Surfactant-based extraction methods

Dispersive surfactant micelle-mediated extraction combined with a smartphone-based portable colorimeter: a cost-effective and simple approach for cobalt determination

In this research, we present a cost-effective, environmentally friendly methodology for the precise determination of trace levels of cobalt in various environmental matrices, based on a new surfactant micelle-mediated extraction combined with digital image analysis. Specifically, cetyltrimethylammonium bromide (CTAB) serves as the key surfactant. Prior to extraction, the conversion of Co2+ ions into hydrophobic species is achieved through the utilization of 1-nitroso 2-naphthol as a chelating agent. The procedure involves injecting a tetrahydrofuran (THF) solution of CTAB into water samples containing the target analytes and some added KI, resulting in the formation of a turbid solution due to CTAB dispersion within the medium. Following centrifugation, the resulting precipitate is re-dissolved in 1 mL of dimethylformamide and subjected to analysis using a self-constructed colorimeter, which is based on a mobile device. In the colorimeter, digital image analysis is conducted using the RGB color space, with the G channel value serving as the analytical signal. Our investigation encompasses the exploration and optimization of several critical parameters influencing the extraction and complex formation processes. Under optimal conditions, a linear range spanning 10-2.00 × 102 μg L-1 is achieved, exhibiting a correlation coefficient of 0.994. The detection limit (DL) is determined to be 4.1 μg L-1. The relative standard deviations for the determination of Co2+ at concentrations of 40 and 100 μg L-1 are found to be 7.0 and 6.6, respectively, for five replicates. Further assessments include an evaluation of the impact of common cations and anions on the proposed method, which subsequently qualifies it for the efficient preconcentration and quantification of cobalt in diverse environmental matrices.

Effect of hydrophilic/lipophilic balance on the porogenic properties of non-ionic surfactants for monolith preparation and chromatographic separation

The effect of hydrophilic/lipophilic balance (HLB) of polyoxyethylene ethers of different chain lengths on the microporogenic properties of the Brij surfactants has been studied. The objective of this work is to help better understand the role of each porogen and to set criteria for selecting the proper non-ionic surfactant, based on the HLB value. Seven recipes of different porogen compositions were first prepared and the highest efficiency was achieved using decane/decanol/dodecanol mixture with Brij® 30. Then, four other Brij surfactants covering the entire HLB scale were tested, and the prepared monoliths were characterized by SEM, BET, FT-IR and chromatography. The results showed that increasing the HLB from 9.72 to 18.84 was accompanied by an increase in monolith density and surface areas. The optimum HLB range was found to be 10 to 15. Surfactants of lower HLB formed either nonporous or less efficient columns, while those of higher HLB formed non-permeable columns. Adjusting the HLB was possible by mixing surfactants of different HLB. The prepared monoliths could be used in the isocratic mode with a mobile phase consisting of a mixture of ACN and water (20:80, v/v) at a flow rate of 1.5 μL min^-1 to separate five sulfa drugs. The separation results showed that the elution order of the compounds correlated with their lipophilicity, with sulfamerazine (logp = 0.52) being the first to elute, and sulfaquinoxoline (logp=1.70) being the most retained. The asymmetry factors of the separated compounds ranged between 1.18 and 1.25, and the resolution was found to be in the range 2.92-7.80. The prepared monoliths could be also successfully separate a mixture of four different nonsteroidal anti-inflammatory drugs and a mixture of four benzoic acid derivatives. This work assists in optimizing the surfactant-based porogenic mixture to meet the desired porosity, surface area, morphology and chromatographic separation requirements.

Nanomaterials-Based Electrochemical Δ9-THC and CBD Sensors for Chronic Pain

Chronic pain is now included in the designation of chronic diseases, such as cancer, diabetes, and cardiovascular disease, which can impair quality of life and are major causes of death and disability worldwide. Pain can be treated using cannabinoids such as Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) due to their wide range of therapeutic benefits, particularly as sedatives, analgesics, neuroprotective agents, or anti-cancer medicines. While little is known about the pharmacokinetics of these compounds, there is increasing interest in the scientific understanding of the benefits and clinical applications of cannabinoids. In this review, we study the use of nanomaterial-based electrochemical sensing for detecting Δ9-THC and CBD. We investigate how nanomaterials can be functionalized to obtain highly sensitive and selective electrochemical sensors for detecting Δ9-THC and CBD. Additionally, we discuss the impacts of sensor pretreatment at fixed potentials and physiochemical parameters of the sensing medium, such as pH, on the electrochemical performance of Δ9-THC and CBD sensors. We believe this review will serve as a guideline for developing Δ9-THC and CBD electrochemical sensors for point-of-care applications.

