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C Treiner

Publications and source records attributed to C Treiner.

12 recordsLinked to original sources
PubMed2003

Analytical investigation of the self-desorption of the oligomers of mixtures of a polydisperse ethoxylated surfactant with sodium dodecylsulfate from a silica/water interface.

The adsorption isotherms onto a hydrophilic silica of mixtures of sodium dodecylsulfate (SDS) and of all the oligomers of a polydisperse nonylethylene glycol n-dodecyl ether (C(12)E(9)) surfactant were determined using a high-performance liquid chromatography (HPLC) technique. Incorporation of the anionic surfactant to the negatively charged silica surface is favored by the adsorption of the nonionic surfactant. Comparison between the adsorption isotherms of mixtures of SDS with a monodisperse C(12)E(9) and a polydisperse C(12)E(9) shows that the adsorption of SDS at the silica/water interface is stronger with the latter material than with the former in a large surface coverage domain. The composition of the surface aggregates and the variation of the oligomer distribution in these aggregates were determined. The previously described phenomena called self-desorption which was observed for the global C(12)E(9) and SDS surfactant mixtures was confirmed: increasing the total concentration at a fixed surfactant ratio induces at high concentration a desorption of the anionic surfactant and all of the less polar oligomers from the solid/water interface. An interpretation scheme is proposed which assumes that the interaction of SDS is larger with the less polar oligomers than with the polar ones. The self-desorption effect could then be considered as the consequence of the polydispersity of the nonionic surfactant and to the net repulsion interaction between SDS and the silica surface as the mole fraction of SDS in the surfactant mixture increases.

Adsorption↗
PubMed2000

Adsorption Isotherms of Cetylpyridinium Chloride with Iron III Salts at Air/Water and Silica/Water Interfaces.

The interaction of iron III salts and cetylpyridinium chloride (CPC) has been studied at the air/water and silica/water interfaces. The surface tension of cetylpyridinium chloride has been determined in aqueous solutions in the presence of iron III chloride and iron III nitrate at two constant pH values, namely, 3.5 and 1.2. It is shown that the surface tension of the cationic surfactant depends upon the ionic strength of the solution through the pH adjustment in the presence of the former salt but not in the presence of the latter. The effect of iron III nitrate on the surface tension of CPC is similar to that of potassium nitrate, indicating that the iron III various-hydrolyzed species do not interfere with the composition of the air/water interface. The competitive adsorption of iron III nitrate salt and the cationic surfactant at a silica/water interface was next investigated. The adsorption isotherms were determined at pH 3.5. It is shown that although the iron III ions, which were added to the silica dispersion in the presence of the cetylpyridinium ions, were strongly bound to the anionic surface sites, the surfactant ions are not salted out in the solution but remain in close vicinity of the silica surface. Conversely as the cationic surfactant is added first to the silica dispersion in the presence of the adsorbed iron III ions, the metal ions and the surfactant ions are both coadsorbed onto the silica surface. It is suggested that iron III hydrolyzed or free cations and the cationic surfactant molecules may not compete for the same adsorption sites onto the silica surface. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Coadsorption of the sodium salts of two steroid molecules at a silica/interface as induced by the adsorption of a cationic surfactant.

The incorporation of two ionic steroids, namely the sodium salts of hydrocortisone 21-hemisuccinate (HNa) and prednisolone 21-succinate (PNa), at a silica/water interface in the presence of adsorbed cetyltrimethylammonium bromide has been investigated first at a constant pH value. It is shown that this coadsorption effect is qualitatively similar to the adsolubilization effect which is described for neutral molecules. The adsorption of the cationic surfactant induces the coadsorption of the anionic drug molecules although the silica surface is negatively charged. At surfactant equilibrium concentration above the critical micelle concentration the drug molecules are distributed between the adsorbed aggregates and the free micelles. At larger surfactant concentration, the drugs may be completely depleted from the silica/water interface. Based upon Langmuir-type isotherms, the equilibrium constants of the drug molecules with the adsorbed aggregates and the free micelles are calculated. The constants are about three times larger for the former than for the latter aggregates. The signification of such results is discussed. The coadsorption of HNa at low surfactant surface coverage was also investigated in the pH interval between 3 and 9. HNa is strongly coadsorbed at lower pH onto the silica surface. The coadsorption goes through a maximum at a pH value which may be considered as equal to the apparent pK of the drug and decreases to zero at higher pH values. A pK value equal to 4.2 is proposed for HNa. This behaviour is interpreted as the result of the interplay of the drug dissociation and that of the surface silanol groups upon the change of pH.

Adsorption↗
PubMed2000

Simultaneous quantitative trace analysis of anionic and nonionic surfactant mixtures by reversed-phase liquid chromatography.

