Polyoxyethylene Sorbitan Monolaurate Research Articles

Reversal Potentials of Tween 20 in ABC Transporter-Mediated Multidrug-Resistant Cancer and Treatment-Resistant Depression Through Interacting with Both Drug-Binding and ATP-Binding Areas on MDR proteins

Drug efflux transporters, especially those belonging to the ATP-binding cassette (ABC) transporter superfamily, play a crucial role in various drug resistance issues, including multidrug resistance (MDR) in cancer and treatment-resistant depression (TRD) in individuals with major depressive disorder. Key transporters in this context include P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), and breast cancer resistance protein (BCRP). This study aimed to investigate the modulatory effects of polyoxyethylene (20) sorbitan monolaurate (Tween 20) on these efflux transporters in vitro and to evaluate its potential for overcoming drug resistance in two models: an in vitro cancer MDR model and an in vivo TRD model. The findings indicated that 0.001% Tween 20 significantly inhibited the efflux actions of all three transporters. Additionally, 0.005% Tween 20 effectively reversed resistance to paclitaxel, vincristine, doxorubicin, and mitoxantrone in various cancer MDR cell lines. In the in vivo depression-like behavior model, 0.01% Tween 20 markedly enhanced the antidepressant and anxiolytic effects of fluoxetine. Given its strong inhibitory effects on P-gp, MRP1, and BCRP, along with its capacity to reverse drug resistance both in vitro and in vivo, Tween 20 is a compelling candidate for tackling transporter-mediated drug resistance.

Effects of Linear Alkylbenzene Sulfonate and Polyoxyethylene Sorbitan Monolaurate Surfactants on Pristine and Aged Microplastic Removal by Electrocoagulation

Effects of Linear Alkylbenzene Sulfonate and Polyoxyethylene Sorbitan Monolaurate Surfactants on Pristine and Aged Microplastic Removal by Electrocoagulation

Critical Assessment of Micellar Surface Charge-Dependent Disaggregation and Reaggregation of a Bis-Indole Self-Aggregate: What Should Be Our Case-Dependent Choice?

"Aggregation-caused quenching" is a deep-seated mechanism and has been widely used by the researchers as the possible basis for new sensor development. Contrast to aggregation, its turn around process, disaggregation, has gained much less consideration so far. Unfortunately, study of the further scope for reaggregation of the disaggregated probe assembly in the same solution, as and when required, is still under the rare category. The central theme of the current study is focused on this aspect. For this purpose, the effects of headgroup charge (cationic, anionic, and nonionic) and polarity of the micelles on the degree of disaggregation and subsequent emission amelioration of a synthesized bis-indole derivative, 3,3'-bisindolyl(phenyl)methane (BIPM), are studied using steady-state and time-resolved spectroscopic techniques. The relative emission yield of BIPM (φf = 0.01) is significantly enhanced in the presence of cetyltrimethylammonium bromide (φf = 0.21) and polyoxyethylene (20) sorbitan monolaurate (φf = 0.24), whereas comparatively less emission enhancement is recorded within the sodium dodecyl sulfate system (φf = 0.07). In contrast, addition of an external biophilic agent, uric acid, causes requenching of the enhanced emission because of the reaggregation of the disaggregated probes. Detailed microscopic and calorimetric studies are also adopted to investigate the disaggregation-reaggregation mechanism of BIPM associations. The study will provide prior insights about the use of suitable micellar systems for the required degree of disaggregation as well as for the modulation of emission efficiency by controlled tuning of the disaggregation-reaggregation equilibrium for similar probe associations in pure aqueous medium avoiding any chemical transformation.

Effect of surfactants on the interfacial viscoelasticity and stability of silk fibroin at different oil-water interfaces.