Interfacial Characterization of Ruthenium-Based Amphiphilic Photosensitizers

Nonreactive surfactant molecules have long been used and characterized for a wide range of applications in industries, life science, and everyday life. Recently, new types of functional amphiphilic molecules have emerged that bear another function, for example, a light-absorbing action, or catalytic properties. However, the surfactant properties of these molecules remain to date essentially unknown. In this context, we investigated here the interfacial activity of photocatalytic surfactants based on a ruthenium(II) tris-bipyridine core, functionalized with two alkyl tails. We realized a systematic characterization of the surfactant properties of these molecules at a water-air interface and studied the effect of the alkyl chain length and of the counterions (hexafluorophosphate or chloride) on these properties. Our data demonstrate that ruthenium surfactants with chloride counteranions form a denser layer at the interface, but their surfactant properties can dramatically deteriorate when the chain length of the alkyl tail increases, leading to simple hydrophobic molecules with poor surfactant properties for the longest chains (C17). These findings pave the way for a better use and understanding of photocatalytic soft interfaces.

An overview on nanostructure-modified supported liquid membranes for the electromembrane extraction method

Electromembrane extraction (EME) is an extraction method on the micro scale, in which charged compounds are extracted from a donor phase (sample solution) into an acceptor phase via a supported liquid membrane (SLM) containing a water-immiscible organic solvent. To enhance the extraction efficiency and selectivity in this method, some studies have focused on the modification of the SLM, and thus many strategies have been reported for this purpose. One of these techniques is the introduction of nanomaterials in the SLM structure, which can enhance the extraction efficiency. In the current study, the different nanostructures used for SLM modification in the EME method are reviewed. Furthermore, the related analytical parameters of the developed techniques are classified and tabulated. It is hoped that this review will motivate further research in this field using other nanostructures.

Interfacial Polyelectrolyte-Surfactant Complexes Regulate Escape of Microdroplets Elastically Trapped in Thermotropic Liquid Crystals

Polyelectrolytes adsorbed at soft interfaces are used in contexts such as materials synthesis, stabilization of emulsions, and control of rheology. Here, we explore how polyelectrolyte adsorption to aqueous interfaces of thermotropic liquid crystals (LCs) influences surfactant-stabilized aqueous microdroplets that are elastically trapped within the LCs. We find that adsorption of poly(diallyldimethylammonium chloride) (PDDA) to the interface of a nematic phase of 4-cyano-4'-pentylbiphenyl (5CB) triggers the ejection of microdroplets decorated with sodium dodecylsulfate (SDS), consistent with an attractive electrical double layer interaction between the microdroplets and LC interface. The concentration of PDDA that triggers release of the microdroplets (millimolar), however, is three orders of magnitude higher than that which saturates the LC interfacial charge (micromolar). Observation of a transient reorientation of the LC during escape of microdroplets leads us to conclude that complexes of PDDA and SDS form at the LC interface and thereby regulate interfacial charge and microdroplet escape. Poly(sodium 4-styrenesulfonate) (PSS) also triggers escape of dodecyltrimethylammonium bromide (DTAB)-decorated aqueous microdroplets from 5CB with dynamics consistent with the formation of interfacial polyelectrolyte-surfactant complexes. In contrast to PDDA-SDS, however, we do not observe a transient reorientation of the LC when using PSS-DTAB, reflecting weak association of DTAB and PSS and slow kinetics of formation of PSS-DTAB complexes. Our results reveal the central role of polyelectrolyte-surfactant dynamics in regulating the escape of the microdroplets and, more broadly, that LCs offer the basis of a novel probe of the structure and properties of polyelectrolyte-surfactant complexes at interfaces. We demonstrate the utility of these new insights by triggering the ejection of microdroplets from LCs using peptide-polymer amphiphiles that switch their net charge upon being processed by enzymes. Overall, our results provide fresh insight into the formation of polyelectrolyte-surfactant complexes at aqueous-LC interfaces and new principles for the design of responsive soft matter.

