A novel cloud-point extraction process for preconcentrating selected polycyclic aromatic hydrocarbons in aqueous solution

Electrochemical determination of thiabendazole pesticide extracted and preconcentrated from tomato samples by cloud point extraction

A procedure for electroanalytical determination of the fungicide TBZ extracted and preconcentrated from tomatoes by the cloud-point extraction (CPE) technique was developed and validated in this work. The analytical technique used for this determination was HPLC coupled to an electrochemical detector (HPLC/EC), with a BDD electrode. The main variables of the CPE process were evaluated using a 24 full factorial design. The optimal condition of CPE was achieved by using Tergitol (19% v/v), NaCl (0.83 g), ultrasonic stirring time of 15 min and a temperature of 36 °C. Under these conditions, the preconcentration factor obtained was 5.7. The limits of detection (LOD) and quantification (LOQ) were 2.7 × 10-8 mol L-1 (or 5.4 μg L-1) and 5.5 × 10-8 mol L-1 (or 11 μg L-1), respectively. The average recovery values varied from 80.7% to 115.1% and the precision (average of 3 days) was less than 15%, indicating the good accuracy and precision of the method developed here. Upon applying the method to examine commercial tomatoes, TBZ was detected in one of the three analyzed samples.

Cloud point extraction coupled with back extraction: a green methodology in analytical chemistry

Recently, cloud point extraction (CPE) coupled with back extraction (BE) has been suggested as a promising alternative to liquid-liquid extraction. In CPE, non-ionic surfactants in aqueous solutions form micelles and the solution becomes turbid when heated to the cloud point temperature. Microwave- or ultrasonic-assisted BE can be performed after CPE and before injection of the sample for instrumental analysis by ultraviolet-visible spectroscopy, high-performance liquid chromatography, gas chromatography, gas chromatography-mass spectrometry, or liquid chromatography-mass spectrometry. This article reviews selected published scientific research on the application of CPE-BE to the determination of alkaloids, drugs and organophosphorus compounds from several complex matrices. This method could be scaled-up for use in forensic science.

Analysis of sulfonamides in soil, sediment, and sludge based on dynamic microwave-assisted micellar extraction

A green and high-throughput analytical method was described for the simultaneous determination of ten sulfonamides (SAs) from soil, sediment, and sludge in northeast China. None of potentially hazardous organic solvents was used in the whole sample preparation procedure, and the total preparation time of 15 samples was about 18 min. The limits of detection for the SAs were in the range of 0.42-0.68 ng g(-1). The intra-day and inter-day precisions, expressed by the relative standard deviation, were below 7 %. Under the optimum conditions, the recoveries of ten SAs were between 69.7 and 102.7 %. The proposed method was successfully applied to analyze the SAs residues in agricultural soils, river sediments, and sewage sludge. SAs were found at the levels of 1.40-2.31 ng g(-1) and 3.77-29.29 ng g(-1) in the sediments and sludge, respectively. The aging effect of spiked soil samples on the SAs recoveries was examined, and the results demonstrate that eight SAs could persist in five soils for 3 months. Compared with the traditional method, the proposed method could reduce the consumption of the organic solvent, shorten the sample preparation time, and increase the sample throughput.

A new approach to the determination of folic acid at trace levels: using a Fe(iii)-folic acid complex to amplify analytical signal

A fast, efficient, and cost-effective, and environmental friendly analytical methodology was developed for preconcentration and determination of trace folic acid in food samples prior to HPLC-DAD.

Extraction and determination of polycyclic aromatic hydrocarbons in water samples using stir bar sorptive extraction (SBSE) combined with dispersive liquid–liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) followed by HPLC-UV

The proposed method offers advantages, such as low consumption of organic solvents, high enrichment factors and good linearity, over the investigated concentration range.

Cloud Point Extraction of Polycyclic Aromatic Hydrocarbons in Aqueous Solution with Nonionic Surfactants

A cloud point extraction (CPE) process using the two nonionic surfactants, Tergitol 15-S-9 and Tergitol 15-S-7, mixtures of secondary ethoxylated alcohols, to extract selected polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions at 25°C was investigated. Cloud point temperatures (CPTs) of selected nonionic surfactants were studied against the effect of added electrolytes on their cloud points. Sodium iodide could increase the cloud points of selected nonionic surfactants, i.e., the salt-in effect, whereas sodium chloride, sodium phosphate and sodium sulfate could decrease the cloud point, i.e., the salt-out effect. Cloud point temperatures (CPTs) of these micellar solutions were regulated and reduced enough with addition of sodium phosphate and sodium sulfate, so that the cloud point extraction (CPE) process could be facilitated at 25°C. It was found that a higher preconcentration factor could be achieved in the micellar solution having a lower surfactant concentration. The average preconcentration factor was also discussed as a function of surfactant concentration used in the CPE process.

