Study of the Cloud Point of the Phenothiazine Drug Chlorpromazine Hydrochloride: Effect of Surfactants and Polymers

Surfactants/polymers are used extensively in drug delivery as drug carriers. We herein report the effect of surfactants and polymers on the cloud point (CP) of amphiphilic drug chlorpromazine hydrochloride. At fixed drug concentration (50 mM) and pH (6.7) these additives affect the CP in accordance to their nature and structure: anionic surfactants show an increase followed by a decrease, whereas cationic (conventional as well as gemini) and nonionic surfactants show continous increase. The behavior with polymers is dictated by the number of units present in a particular polymer. Increase in drug concentration and pH, in presence of fixed amounts of CTAB, increases and decreases the CP, respectively. Variation of CP with pH at various fixed gemini concentrations shows that gemini surfactants are better candidates for drug delivery.     

Influence of surfactants on the adsorption and elektrokinetic properties of the system: guar gum/manganese dioxide

The adsorption of non-ionic polysaccharide—guar gum (GG) in the presence or absence of the surfactants: anionic SDS, cationic CTAB, nonionic TX-100 and their equimolar mixtures SDS/TX-100, CTAB/TX-100 from the electrolyte solutions (NaCl, CaCl₂) on the manganese dioxide surface (MnO₂) was studied. The increase of GG adsorption amount in the presence of surfactants was observed in every measured system. This increase results from formation of complexes between the GG and the surfactant molecules. This observation was confirmed by the determination of the influence of GG on surfactants adsorption on the MnO₂ surface. The increase of GG adsorption on MnO₂ was the largest in the presence of the surfactant mixtures (CTAB/TX-100; SDS/TX-100) which is the evidence of the synergetic effect. The smallest amounts of adsorption were obtained in the presence of TX-100, which results from non-ionic character of this surface active agent. In the case of single surfactant solution CTAB has the best efficiency in increasing the amount of GG adsorption on MnO₂ which results from strong interactions with GG and also with the negatively charged surface of the adsorbent. In order to determine the electrokinetic properties of the system, the surface charge density of MnO₂ and the zeta potential measurements were performed in the presence of the GG macromolecules and the above mentioned surfactants and their mixtures. The obtained data showed that the adsorption of GG or GG/surfactants complexes on the manganese dioxide surface strongly influences the diffused part of the electrical double layer (EDL)—MnO₂/electrolyte solution, but has no influence on the compact part of the electric double layer. This is the evidence that the polymers chains are directly bonded with the surface of the solid and the surfactants molecules are present in the upper part of the EDL.     

Mutual influence of cetyltrimethylammonium bromide and Triton X-100 on their adsorption at the water–air interface

On the basis of surface tension values of the aqueous solution of cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) mixtures measured at 293 K as a function of CTAB or TX-100 concentration at constant TX-100 or CTAB concentration, respectively, the real surface area occupied by these surfactants at the water–air interface was established which is inaccessible in the literature. It appeared that at the concentration of the CTAB and TX-100 mixture in the bulk phase corresponding to the unsaturated monolayer at the water air-interface this area is the same as in the monolayer formed by the single surfactant at the same concentration as in the mixture. In the saturated mixed monolayer at this interface the area occupied by both surfactants is lower than that in the single surfactant monolayer corresponding to the same concentration in the aqueous solution. However, the decrease of the CTAB adsorption is lower than that of TX-100 and the total area occupied by the mixture of surfactants is also lower than that of the single one. The area of particular surfactants in the mixed saturated monolayer changes as a function of TX-100 and CTAB mixture concentration and at the concentrations close to CMC or higher the area occupied by both surfactants is the same. The changes of the composition of the mixed surface monolayer are connected with the synergetic effect in the reduction of the water surface tension by the adsorption of CTAB and TX-100 at the water–air interface. This effect was confirmed by the values of the standard Gibbs free energy of adsorption of both individual surfactants and their mixtures with different compositions in the bulk phase determined by using the Langmuir equation if RT instead of nRT was applied in this equation.     