Development of novel experimental and modelled low density polyethylene (LDPE)-water partition coefficients for a range of hydrophobic organic compounds

Knowledge about partitioning constants of hydrophobic organic compounds (HOCs) between the polymer and aqueous phases is critical for assessing chemical environmental fate and transport. The conventional experimental method is characterized by large discrepancies in the measured values due to the limited water solubility of HOCs and other associated issues. In the current work, a novel three-phase partitioning system was evaluated to determine accurate low-density polyethylene (LDPE)-water partition coefficients (K_PE-w). By adding sufficient surfactant (Brij 30) to form the micellar pseudo-phase within the polymer/water system, the K_PE-w values were obtained from a combination of two experimentally measured values, that is, the micelle-water partition coefficient (K_mic-w) and the LDPE-micelle partition coefficient (K_PE-mic). The method presented here is capable of shortening the equilibration time to half a month, and avoiding defects of the traditional method with respect to directly measured aqueous phase concentrations. Herein, the K_PE-w values were determined for HOCs with little errors. Meanwhile, based on the 120 experimental K_PE-w data, several in silico models were also developed as valid extrapolation tools to estimate missing or uncertain values. Analysis of the underlying solubility interactions in the nonionic surfactant micelles were investigated, providing additional support for the reliability of the proposed method.

Nanomicellar Extraction of Polyphenols-Methodology and Applications Review

The selection of the appropriate extraction method is crucial, especially for the receiving of active substances from plant material. The extraction using supercritical liquids and micellar-mediated extraction (MME) is the most advantageous among the alternative methods to classical solid-liquid extraction. However, the latter seems to be the best solution when the desired actives are polar. The following article presents a comprehensive review of the micellar-mediated extraction method in the last decade. The theoretical principle of the process was also refreshed and the current state of knowledge on the applications for analytical and manufacturing purposes was summarized.

Removal of Disperse Blue 56 from synthetic textile effluent using ionic flocculation

The textile industry is one of the main generators of industrial effluent due to the large volumes of water containing a wide variety of pollutants, including dyes. Thus, the present study aimed to remove the Disperse Blue 56 dye present in synthetic textile effluent using ionic flocculation through surfactant flocs produced from animal/vegetable fat, assessing the system at different surfactant concentrations and temperatures. The process kinetics, adsorption mechanism and equilibrium were evaluated. The results show that the kinetics was better described by the Elovich model when compared to pseudo-first order and pseudo-second order models, indicating that chemical adsorption occurs during the process. The study of the adsorption mechanism obtained lower outer layer diffusivities than their intra-particle counterparts, demonstrating that the dye transport to the surfactant floc is controlled through the outer layer. The Langmuir isotherm was suitable for equilibrium data and the separation factor calculated showed that the isotherm is classified as favorable. Dye removal efficiency reached 87% after 360 minutes of contact between the effluent and the surfactant flocs, indicating that ionic flocculation is an efficient alternative in the treatment of textile effluent containing disperse dye.

Sequential extraction and enrichment of flavonoids from Euonymus alatus by ultrasonic-assisted polyethylene glycol-based extraction coupled to temperature-induced cloud point extraction