Optimization of a greener method for removal phenol species by cloud point extraction and spectrophotometry

A greener method based on cloud point extraction was developed for removing phenol species including 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 4-nitrophenol (4-NP) in water samples by using the UV-Vis spectrophotometric method. The non-ionic surfactant DC193C was chosen as an extraction solvent due to its low water content in a surfactant rich phase and it is well-known as an environmentally-friendly solvent. The parameters affecting the extraction efficiency such as pH, temperature and incubation time, concentration of surfactant and salt, amount of surfactant and water content were evaluated and optimized. The proposed method was successfully applied for removing phenol species in real water samples.

Cloud point extraction of parabens using non-ionic surfactant with cylodextrin functionalized ionic liquid as a modifier

A cloud point extraction (CPE) process using non-ionic surfactant (DC193C) to extract selected paraben compounds from water samples was investigated using reversed phase high performance liquid chromatography (RP-HPLC). The CPE process with the presence of β-cyclodextrin (βCD) functionalized ionic liquid as a modifier (CPE-DC193C-βCD-IL) is a new extraction technique that has been applied on the optimization of parameters, i.e., pH, βCD-IL concentration and phase volume ratio. This CPE-DC193C-βCD-IL method is facilitated at 30 °C, showing great losses of water content in the surfactant-rich phase, resulting in a high pre-concentration factor and high distribution coefficient. The developed method CPE-DC193C-βCD-IL did show enhanced properties compared to the CPE method without the modifier (CPE-DC193C). The developed method of CPE-DC193C-βCD-IL gives an excellent performance on the detection of parabens from water samples with the limit of detection falling in the range of 0.013-0.038 µg mL-1. Finally, the inclusion complex formation, hydrogen bonding, and π-π interaction between the βCD-IL, benzyl paraben (ArP), and DC 193C were proven using 1H NMR and 2D NOESY spectroscopy.

Highly selective detection of polycyclic aromatic hydrocarbons using multifunctional magnetic-luminescent molecularly imprinted polymers

A facile method is presented for the selective luminescence detection of trace polycyclic aromatic hydrocarbons (PAHs) based on a combination of the specific recognition of molecularly imprinted polymers (MIPs) and magnetic separation (MS). Multifunctional magnetic-luminescent MIP nanocomposites were fabricated via a one-pot emulsion strategy using polystyrene-co-methacrylic acid copolymer, hydrophobic Fe3O4 nanoparticles and luminescent LaVO4:Eu(3+) nanoparticles as building blocks with a phenanthrene template. The resulting nanocomposites can be employed in a simple method for the luminescence detection of phenanthrene. Furthermore, magnetic separation of the nanocomposites from the target mixture prior to luminescence detection of phenanthrene affords significantly enhanced selectivity and sensitivity, with a 3σ limit of detection (LOD) as low as 3.64 ng/mL. Milk samples spiked with phenanthrene (5.0 μg/mL) were assayed via this method and recoveries ranging from 97.11 to 101.9% were obtained, showing that our strategy is potentially applicable for the preconcentration, recovering, and monitoring of trace PAHs in complex mixtures.

Solubilization of phenanthrene above cloud point of Brij 30: a new application in biodegradation

In the present study a new application of solubilization of phenanthrene above cloud point of Brij 30 in biodegradation was developed. It was shown that a temporal solubilization of phenanthrene above cloud point of Brij 30 (5wt%) permitted to obtain a stable increase of the solubility of phenanthrene even when the temperature was decreased to culture conditions of used microorganism Pseudomonas putida (28°C). A higher initial concentration of soluble phenanthrene was obtained after the cloud point treatment: 200 against 120μM without treatment. All soluble phenanthrene was metabolized and a higher final concentration of its major metabolite - 1-hydroxy-2-naphthoic acid - (160 against 85μM) was measured in the culture medium in the case of a preliminary cloud point treatment. Therefore a temporary solubilization at cloud point might have a perspective application in the enhancement of biodegradation of polycyclic aromatic hydrocarbons.