The interplay of hydrophobic and electrostatic effects in the surfactant-induced aggregation/deaggregation of chlorin p6

The aggregation/deaggregation of chlorin p6 with the surfactants CTAB, SDS, and TX 100 have been studied by using absorption, fluorescence, and light scattering techniques. The ionic surfactants are found to cause aggregation of fluorophore at submicellar concentrations. The aggregates dissolve at higher surfactant concentrations to yield micellized monomers. This is rationalized by the interplay of electrostatic and hydrophobic effects. A prominent pH effect is observed in the ionic surfactant induced aggregation process as the charge on the fluorophore is controlled by the pH of the medium. Interestingly, the neutral TX-100 also induces aggregation of chlorin p6 at low concentrations, indicating that hydrophobic effects by themselves can cause aggregation unless there is a hindrance by repulsive electrostatic effects.     

Behaviour of phenol red pH-sensors in the presence of different surfactants using the sol-gel process

Phenol red was immobilised into a polysiloxane matrix using a sol-gel process to form pH optical sensors. The sol-gel was obtained by hydrolysis of tetraethoxysilane (TEOS) in the presence of phenol red (PR) and the appropriate surfactant. Different surfactants, namely cetyltrimethylammonium bromide (CTAB), dodecyldimetyl amino-oxide (GLA) and Triton X-100 (TX-100), were employed. Interestingly, the use of surfactants significantly improved the mesostructure of the silica and increased the porosity of the system. The two response pH ranges were shifted to pH 0.0–3.0 and pH 10.5–1.5M [OH^?] compared with those of the free PR (pH 0.0–3.0 and pH 6.5–9.5). It is found that the pH response and the pKa shift of the phenol red were dependent, not only on the silica matrix but also on the ionic properties of surfactants. In the case of ionic surfactants such as CTAB or GLA, there was further shift to more acidic and more basic pH, whereas in the case of non-ionic surfactants such as TX-100 no significant change of the pH curve was observed.     

Clouding Behavior and Thermodynamic Study of Nonionic Surfactants in Presence of Additives

The present study investigates the effect of different additives on the cloud point (CP) of nonionic surfactants Triton X-100 (TX-100) and Triton X-114 (TX-114) in aqueous solutions. The thermodynamic parameters of these mixtures were calculated at different additive concentrations. The cloud point of nonionic surfactants TX-100 and TX-114 decreased with the increment of electrolyte concentrations and increased with alcohol concentrations. The standard Gibbs free energy was found to be positive for both the surfactants, whereas the enthalpy and the entropy of the clouding phenomenon were found to be positive with alcohols and negative with electrolytes. The overall clouding process was endothermic for alcohols and exothermic for electrolytes.     

吲哚方酸菁染料在表面活性剂水溶液中的光降解

考察了4种含有不同N位取代基的对称吲哚方酸菁染料在阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)、阴离子表面活性剂十二烷基硫酸钠(SDS)和非离子表面活性剂曲拉通(TX-100)水溶液中的光降解行为,结果表明,表面活性剂对染料分子具有保护作用,其影响大小为CTAB>TX-100>SDS,分子中有羧基的染料受影响程度最大。在表面活性剂浓度较低时,染料光降解程度随着表面活性剂浓度的增加而增加,但形成胶束后,染料的光降解程度则随着表面活性剂浓度的升高而降低。     

Interaction of Nonionic Surfactant Triton-X-100 with Ionic Surfactants

The interaction in two mixtures of a nonionic surfactant Triton-X-100 (TX-100) and different ionic surfactants was investigated. The two mixtures were TX-100/sodium dodecyl sulfate (SDS) and TX-100/cetyltrimethylammonium bromide (CTAB) at molar fraction of TX-100, α_TX-100 = 0.6. The surface properties of the surfactants, critical micelle concentration (CMC), effectiveness of surface tension reduction (γ_CMC), maximum surface excess concentration (Γ_max), and minimum area per molecule at the air/solution interface (A _min) were determined for both individual surfactants and their mixtures. The significant deviations from ideal behavior (attractive interactions) of the nonionic/ionic surfactant mixtures were also determined. Mixtures of both TX-100/SDS and TX-100/CTAB exhibited synergism in surface tension reduction efficiency and mixed micelle formation, but neither exhibited synergism in surface tension reduction effectiveness.     

