Application of cloud-point extraction-reversed-phase high-performance liquid chromatography. A preliminary study of the extraction and quantification of vitamins A and E in human serum and whole blood

Symbioses shape feeding niches and diversification across insects

For over 300 million years, insects have relied on symbiotic microbes for nutrition and defence. However, it is unclear whether specific ecological conditions have repeatedly favoured the evolution of symbioses, and how this has influenced insect diversification. Here, using data on 1,850 microbe-insect symbioses across 402 insect families, we found that symbionts have allowed insects to specialize on a range of nutrient-imbalanced diets, including phloem, blood and wood. Across diets, the only limiting nutrient consistently associated with the evolution of obligate symbiosis was B vitamins. The shift to new diets, facilitated by symbionts, had mixed consequences for insect diversification. In some cases, such as herbivory, it resulted in spectacular species proliferation. In other niches, such as strict blood feeding, diversification has been severely constrained. Symbioses therefore appear to solve widespread nutrient deficiencies for insects, but the consequences for insect diversification depend on the feeding niche that is invaded.

Polycyclic aromatic hydrocarbons residues and the carcinogenic risk assessment to pregnant women in Nantong, China using QuEChERS method and HPLC-A pilot case study

A high-performance liquid chromatographic method with a modified QuEChERS extraction for the determination of polycyclic aromatic hydrocarbons (PAHs) in blood serum was developed to investigate the internal exposure level and the carcinogentic toxicity contribution rate of PAHs for pregnant women in Nantong, China. Venous blood (n = 48) was collected in the local hospital and the internal exposure level of 16 PAHs and the contribution rate of carcinogenicity to pregnant women were analyzed. Among all of the detected PAHs, the detection rate of pyrene (77.08%) was the highest, followed by naphthalene (64.58%) and benzo[a]anthracene (BaA, 45.83%). The carcinogenicity contribution rate of BaA (37.37%) was the highest, followed by fluorene (32.96%) and acenaphthylene (22.01%). The results showed that many kinds of carcinogenic PAHs can be detected in the serum of pregnant women in Nantong city, among which BaA should be paid most attention because of its high internal exposure level and carcinogenic risk. Meanwhile, the origins of general PAHs in serum samples were analyzed using the characteristic ratio analysis method. The PAH pollution level of air samples (n = 42) during the collection time of blood samples was also analyzed to compare the possible correlations between the two different results.

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.

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.

Uptake of phosphorus from surfactant solutions by wheat leaves: spreading kinetics, wetted area, and drying time

The delivery and uptake of nutrients at the surface of plant leaves is an important physicochemical phenomenon that depends on leaf surface morphology and chemistry, fertilizer formulation chemistry (including adjuvant and associated surfactants), wetting dynamics, and many other physical, chemical and biological factors. In this study, the role of spreading dynamics in determining uptake of the macronutrient phosphorus from phosphoric acid fertilizer solution in combination with three different adjuvants was measured in the absence of droplet run-off and splashing. When run-off and splashing losses were zero, spreading and drying rates had a small to negligible effect on the uptake efficiency. The results suggest that uptake may be much less sensitive to the specific choice of adjuvant and long time-scale spreading behaviour than one might intuitively expect.

Antioxidant Activity and Thermal Stability of Oleuropein and Related Phenolic Compounds of Olive Leaf Extract after Separation and Concentration by Salting-Out-Assisted Cloud Point Extraction

A fast, clean, energy-saving, non-toxic method for the stabilization of the antioxidant activity and the improvement of the thermal stability of oleuropein and related phenolic compounds separated from olive leaf extract via salting-out-assisted cloud point extraction (CPE) was developed using Tween 80. The process was based on the decrease of the solubility of polyphenols and the lowering of the cloud point temperature of Tween 80 due to the presence of elevated amounts of sulfates (salting-out) and the separation from the bulk solution with centrifugation. The optimum conditions were chosen based on polyphenols recovery (%), phase volume ratio (V_s/V_w) and concentration factor (F_c). The maximum recovery of polyphenols was in total 95.9%; V_s/V_w was 0.075 and F_c was 15 at the following conditions: pH 2.6, ambient temperature (25 °C), 4% Tween 80 (w/v), 35% Na₂SO₄ (w/v) and a settling time of 5 min. The total recovery of oleuropein, hydroxytyrosol, luteolin-7-O-glucoside, verbascoside and apigenin-7-O-glucoside, at optimum conditions, was 99.8%, 93.0%, 87.6%, 99.3% and 100.0%, respectively. Polyphenolic compounds entrapped in the surfactant-rich phase (V_s) showed higher thermal stability (activation energy (Ea) 23.8 kJ/mol) compared to non-entrapped ones (Ea 76.5 kJ/mol). The antioxidant activity of separated polyphenols remained unaffected as determined by the 1,1-diphenyl-2-picrylhydrazyl method.

