Combination of cloud point extraction and flame atomic absorption spectrometry for preconcentration and determination of trace iron in environmental and biological samples

In the presented work, the conditions for cloud point extraction of iron from aqueous solutions using 7-iodo-8-hydroxyquinolin-5-sulphonic acid (Ferron) was investigated and optimized. The procedure is based on the separation of its ferron complex into the micellar media by adding the surfactant Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1.0 M HNO3 in methanol. Iron was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities, incubation time, temperature, viscosity, sample volume, and interfering ions were investigated. The effects of the matrix ions were also examined. The detection limits for three times the standard deviations of the blank for iron was 0.4 ng m L-1, enrichment factor of 19.6 and preconcentration factor of 30 could be achieved. The validity of cloud point extraction was checked by employing real samples including soil, blood, spinach, milk, meat, liver and orange juice samples using the standard addition method, which gave satisfactory results.In the presented work, the conditions for cloud point extraction of iron from aqueous solutions using 7-iodo-8-hydroxyquinolin-5-sulphonic acid (Ferron) was investigated and optimized. The procedure is based on the separation of its ferron complex into the micellar media by adding the surfactant Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1.0 M HNO₃ in methanol. Iron was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities, incubation time, temperature, viscosity, sample volume, and interfering ions were investigated. The effects of the matrix ions were also examined. The detection limits for three times the standard deviations of the blank for iron was 0.4 ng m L⁻¹, enrichment factor of 19.6 and preconcentration factor of 30 could be achieved. The validity of cloud point extraction was checked by employing real samples including soil, blood, spinach, milk, meat, liver and orange juice samples using the standard addition method, which gave satisfactory results.      

Separation of phenols from aqueous micellar solutions by cloud point extraction

The cloud point technique was used to recover phenol, 4-methylphenol, and 4-nitrophenol from aqueous solutions using oxyethylated methyl dodecanoates as nonionic surfactants. Oxyethylated methyl dodecanoates are convenient nonionic surfactants for such separations. Their cloud points can be easily modified by a change in surfactant hydrophilicity or by the addition of a second nonionic surfactant and/or an electrolyte. The use of the hydrophile lipophile balance is preferred to model the cloud point of oxyethylated methyl dodecanoates and their mixtures with other surfactants. The composition of the surfactant-rich phase depends on electrolyte type and the overheating. The phase can contain only 5-15% of water. Recovery of phenols changes in the order 4-nitrophenol >4-methylphenol > phenol and is increased in the presence of sodium chloride. The presence of salting-out electrolytes is preferred both to decrease the cloud point and to increase the efficiency of extraction.     

Determination of photoinitiator 4‐methylbenzophenone in milk by cloud point extraction

An efficient and easy sample pretreatment methodology was proposed for the detection of photoinitiator 4‐methylbenzophenone from milk before high‐performance liquid chromatography. Appropriate conditions for demulsification were studied. The parameters affecting cloud point extraction, such as concentration of Tween‐20, electrolyte salt, equilibration temperature, and time, have been investigated. When the spiked level was 200–1000 μg/kg, the average addition standard recovery was 99.14–105.98% with the optimum cloud point extraction conditions (concentration of Tween‐20, 138 g/L; mass of anhydrous sodium sulfate, 0.75 g; equilibration temperature, 65°C; equilibration time, 30 min). To decrease the detection limits, further work about the organic solvent, shaking time, and ultrasonic parameters was carried. When the spiked level was 10–100 μg/kg, the average addition standard recovery was 70.40–106.91% with the optimum cloud point extraction and enrichment conditions (optimum cloud point extraction conditions; volume of cyclohexane, 30 mL; shaking time, 20 min; time of ultrasonic, 20 min; temperature of ultrasonic bath, 45°C).     

