Alkyl Ether Carboxylic Acids Research Articles

Optimization of Toxicity, Biodegradability, and Skin Irritation in Formulations Containing Mixtures of Anionic and Nonionic Surfactants Combined with Silica Nanoparticles.

Surfactants play a crucial role in various industrial applications, including detergents and personal care products. However, their widespread use raises concerns due to their potential environmental impact and health risks, particularly in aquatic ecosystems, where they can disrupt the balance of marine life and accumulate in water sources, posing challenges to sustainable development. This study investigates the environmental and health implications of anionic and nonionic surfactants, focusing on their toxicity, biodegradation, and skin irritation potential profiles, especially when combined with silica nanoparticles. Toxicity assessments were conducted using bacteria Vibrio fischeri for aquatic toxicity and Lepidium sativum seeds for terrestrial plant effects, revealing that individual surfactants like the anionic alkyl ether carboxylic acid EC-R12-14E3 exhibit high toxicity levels, while the nonionic fatty-alcohol ethoxylate FAE-R12-14E11 shows comparatively lower environmental impact. The toxicity of surfactant mixtures was analysed, revealing both antagonistic and synergistic effects depending on the surfactants used. The addition of silica nanoparticles generally mitigates the overall toxicity of surfactants, whether used individually or in mixtures. Biodegradation studies followed OECD 301E and 301F guidelines, indicating that individual surfactants generally meet or approach the mineralization threshold, whereas the addition of nanoparticles reduced biodegradation efficacy. Potential skin irritation was predicted through the zein number (ZN), finding that some surfactant combinations with silica nanoparticles reduce irritation levels, highlighting their potential for safer formulation in products that come into direct contact with the skin. Overall, the findings emphasize the need for careful selection of surfactant mixtures and nanoparticle integration to minimize environmental toxicity and potential skin irritation and increase their biodegradability.

Formulating additives in thermoresponsive surfactant-based nematic liquid crystals

Abstract Bicelles can be formed by mixing in given mole fractions two ethoxylated alkyl ether carboxylic acid surfactants of very different HLB in water. We determine the effect of adding three of the most used additives in formulation in health- and home care: propylene glycol, glycerol, and ethanol. The effects of additives are determined and compared in a concentrated isotropic phase above the LCST, a pseudo-lamellar phase, and a discotic nematic phase. The two latter are birefringent, and the nematic phase is viscoelastic. Propylene glycol acts as a co-solvent, improving the temperature stability of the nematic phase up to 20 wt% propylene glycol. Further addition of propylene glycol reduces the phase transition temperatures, inducing microstructural changes due to headgroup dehydration and preferential solubilization of the hydrophilic short chain surfactant. Glycerol acts as an anti-solvent, progressively decreasing phase transition temperatures by dehydration of headgroups. Ethanol is a good co-solvent for the surfactant-mixture. Adding up to 5 wt% ethanol increases the temperature stability of the nematic phase. Higher concentrations of ethanol lead to a single isotropic phase with increasingly molecular dissolution of the surfactants. The effect of the considered additives on molecular packing is followed by high resolution X-ray scattering.

A dilute nematic gel produced by intramicellar segregation of two polyoxyethylene alkyl ether carboxylic acids

MotivationSurfactants like C8E8CH2COOH have such bulky headgroups that they cannot show the common sphere-to-cylinder transition, while surfactants like C18:1E2CH2COOH are mimicking lipids and form only bilayers. Mixing these two types of surfactants allows one to investigate the competition between intramicellar segregation leading to disc-like bicelles and the temperature dependent curvature constraints imposed by the mismatch between heads and tails. ExperimentsWe establish phase diagrams as a function of temperature, surfactant mole ratio, and active matter content. We locate the isotropic liquid-isotropic liquid phase separation common to all nonionic surfactant systems, as well as nematic and lamellar phases. The stability and rheology of the nematic phase is investigated. Texture determination by polarizing microscopy allows us to distinguish between the different phases. Finally, SANS and SAXS give intermicellar distances as well as micellar sizes and shapes present for different compositions in the phase diagrams. FindingsIn a defined mole ratio between the two components, intramicellar segregation wins and a viscoelastic discotic nematic phase is present at low temperature. Partial intramicellar mixing upon heating leads to disc growth and eventually to a pseudo-lamellar phase. Further heating leads to complete random mixing and an isotropic phase, showing the common liquid–liquid miscibility gap. This uncommon phase sequence, bicelles, lamellar phase, micelles, and water-poor packed micelles, is due to temperature induced mixing combined with dehydration of the headgroups. This general molecular mechanism explains also why a metastable water-poor lamellar phase quenched by cooling can be easily and reproducibly transformed into a nematic phase by gentle hand shaking at room temperature, as well as the entrapment of air bubbles of any size without encapsulation by bilayers or polymers.