Analysis of Mogroside V in Siraitia grosvenorii with micelle-mediated cloud-point extraction

INTRODUCTION

Mogroside V is the main effective ingredient of Siraitia grosvenorii used as a natural sweet food as well as a traditional Chinese medicine. The sample pre-treatment prior to chromatographic analysis requires large amounts of toxic organic solvents and is time consuming.

OBJECTIVE

To develop an effective and simple method for extracting and determining mogroside V of Siraitia grosvenorii.

METHODS

Mogroside V was extracted and preconcentrated by micelle-mediated cloud-point extraction with nonionic surfactant isotridecyl poly (ethylene glycol) ether (Genapol® X-080). The obtained solutions containing mogroside V were analysed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The chromatographic separation was performed on a C18 -column using gradient elution with acetonitrile and water at 203 nm.

RESULTS

The cloud-point extraction yield was 80.7% while the pre-concentration factor was about 10.8. The limit of detection was 0.75 µg/mL and the limit of quantification was 2 µg/mL. The relative standard deviations for intra- and interday precisions of mogroside V were less than 8.68% and 5.78%, respectively, and the recoveries were between 85.1% and 103.6%.

CONCLUSION

The HPLC-UV method based on micelle-mediated cloud-point extraction for determination mogroside V in Siraitia grosvenorii was environmentally friendly, simple and sensitive.

Evaluation of the suitability of low hazard surfactants for the separation of phenols and carotenoids from red-flesh orange juice and olive mill wastewater using cloud point extraction

Natural antioxidants derived from plant sources attract considerable scientific interest. While classic extraction methods consume high volumes of toxic organic solvents, cloud point extraction requires surfactant not exceeding 15% of the waste volume. In preliminary tests, the suitability of various low hazard surfactants (Span 20, PEG 400, Tween 80 and 20) was explored for separation of phenols and carotenoids from olive mill wastewater and red-flesh orange juice. Tween 80 showed the highest recovery and further applied to the next experiments. The most appropriate surfactant concentrations were 5% (for olive mill wastewater) and 7% (for orange juice) as indicated by recovery % and the rest cloud point extraction parameters (analyte concentration, concentration factor, and phase volume ratio). A double step CPE with 5% + 5% of Tween 80 recovered up to 94.4% of the total phenols from olive mill wastewater, while a 7% + 7% of Tween 80 recovered up to 72.4% of the total carotenoids from orange juice. Evaluation of the final effects and extraction efficiency of single and double step cloud point extraction shows that double step scheme seems to be preferable in both cases. Finally, phenols and carotenoids recovered by Tween 80 maintained high antiradical activity (DPPH test).

Cloud point extraction with Triton X-114 for separation of metsulfuron-methyl, chlorsulfuron, and bensulfuron-methyl from water, soil, and rice and analysis by high-performance liquid chromatography

A new and efficient analytic methodology based on cloud point extraction (CPE) was developed for determination of pesticide residues of metsulfuron-methyl (MSM), chlorsulfuron (CS), and bensulfuron-methyl (BSM) in water, soil, and rice grain by high-performance liquid chromatography (HPLC). Multiple experimental conditions that affected CPE efficiency-including surfactant type and concentration, equilibration temperature and duration, ionic strength, and solution pH were identified. CPE conditions were optimized as follows: 1.5% Triton X-114 (w/v), 12% Na(2)SO(4) (w/v) solution (pH 2.0), and heat-assisted at 50 °C for 15 min. The calibration curves for all analytes were linear, ranging from 0.05 to 4.0 mg L(-1), with the correlation coefficients >0.9995 by HPLC-ultraviolet detector and were linear, ranging from 0.004 to 2.0 mg L(-1), with correlation coefficients >0.9983 by CPE-HPLC. The average recoveries at the three spiked levels using CPE ranged from 86.0% to 94.5% for water samples with relative SDs (RSDs) of 0.4% to approximately 7.8%; from 85.6% to 94.8% for soil samples with RSDs of 1.2% to approximately 9.5%; and from 81.9% to 91.3% for rice samples with RSDs of 1.7% to approximately 5.8%. The proposed CPE-HPLC method can be successfully used to analyze MSM, CS, and BSM residues from contaminated water, soil, and rice grain samples.

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%.

Cloud point extraction to avoid interferences by structured background on determination in plant materials by FAAS

An analytical procedure based on microwave-assisted digestion with diluted acid and a double cloud point extraction is proposed for nickel determination in plant materials by flame atomic absorption spectrometry. Extraction in micellar medium was successfully applied for sample clean up, aiming to remove organic species containing phosphorous that caused spectral interferences by structured background attributed to the formation of PO species in the flame. Cloud point extraction of nickel complexes formed with 1,2-thiazolylazo-2-naphthol was explored for pre-concentration, with enrichment factor estimated as 30, detection limit of 5 µg L-1 (99.7% confidence level) and linear response up to 80 µg L-1. The accuracy of the procedure was evaluated by nickel determinations in reference materials and the results agreed with the certified values at the 95% confidence level.