One-Step Extraction of Olive Phenols from Aqueous Solution Using β-Cyclodextrin in the Solid State,a Simple Eco-Friendly Method Providing Photochemical Stability to the Extracts

The extraction of phenolic compounds from olive mill wastes is important, not only to avoid environmental damages, but also because of the intrinsic value of those biophenols, well-known for their high antioxidant potential and health benefits. This study focuses on tyrosol (Tyr) and hydroxytyrosol (HT), two of the main phenolic compounds found in olive mill wastes. A new, simple, and eco-friendly extraction process for the removal of phenolic compounds from aqueous solutions using native β-cyclodextrin (β-CD) in the solid state has been developed. Several β-CD/biophenol molar ratios and biophenol concentrations were investigated, in order to maintain β-CD mostly in the solid state while optimizing the extraction yield and the loading capacity of the sorbent. The extraction efficiencies of Tyr and HT were up to 61%, with a total solid recovery higher than 90% using an initial concentration of 100 mM biophenol and 10 molar equivalents of β-CD. The photochemical stability of the complexes thus obtained was estimated from ∆E*ab curve vs. illumination time. The results obtained showed that the phenols encapsulated into solid β-CD are protected against photodegradation. The powder obtained could be directly developed as a safe-grade food supplement. This simple eco-friendly process could be used for extracting valuable biophenols from olive mill wastewater.     

Cloud Point Studies of Tween and Glycol in the Presence of Salts

This article deals with the cloud point studies of ethoxylated sorbitan ester, Tween in the presence of glycols, and salts. Cloud point temperature of Tween 20 (5 mol dm^?3) and Tween 80 (1 mol dm^?3) has been determined in the presence of various salts in addition to glycols. The glycols chosen for these studies were triethylene glycol (TEG), and ethylene glycol mono butylether (EGMBE). At concentration below 0.02 M these salts have no significant effect on cloud point temperature in all cases. The cloud point temperature of Tween+TEG and Tween+EGMBE found to decrease in the presence of sodium chloride (NaCl) and potassium chloride (KCl). The cloud point temperature of Tween 20 + TEG and Tween 20 + EGMBE found to increase in the presence of urea and nicotinamide. The change in cloud point was found to be more in case of nicotinamide as compare to urea. The influence of an additive on the cloud point depends on how it affects the intermicellar interactions. An effort has been made to understand the interaction between solvent and additives leading to a change in solubility of Tween.     

Ligandless cloud point extraction of Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II) ions in environmental samples with Tween 80 and flame atomic absorption spectrometric determination

A cloud point extraction (CPE) procedure has been developed for the determination trace amounts of Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II) ions by using flame atomic absorption spectrometry. The proposed cloud point extraction method was based on cloud point extraction of analyte metal ions without ligand using Tween 80 as surfactant. The surfactant-rich phase was dissolved with 1.0 mL 1.0 mol L⁻¹ HNO₃ in methanol to decrease the viscosity. The analytical parameters were investigated such as pH, surfactant concentration, incubation temperature, and sample volume, etc. Accuracy of method was checked analysis by reference material and spiked samples. Developed method was applied to several matrices such as water, food and pharmaceutical samples. The detection limits of proposed method were calculated 2.8, 7.2, 0.4, 1.1, 0.8 and 1.7 μg L⁻¹ for Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II), respectively.     

Rapid and quantitative extraction method for the determination of chlorophylls and carotenoids in olive oil by high-performance liquid chromatography

Colour is an organoleptic characteristic of virgin olive oil and an important attribute that affects the consumer perception of quality. Chlorophylls and carotenoids are the main pigments responsible for the colour of virgin olive oil. A simple analytical method for the quantitative determination of chlorophylls and carotenoids in virgin olive oils has been developed. The pigments were isolated from small samples of oil (1.0 g) by solid-phase extraction using diol-phase cartridges (diol-SPE), and the extract was analysed by reverse-phase HPLC with diode-array UV detection. Chromatographic peak resolution, reproducibility (coefficient of variation (C.V.) <4.5%) and recovery (>98.4%) for each component were satisfactory. A comparative study of the proposed method was performed versus classical liquid-liquid extraction (LLE) with N,N′-dimethylformamide and solid-phase extraction using a C18 column (C18-SPE). While 96.4% of the pigments were recovered by LLE, only 51.3% were isolated by C18-SPE in comparison to diol-SPE. Likewise, a higher alteration of pigment composition was observed when such LLE and C18-SPE procedures were used. In this sense, a higher ratio of pheophytin in comparison to that isolated by the diol-SPE procedure was achieved with both extraction procedures, indicating a greater extent of the pheophytinization reaction. Therefore, quantification of pigments from virgin olive oil by diol-SPE followed by RP-HPLC was found to be rapid, simple, required only a small amount of sample, consumed only small amounts of organic solvents, and provided high recoveries, accuracy and precision.     