A green method for simultaneous extraction and enrichment of flavonoids from Euonymus alatus was developed by ultrasonic-assisted extraction (UAE) and temperature-induced cloud point extraction (TICPE) using PEG-base aqueous solution as the extractant. Based on screening different molecular weights of PEGs, PEG-400/water was used as the extractant, and the effects of key factors on extraction yields of flavonoids were investigated by single-factor experiments and response surface methodology (RSM). The optimum conditions of UAE were as follows: PEG-400 concentration of 16% (w/w), particle size of 80 mesh, solvent-to-material ratio of 60:1, extraction temperature of 90 °C and extraction time of 15 min. The results obtained by validation experiments were consistent with the values predicted by RSM. Temperature-induced formation of the aqueous two-phase system (ATPS) and TICPE process were further investigated by controlling temperature and adding (NH₄)₂SO₄. In the presence of (NH₄)₂SO₄, the ATPS formed at 75 ℃ and pH 3.5 could effectively improve separation and recovery of flavonoids with enrichment factor of above five times. Gallic acid, catechin, dihydromyricetin and ellagic acid in the extract were identified and confirmed by UPLC-Q-TOF-MS and the corresponding standards. The UAE-TICPE coupled to HPLC was successfully applied for extraction and determination of flavonoids in two batches of Euonymus alatus. The extraction yields of catechin, dihydromyricetin and total flavonoids were 0.377-0.684 mg/g, 1.091-1.353 mg/g and 2.612-3.146 mg/g, respectively. Compared to conventional extraction methods, PEG-based UAE integrated with TICPE in one-step procedure exhibited higher extraction efficiency and better extraction selectivity.

Solvent stir bar microextraction technique with three-hollow fiber configuration for trace determination of nitrite in river water samples

In this work, trace determination of nitrite in river water samples was studied using solvent stir bar microextraction system with three-hollow fiber configuration (3HF-SSBME) as a preconcentration step prior to UV-Vis spectrophotometry. The obtained results showed that the increase in the number of solvent bars can improve the extraction performance by increasing the contact area between acceptor and sample solutions. The extraction process relies on the well-known oxidation-reduction reaction of nitrite with iodide excess in acidic donor phase to form triiodide, and then its extraction into organic acceptor phase using a cationic surfactant. Various extraction parameters affecting the method were optimized and examined in detail. Detection limit of 1.6 μg L^-1 and preconcentration factor of 282 can be attained after an extraction time of 8 min under the optimum conditions of this technique. The proposed method showed a linear response up to 1000 μg L^-1 (r² = 0.996) with relative standard deviation values less than 4.0%. The accuracy of the developed method was assessed using the Griess technique. Finally, the proposed method was successfully employed for quantification of nitrite in river water samples (Ghezelozan, Zanjan, Iran).

Supramolecular Solvent Based Liquid-Liquid Microextraction for Preconcentration of Selected Fluoroquinolone Antibiotics in Environmental Water Sample Prior to High Performance Liquid Chromatographic Determination

Background and Objective:

A rapid, simple and environmental friendly supramolecular solvent (SUPRAS) based liquid-liquid microextraction method for preconcentration of ciprofloxacin (CIPRO), danofloxacin (DANO) and enrofloxacin (ENRO) from wastewater was developed.

Methods:

This microextraction technique was coupled with high-performance liquid chromatography equipped with a diode array detector (HPLC-PDA) for detection and separation of the antibiotics. The SUPRAS composed of decanoic acid and tricaprylymethylammonium chloride. Optimum conditions for the extraction and preconcentration of all the antibiotics were obtained using surface response methodology (RSM) based on Box-Behnken design.

Results:

Under optimum conditions, the limits of detection (LOD) and limit of quantification (LOQ) ranged from 0.06-0.14 µg L−1 and 0.22-0.47 μg L−1, respectively with the preconcentration factors ranging from 153-241. The linear dynamic ranges were between LOQ and 850 µg L−1 with correlation coefficients ranging from 0.9928 to 0.9999. The intra-day (n = 15) and inter-day (n = 5) precisions (expressed in terms of %RSD) for 50 µg L−1 of CIPRO, DANO and ENRO were in the range of 3.3–4% and 4.1–5.8%, respectively.

Conclusion:

Lastly, the developed method was used for the extraction, preconcentration and quantification of selected CIPRO, DANO and ENRO in influent and effluent wastewater samples.