Novel PFAS-specific monitoring approach for highly impacted surface waters

In regulatory environmental monitoring programs, only a very small fraction of the vast number of per- and polyfluoroalkyl substances (PFAS) are investigated by target analysis. Therefore, non-target analysis (NTA) studies are increasingly conducted to detect unknown or unnoticed PFAS. These studies are often based on a few grab samples. Thus, discontinuously emitted PFAS from industrial batch processes might be easily overlooked. To address this deficiency and obtain in-depth information on the occurrence and temporal trend of PFAS in surface water impacted by treated industrial waste water, a comprehensive target and NTA study was implemented for 29 months.Elevated PFAS concentrations with up to 10.8 μg L−1 were detected in the river water by target analysis. In addition to PFAS target analysis, the water samples were analyzed by liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS/MS). Data processing strategies and various filtering steps were applied to prioritize PFAS. Substances were identified by comparing data to available internal and external PFAS suspect lists, a fragment ion and neutral loss list, and spectral libraries. Several compounds were unequivocally identified based on reference standards.Fifty-five PFAS were (tentatively) identified using NTA. Of those, 43 could be assigned to 13 different homologous series. Partly fluorinated short-chain carboxylic acids (H-PFCA) and sulfonic acids (H-PFSA) were predominantly found in addition to perfluoroalkyl carboxylic acids (PFCA) and the alkyl ether carboxylic acid DONA. To the best of our knowledge, 12 PFAS were reported in surface water for the first time. Signal intensities of individual PFAS and signal ratios varied widely over time, which may indicate batch operations leading to discontinuous emission. Results and insights from this screening approach on PFAS can be used to optimize forthcoming surface water monitoring programs by including newly identified PFAS and selecting appropriate sampling intervals.

Unveiling the microstructures of micelles from polyoxyethylene alkyl ether-based multi-responsive nonionic amphiphile

The present study was undertaken to unveil the self-assembly of a polyoxyethylene alkyl ether carboxylic acids based nonionic amphiphile known as Akypo® RO90 VG (hereafter written as Akypo) in aqueous medium using cloud point (CP), solution viscosity, dynamic light scattering (DLS), small-angle neutron scattering (SANS) measurements. Surfactants belonging to Akypo family have an average formula C x EO y CH 2 COOH (i = 8–18, j = 2.5–10) [1] . The surfactant micellizes in aqueous media analogous to conventional surfactants but with some dissimilarity. The influence of external stimuli viz. temperature, pH and electrolyte has been examined to assess the response on the microstructural changes in micelles. SANS experiments provided the exact size and shape of micelles; the micellar growth proposed by high solution viscosity and hydrodynamic diameter (D h ) of micelles from DLS and further reinforced by SANS data. This further divulges that increase of temperature and addition of electrolyte persuade the ellipsoidal to worm-like micellar transition. Change of pH towards an alkaline medium favors the transformation of ellipsoidal micelles into spherical ones which can be correlated with deprotonation of carboxylic acid groups that results in increased solubility of Akypo. The current study authorizes how the size of Akypo micelles can effortlessly be amended in the presence of external stimuli to the desired extent. • Akypo self-assemble to form micelles in analogy to conventional surfactants. • Thermo-responsive Akypo exhibit micellar transition at elevated temperature. • Increase of solution pH facilitate ellipsoidal to spherical micellar transition.

On the effect of the nature of counterions on the self-assembly of polyoxyethylene alkyl ether carboxylic acids.

In this contribution, we investigate the effect of the type of counterion on the properties of dilute solutions of polyoxyethylene alkyl ether carboxylic acids. Two different surfactants, presenting an oleic acid alkyl chain and on-average five and nine ethylene oxide units, and terminated by a weakly anionic carboxymethyl group were studied. The surfactants were gradually ionized with sodium hydroxide, arginine, and choline hydroxide. The solutions properties were probed by light scattering, electrophoretic mobility, density and sound velocity measurements, as well as by small-angle neutron scattering. To our initial surprise, no specific effect arising from the nature of the counterion could be determined. We ascribe this phenomenon to the fact that the presence of the ethylene oxide units markedly dilutes the surfactant head group charge density, reducing counterion condensation and subsequent counterion specific effects.