Cloud point extraction and flame atomic absorption spectrometric determination of cadmium(II), lead(II), palladium(II) and silver(I) in environmental samples

The phase-separation phenomenon of non-ionic surfactants occurring in aqueous solution was used for the extraction of cadmium(II), lead(II), palladium(II) and silver(I). The analytical procedure involved the formation of understudy metals complex with bis((1H-benzo [d] imidazol-2yl)ethyl) sulfane (BIES), and quantitatively extracted to the phase rich in octylphenoxypolyethoxyethanol (Triton X-114) after centrifugation. Methanol acidified with 1molL(-1) HNO(3) was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The concentration of BIES, pH and amount of surfactant (Triton X-114) was optimized. At optimum conditions, the detection limits of (3 sdb/m) of 1.4, 2.8, 1.6 and 1.4 ng mL(-1) for Cd(2+), Pb(2+), Pd(2+) and Ag(+) along with preconcentration factors of 30 and enrichment factors of 48, 39, 32 and 42 for Cd(2+), Pb(2+), Pd(2+) and Ag(+), respectively, were obtained. The proposed cloud point extraction has been successfully applied for the determination of metal ions in real samples with complicated matrix such as radiology waste, vegetable, blood and urine samples.

Determination of arbidol in rat plasma by HPLC-UV using cloud-point extraction

A method based on cloud-point extraction (CPE) was developed to determine arbidol in rat plasma by high performance liquid chromatography separation and ultraviolet detection (HPLC-UV). The non-ionic surfactant Triton X-114 was chosen as the extract solvent. Variable parameters affecting the CPE efficiency were evaluated and optimized. A Zorbax SB-C(18) column (4.6 mm i.d. x 150 mm, 5 microm particle size) was used for isocratic elution separation at 40 degrees C with detection wavelength at 316 nm. Under the optimum conditions, the method was shown to be reproducible and reliable with intraday precision below 6.6%, interday precision below 8.8%, accuracy within +/-5.0% and mean extraction recovery more than 89.7%, which were all calculated using a range of spiked samples at three concentrations of 0.2, 2 and 16 microg/ml for arbidol in plasma. The linear range was from 0.08 to 20 microg/ml. After strict validation, the method was successfully applied to the pharmacokinetic study of arbidol in rats after oral and intravenous administration, respectively.

Comparison of a novel ultra-performance liquid chromatographic method for determination of retinol and α-tocopherol in human serum with conventional HPLC using monolithic and particulate columns

Retinol and alpha-tocopherol are biologically active compounds often monitored in blood samples because of their evident importance in human metabolism. In this study a novel ultra-performance liquid chromatographic (UPLC) method used for determination of both vitamins in human serum has been compared with conventional HPLC with particulate and monolithic C(18) columns. In UPLC a sub-two-micron particle-hybrid C(18) stationary phase was used for separation, in contrast with a five-micron-particle packed column and a monolithic column with a highly porous structure. Methanol, at flow rates of 0.48, 1.5, and 2.5 mL min(-1), respectively, was used as mobile phase for isocratic elution of the compounds in the three methods. Detection was performed at 325 nm and 290 nm, the absorption maxima of retinol and alpha-tocopherol, respectively. Analysis time, sensitivity, mobile-phase consumption, validation data, and cost were critically compared for these different chromatographic systems. Although cost and mobile-phase consumption seem to make UPLC the method of choice, use of the monolithic column resulted in almost the same separation and performance with a slightly shorter analysis time. These methods are alternatives and, in routine laboratory practice, more economical means of analysis of large numbers of biological samples than use of a traditional particulate column.

Cloud point extraction applied to casein proteins of cow milk and their identification by mass spectrometry

This work describes the optimization of a cloud point extraction (CPE) method for casein proteins from cow milk samples. To promote phase separation, polyoxyethylene(8) isooctylphenyl ether (Triton X-114) and sodium chloride (NaCl) were used as nonionic surfactant and electrolyte, respectively. Using multivariate studies, four major CPE variables were evaluated: Triton X-114 concentration, sample volume, NaCl concentration, and pH. The results show that surfactant concentration and sample volume were the main variable affecting the CPE process, with the following optimized parameters: 1% (w/v) Triton X-114 concentration, 50 microL of sample volume, 6% (w/v) NaCl concentration and extractions carried out at pH 7.0. At these conditions, 923+/-66 and 67+/-2 microg mL(-1) of total protein were found in the surfactant-rich and surfactant-poor phases, respectively. Finally, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was then used to evaluate those target proteins (alpha(s1)-casein, alpha(s2)-casein and beta-casein) separation as well as to check the efficiency of the extraction procedure, making a fingerprint of those target proteins possible.