Micellar systems of aliphatic alcohol ethoxylates as a sustainable alternative to extract soybean isoflavones

Ethoxylated aliphatic surfactants belonging to the Genapol and Tergitol series were assessed as extraction systems of isoflavones. They showed good extraction properties when compared with different solvents, the Genapol X-080 exhibiting the best performance. Available commercial isoflavone pills were used, as a starting simple matrix, to determine the parameters that affect the extraction procedure. The temperature and the surfactant concentration showed to be factors that favored significantly the extraction performance. The application of optimized variables (Genapol X-080 11% m/m, pH 4.5; extraction temperature of 54 °C and extraction time of 60 min) on soybean flour (natural) allowed extracting 3.237 ± 0.173 mg of isoflavone per gram of treated flour. This result was three times what it was for methanol under identical conditions. Extraction with these micellar systems represents a sustainable alternative methodology for industrial purposes due to its low cost, biodegradability, non-toxicity and easy scaling up.

Vortex assisted-supramolecular solvent based microextraction coupled with spectrophotometric determination of triclosan in environmental water samples

A simple, fast and environmental friendly vortex assisted-supramolecular solvent based microextraction (VA-SSME) method was developed for the preconcetration of triclosan in wastewater prior to UV spectrophotometric determination. To achieve maximum sensitivity and accuracy for the target analyte, the experimental parameters affecting the VA-SSME procedure were optimized using response surface methodology (RSM). Under optimised conditions, the correlation coefficient (R2) and recoveries were 0.9994 and 100.31-118.5%, respectively. The intra-day (repeatability) and inter-day (reproducibility) precisions expressed in terms of relative standard deviation (RSD) were 2-4% and 5.2%, respectively. The preconcentration factor and limits of detection (LOD) and quantification (LOQ) were found to be 90, 0.28 μg L−1 and 0.92 μg L−1, respectively. The developed VA-SSME/UV method was applied for the determination of triclosan in real samples collected over a period of three months. The analytical results obtained showed that triclosan was frequently detected in influent wastewater samples but was not detected in effluent samples.

Non-ionic detergent Triton X-114 Based vortex- synchronized matrix solid-phase dispersion method for the simultaneous determination of six compounds with various polarities from Forsythiae Fructus by ultra high-performance liquid chromatography

A simple nonionic detergent - based vortex- synchronized matrix solid-phase dispersion (ND-VSMSPD) method was developed to extract bioactive compounds in Forsythiae Fructus coupled with ultra high-performance liquid chromatography (UHPLC). Nonionic detergent Triton 114 was firstly used as a green elution reagent in vortex- synchronized MSPD procedure. The optimum parameters were investigated to attain the best results, including Florisil as sorbent, 2mL 10% (v/v) nonionic detergent Triton X-114 as the elution reagent, 1:1 of sample/sorbent ratio, grinding for 3min, and whirling for 2min. The recoveries of the six compounds in Forsythiae Fructus were in the range of 95-104% (RSD <4.6%) and the method displayed a good linearity within the range of 0.08-20μgmL^-1 for caffeic acid, 0.6-150μgmL^-1 for forsythoside A, 0.4-100μgmL^-1 phillyrin, 0.2-50μgmL^-1 for quercetin, isorhamnetin and arctigenin (r≥0.999). It was proved that the extraction yields of almost all compounds attained by the established vortex- synchronized MSPD, which required lower sample, reagent and time, were higher than the normal MSPD and the traditional ultrasonic-assisted extraction. Consequently, this developed vortex- synchronized MSPD coupled with simple UHPLC method could be efficiently applies to extract and analyze the target compounds in real Forsythiae Fructus samples.

Heat-induced coacervation for purification of Lycium barbarum polysaccharide based on amphiphilic polymer–protein complex formation

Heat-induced coacervation of triblock copolymer solution was described, and its application in the purification of Lycium barbarum polysaccharide (LBP) was investigated. The formation of coacervate micelles–protein complex combined with the incompatibility between coacervate micelles and polysaccharide made it an ideal system for the separation of protein and LBP. This separation process was governed by a series of parameters including polymer concentration, amount of crude LBP solution, and pH. In the primary coacervation extraction process, LBP was preferentially distributed to dilute phase with a high recovery ratio of 82%, whereas 87% of protein was partitioned to the coacervate phase. The coacervate micelles–protein interaction and the interphase potential was regulated by temperature and electrolytes, respectively, which contributed to the recovery and recycling of the polymer. After phase separation, LBP was precipitated with the addition of ethanol. The FTIR spectrum was used to identify LBP. In addition, the antioxidant activity of LBP was measured.