Chromatographic behavior and characterization of polydisperse surfactants using Ultra-High-Performance Liquid Chromatography hyphenated to High-Resolution Mass Spectrometry

Surfactants are widely used in various petrochemical applications. Thus, it is essential to have highly efficient analytical tools to monitor the different classes of surfactants commonly used. Three among the four known classes of surfactants were studied in the present work: anionic (i.e. alkylbenzene sulfonate, alkyl ether carboxylic acid), nonionic (i.e. alkylcyclohexyl alcohol ethoxylated, alkyl alcohol ethoxylated) and cationic (i.e. alkyl trimethylammonium). Thanks to high-resolution mass spectrometry (HRMS), a useful mass list was created including 119 m/z values (error in mass around 5 ppm). This list was the foundation of a HRMS database, which, for the sake of simplicity, will be further denoted only “database”. To avoid ion competition and streamline attribution of structural formulas for isobar molecules, a suitable chromatographic method was used before MS. The retention behavior of six surfactants (trimethyloctadecylammonium bromide, myristyltrimethylammonium bromide, Brij®C10, Triton X-100 reduced, glycolic acid ethoxylate lauryl ether, 4-dodecylbenzenesulfonic acid) was evaluated under three separation modes: reversed-phase liquid chromatography (RPLC), hydrophilic interaction chromatography (HILIC) and mixed-mode chromatography (combination of anion-exchange and reversed-phase mechanisms). In RPLC mode, six columns were tested including C4, C18, C30, polar-embedded C18, PFP and phenyl chemistries. Two HILIC columns were also tested including bare silica and urea chemistries. An anion-exchange combined with RPLC mechanism was investigated as mixed-mode mechanism. Using ammonium formate at 10 mM as buffer provided the best signal in HRMS. In liquid chromatography, acid conditions (pH 3.5) were preferred, to avoid peak tailing due to residual silanols. The mixed-mode separation mode clearly appears as the best compromise for the characterization of the three surfactants classes. Nevertheless, the orthogonality observed for the separations obtained in HILIC and RPLC modes offers some possibilities for further multidimensional separations.

AuCu/CeO2 bimetallic catalysts for the selective oxidation of fatty alcohol ethoxylates to alkyl ether carboxylic acids

We describe in this work the preparation of a series of bimetallic Au-Cu catalysts supported over nanoceria for the direct oxidation of C12-C14-alcohol polyethyleneglycol ether with on average 7 ethyl oxide units (AEO7) to polyoxyethylene lauryl ether carboxylic acid (AECA6), using H2O2 as an oxidant, under basic conditions. Different preparation methods have been used, including deposition-precipitation, incipient wetness impregnation and wet impregnation for engineering the interaction between Au, Cu and nanoceria. The structure of the bimetallic catalysts is discussed in detail on the basis of refined characterization by XRD, HR-TEM, STEM-EDX-SDD, XPS and ICP-AES. The formation of a AuCu alloy over nanoceria at a Cu/Au molar ratio of 0.11 on Au allows a significant enhancement of the catalytic activity, resulting in an AECA6 yield up to 80% with a selectivity of 90%. The catalyst can be recycled and reused for at least 10 consecutive runs without apparent loss of activity. Detailed DFT calculations on Au, Cu and Au-Cu model alloys reveal a positive role of Cu on Au by favoring the adsorption of AEO7, H2O2 and OH− on the catalyst surface compared to pure Au, as well as by reducing the energy barrier for H2O2 cleavage. Isolated Cu sites on the Au-Cu alloy appear as crucial for enhancing the catalytic properties for AEO7 oxidation.

Micellization of a weakly charged surfactant in aqueous salt solution: Self-consistent field theory and experiments

Self-consistent field (SCF) calculations and light scattering experiments were performed to study the pH and salt response of micelles composed of surfactants with a single weak acid group in aqueous salt solution. To this end, the common surfactant Brij 35 was oxidized to yield a polyoxyethylene alkyl ether carboxylic acid with a single terminal weakly charged carboxylic acid group in alkaline media. At low pH values, the micellar hydrodynamic radii (Rh) are independent of the salt concentration. By contrast, at pH values around the acid dissociation constant (pH ≈ pKa ± 1), the micellar radius decreases upon increasing pH until a salt-dependent plateau value is reached. The reduction in micellar size is more pronounced for lower salt concentrations. The SCF computations are in qualitative agreement with the experimental results and further reveal a limiting value for Rh corresponding approximately to the Debye length λD. Self-assembly into micelles is suppressed for low salt concentrations that would yield Rh < λD. Instead, the surfactants remain as unimers in solution. The results are summarized in a state diagram displaying the preferred surfactant configuration in solution as a function of Rh/λD, pH and salt concentration.

A mild hand cleanser, alkyl ether sulphate supplemented with alkyl ether carboxylic acid and alkyl glucoside, improves eczema on the hand and prevents the growth of Staphylococcus aureus on the skin surface.