The biocompatible amphiphilic silk fibroin, extracted from domesticated silkworms, can adsorb at the oil-water interface and form elastic interfacial layers. In this study, three surfactants (cationic cetyltrimethylammonium bromide, the nonionic polyoxyethylene sorbitan monolaurate, and the anionic sodium dodecyl sulfate) were selected to investigate, through interfacial shear rheology, the influences of surfactants on the interfacial viscoelasticity and stability of silk fibroin at the interfaces between water and two different oils. The presence of surfactant prolongs the equilibration time and enhances the interfacial elastic modulus and toughness of the interfacial silk fibroin layers, especially at the nonpolar dodecane-water interface. However, when the surfactant exceeds a critical concentration, the shear modulus and stability of interfacial silk fibroin layers begin to decrease due to the competitive adsorption of surfactant molecules and the weakening of the protein network. Owing to electrostatic interactions, the ionic surfactants cetyltrimethylammonium bromide and sodium dodecyl sulfate can form more hydrophobic complexes with silk fibroin, which results in higher shear moduli than for silk fibroin and silk fibroin-polyoxyethylene sorbitan monolaurate mixture. Both the surfactant type and oil polarity play important roles in the adsorption, shear viscoelasticity, and stability of silk fibroin at the oil-water interface. Enhanced interactions between a silk fibroin-surfactant mixture and the oil phase delay the equilibration of the adsorption layers but strengthen the stability of interfacial layers. © 2023 Society of Chemical Industry.

Synergistic effect of Tween 20 and TESPT compatibilizers on the performance characteristics of latex imprinted silica-reinforced green tyre tread formulation

The present study has a prime goal to develop a green tyre tread formulation with enhanced performance characteristics including low rolling resistance, improved wet grip, low heat build-up and enhanced mechanical properties which are essential for a high-performance tyre tread compound. A base formulation of natural rubber/polybutadiene (NR/BR) blend with minimum carbon filler was formulated initially without compromising the physical properties much by balancing the properties by incorporating precipitated silica. Enhanced surface area for silica was obtained through the latex imprinting method which had an ultimate effect on the interaction between the matrix macromolecules and filler particles positively. Further, ENR was used as a compatibilizing agent to upgrade physical properties in terms of 20% improvement in tensile and around 10% improvement in tear strength. Additional improvement in physical as well as rolling resistance performance was achieved via the incorporation of coupling agents including TESPT and polyoxyethylene(20) sorbitan monolaurate (Tween 20). Apart from the improvement in mechanical properties, rolling resistance and heat build-up properties are promising for the final tyre tread formulation as both the values tend to reduce considerably by 35% and 63% respectively concerning the base formulation.

Surfactant mediated silver synthesis: Influence of surfactant molecular structure on the size and shape of silver particles

The current work employs non-ionic surfactants polyethylene glycol tert-octylphenyl ether (Triton X-114) and polyoxyethylene (20) sorbitan monolaurate (Tween 20) as capping agents for synthesizing silver particles. Formation of icosahedrons and Wulff polyhedrons are thermodynamically preferable for FCC silver, and anisotropic morphologies such as triangular/hexagonal platelets are less likely. Yet, with the use of Triton X-114, appreciable quantity of platelets is obtained. Beyond the molar ratio of 2.5 (Triton X-114: AgNO3), only anisotropic particles are identified. It is believed that preferential adsorption of the surfactant inhibits crystal growth along 〈111〉 direction. Instead, the particles grow along the edges of the hexagonal/triangular plates. In contrast, the use of Tween 20 yielded silver (nano)particles with spherical shape. The presence of multiple polymeric chains in the Tween 20 molecule exhibits strong interaction with the silver particles by restricting growth along multiple facets. These observations indicate the significant role of the molecular structure of capping agents in determining particle size and morphology.

