Micelle-mediated extraction

In Situ Formation of a Relatively Transparent Ion-Associate Liquid Phase from an Aqueous Phase and Its Application to Microextraction/High-Performance Liquid Chromatography-Fluorescence Detection of Bisphenol A in Water

The design of a simple approach enabling the detection of bisphenol A (BPA) in water samples without the need for large amounts of solvents is of utmost importance. This paper reports a simple method for the separation, concentration, and quantification of BPA in water samples using high-performance liquid chromatography with fluorescence detection (HPLC-FLD) after its microextraction into an in situ formed organic ion-associate (IA) liquid phase (LP). Novel IA phase components without conjugated double bonds, such as benzene rings, were investigated. Ethylhexyloxypropylamine hydrochloride and sodium dodecyl sulfate solutions were added to the water samples to form IAs. The aqueous phase and ion-associate liquid phase (IALP) were separated by centrifugation. The aqueous phase was removed, and the liquid phase was recovered and measured using HPLC-FLD or HPLC-electrochemical detection (ECD). The concentrated phase (IALP) had a relatively low viscosity and could be injected directly into the chromatograph without dissolving it in organic solvents. The detection limits for BPA by HPLC-FLD and HPLC-ECD were 0.009 and 0.3 µg L-1, respectively.

What is the role of PEO chains in the assembly of core-corona supraparticles in aqueous dispersions?

Hypothesis The assembly of core-corona supraparticles in aqueous dispersions has been regularly assisted by auxiliary monomers/oligomers which modify the individual particles with, e.g., surface grafting of polyethylene oxide (PEO) chains or other hydrophilic monomers. However, this modification complicates the preparation and purification procedures and increases potential upscaling efforts. Hybrid polymer-silica core-corona supracolloids could be more simply assembled if the PEO chains from surfactants, typically used by default as polymer stabilizers, concomitantly act as assembly promotors. The supracolloids assembly could therefore be more easily achieved without requiring particles functionalization or post-purification steps. Methods The self-assembly of supracolloidal particles prepared with PEO-surfactant stabilized (Triton X-405) and/or PEO-grafted polymer particles is compared to differentiate the roles of the PEO chains in the assembly of core-corona supraparticles. Using time-resolved dynamic light scattering (DLS) and cryogenic transmission electron microscopy(cryo-TEM), the effect of concentration of PEO chains (from surfactant) on the kinetics and dynamics of supracolloids assembly is investigated. Self-consistent field (SCF) lattice theory was used to numerically study the distribution of PEO chains at the interfaces present in the supracolloidal dispersions. Findings The PEO based surfactant can be used as assembly promoter of core-corona hybrid supracolloids due to its amphiphilic nature and via establishing hydrophobic interactions. The concentration of the PEO surfactant, and especially the PEO chains distribution over the different interfaces, crucially affect the supracolloids assembly. A simplified pathway for preparing hybrid supracolloidal particles with a well-controlled corona coverage over polymer cores is presented.

A rapid room-temperature cloud point extraction for spectrophotometric determination of Copper (II) with 6,7-dihydroxy-2,4-diphenylbenzopyrylium chloride

The conditions for the surfactant rich phase of Triton X-100 formation and the extraction of Copper (II) as a complex with 6,7-dihydroxy-2,4-diphenylbenzopyrylium chloride at room temperature have been optimized. It was shown that the sodium salt of p-toluic acid can be used as a chemical initiator of cloud point extraction. The optimal conditions for room temperature cloud point extraction were found to be: pH 5.0; 1 v/v.% Triton X-100; 3.75·10^-2 M sodium salt of p-toluic acid and the addition of 0.5 M H₂SO₄ solution to pH 5.0. The formation of the surfactant rich phase begins instantly. The 2-propanol was proposed as a diluent for the surfactant rich phase. The calibration graph is linear in the range of Copper (II) concentrations of 6-870 μg/L, and the limit of detection and limit of determination are 1.8 and 6 μg/L, respectively. The proposed method was successfully applied for the spectrophotometric determination of Copper (II) in water samples with a relative standard deviation not exceeding 4.5%.

