Sodium N-dodecyl Sulphate Concentration Research Articles

Application of chemometrics in determination of the acid dissociation constants (pKa) of several benzodiazepine derivatives as poorly soluble drugs in the presence of ionic surfactants

In this study, the acid dissociation constants (pKa) of some benzodiazepine derivatives including chlordiazepoxide, clonazepam, lorazepam, and oxazepam in aqueous micellar solution were determined spectrophotometrically at an ionic strength of 0.1M at 25°C.The effect of cetyl trimethylammonium bromide (CTAB) as a cationic and sodium n-dodecyl sulfate(SDS) as an anionic surfactant on the absorption spectra of benzodiazepine drugs at different pH values were studied. The acidity constants of all related species are estimated by considering the surfactant concept and the application of chemometric methods using the whole spectral fitting of the collected data to an established factor analysis model. DATAN® software (Ver. 5.0, Multid Analyses AB, and Goteborg, Sweden) was applied to determine the acidity constants. In this study, a simple and fast method to determine the ionization constant (pKa) of poorly soluble drugs was developed using surfactants. The acidity constant (i.e. pKa) for chlordiazepoxide, clonazepam, lorazepam, and oxazepam were reported as 4.62, pKa1 value of 1.52 and pKa2 value of 10.51, pKa1 value of 1.53 and pKa2 value of 10.92 and pKa1 value 1.63 and pKa2 value of 11.21 respectively. The results showed that the peak values in the spectrophotometric absorption spectra of drugs are influenced by the presence of anionic and cationic surfactants. According to the results, by changing the SDS concentration from 0 to 0.05M, the pKa of chlordiazepoxide was increased to 5.9, the pKa1 of lorazepam was decreased to 0.1 while the pKa2 was increased to 11.5. Increase in SDS concentration has not shown significant alteration in pKa of clonazepam and oxazepam.Results indicate that by Changing the CTAB concentration from 0 to 0.05M, the pKa of chlordiazepoxide was reduced to 4.4, the pKa1 of clonazepam was decreased to 0.1 and the pKa2 was decreased to 9.1, the pKa1 of lorazepam was decreased to 0.4 and the pKa2 was decreased to 9.4, the pKa1 of oxazepam was decreased to 0.3 and the pKa2 was decreased to 9.7.Based on the results obtained from the study, charge of anionic and cationic surfactants leads to an electrostatic interaction between surfactant and the protonated form of the drug molecule. The electrostatic interactions can be attractive or repulsive forces and influence of separation of protons and consequently increase or decrease the acidity constants.

Emulsion grafting of glycidyl methacrylate onto polyethylene fiber

Graft polymerization of glycidyl methacrylate (GMA) onto polyethylene fiber was carried out in emulsion solution obtained by dissolving GMA in water with sodium n-dodecyl sulfate (SDS) as a surfactant. GMA micelles diameter was 415 nm at 5% GMA with 4% SDS and increased up to 1840 nm at 10% GMA with 12% SDS. Degree of grafting (Dg) which was estimated by the weight gain after grafting increased with the increment of GMA concentration in the range 2 to 8% and slightly reduced at 10% GMA. The increment in SDS concentration from 4% to 16% at 5% GMA reduced Dg from 120% to 18%. In emulsion graft polymerization, Dg was affected by covered area by GMA/SDS micelles on the fiber.

Influence of surfactant properties on thermal behavior and sol–gel transitions in surfactant‐HPMC mixtures

AbstractFour surfactants, namely, sodium n‐decyl sulfate (SDeS), sodium n‐hexadecyl sulfate (SHS), sodium n‐dodecyl sulfate (SDS), and Triton X‐100, were used as additives to study thermal behavior and sol–gel transformations in dilute aqueous hydroxypropyl methyl cellulose (HPMC)/surfactant mixtures using micro‐differential scanning calorimetry. The influence of anionic surfactant, SDS on the gelation varied with SDS concentration where the sol–gel transition started at a higher temperature. Shape of the thermograms changed from single mode to dual mode at the SDS concentration of 6 mM and higher. SDeS and SHS, however, resulted in “salt‐in” effect of a different magnitude during gelation. Triton X‐100, being a non‐ionic surfactant, showed a minor “salt‐out” effect on the thermo‐gelation process. On the basis of different thermal behavior of anionic and non‐ionic surfactant/HPMC systems, a mechanism is proposed explaining how the chemical structure and electro‐charge of the surfactants affect the polymer/surfactant binding and polymer/polymer aggregation because of hydrophobic interaction during the sol–gel transition. © 2009 Wiley Periodicals, Inc. Journal of Applied Polymer Science, 2009

Potentiometric Study of the Effect of Sodium Dodecylsulfate and Dioxane on the Hydrolysis of the Aluminum(III) Ion