浊点萃取-火焰原子吸收光谱法测定食品和饮料中的痕量铜

研究了基于非离子表面活性剂TritonX-114和螯合剂二乙基氨基二硫代甲酸钠(DDTC)的浊点萃取-火焰原子吸收光谱法测定痕量铜的分析方法.考察了影响浊点萃取效率的参数,包括pH值、DDTC浓度、TritonX-114用量、平衡温度及时间等.在优化条件下,本法的检出限(3σ)为1.55μg/L,相对标准偏差RSD为3.4%(n=7,c=100μg/L),线性范围为0～250μg/L.将该法应用于茶叶标准样品(GBW07605)、奶粉和矿泉水等样品中痕量铜的测定,其回收率在96.7%～113.5%之间.     

浊点萃取-石墨炉原子吸收光谱法测定膨化食品中铅

以8-羟基喹啉(8-HQ)为螯合剂,在pH 9缓冲溶液中,痕量铅(Ⅱ)与8-HQ生成螯合物,加入表面活性剂Triton X-100用浊点萃取分离富集样品中痕量铅。分取部分表面活性剂相用0.1mol·L-1硝酸溶液定容至2mL,所得溶液直接用石墨炉原子吸收光谱法进行测定。对影响浊点萃取的因素和共存离子的干扰等进行了试验并予以优化。方法的检出限(3σ)为0.85pg。应用所提出的方法测定了膨化食品样品中铅的含量,在5种样品中用标准加入法进行方法的回收试验,测得回收率在91.7%～101.7%之间。     

Comparative effects of different cosurfactants on sterile prednisolone acetate ocular submicron emulsions stability and release

Pluronic F68 is a nonionic, thermogelling block copolymer showing a high dehydration resistance during autoclaving due to its high cloud point (>100 °C). Tween 80 (with cloud point of 72.5 °C), is a polyoxyethylene-based cosurfactant, susceptible to temperature because of a decrease in its solubility by temperature increase. This study was done to explore whether or not, when compared with Tween 80, Pluronic F68 could be used blindly as a suitable cosurfactant for the preparation of terminally sterilized ocular submicron emulsions containing a lipid soluble drug, prednisolone acetate (PA). Various oils of variable viscosities were also tried. The results proved that no prediction can be made based on previously known physico-chemical properties alone and that emulsion stability depends on the contribution of the various emulsion components including: oil, surfactant and cosurfactant, in addition to the drug properties.     

Biogas Potential of the Side Streams Obtained in a Novel Phenolic Extraction System from Olive Mill Solid Waste

The olive oil production is an important industrial sector in many Mediterranean areas, but it is currently struggled by the necessity of a proper valorisation of the olive mill solid waste or alperujo. The alperujo is the main by-product generated during the two-phase olive oil extraction, accounting for up to 80% of the initial olive mass. The alperujo is a source of valuable compounds, such as the pomace olive oil or highly interesting phenolic compounds. In the present research, a novel biorefinery approach has been used for phenolic compounds recovery. However, the extraction of these valuables compounds generates different exhausted phases with high organic matter content that are required to be managed. This study consists of the evaluation of the anaerobic biodegradability of the different fractions obtained in a novel biorefinery approach for the integral valorisation of alperujo. The results show that the different phases obtained during the biorefinery of the alperujo can be effectively subjected to anaerobic digestion and no inhibition processes were detected. The highest methane yield coefficients were obtained for the phases obtained after a two-months storages, i.e., suspended solids and liquid phase free of suspended solids, which generated 366 ± 7 mL CH₄/g VS and 358 ± 6 mL CH₄/g VS, respectively. The phenol extraction process reduced the methane yield coefficient around 25% due to the retention of biodegradable compounds during the extraction process. Regardless of this drop, the anaerobic digestion is a suitable technology for the stabilization of the different generated residual phases, whereas the high market price of the extracted phenols can largely compensate the slight decrease in the methane generation.     