Hydrothermal Preparation of Faceted Vesicles Made of Span 40 and Tween 40 and Their Characterization

The Span 40 (sorbitan monooleate)/Tween 40 (polyoxyethylene sorbitan monolaurate) system gives faceted vesicles with angular surfaces, rather than spherical vesicles. Herein, a continuous and facile preparation method, based on the subcritical water-assisted emulsification and solvent diffusion, was presented to yield faceted vesicles with two major and minor axes (Type A) and vesicles closer to a polyhedron (Type B). Type A, rather than Type B, vesicles were likely to be formed. From the measurements concerning ζ-potential, membrane fluidity, and the polarization environment of the membranes, faceted vesicles could be obtained at 0.25 wt% of the surfactant concentration. The phase-separated behavior of Span 40 and Tween 40 within vesicle membranes could explain the structural feature of faceted vesicles and calcein leakage behavior. The significant advantage is that Type A vesicles would be utilized as alternative drug carriers for others with low encapsulation efficiency, although the present technical limitations cause difficulty in the selective formation of Type A and B vesicles and the selection of adequate solvent to accelerate the solvent diffusion step.

Effect of Silica Nanoparticles and Modified Silica Nanoparticles on the Mechanical and Swelling Properties of EPDM/SBR Blend Nanocomposites

The influences of nanosilica and modified nanosilica on cure, compression set, mechanical and swelling characteristics are studied in blends of ethylene-propylene-diene monomer (EPDM)/styrene-butadiene rubber (SBR). In EPDM/SBR composites, the nanosilica made from rice husk ash (RHA) was utilised as a reinforcing nanofiller. The interaction between the nanosilica and the EPDM/SBR matrix at the interface is crucial for the production of rubber composites. This study uses bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) and polyoxyethylene (20) sorbitan monolaurate (TWEEN-20) as a silica modifier, with the ratio of TESPT to TWEEN-20 maintained at 2:1. The cure and mechanical characteristics, compression set, abrasion and swelling resistance increased with the incorporation of nanosilica and modified nanosilica. By interacting at the interface between silica nanoparticles and the EPDM/SBR rubber matrix, TESPT with the TWEEN-20 modifier exhibits a considerable effect on cure characteristics, mechanical qualities, and swelling resistance.

Potential bio-herbicide from Streptomyces sp. KR0005 to control weeds in a horticultural field

ABSTRACT Herbicidal active metabolites obtained from actinomycetes provide valuable sources in the search for new candidates. They might be striking alternatives to synthetic herbicides. In the present study, actinobacteria strains were isolated from soil samples and their herbicidal activities were screened. In the screening, Streptomyces sp. strain KR0005 broth culture exhibited the highest phytotoxic activity. Thus, it was selected for further studies. The herbicidal active compound purified from this selected strain was identified as cycloheximide (MW, 281.; C15H23NO4) based on 1H-NMR, 13C-NMR, 2D-NMR, and high-resolution electrospray ionisation mass spectrometry analyses. Dose–response experiments revealed that the GR50 value of Digitaria ciliaris was 1.37 g L−1 to Streptomyces sp. strain KR0005 culture filtrate. In general, the inclusion of v/v 0.1% of LES270 (Alcohols, (C12-14), ethoxylated, mono ethers with sulphuric acid, sodium salts) and SF90 (Alcohols, C12-14-secondary, ethoxylated) surfactants resulted in a 14.3% decrease and a 24.1% increase in herbicidal activity, respectively, compared with Tween-20 (Polyoxyethylene sorbitan monolaurate). Mode of action experiments revealed that the KR0005 culture filtrate acted as both photosynthesis and cell membrane integrity inhibitors in a dose-dependent manner. However, further studies such as mutation and/or specific culture conditions are needed to increase the herbicidal activity of this selected strain.