Sr(ii) extraction by crown ether in HFC: entropy driven mechanism through H2PFTOUD

The solvent extraction of Sr(ii) was carried out using dicyclohexano-18-crown-6 (DCH18C6) and two HFC mixed solvents MS1 and MS2, where MS1 was composed of 30/60 (w/w)% trans-1,2-dichloroethylene/HFC-43 (HFC-43: 1,1,1,2,2,3,4,5,5,5-decafluoropentane) and MS2 was 5/95 (w/w)% heptane/HFC-43. Nitric acid and perfuruoro-3-6-9-trioxaundecane-1,11-dioic acid (H₂PFTOUD) were used to study the effect of acid on the extraction. The maximum distribution ratio of Sr(ii) (D_Sr) observed for H₂PFTOUD conditions was ∼180, and >10 times larger than aqueous nitric acid conditions. The D_Sr value was influenced by concentrations of the DCH18C6, Sr(ii), and acid, and by temperature. The composition of extracted complexes was estimated using slope analysis as an Sr(ii)–anion–DCH18C6 ratio of ∼1 : 2 : 1. From the extended X-ray absorption fine structure (EXAFS) measurements of Sr(ii) in the aqueous and organic phases, it is inferred that regardless of the acid used, DCH18C6 coordinates to the first coordination sphere of the Sr(ii) extracted complexes and Sr(ii) is hydrated (complexation with H₂PFTOUD cannot be distinguished) in the aqueous phase. Thermodynamic data were significantly changed by choice of acid, i.e., both enthalpy and entropy values were negative for nitric acid conditions, on the other hand, entropy values were large and positive for H₂PFTOUD conditions. These results have demonstrated that the combination of HFC solvent and crown ether is applicable for metal extraction.

The solvent extraction of Sr(ii) was carried out using DCH18C6, and two HFC mixed solvents composed of organic solvents and HFC-43 (HFC-43: 1,1,1,2,2,3,4,5,5,5-decafluoropentane), and two acids (nitric acid and H₂PFTOUD).

Micelles of Oxyethylated Isononylphenols in Aqueous Solutions and Hydrophilic-Lipophilic Balance

We have measured the self-diffusion coefficients and calculated the effective hydrodynamic radii of micelles of ethoxylated isononylphenols in aqueous solutions in the presence of sodium chloride, as well as in their binary mutual mixtures, when approaching cloudy conditions. These cloudy conditions were created by an increase in temperature, a change in the concentration of an electrolyte in the solution, or a mutual ratio of neonols in their binary mixtures. The results are discussed within the concept of the hydrophilic-lipophilic balance.

Pre-Concentration Based on Cloud Point Extraction for Ultra-Trace Monitoring of Lead (II) Using Flame Atomic Absorption Spectrometry

The cloud point extraction (CPE) method was successfully used for the isolation and pre-concentration of ultra-low concentration of Pb prior to its determination by flame atomic absorption spectrometry (FAAS). Lead(II) reacts with methyl 4,20-diisobutyl-2,5,8,16,19,22- hexaoxo-7,17-dipropyl-3,6,9,15,18,21-hexaaza-1(2,6)-pyridinacyclo-docosaphane-10-carboxylate (DLNL) as chelating agent in the presence of octylphenoxypolyethoxyethanol (Triton X-114) as a nonionic surfactant giving a surfactant-rich phase chelate which could be used for CPE. Factors affecting the CPE such as solution pH, concentrations of the chelating ligand and surfactant, temperature of equilibration, and time were optimized. The efficacy features of the proposed protocol such as linear range, lower limit of detection, pre-concentration, and progress factors were evaluated. The method revealed a wide linear range in the range of 7–250 ng/mL of Pb2+ with a limit of detection of 5 ng/mL using FAAS. Validation of the presented protocol revealed good performance characteristics including high between-batch repeatability, high precision, wide linear range, low limit of detection, and acceptable accuracy. The presented procedure was successfully introduced for the separation and quantification of lead (II) in wastewater samples with acceptable results.

Green analytical chemistry – the use of surfactants as a replacement of organic solvents in spectroscopy

This chapter gives an introduction to the many practical uses of surfactants in analytical chemistry in replacing organic solvents to achieve greener chemistry. Taking a holistic approach, it covers​ some background of surfactants as chemical solvents, their properties and as green chemicals, including their environmental effects. The achievements of green analytical chemistry with micellar systems are reviewed in all the major areas of analytical chemistry where these reagents have been found to be useful.

Understanding the fate and biological effects of Ag- and TiO₂-nanoparticles in the environment: The quest for advanced analytics and interdisciplinary concepts

Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Speciation of platinum in blood plasma and urine by micelle-mediated extraction and graphite furnace atomic absorption spectrometry

A highly sensitive and selective technique for the speciation of platinum by cloud point extraction prior to determination by graphite furnace atomic absorption spectrometry (GFAAS) was described. The separation of Pt(II) from Pt(IV) was performed in the presence of 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) as chelating agent and Triton X-114 as a non-ionic surfactant. The extraction of Pt(II)-HCPTS complex needs temperature higher than the cloud point temperature of Triton X-114 and pH = 7, while Pt(IV) remains in the aqueous phase. The Pt(II) in the surfactant phase was analyzed by GFAAS, and the concentration of Pt(IV) was calculated by subtraction of Pt(II) from total platinum which was directly determined by GFAAS. The effect of pH, concentration of chelating agent, surfactant, and equilibration temperature were investigated. An enrichment factor of 42 was obtained for the preconcentration of Pt(II) with 50 mL solution. Under the optimum experimental conditions, the calibration curve was linear up to 30 μgL(-1) with detection limit of 0.08 μgL(-1) and the relative standard deviation was 1.8%. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing different spiked samples (tap water, blood plasma and urine). The proposed method was applied to the speciation analysis of Pt in blood plasma and urine with satisfactory results.