The aim of this work was to simultaneously analyse mixtures of a polydisperse polyethylene oxide (PEO) nonionic surfactant and an anionic surfactant (sodium dodecylsulphate, SDS) in water containing sodium chloride in order to quantify trace amounts of these mixtures after their adsorption at water-solid interfaces. A fractional factorial design was then used to optimise the separation by ion-pair reversed-phase liquid chromatography as a function of six factors: the chain length of the tetraalkylammonium salt used as ion-pairing reagent which varied from methyl (C1) to n-propyl (C3); the concentration of this ion-pairing salt; the acetonitrile percentage in water used as organic modifier; the flow-rate; the temperature of analysis and also the sodium chloride concentration. The factorial design enabled in a limited number of analyses, not only to determine which factors had significant effects on retention times or on resolution between a pair of nonionic oligomers, but also to modelize and then find the interesting and rugged area where this resolution was optimal as well as the conditions where time of analysis was not prohibitive. After optimisation of HPLC analysis, we used a trace enrichment procedure to quantify very low concentrations of SDS and C12E9 polydisperse PEO in water. A C18 cartridge and a strong anionic exchange cartridge were coupled and the conditions of elution were optimised in order to obtain concentrated samples which were injected in the same eluent than the HPLC mobile phase. Under such conditions, we were able to quantify, in a single run, mixtures of anionic and nonionic surfactants at concentrations as low as 3.6 microg l(-1) for SDS and 2.5 microg l(-1) for each PEO oligomer in water.

Anions↗
PubMed1998

Polydispersity of a Non-ionic Surfactant as Related to Its Adsorption Characteristics on Porous Silica Particles in Water.

The effect of particle porosity on the adsorption of the oligomers of a polydispersed non-ionic surfactant of the alkylpolyoxyethylene series has been investigated at a silica/water interface using a HPLC technique. This surfactant displayed a high degree of polydispersity relative both to alkyl chains and to polar chains. The results obtained are compared to previously determined adsorption isotherms for the same surfactant on a nonporous silica. It is observed that qualitatively, the shape of the isotherms are similar on both silicas with minor differences below the adsorption plateaus. However, quantitatively, the adsorption density is about four times lower on the porous material as compared to the nonporous one. These findings are interpreted using available information on the porosity and on the size of the primary particles. The composition of the adsorbed micellar-like aggregates is shown to be independent upon the structure of the surface particles. Preferential adsorption of the oligomers with the shorter ethoxychains is displayed on both silicas. The polydispersed surfactant used did not follow a Poisson distribution with respect to the ethoxychains and the presence of polydispersed alkyl chains did not influence the shape of the polar chains distribution. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Adsorption Isotherm of Sodium Octylbenzenesulfonate on Iron Oxide Particles in Aqueous Solutions.

The adsorption isotherm of sodium octylbenzene sulfonate has been determined at two pH values on dispersed maghemite particles in water. The isotherms present an adsorption maximum in the region of the surfactant critical micelle concentration. Additional adsorption experiments at the alumina/water interface as well as at the air/water interface in the presence of ferric ions suggest that the adsorption maximum in the case of the iron oxide particles is due to the presence of very small concentrations of ferric ions in the aqueous solution. These ions form surface active complexes with sodium octylbenzenesulfonate. These complexes are adsolubilized in the surfactant layers on the particles below the critical micelle concentration. They are desorbed from the surface and transferred into free micelles above the critical micelle concentration. These two phenomena are shown to be responsible for the adsorption maximum observed. The presence of ferric ions induces a surface tension minimum of the anionic surfactant at the air/water interface. This effect is discussed in relation to the adsorption maximum at the solid/water interface. Copyright 1998 Academic Press.

Journal Article↗
PubMed1997

Adsorption Isotherms at a Silica/Water Interface of the Oligomers of Polydispersed Nonionic Surfactants of the Alkylpolyoxyethylated Series

Adsorption isotherms of the oligomers of three commercial alkylethoxylated nonionic surfactants at a silica/water interface have been determined using a HPLC method. The surfactants investigated are of the type used in detergency. The compounds, here noted A, B, and C, were mixtures of surfactants. A and B were of the general formulas C13E7 + C15E7 and C13E10 + C15E10, respectively. Compound C was a mixture of oligomers ranging from C12E7 to C16E7 in various proportions. About 10 isotherms are presented for the most important oligomers for each of these detergents. Compound C could be more thoroughly discussed than compounds A and B because adsorption data for the pure surfactant of the same surfactant series with even numbers of carbon atoms in the alkyl chain were made available. Thus, the behavior of representative oligomers of C could be compared with that of the same pure surfactants at the silica/water interface. It is shown that at low surface coverage, polydispersity effects of either alkyl chains or ethoxy groups on global surfactant adsorption are negligible and the oligomers behave essentially as pure, single surfactants. At higher surface coverage, the simultaneous presence of oligomers with long chain lengths or with small numbers of ethoxy groups does not favor the formation of large structures, disks, or patched bilayers at the silica surface as do single pure surfactants. However, it is demonstrated that the opposing effects of oligomers with small and large alkyl chain lengths cancel out in the global isotherms. So it may be concluded that polydispersity in the case of commercial nonionic surfactants of the type used in the present investigation does not affect to any great extent the behavior of such compounds at a silica/water interface. The consequences of these findings can be extended to other nonionic surfactant series. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Adsorption of Pure Nonionic Alkylethoxylated Surfactants down to Low Concentrations at a Silica/Water Interface as Determined Using a HPLC Technique