Moment Analysis of Solute Permeation Kinetics at an Interface of Mixed Micelles of Anionic and Nonionic Surfactants

Abstract Solubilization phenomena of neutral solutes into mixed micelles of anionic and nonionic surfactants were studied by means of micellar electrokinetic chromatography (MEKC). MEKC experiments were conducted by using mixed micelles consisting of sodium dodecylsulfate (SDS) and polyoxyethylene sorbitan monolaurate (Tween 20) or monostearate (Tween 60) as pseudo-stationary phases while changing the concentration of SDS-Tween mixed micelles and the molar fraction of Tween 20 or 60 in mixed micelles. Elution peak profiles measured by MEKC were analyzed on the basis of the moment theory to determine the solute partition equilibrium constant (Kp) and the rate constants of solute permeation at the interface of mixed micelles (kin and kout). It seems that the values of Kp, kin, and kout are increased by adding Tween 20 or 60 and that the influence of the addition of Tween 60 on their values is more remarkable than that of Tween 20. It was demonstrated that moment analysis of MEKC data is effective for studying solubilization phenomena of surfactant micelles under the conditions that both immobilization and chemical modification (i.e., fluorescence labeling) of solute and micelles are not required.

Surfactant Tween 20 Controlled Perovskite Film Fabricated by Thermal Blade Coating for Efficient Perovskite Solar Cells.

In recent years, additive engineering has received considerable attention for the fabrication of high-performance perovskite solar cells (PSCs). In this study, a non-ionic surfactant, polyoxyethylene (20) sorbitan monolaurate (Tween 20), was added as an additive into the MAPbI3 perovskite layer, and the thermal-assisted blade-coating method was used to fabricate a high-quality perovskite film. The Tween 20 effectively passivated defects and traps in the MAPbI3 perovskite films. Such a film fabricated with an appropriate amount of Tween 20 on the substrate showed a higher photoluminescence (PL) intensity and longer carrier lifetime. At the optimal concentration of 1.0 mM Tween 20, the performance of the PSC was apparently enhanced, and the champion PSC demonstrated a PCE of 18.80%. Finally, this study further explored and compared the effect on the device performance and ambient stability of the MAPbI3 perovskite film prepared by the spin-coating method and the thermal-assisted blade coating.

Influence of surfactant charge and concentration on the surface and foaming properties of biocompatible silk fibroin

As a kind of fibrous amphiphilic protein, the biocompatible silk fibroin (SF) extracted from domesticated silkworms can adsorb at the air/water interface, form thick interfacial layers, and stabilize foams that can be used to fabricate porous scaffolds and regenerate soft tissue. In this study, three surfactants, cationic cetyl trimethyl ammonium bromide (C16TAB), nonionic polyoxyethylene sorbitan monolaurate (Tween 20), and anionic sodium dodecyl sulphate (SDS) were utilized to investigate the effects of surfactant charge and concentration on the adsorption dynamics, interfacial viscoelasticity, and foaming properties of SF. SF is negatively charged at neutral pH in aqueous solution. All these surfactants tend to enhance the surface activity of SF, thus leading to faster interfacial adsorption and establishment of the adsorption equilibrium, thicker interfacial layers, and an increase in the foaming rate. Meanwhile, these surfactants also improve the toughness of interfacial SF networks, and then promote the foam stability. However, at high concentrations, the nonionic Tween 20 and anionic SDS reduce the interfacial elasticity and stability due to the emergence of surfactant domains that interrupt the interfacial SF networks, while the cationic C16TAB thickens the interfacial layers and significantly decreases the interfacial stability and foamability due to its counter-ion screening effect that promotes the aggregation of SF molecules.

How surfactants affect the depuration of polycyclic aromatic hydrocarbons adsorbed on the mangrove leaf surfaces: insight from an in situ method.

The effects of sodium dodecyl benzene sulfonate (SDBS), polyoxyethylene (20) sorbitan monolaurate (Tween 20), and their mixtures on the depuration of anthracene (Ant) and fluoranthene (Fla) individually adsorbed on the Kandelia obovata (Ko) leaf surfaces were in situ investigated. The Ko original leaf-wax microstructures have been destroyed by SDBS, Tween 20, and their mixtures at or above their critical micelle concentration (CMC). The volatilization rate constants (kV) of the adsorbed PAHs decreased with surfactants at or above their CMC resulting from the plasticizing effect and a decrease in the polarity of the Ko leaf-waxes induced by surfactants. Moreover, the photolysis rate constants (kP) of the adsorbed PAHs decreased with SDBS while increased with Tween 20 and their mixtures at or above their CMC, which can be attributed to effects of surfactants on the light adsorption behavior of Ko leaf-waxes. Overall, the effects of surfactants on the depuration of the adsorbed PAHs were dependent not only on the physical-chemical properties of surfactants but also on the micro-environment of the substrates adsorbed the PAHs. These results are of great significance for further understanding the accumulation of PAHs and could expand our knowledge about the migration mechanism of PAHs from the atmosphere by mangrove leaf surface micro-zones.