An environmentally friendly method for the extraction and determination of priority phenols in soils using microwave-assisted micellar extraction

A non-ionic surfactant, polyoxyethylene 10 lauryl ether (POLE), was used for the microwave-assisted extraction (MAE) of priority phenolic compounds from soil samples. A central composite design was applied to optimize the extraction parameters, namely, time and power. Under the optimized conditions, the method was applied to different soil samples in order to analyze the influence of soil characteristics on the phenol extraction. Results demonstrated that most of these compounds can be recovered from the soils investigated in good yields (higher than 80%). The standard deviation is lower than 9% (n = 6) for most analytes. Validation of the method by analyzing a reference soil sample containing eight phenols and a comparison with Soxhlet extraction are also reported.     

浊点萃取-火焰原子吸收光谱法测定样品中的痕量钴

研究了基于表面活性剂Triton X-114和络合剂吡咯烷二硫代氨基甲酸铵（APDC）浊点萃取钴的样品前处理方法.优化了浊点萃取条件参数,包括pH值、Triton X-114用量、APDC浓度、平衡温度及时间等,建立了浊点萃取-火焰原子吸收光谱法测定痕量钴的方法.该法的检测限（3σ）为2.6μg/L,相对标准偏差RSD为6.2%（n=7,c=200μg/L）.该法成功地应用于海带、维生素B12注射液等样品中钴的测定.     

Electrochemical treatment of olive oil mill wastewater

The possibility of oxidizing at a PbO2 anode the phenols and polyphenols, present in the olive oil mill wastewater, has been studied as a pretreatment for the submission of such wastewater to the traditional biological treatments. The results obtained operating at current densities ranging 500 to 2000 A/m2 show that it is possible to reduce the concentration of the phenolic components, which interfere with the biological treatments, down to low values without decreasing too much the total organic content of the wastewater.     

Cloud point curve of nonionic surfactant related to the structures of mesoporous materials

We have investigated the phase behavior of a fluorinated surfactant R(7)(F)(EO)(7) in water. The cloud point is situated at 19 degrees C for 2 wt% of surfactant. Using this surfactant, mesoporous materials have been synthesized with micellar solution prepared either at 10 degrees C (below the cloud point) or at 40 degrees C (above the cloud point). Results show that whatever the syntheses conditions, only wormhole-like structure is recovered. The effect of perfluorodecalin addition on the fluorinated surfactant/water system was also investigated. Swollen micelles, microemulsion, and lamellar (L(alpha)) liquid crystals were identified. When perfluorodecalin is added, the cloud point is shifted toward higher temperature. As regards the mesoporous syntheses, perfluorodecalin plays a dual role. First, incorporation of perfluorodecalin leads to the formation of well ordered materials. Secondly, the pore size enlargement occurs when perfluorodecalin is added. Our results evidence that the ratio between the volume of the hydrophilic headgroup (V(H)) and the hydrophobic part (V(L)) of the surfactant is not an efficiency parameter to explain the ordering improvement of mesoporous materials and that we should rather consider the existence of the cloud point curve, which disturbs the cooperative templating mechanism (CTM).     

Cloud point preconcentration prior to capillary zone electrophoresis: simultaneous determination of platinum and palladium at trace levels

The incorporation of a cloud point extraction (CPE) step prior to capillary electrophoresis (CE) for simultaneously determining platinum and palladium at sub-microg/L levels is presented and evaluated. The analytes were extracted as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes, at pH 2.0, mediated by micelles of the nonionic surfactant polyethyleneglycolmono-p-nonylphenyl ether (PONPE 7.5). The separation-determination step was developed from 150 microL of the extracted surfactant-rich phase diluted with 50 microL of acetonitrile (ACN). An exhaustive study of the variables affecting the cloud point extraction with PONPE 7.5 and the CZE step was done. The type and composition of the background electrolytes (BGEs) were investigated with respect to separation selectivity, reproducibility, and stability. A BGE of 50 mM monobasic sodium phosphate containing 30% ACN, pH 4.53 was found to be optimal for the separation of metal chelates. Detection was performed at 576 nm. An enrichment factor of 250 was obtained for the preconcentration of 50 mL of sample solution. The detection limits for the preconcentration of 50 mL of sample were 0.04 microg/L for Pt and 0.08 microg/L for Pd. As an analytical demonstration, ultratrace concentrations of platinum and palladium were conveniently quantitated in spiked water and urine samples.     