Interaction of poly(vinylpyrrolidone) with cationic and nonionic surfactants in aqueous solution studied by <Superscript>1</Superscript>H NMR

Aqueous solutions of surfactant at various concentrations with 0.2% poly(vinylpyrrolidone) (PVP) were studied by ¹H NMR methods, including relaxation time and self-diffusion coefficient measurements and two-dimensional nuclear Overhauser enhancement spectroscopy. Two surfactants were concerned: cationic cetyltrimethylammonium bromide (CTAB) and nonionic Triton X-100 (TX-100). In the presence of 0.2% PVP, the variation of the T ₂ values of CTAB protons is similar to that in the absence of PVP. Relaxation times of PVP protons are not significantly affected by the increasing concentration of CTAB. This indicates that no interaction between PVP and CTAB could be detected. However, in the presence of 0.2% PVP, TX-100 micelles are formed at a concentration lower than its normal critical micellization concentration. According to the results of relaxation time measurement of water protons, the presence of 0.2% PVP also induces the contraction of the hydrophilic layer of the TX-100 micelle. This indicates some interaction between PVP and TX-100, but the mechanism of this interaction needs further investigation.     

Influence of Nonionic Surfactant on Alkaline Hydrolysis of Methyl Violet Catalyzed by Cetyltrimethylammonium Bromide

The alkaline hydrolysis of methyl violet (MV) was studied by spectrophotometric method under pseudo-first-order conditions at 298 K. Cationic surfactant cetyltrimethylammonium bromide (CTAB) catalyzed the reaction. Addition of nonionic surfactant Triton X-100 (TX-100) exhibited significant influence on the CTAB catalyzed reaction by lowering the extent of catalysis. The kinetic data were analyzed by Piszkiewicz model of positive cooperativity. Linear Hill-type plots were generated with indices of cooperativity values greater than unity. The effect of counterions on the reaction rates was also studied in the presence of cationic surfactant (CTAB) and cationic–nonionic mixed surfactants (CTAB/TX-100).     

混合表面活性剂与调节pH值法高效合成MCM-48

以正硅酸乙酯（TEOS）为硅源、十六烷基三甲基溴化铵（CTAB）与曲拉通X- 100(TX-100)热合成中孔MCM-48．在合成过程中通过调节溶液pH值可有效提高MCM- 48的收率和水热稳定性，同时采用剂使模板剂的利用效率达到了6.0TEPOS／1.0 Surf．并通过XRD、N_2-吸附／脱附和FT-IR等测试手段对产物进行了表征.     

Phase Separation Phenomenon in Non-ionic Surfactant TX-114 Micellar Solutions: Effect of Added Surfactants and Polymers

Clouding (or phase separation) in non-ionic surfactants is a well-known phenomenon. Clouding is to be avoided in some applications whereas in others it is preferred. Herein the results of CP (cloud point—the temperature at which solution separates into two phases) measurements of the non-ionic surfactant Triton X-114 (TX-114) in the presence of surfactants and polymers are presented. Cationic and nonionic surfactants, in the absence and presence of the quaternary salt tetrabutylammonium bromide (TBAB), increase the CP of TX-114. Anionic surfactants, in the absence of TBAB, increase the CP; in the presence of TBAB, these surfactants decrease the CP. Polymers of PEG and PVP series have been found to decrease the CP. The results are discussed by taking into consideration the nature of the added surfactants and polymers.     