Polyoxyethylene Sorbitan Monolaurate induced vesicle-to-micelle transition of aqueous dimethyldioctadecylammonium bromide dispersion

The interactions of micelle forming nonionic surfactant, Polyoxyethylene Sorbitan Monolaurate (Tween 20), with spontaneously formed vesicle dispersions of Dimethyldioctadecylammonium bromide (DDOAB) have been investigated. DDOAB vesicles are solubilized in the Tween 20 micelles and undergo vesicle-to-micelle transition. Differential scanning calorimetry (DSC) measurements show that the addition of Tween 20 lowers the gel-to-liquid crystalline phase transition temperature (Tm) of DDOAB vesicles. The thermogram peak shifts to a lower temperature, broadens and ultimately disappears when the vesicle-to-micelle transition is complete. Fluorescence anisotropy and Turbidity data indicate that the vesicle-to-micelle transition takes place in three stages: the vesicle bilayer is first saturated with Tween 20, the bilayer then disintegrates, and finally a complete solubilization takes place, leading to the formation of mixed micelles. Dynamic light scattering study shows an initial increase of the average vesicle size upon the addition of Tween 20 up to the saturation point and then a decrease upon complete solubilization of vesicles into mixed micelles. The results have been confirmed by observing Transmission Electron Microscopy (TEM). TEM images show evidence of direct transformation of the vesicles to mixed micelles without the formation of intermediate aggregates.

Improved Bioavailability of Ebastine through Development of Transfersomal Oral Films.

The main objective of this research work was the development and evaluation of transfersomes integrated oral films for the bioavailability enhancement of Ebastine (EBT) to treat allergic rhinitis. The flexible transfersomes, consisting of drug (EBT), lipid (Phosphatidylcholine) and edge activator (EA) Polyoxyethylene sorbitan monooleate or Sorbitan monolaurate, were prepared with the conventional thin film hydration method. The developed transfersomes were further integrated into oral films using the solvent casting method. Transfersomes were evaluated for their size distribution, surface charge, entrapment efficiency (EE%) and relative deformability, whereas the formulated oral films were characterized for weight, thickness, pH, folding endurance, tensile strength, % of elongation, degree of crystallinity, water content, content uniformity, in vitro drug release and ex vivo permeation, as well as in vivo pharmacokinetic and pharmacodynamics profile. The mean hydrodynamic diameter of transfersomes was detected to be 75.87 ± 0.55 nm with an average PDI and zeta potential of 0.089 ± 0.01 and 33.5 ± 0.39 mV, respectively. The highest deformability of transfersomes of 18.52 mg/s was observed in the VS-3 formulation. The average entrapment efficiency of the transfersomes was about 95.15 ± 1.4%. Transfersomal oral films were found smooth with an average weight, thickness and tensile strength of 174.72 ± 2.3 mg, 0.313 ± 0.03 mm and 36.4 ± 1.1 MPa, respectively. The folding endurance, pH and elongation were found 132 ± 1, 6.8 ± 0.2 and 10.03 ± 0.4%, respectively. The ex vivo permeability of EBT from formulation ETF-5 was found to be approximately 2.86 folds higher than the pure drug and 1.81 folds higher than plain film (i.e., without loaded transfersomes). The relative oral bioavailability of ETF-5 was 2.95- and 1.7-fold higher than that of EBT-suspension and plain film, respectively. In addition, ETF-5 suppressed the wheal and flare completely within 24 h. Based on the physicochemical considerations, as well as in vitro and in vivo characterizations, it is concluded that the highly flexible transfersomal oral films (TOFs) effectively improved the bioavailability and antihistamine activity of EBT.