Thermo-responsive Metal-chelating Surfactants: Properties and Use in Cloud Point Extraction of Uranyl Nitrate∗

The properties of new thermo-responsive functional surfactants, capable of forming a metal chelate, synthesized by grafting a diamide group (amino-acid residue) to the tip hydrophilic endgroup or in a branched position to polyoxyethylene nonionic surfactants [CiEj: CiH2i+1(OCH2CH2)jOH)], are studied. Their use in cloud point extraction of uranyl nitrate is tested. The reversible temperature-dependent behavior of classical non-ionic surfactants associated to phase separation of micellar solutions known as clouding behavior is exploited for separation based on cation specific binding to the chelating group. The functional surfactants under investigation combine surface-active properties and characteristic thermoreversible behavior with a capacity to bind uranyl cation. The influence of the complexation on the cloud points of functional surfactants is determined. The chelating surfactants are found efficient for the cloud point extraction of uranyl nitrate at low surfactant-to-uranyl ratio. These new thermoresponsive surfactants with chelating properties hold most promise for the development of new solvent free extraction processes.

Effect of sweet grass (Hierochloe odorata) on the physico-chemical properties of liver cell membranes from rats intoxicated with ethanol

Changes in the composition and physicochemical properties of liver cell membranes due to ethanol intoxication are due mainly to reactive oxygen species (ROS). The destructive action of free radicals can be neutralized by administration of antioxidants. The purpose of this study was to investigate the efficacy of sweet grass on the physicochemical and biochemical properties of the rat liver membrane altered by chronic ethanol intoxication. Qualitative and quantitative composition of phospholipids and proteins in the membrane were determined by HPLC. Ethanol increased phospholipid levels and altered the level of integral proteins as determined by decreased phenylalanine, cysteine and lysine. Ethanol significantly enhanced changes in the surface charge density of the liver cell membranes as determined by electrophoresis. Administration of sweet grass to rats intoxicated with ethanol significantly protects lipids and proteins against oxidative modifications. Therefore, sweet grass protects against some of the deleterious membrane changes associated with ethanol exposure.

Altered membrane amino acids composition in human colorectal cancer tissue

Cancer transformation is characterized by changes in cell metabolism, which can alter the structure and function of cell membrane components, including integral membrane proteins. Qualitative and quantitative estimations of integral membrane protein are necessary for studies aimed at understanding their modifications under pathological conditions. Herein, we used a high-performance liquid chromatography (HPLC)-based approach that involved selective hydrolysis of isolated tissue cell membrane proteins to peptides, resolution by chromatography and determination of the amino acid content (phenylalanine (Phe), tyrosine (Tyr), cysteine (Cys) and lysine (Lys)) in individual peptides. The results demonstrate decrease in peptide levels and their amino acids content in integral membrane proteins in human colorectal cancer tissue. Therefore, cancer transformation causes a decrease in the levels of integral membrane proteins, which may in turn lead to an increase in the levels of other charged molecules on the cell surface, such as phospholipids. It might lead to the reconstruction and functional rearrangement of the cell membrane, for example: the permeability, electric properties, fluidity etc.

Protective effect of blackcurrant on liver cell membrane of rats intoxicated with ethanol

Chronic ethanol intoxication oxidative stress participates in the development of many diseases. Nutrition and the interaction of food nutrients with ethanol metabolism may modulate alcohol toxicity. One such compound is blackcurrant, which also has antioxidant abilities. We investigated the effect of blackcurrant as an antioxidant on the composition and electrical charge of liver cell membranes in ethanol-intoxicated rats. Qualitative and quantitative phospholipid composition and the presence of integral membrane proteins were determined by high-performance liquid chromatography. Electrophoresis was used to determine the surface charge density of the rat liver cell membranes. Ethanol intoxication is characterized by changes in cell metabolism that alter the structure and function of cell membrane components. Ethanol increased phospholipid levels and altered the level of integral proteins as determined by decreased phenylalanine, cysteine, and lysine. Ethanol significantly enhanced changes in the surface charge density of the liver cell membranes. Administration of blackcurrant to rats intoxicated with ethanol significantly protected lipids and proteins against oxidative modifications. It is possible that the beneficial effect of blackcurrant is connected with its abilities to scavenge free radicals and to chelate metal ions.