Effect of Surfactant Microenvironment on SOD-like Activity of Cu(II)-Salicylate Complex

Cu(II)-salicylate was synthesized and characterized by X-ray diffraction. The reaction mechanism of the Cu(II) complex with superoxide anion was studied by ESR spectroscopy, and its (superoxide dismutase) SOD-like activity was determined by a modified illumination method in phosphate buffer (pH = 7.8), micelle solutions and lamellar liquid crystals formed from surfactants CTAB and TX-100. X-ray diffraction indicated that the Cu(II) complex had a formula Cu₂(Hsal)₄EtOHH₂O and a similar structure to the SOD active site. EPR spectra proved that the reaction mechanism of the Cu(II) complex catalyzing O ₂ ^.- dismutation was the same as that of the proposed dismutation reaction catalyzed by SOD. Results obtained by the NBT method indicated that the Cu(II)-complex showed SOD-like activity, and the effect of microenvironment created by surfactants on its activity was same as on SOD activity. The order of the inhibition of NBT reduction by the Cu(II)-complex in different microenvironments was: in phosphate buffer (pH = 7.8) > in TX-100 micelle > in TX-100 liquid crystal, and in nonionic TX-100 organized assemblies > in cationic CTAB organized assemblies. These results were explained by the catalytic effect of micelles, and by the space restriction and high viscosity of organized assemblies of surfactants.     

Stability of manganese dioxide by guar gum in the absence or presence of surfactants

Stability of the manganese dioxide (MnO₂) suspensions by non-ionic guar gum (GG) in the absence or presence of the surfactants: anionic sodium dodecyl sulphate (SDS), cationic hexadecyltrimethylammonium bromide (CTAB) and non-ionic Triton X-100 (t-octylphenoxypolyethoxyethanol) and their equimolar mixtures (SDS/TX-100; CTAB/TX-100) was measured using turbidity. The obtained results of the manganese dioxide suspensions stability were discussed together with the adsorption data and with the data concerning the thicknesses of the adsorption layers. In order to gain more information about the structure of the electric double layer surface charge density and the zeta potential measurements were performed. The obtained results show that the addition of guar gum to the MnO₂ suspensions increases MnO₂ stability. The larger this increase is, the higher is the concentration of the polymer (concentration range 10–200 ppm). Moreover, the addition of single surfactants also causes the increase in the effectiveness of stabilizing the manganese dioxide suspensions. The reason for that is formation of multilayer complexes between the polymer and the surfactants. In such a system both the adsorption of polymer and the thickness of polymer adsorption layer increase. The greatest increase in the stability of MnO₂/GG suspensions was provided by the mixture of anionic and non-ionic surfactants due to a strong synergistic effect. Also, mixing the polymer and two surfactants reduces the stability of the suspension.     

Study of Spontaneous Imbibition of Water by Oil-Wet Sandstone Cores Using Different Surfactants

The mechanism of spontaneous imbibition of water by sandstone cores and the relationship between reservoir wettability and imbibition recovery were studied by investigating factors influencing the spontaneous imbibition of different surfactants by oil-wet sandstone cores. Ultimate oil recovery of cores using the cationic surfactant CTAB was higher than that of the cores using the nonionic surfactant TX-100 and the anionic surfactant POE (1) at the same concentration. For CTAB and TX-100, the ultimate oil recovery by spontaneous imbibition increased with increase in surfactant concentration. In regard to imbibition recovery, TX-100 and POE(1) at high temperatures were superior to those at low temperatures. Ultimate oil recovery of the high-permeability core was higher than that of the low-permeability core at room temperature. According to changes in the driving force during the imbibition process, the imbibition curve could be divided into three regions: (1) mainly capillary force, (2) both capillary and gravity forces, and (3) mainly gravity force. The stronger the hydrophilicity of the rock surface, the higher the spontaneous imbibition recovery.     

Studies on the molecular interaction of safranin-T with surfactants

The spectrophotometric studies of safranin-T (Saf-T) dye in an aqueous solution containing three different types of surfactants such as CTAB (cationic), SLS (anionic) and Triton X-100 (TX-100), Tween-20, 40, 60 and 80 (nonionic) show that Saf-T forms a 1:1 molecular complex with TX-100, Tweens and SLS. Such a type of interaction is absent in Saf-T and CTAB. The thermodynamic and spectrophotometric properties of these complexes suggest that Saf-T forms a strong charge transfer (CT) complex with TX-100 and Tweens, whereas the interaction of Saf-T with SLS is coulombic in nature. Photogalvanic and photoconductometric studies also support the above interactions. In addition to this, the electron-donating ability among the nonionic surfactants i.e. TX-100 and Tweens towards dye, role of surface in CT interaction, the site of CT interaction and the intensity and stability of CT interaction between Saf-T and nonionic surfactants have been pointed out.     