Effect of total replacement of fish oil with tallow and emulsifier in diet on growth, feed utilization, and immunity of olive flounder (Paralichthys olivaceus)

AbstractThe supplementary effects of an emulsifier mixture (polyoxyethylene (20) sorbitan monolaurate and distilled monoglycerides) were investigated on feed utilization, growth performance, and immunity of olive flounder, Paralichthys olivaceus, replacing fish oil with beef tallow. A fish oil containing diet was considered as positive control (PC) and a diet containing beef tallow instead of fish oil was considered as negative control (TW). Two other diets (EM01 and EM02) were prepared by adding 0.01 and 0.02% of the emulsifier into the TW diet. After 8 weeks of a feeding trial, growth performance and feed utilization were significantly higher in fish fed EM01, EM02, or PC diets compared to those fed the TW diet. Dry matter digestibility was higher in EM01 and EM02 diets than the TW diet and comparable to PC diet. Lipid digestibility was significantly higher in PC diet compared to TW diet. Liver EPA and DHA levels were lower, and oleic acid level was higher in fish fed diets containing tallow compared to PC group. Significantly increased aspartate aminotransferase and triglyceride levels were observed in TW group. Dietary supplemented emulsifier restored the reduced performance of olive flounder fed diets containing tallow instead of fish oil. However, the optimum inclusion level of the emulsifier should be elucidated in future studies.

Production of calcium magnesium phosphate microspheres in a water-in-oil-in-water dispersion

Interfacial reaction in a multiple water-in-oil-in-water dispersion, or double emulsion, was carried out to produce microspheres in a system containing calcium, magnesium and phosphate ions. The inner aqueous phase comprised dipotassium hydrogen phosphate solution. The outer aqueous phase comprised calcium chloride and magnesium chloride solution, in which polyoxyethylene(20) sorbitan monolaurate was dissolved as a stabiliser for the oil droplets. The oil phase comprised cyclohexane, in which sorbitan monooleate was dissolved as a stabiliser for the inner aqueous droplets. Hollow microspheres were generated by this reaction, where the surface state changed from rough to smooth with increasing magnesium content in the outer aqueous phase. The morphology of the primary particles was altered from sheet-like to spherical. The crystalline phase was identified as calcium-deficient hydroxyapatite at lower magnesium contents and as magnesium-substituted β-tricalcium phosphate at higher magnesium contents by considering the lattice parameters and ionic ratio of the products. The existence of an amorphous phase was detected, irrespective of the magnesium content. The magnesium content in the product was lower than that of the reactant solution, suggesting that magnesium was eliminated through a purification process accompanied by crystallisation of the amorphous phase. The location of the reaction site and how the outer aqueous phase is transported thereto were discussed by comparison of the magnesium content of the products formed by the solution reaction with that of the product from the interfacial reaction.

Effect of ZnO nanoparticles doping on structural, dielectric and interfacial behavior of polyoxyethylene (20) sorbitan/ethylene glycol lyotropic phases

ABSTRACT We are reporting on the interaction of zinc oxide (ZnO) nanoparticles (NPs) with the lyotropic phase comprises of Polyoxyethylene (20) sorbitan monolaurate and protic solvent ethylene glycol. The concentration of the NPs has been varying from 0.05 to 0.5 wt%. Multiwall lamellar and inverse phases have been observed at lower and higher concentration of ZnO NPs doping. Interestingly, the organization of ZnO NPs on the periphery and inside the periphery of ring-like structures has been observed at lower and higher concentration of the dopant, respectively. Such organization of the NPs can be explained considering interfacial interaction amid host and dopant and may also attribute to the adsorption mechanisms of surfactant. Effects of NPs doping on the dielectric dynamics has also been examined. About 32.6% decrease in the dielectric permittivity has been noticed at higher NPs doping. Such decrement in permittivity could be a result of the screening of the ZnO NPs dipole moment by the adsorption of surfactant molecules on their surface. Relaxation and optical parameters of the non-doped and doped mixtures have also been discussed.