Determination of carotenoids in tomato juice by liquid chromatography

A high-performance liquid chromatography method was developed to determine the various carotenoids in tomato juice. A C30 column and a mobile phase of acetonitrile-1-butanol (7:3, v/v) (A) and methylene chloride (B) with the following gradient elution were used: 99% A and 1% B intitally, increased to 4% B in 20 min, 10% B in 50 min and returned to 1% B in 55 min. Sixteen carotenoids, including all-trans-lutein, all-trans-beta-carotene, all-trans-lycopene and their 13 cis isomers were identified and resolved within 52 min with flow-rate at 2.0 ml/min and detection at 476 nm. Of the various extraction solvent systems, the best extraction efficiency of carotenoids in tomato juice was achieved by employing ethanol-hexane (4:3, v/v). Lycopene was found to be present in largest amount in tomato juice, followed by beta-carotene and lutein.     

修饰聚合物液-固亲和萃取体系分离钪与钕及机理探讨

研究了加修饰聚合物(PEG-IDA)的吐温(Tween)80-盐水液-固体系亲和萃取稀土(RE)离子时体系酸度对萃取率的影响,并控制萃取酸度实现了Sc与Nd的定量分离,平均回收率Sc：99．72％;Nd：100.88％。测定新络合物的稳定常数,两者相差4倍,是分离的原因。对该体系分离Sc与Nd的机理进行探讨表明,RE-PEG-IDA络合物主要是与Tween 80形成了氢键。     

浊点萃取-分光光度法测定自来水及酒类样品中的痕量铁

利用非离子表面活性剂TritonX-100在温度高于其浊点时形成相分离行为,建立了浊点萃取-分光光度法测定痕量铁的新方法,探讨优化了以KSCN为显色剂,TritonX-100浊点萃取富集痕量铁的实验条件.研究发现:加入正辛醇可使TritonX-100的浊点降低约30℃,有利于萃取实验的进行;同时,加入的正辛醇与TritonX-100对痕量铁起到了协同萃取作用.在优化了的实验条件下,进行了痕量铁的分析,检出限为0.02mg·L-1,加标回收率为97.4%～101.6%,应用于自来水及酒类样品中痕量铁的测定,结果满意.     

LC/MS method using cloud point extraction for the determination of permitted and illegal food colors in liquid, semiliquid, and solid food matrixes: single-laboratory validation

A cloud point extraction method is reported using LC/MS for the determination of regulated water-soluble food colors (Allura Red, Sunset Yellow, erythrosine, and tartrazine) and banned fat-soluble synthetic azo dyes (Sudan I, II, III, and IV; Red B; 7B; Black B; Red G; Metanil Yellow; and Rhodamine B). The extraction of all 14 colors was carried out with cloud point extraction using the nonionic surfactant Triton X 114. Optimized conditions for cloud point extraction were 3% Triton X 114 (w/v), 0.1 M ammonium acetate, and heating at 50 degrees C for 30 min. This approach proved effective in giving quantitative recoveries from a diverse range of food matrixes, and optimized LC gave baseline chromatographic separation for all colors including Sudan IV and Red B. Single-laboratory validation was performed with spiking into liquid matrixes (wine and homemade wine), semiliquid matrixes (sauce and homemade paprika paste), and solid matrixes (spice and homemade chili powder) using the respective blank matrixes for matrix-matched calibration. The LOQ values for water-soluble colors were in the range of 15-150 mg/kg, and for the fat-soluble colors, 0.1-1.5 mg/kg. The mean recovery values were in the range of 69.6-116.0% (except Allura Red and Sunset Yellow in wine, for which recoveries were lower). The mean RSDs for colors were in the range of 4.0-14.8%. A small survey was conducted of samples of confectionery products, dried fruits, wines, bitter sodas, juices, sauces, pastes, and spices, which demonstrated the applicability of the method to a diverse selection of real food samples. Allura Red was detected in strawberry jelly and Sunset Yellow in artificial saffron.