Studies on the molecular interaction of Erythrosine ‘B’ with surfactants

The spectroscopic investigation on anionic dye, Erythrosine ‘B’(EB) with three different types of surfactants such as CTAB (cationic), sodium lauryl sulphate (SLS; anionic) and Triton X-100 (TX-100),Tween-20, 40, 60 and 80 (nonionic) in aqueous media shows that EB forms a 1:1 molecular complex with TX-100, Tweens and CTAB. No interaction is observed between EB and SLS. The thermodynamic and spectrophotometric properties of these complexes suggest that EB forms a strong charge transfer (CT) complex with TX-100 and Tweens whereas the interaction of EB with CTAB is coulombic in nature. Photogalvanic and photoconductometric studies also support the above interactions. In addition to this, the electron-donating ability among the nonionic surfactants, i.e. TX-100 and Tweens towards dye, role of surface in CT interaction, the site of CT interaction and the intensity and stability of CT interaction between EB and nonionic surfactants have been pointed out.     

Effect of Sodium Barbital on the Physico‐chemical Properties of Surfactants with Different Charges

The effects of sodium barbital (SB) on the solubility of different kinds of surfactants viz., CTAB (cationic head group), SDS (anionic head group) and Triton X‐100 (non ionic head group) in solution phase as well as their first and second critical micelle concentrations (CMC1 and CMC2), the change in Kraft temperatures (T_K) and cloud points (CP) have been studied. Furthermore, the article reports SB‐surfactant interaction study, which is application oriented and highlights the underlying physico‐chemical aspects of the system through florescence and conductivity measurements. The results show that the solubility of CTAB and Triton X‐100 increases with the addition of SB, and that of SDS increases in the presence of small amounts of SB and decreases in the presence of large amounts of SB. With the increasing SB concentration, the CMC of CTAB and CMC1 of Triton X‐100 both increase, while the CMC of SDS decreases, and the CMC2 of Triton X‐100 has no obvious change. The addition of SB decreases the T_K of CTAB sharply, but it increases the T_K of SDS and the CP of Triton X‐100. The different effects of SB on the physico‐chemical properties of differently charged surfactants may be related to its different interactions with the surfactants.     

Polarographic behavior of nicotinamide in surfactant media and its determination in cetyltrimethylammonium bromide surfactant system

The behavior of nicotinamide has been studied by differential pulse polarography and cyclic voltammetry in the presence of certain ionic and nonionic surfactants, viz. cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS) and Triton X-100 (TX-100). The cathodic peak potential (E(p(c))) and peak current (I(p(c))) of nicotinamide were found to be remarkably dependent on the charge and concentration of the surfactant. The presence of SDS and that of TX-100 cause a shift in peak potential and a change in peak current of nicotinamide. In the presence of the cationic surfactant, CTAB, an enhancement in the sensitivity of nicotinamide was observed. A sharp peak with more than two-fold increase in current was used to determine the limit of detection and linear working range using the differential pulse polarographic technique. The present method was successfully used for the simultaneous determination of nicotinamide and pyridoxine hydrochloride, and for the determination of nicotinamide in multivitamin pharmaceutical preparations.     

Cloud point variation of amphiphilic drug promethazine hydrochloride with added surfactants

In this paper we report clouding phenomenon occurring in an amphiphilic phenothiazine drug promethazine hydrochloride (PMT) in presence of surfactants. Cationic and nonionic surfactants increase the CP of 75 mM PMT solutions (prepared in 10 mM sodium phosphate buffer). These surfactants form mixed micelles with PMT. Anionic surfactants also form mixed micelles with the drug but the CP behavior is different by showing a peaked behavior. At low concentrations, anionic surfactants hinder micelle formation by forming ion-pairs whereas the usual CP decreasing effect at higher concentrations is due to mixed micellization. The CP behavior of 75 mM PMT+50 mM TBAB+surfactant systems is also explored which is found similar to PMT+surfactant systems with the difference only in magnitude of the clouding temperature.