Washing the hands using cleansers with antiseptic materials is the most popular method for hand hygiene and helps maintain health by preventing food poisoning and bacterial infections. However, repeated hand washing tends to induce eczema of the hand, such as dryness, cracking and erythema. Moreover, eczema on the hand leads to increased levels in Staphylococcus aureus (S.aureus) on the skin surface in contrast to expectations. Thus, mild hand cleansers which induce less eczema even with repeated washings are desired. Here, we evaluated the efficacy of a hand cleanser formulated with alkyl ether sulphate (AES), alkyl ether carboxylic acid (AEC) and alkyl glucoside (AG) that contains isopropyl methylphenol (IPMP) on skin symptoms and S.aureus levels. Eczema of the hand and the presence of S.aureus on the skin surface were analysed prior to and following 4weeks of usage of the hand cleanser. A soap-based hand cleanser with IPMP was used as a reference cleanser. Eczema and cutaneous conditions were evaluated by visual grading, transepidermal water loss (TEWL), stratum corneum moisture-retention ability (MRA) and skin surface pH. The repeated use of the soap-based hand cleanser significantly worsened the hand dryness, scaling and cracks on the tips of the fingers and significantly increased the TEWL and decreased the MRA. In contrast, usage of the test cleanser only induced a significant increase in skin dryness but did not induce skin scaling or cracking and did not increase TEWL or decrease the MRA. Corresponding to these changes in skin symptoms, the presence of S.aureus increased the following use of the reference cleanser but not the test cleanser. There was no significant difference in skin surface pH between the two cleansers. Moreover, the increase in S.aureus was significantly correlated to the worsening of skin dryness and scaling. These results suggest that not only antimicrobial activity but also the mildness, which minimizes cutaneous effects, are important for hand cleansers to prevent the growth of S.aureus. The cleanser formulated with AES, AEC and AG containing IPMP is mild and is effective to promote hand hygiene.

Selective oxidation of fatty alcohol ethoxylates with H2O2 over Au catalysts for the synthesis of alkyl ether carboxylic acids in alkaline solution

In this paper, we report a green and selective route for the direct oxidation of alcohol ethoxylates (AEOs) into alkyl ether carboxylic acids over supported noble metal catalysts using H2O2 as an oxidant in the presence of a base. The catalytic performance of supported Au, Pt and Pd was assessed in the oxidation of AEO7 consisting of C12–C14-alcohol polyethyleneglycol ether with average 7 EO units. Among the different catalysts tested, Au/Al2O3 and Au/TiO2 displayed a yield up to 88% to polyoxyethylene(7) lauryl ether carboxylic acid (AECA6) at 80°C. The effect of Au particle size, reaction temperature, reaction time, catalyst loading and base amount on the activity, selectivity and stability of Au/Al2O3 was explored in detail. Hydroxyl radicals were generated during the reaction as suggested by a series of poisoning tests using 2,2,6,6-tetramethylpiperidinoxyl and 1,4-benzoquinone as radical scavengers. Au/Al2O3 and Au/TiO2 could only be reused in two consecutive runs, showing a strong deactivation in the third run and beyond due to Au leaching and partial nanoparticle sintering as inferred by combined TEM and ICP-AES analysis. The Au stability could be highly promoted over a bimetallic AuPt/TiO2 formulation, showing a good recyclability and reuse for at least 10 consecutive catalytic cycles.

Phase Behaviour of Ph-Dependent Microemulsions At High Temperature and Salinities

This paper describes the formulation principal for a model microemulsion system which exhibits pH dependent phase behaviour. The system investigated consists of octane, brine, alkyl ether carboxylic acid surfactants and short chain alcohols. The CMCs of these surfactants were lower in acid form of the surfactant (COOH) than for the salt form (COO-), also the micelles formed in acid solutions were smaller than for the salt. Furthermore the surface and interfacial tensions were found to increase with increasing pH. Increasing pH ionises the carboxylic acid head group thereby making the surfactant more hydrophilic. The effect of an increase in pH can be counterbalanced by increasing the electrolyte concentration. Measurements of ultralow interfacial tensions at different salinities and temperatures have been made using a spinning drop apparatus. Three phase microemulsion systems were studied as a function of temperature and pH. It was observed that the presence of ethylene oxide (EO) moiety in the surfactant molecule made the surfactants less sensitive to salinity than anionic surfactants. In addition, the carboxylic ionic head group made the surfactant more stable to temperature than simple EO nonionic surfactants. Thus these surfactants are more robust than either simple anionic or nonionic surfactants and thus these materials have potential in the field of surfactant flooding for tertiary oil recovery.