Hydrolytic equilibria of the aluminum(III) ion were studied in the presence of a surfactant, sodium n-dodecylsulfate (SDS) and, separately, in mixed water + dioxane and water + dioxane + surfactant media at 298.15 K, by using potentiometric measurements with a glass electrode. The concentration of SDS was between 1.25 and 25.0 mmol-dm−3, whereas the volume percent of dioxane was varied from 10 to 50. The supporting strong electrolyte was 0.1 mol-dm−3 LiCl. A general least-squares treatment of the data indicates the formation of mononuclear hydrolytic complexes of the form Al(OH) m 3 − m (m = 1–3) at all studied compositions. At lower concentrations of SDS (≤ 12.5 mmol-dm−3) it was necessary to include polynuclear hydrolytic complexes in the hydrolytic model. On increasing the concentration of SDS, the formation of polynuclear complexes is suppressed, and at the SDS concentration of 25.0 mmol-dm−3, only Al(OH)2+ and Al(OH)2 + are observed in solution. At lower volume percentages of dioxane, the speciation involved polynuclear complexes in addition to mononuclear complexes. At dioxane concentrations higher than 20 vol% only mononuclear complexes are formed. The simultaneous presence of the SDS and dioxane as ionic medium modifiers produces only the mononuclear complexes Al(OH)2+ and Al(OH)2 +, which have significantly higher stability constants than in the pure ionic medium.

Aquamethemoglobin reduction by sodium n-dodecyl sulfate via coordinated water oxidation

The influence of sodium n-dodecyl sulfate (SDS) on hemoglobin reduction has been studied in the presence of 100 mM phosphate buffer (pH 7.0) using spectrophotometry, cyclic voltammetry and chemiluminescence (CL) methods. Spectroscopic studies have revealed that the SDS concentration up to 1 mM reduces the methemoglobin (metHb) to its deoxy form. Such a redox reaction is believed to occur by water oxidation of the sixth coordination in aquametHb. The proposed mechanism is supported by a CL method which monitors H 2O 2 during the conversion of metHb to its deoxy form by addition of SDS at low concentrations (up to 1 mM).

Inhibition of human hemoglobin autoxidation by sodium n-dodecyl sulphate.

The effect of sodium n-dodecyl sulphate (SDS) on hemoglobin autoxidation was studied in the presence of a 100 mM phosphate buffer (pH 7.0) by different methods. These included spectrophotometry, fluorescence technique, cyclic voltametry, differential scanning calorimetry, and densitometry. Spectroscopic studies showed that SDS concentrations up to 1 mM increased deoxy-, decreases oxy-, and had no significant effect on the met- conformation of hemoglobin. Therefore, a SDS concentration up to 1 mM increased the deoxy form of hemoglobin as the folded, compact state and decreases the oxy conformation. The turbidity measurements and differential scanning calorimetry techniques indicated a more stable conformation for hemoglobin in the presence of SDS up to 1 mM. Electrochemical studies also confirmed a more difficult oxidation under these conditions. The induction of the deoxy form in the presence of SDS was confirmed by densitometry techniques. The compact structure of deoxyhemoglobin blocks the formation of met-conformation in low SDS concentrations.

Thermodynamic studies on the interaction between sodium n-dodecyl sulphate and histone H 2A

The thermodynamic parameters of interaction between histone H 2A and sodium n-dodecyl sulphate (SDS) in aqueous solutions of pH 3.2, 6.4 and 10, measured over a wide range of SDS concentration by equilibrium dialysis at 27°C and 37°C, are discussed. The data are used to determine the free energy from the Wyman binding potential theoretical model, and the enthalpy of interaction from the temperature dependence of the equilibrium constants using the van't Hoff relation. The data obtained for H 2A are also compared with corresponding data for histone H 2B.

Thermochemical studies on the interaction between sodium n-dodecyl sulphate and catalases

The enthalpies of interaction between bovine catalase and sodium n-dodecyl sulphate (SDS) in aqueous solutions of pH 3.2,6.4 and 10.0 have been measured over a range of SDS concentrations by microcalorimetry at 25°C. The enthalpies increase with decreasing pH and with increasing SDS concentration and largely arise from the interations between the anionic head group of SDS and the cactionic amino acid residues on the protein. Chemically modified catalase in which a proportion of carboxylic acid groups have been coupled with either glycine methyl ester or ethylenediamine have been prepared and characterized in terms of their enzymic activities, spectral properties and sedimentation behaviour. The enthalpies of interaction of these catalases with SDS have been studied at pH 6.4. The results of the experiments suggest that the enthalpies of interaction with SDS can be correlated with the ratio of cationic to anionic amino acid residues on the surface of the catalase molecules and hence the nominal net surface charge. The variation in the enthalpy of interaction of catalases with surface charge, as a consequence of variation in pH, differs from the variation with charge at constant pH possibly due to the thermal effect of proton binding to the catalase—complexes.

Enthalpy of interaction between some globular proteins and sodium n-dodecyl sulphate in aqueous solution

The enthalpy of binding of sodium n-dodecyl sulphate (SDS) to serum albumin, ovalbumin and ribonuclease A has been measured by microcalorimetry over the temperature range 18.5 to 32.0°C. The amount of SDS bound to the proteins has been measured over a wide range of SDS concentration by equilibrium dialysis. Changes in protein conformation have been monitored by viscometry. The results are consistent with a mechanism in which SDS binds initially to ionic sites on the protein molecules and initiates chain unfolding. At high binding levels the interaction is predominantly of a hydrophobic nature.