Determination of triazole fungicides in environmental water samples by high performance liquid chromatography with cloud point extraction using polyethylene glycol 600 monooleate

A preconcentration technique known as cloud point extraction was developed for the determination of trace levels of triazole fungicides tricyclazole, triadimefon, tebuconazole and diniconazole in environmental waters. The triazole fungicides were extracted and preconcentrated using polyethylene glycol 600 monooleate (PEG600MO) as a low toxic and environmentally benign nonionic surfactant, and determined by high performance liquid chromatography/ultraviolet detection (HPLC-UV). The extraction conditions were optimized for the four triazole fungicides as follows: 2.0 wt% PEG600MO, 2.5 wt% Na(2)SO(4), equilibration at 45°C for 10 min, and centrifugation at 2000 rpm (533 × g) for 5 min. The triazole fungicides were well separated on a reversed-phase kromasil ODS C(18) column (250 mm × 4.6 mm, 5 μm) with gradient elution at ambient temperature and detected at 225 nm. The calibration range was 0.05-20 μg L(-1) for tricyclazole and 0.5-20 μg L(-1) for the other three classes of analytes with the correlation coefficients over 0.9992. Preconcentration factors were higher than 60-fold for the four selected fungicides. The limits of detection were 6.8-34.5 ng L(-1) (S/N=3) and the recoveries were 82.0-96.0% with the relative standard deviations of 2.8-7.8%.

A nonaqueous lyotropic liquid crystal fabricated by a polyoxyethylene amphiphile in protic ionic liquid

The aggregation behaviors of oleyl polyoxyethylene (10) ether, Brij 97, in room temperature ionic liquids, ethylammonium nitrate (EAN), pyrrolidinium nitrate ([Pyrr][NO(3)]), ethylammonium butyrate (EAB), 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF(6)]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]), have been investigated. Only in the Brij 97/EAN binary system is the hexagonal liquid crystalline phase formed, and its ordering is found to decrease with increasing temperature. The lattice spacing values measured from the small-angle X-ray scattering (SAXS) shrink with reduction of ionic liquid content at room temperature. The general rules for aggregate formation in these ionic liquids are discussed and compared with that in water. A degraded ability to produce the ordered self-assembly of Brij 97 from H(2)O to EAN to [Bmim][PF(6)], [Bmim][BF(4)], [Pyrr][NO(3)], and EAB is found and analyzed based on the molecular packing and Gordon parameters and also hydrogen-bonding or solvophobic interactions. Steady-shear rheological measurements combined with the frequency sweep data indicate the highly viscoelastic nature of this liquid crystalline phase.

Determination of carbaryl and its metabolite 1-naphthol in water samples by fluorescence spectrophotometer after anionic surfactant micelle-mediated extraction with sodium dodecylsulfate

Anionic surfactant micelle-mediated extraction with sodium dodecylsulfate (SDS) was applied as preconcentration step prior to fluorescence spectrophotometer without further cleanup step. The obtained surfactant-rich phase was diluted to a fixed volume with water-miscible solvents. Carbaryl and its metabolite 1-naphthol were used as test compounds. The detection limits (LODs) of the method were in the microgram per liter area. Recoveries obtained from four real water samples ranged from 90.7 to 98.6%. Under the optimum experimental conditions, the method described showed a good precision, with relative standard deviations (R.S.D.) of less than 6%. According to the results, this approach reduced the viscidity of the surfactant-rich phase and made the combination of fluorescence spectrophotometer with anionic surfactant micelle-mediated extraction much easier.

Cloud point extraction coupled with HPLC-UV for the determination of phthalate esters in environmental water samples

A method based on cloud point extraction was developed to determine phthalate esters including di-ethyl-phthalate (DEP), di-(2-ethylhexyl)-phthalate (DEHP) and di-cyclohexyl-phthalate (DCP) in environmental water samples using high-performance liquid chromatography separation and ultraviolet detection (HPLC-UV). The non-ionic surfactant Triton X-114 was chosen as extraction solvent. The parameters affecting extraction efficiency, such as concentrations of Triton X-114 and Na2SO4, equilibration temperature, equilibration time and centrifugation time were evaluated and optimized. Under the optimum conditions, the method can achieve preconcentration factors of 35, 88, 111 and detection of limits of 2.0, 3.8, 1.0 ng/ml for DEP, DEHP and DCP in 10-ml water sample, respectively. The proposed method was successfully applied to the determination of trace amount of phathalate esters in effluent water of the wastewater treatment plant and the lixivium of plastic fragments.