600 rpm, and alginate to CaCl2 solution ratio 4. Both empty and B. pertussis loaded microparticles exhibited smooth surface texture and relatively spherical shape. The B. pertussis encapsulated microspheres fabricated under optimized conditions showed mean particle size 151.1 μm, polydispersity index 0.43, loading efficiency 89.6%, loading capacity 36.3%, and relatively constant release rate lasted to 15 days. In vivo immunogenicity and protection study against wild type challenge showed strongly higher potency (approximately 2.5 fold) of encapsulated B. pertussis organisms than non-encapsulated conventional aluminum hydroxide adsorbed vaccine. It can be concluded that microencapsulation of inactive B. pertussis cells appears to be a suitable approach for improving the wP vaccine quality, specially by obtaining good immunogenicity with low bacterial content.

Mechanisms and control of single-step microfluidic generation of multi-core double emulsion droplets

Single-step generation of monodisperse multi-core double emulsion drops in three-phase glass capillary microfluidic device was investigated using a micro-particle image velocimetry (micro-PIV) system. Phase diagrams were developed to predict the number of encapsulated inner drops as a function of the capillary numbers of inner, middle and outer fluid. The maximum stable number of inner drops cores in uniform double emulsion drops was six. Starting from core/shell drops, the formation of double emulsion drops with multiple cores was achieved by decreasing the capillary number of the outer fluid and increasing the capillary number of the middle fluid. A stable continuous jet of the middle fluid loaded with inner drops was formed at high capillary numbers of the middle fluid. Empirical correlations predicting the size and generation frequency of inner drops as a function of the capillary numbers and the device geometry were developed. Dual-core double emulsion drops were used as templates for the fabrication of polymeric capsules using “on-the-fly” photopolymerisation. The capsule morphology was controlled by manipulating the stability of the inner drops through adjusting the concentration of the lipophilic surfactant in the middle fluid. At low concentration of the lipophilic surfactant, inner drops coalesced during curing and single compartment capsules with thin shells were produced from dual-core drops. The core/shell capsules produced from multi-core drops were monodispersed and larger than those produced from core/shell drops in the same device.

An experimental investigation of the interfacial tension between liquid-liquid mixtures in the presence of surfactants

The property interfacial tension between liquid-liquid interfaces is a crucial quantity on the study and characterization of emulsion flow rheology. The use of surfactant molecules on a membrane avoids for instance coalescence of the oil droplets by reducing the interfacial tension of the mixture. A transient effect occurs due to the redistribution of the surfactant molecules at the liquid-liquid interface. The present work carries out interfacial tension measurement as a function of the continuous phase components volume fraction which is equivalent to a liquid-liquid interface of different viscosity ratios. The dependence of the interfacial tension on the volume fraction of surfactants is also examined. The experiments are carried out in a drop volume tensiometer, based on the balance between buoyancy and capillary forces on a drop that is detached from the edge of a capillary tube. The interfacial tension between mineral oil drop and a glycerol/water solution is then measured for several values of glycerol volume fractions. The interfacial tension between an oil drop and water is also measured for various concentrations of the Span 80 (i.e. lipophilic surfactant) and Tween 80 (i.e. hydrophilic surfactant). Correlation functions are proposed in order to fit the experimental data. The equilibrium time of the surfactant distribution by the mechanisms of adsorption and by the Marangoni stresses resulting from the flow-induced surface tension gradients on the drop surface and the corresponding equilibrium interfacial tension are used as parameters of the correlations. The results show that the relaxation time for the surfactant distribution reaching steady state decreases with surfactant volume fraction. We determine experimentally the critical value of the surfactant volume fraction and its associated relaxation time. We obtain the minimum surfactant concentration to be used in order to guarantee a faster relaxation of the interfacial tension. The surfactant interfacial properties are estimated and related to their structure.