The adsorption of pure nonionic alkylethoxylated surfactants of the C12 En series at silica/water interface has been determined using a very precise HPLC technique. The number of ethoxylated groups was varied from 2 to 9. The adsorption isotherms were constructed with special attention to the very low surface coverage domain. It is shown that at very low concentration, the adsorption amounts are higher as the number of ethoxylated groups increases but the reverse trend is found at higher surfactant concentration and above the critical micelle concentration. It is shown that this behavior is the consequence of the interplay of the primary and secondary adsorption mechanisms depending upon the length of the ethoxylated chain. The maximum adsorption quantities is not a linear function of the number of ethoxylated groups. This and other observations confirm the viewpoint that the behavior of nonionic surfactant aggregates adsorbed at a hydrophilic surface carries many similarities with the properties of this class of nonionic surfactant aggregates in bulk aqueous solutions.

Journal Article↗
PubMed1996

Nonideality of Mixtures of Pure Nonionic Surfactants Both in Solution and at Silica/Water Interfaces

The behavior of two pure alkylethoxylated nonionic surfactants, both as single components and as binary mixtures of various composition, has been studied in solution and at silica/water interfaces. In solution, the variation of cmc with surfactant composition showed large negative and positive deviations from thermodynamic ideality. These results, as obtained from surface tension measurements, may be interpreted by a partial demixing of the micelles into segregated aggregates in the C10E6-rich composition range and by an increased stability of the aggregates in the C14E6-rich domain. Careful determination of individual isotherms of the surfactants either as single components or as components of mixtures was performed at a nonporous silica/water interface using a reversed phase HPLC technique. The pure nonionic surfactants displayed non superimposable isotherms when sufficiently dilute solution can be attained: a single adsorption plateau is observed with the more hydrophobic component, and a two-plateau behavior is obtained with the more hydrophilic compound. Some experiments with the intermediate surfactant C12E6 were also performed showing a single-plateau profile. Experimental confirmation of the demixing process at the silica/water interface was found in the C10E6-rich end of the diagram. However, the larger than usual favorable interaction between the surfactants in the C14E6-end of the diagram could not be deduced directly from the shape of the individual isotherms. The various isotherms were discussed making use of the known properties of these surfactants in solution as micelle-type aggregates and as lamellar phases.

Journal Article↗
PubMed1984

Equilibrium dialysis of barbituric acids up to high concentrations of aqueous sodium alkylsulfonate solutions.

The partition coefficient K of four barbituric acids has been determined by the equilibrium dialysis method in aqueous solutions of sodium alkylsulfonate at 25 degrees C. The results obtained from dilute solutions to 0.3 M surfactant concentration are compared with solubility data for the same systems. The K values as deduced from Langmuir or Freundlich isotherms decrease with increasing surfactant concentration. The detergent used was an impure commercial product of known composition, which could be considered as a mixed surfactant. The change of partition coefficient with surfactant concentration as obtained from equilibrium dialysis experiments has been interpreted by assuming a continuous change of micelle composition.

Alkanesulfonates↗
PubMed1981

Solubility behavior of barbituric acids in aqueous solution of sodium alkyl sulfonate as a function of concentration and temperature.

The solubility of 13 barbituric acids was determined in aqueous solutions of sodium alkyl sulfonate. The effects of concentration and temperature were investigated, and the thermodynamic functions of the solubilization process were calculated. An analysis of the location of a solubilized species within a micelle is suggested in terms of the sign and amplitude of the standard entropy of solubilization, which is strongly positive for micelle penetration and negative for adsorption. A solubilization mechanism through adsorption onto the micellar surface is suggested for most of the barbituric acids studied. The enthalpy/entropy compensation phenomenon was identical for barbituric acids in ionic and nonionic (polyoxyethylene lauryl ether )surfactant solutions with a compensation temperature of 270 degrees K, indicating common behavior of these compounds with respect to micellar solubilization. The concept of molecular surface area was used to correlate the free energy of solubilization of the solutes to their size and structure. A linear relationship was found with an excellent correlation factor for the alkane derivatives of the 5-ethyl-barbituric acids. The specific behavior of some of the barbituric acids investigated is discussed.

Alkanesulfonates↗