Comparative study of oil-in-water emulsions encapsulating fucoxanthin formulated by microchannel emulsification and high-pressure homogenization

In this study, we investigated the formulation and stability characteristics of monodisperse oil-in-water (O/W) emulsions encapsulating fucoxanthin using straight-through microchannel emulsification (MCE). Monodisperse O/W emulsions stabilized by hydrophilically modified lecithin (ML), whey protein isolate (WPI), or polyoxyethylene (20) sorbitan monolaurate (Tw20) were stably formulated using straight-through MCE. The resulting emulsions maintained the droplet sizes steadily at 30.3 ± 0.2 μm (ML), 32.3 ± 0.1 μm (WPI) and 29.0 ± 0.8 μm (Tw20) and the relative span factor (RSF) < 0.5 after 30 days storage at 25 °C. The fucoxanthin retention (RTf) in the collected emulsions, decreased from 100% to 44.3 ± 0.1% (ML), 90.7 ± 5.4% (WPI) and 51.4 ± 10.6% (Tw20) after storage. Subsequently, we compared the characteristics of O/W emulsions which were formulated by 1 wt% Tw20 using high-pressure homogenization (HPH) and MCE under the same storage and digestion conditions. After 15 days storage at 4, 25 and 50 °C, all emulsions revealed good physical stability, and there was no drastic change in the droplet sizes. In terms of chemical stability, MCE was pronouncedly better than HPH at the same level of storage temperature. In contrast, the free fatty acids (FFAs) release and fucoxanthin bioaccessibility in emulsions using HPH were significantly higher than MCE. The findings of our study give useful information for food and pharmaceutical industries which express more concern about the natural bioactive compounds for usage.

Micellar and sub-micellar liquid chromatography of terephthalic acid contaminants using a C18 column coated with Tween 20.

The tremendous amounts of terephthalic acid (TPA) produced globally require consistent monitoring of its contaminants during the different stages of production for quality control purposes. In this paper, a simple, robust and green liquid chromatography method has been developed using an isocratic 100% aqueous mobile phase at pH 2 (dilute sulfuric acid) to separate TPA contaminants (mono-, di-, and tri-carboxylic aromatic acids) on a C18 stationary phase coated with Tween 20 (polyoxyethylene(20)sorbitan monolaurate). After optimization of all chromatographic conditions, near baseline separation of the nine carboxylic acids under investigation was achieved with a 2.5 mL/min flow rate on a 5 micron C18 silica column (100 x 4.6 mm) in under 20 min. The modified stationary phase showed an excellent capability to separate structural isomers in a reasonable time, markedly better that the bare C18 stationary phase. Plots of ln retention factor versus 1/temperature showed the expected linear relationship for the di- and tri-carboxylic aromatic acids (single retention mechanism likely) but a quadratic fit for the mono-carboxylic aromatic acids (dual retention mechanism likely). Due to the stability of the surfactant modified stationary phase, future potential mass spectrometry compatibility was shown through the alternative use of trifluoroacetic acid in the 100% H2O (no Tween) mobile phase but still with UV detection. The developed method with 0.001% (vol/vol) Tween in the mobile phase was successfully used to analyze two different types of TPA industrial samples for all nine components plus revealing some other impurity peaks. The lowest limit of detection was 0.010 nmoles for o-phthalic acid and p-toluic acid (PTA), while the highest was 0.065 nmoles for 4-carboxybenzaldehyde (CBA). The concentrations of these important contaminants, PTA and CBA, in the mother liquor sample were 3348mg/L and 1806mg/L, respectively, while their respective concentrations in the purified TPA powder were 135mg/kg and 17.7mg/kg.