Micelle-mediated extraction and cloud point preconcentration for the analysis of aesculin and aesculetin in Cortex fraxini by HPLC

In this paper, a micelle-mediated extraction and cloud point preconcentration method was developed for the determination of less hydrophobic compounds aesculin and aesculetin in Cortex fraxini by HPLC. Non-ionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) was employed as the extraction solvent. Various experimental conditions were investigated to optimize the extraction process. Under optimum conditions, i.e. 5% Genapol X-080 (w/v), pH 1.0, liquid/solid ratio of 400:1 (ml/g), ultrasonic-assisted extraction for 30 min, the extraction yield reached the highest value. For the preconcentration of aesculin and aesculetin by cloud point extraction (CPE), the solution was incubated in a thermostatic water bath at 55 degrees C for 30 min, and 20% NaCl (w/v) was added to the solution to facilitate the phase separation and increase the preconcentration factor during the CPE process. Compared with methanol, which was used in Chinese Pharmacopoeia (2005 edition) for the extraction of C. fraxini, the extraction efficiency of 5% Genapol X-080 reached higher value.

Optimization and validation of a high performance liquid chromatography method for the simultaneous determination of vitamins A and E in human serum using monolithic column and diode-array detection

In this study a novel, simple and rapid reversed-phase high performance liquid chromatography (HPLC) procedure for simultaneous determination of vitamins A and E (retinol and alpha-tocopherol) in blood serum has been developed and validated using monolithic column and diode-array detection (DAD). The monolithic column Chromolith Performance RP-18e (100 mm x 4.6 mm) was operated at ambient temperature. One hundred percent methanol at flow rate 2.5 ml min(-1) was used as a mobile phase. Detection of both compounds was performed with diode-array detector, retinol was monitored at 325 nm and alpha-tocopherol at 295 nm. The linear dependence between peak area and concentration ranged from 0.25 to 10.00 micromol l(-1) for retinol and 0.5-50.0 micromol l(-1) for alpha-tocopherol. The limit of detection (LOD) for retinol was 0.02 micromol l(-1) and limit of quantification (LOQ) was 0.07 micromol l(-1). The limit of detection (LOD) for alpha-tocopherol was 0.1 micromol l(-1) and limit of quantification (LOQ) was 0.3 micromol l(-1). Retinol was eluted in 0.8 min and alpha-tocopherol in 1.4 min. The simultaneous analysis of vitamin A and E can be achieved in less than 2 min. The implementation of monolithic column Chromolith Performance shortens the time of analysis of both vitamins four times in comparison with using traditional particulate column Pecosphere C18 (150 mm x 4.6 mm), 5 microm. This fact may play an important role for routine clinical analysis of biological samples.

Cloud Point Extraction Coupled with Microwave or Ultrasonic Assisted Back Extraction as a Preconcentration Step Prior to Gas Chromatography

Cloud point extraction of nonionic and anionic surfactants was applied as a preconcentration step prior to gas chromatography. No cleanup step preceded chromatographic analysis. The obtained surfactant-rich phase was treated with water-immiscible solvents, and the target analytes were back extracted by short-term microwave application or ultrasonication. A mixture of six PAHs (naphthalene, acenaphthene, fluorene, anthracene, fluoranthene, pyrene) was used as test compounds. The obtained detection limits were in the microgram per liter area. Recoveries of spiked water and soil samples ranged between 92 and 105% while analysis of certified reference materials gave results in good agreement with the certified values. Under the optimum experimental conditions, there was no interference or blocking of the column. According to our results, this approach presents a convenient solution to the up-to-date problem of combining gas chromatography with micellar cloud point extraction.

Analysis of isoflavone daidzein in Puerariae radix with micelle-mediated extraction and preconcentration

Nonionic surfactant oligo(ethylene glycol) monoalkyl ether (Genapol X-080) was employed as an alternative and effective solvent for the extraction of daidzein from Puerariae radix for the first time. Optimum experimental conditions were established. With 5% Genapol X-080 (w/v), liquid/solid ratio of 25:1 (mL/g), and ultrasonic-assisted extraction for 45 min, the extraction percentage of daidzein reached the highest value. For the preconcentration of daidzein by cloud-point extraction (CPE), sodium chloride was added to the solution to facilitate the phase separation and increase the preconcentration factor by reducing the volume of the surfactant-rich phase. The preconcentration factor for daidzein was about 13. Satisfactory results were obtained for the analysis of daidzein from P. radix with this established method.

Fully automated method for the determination of 24,25(OH)2 and 25(OH) D3 hydroxyvitamins, and Vitamins A and E in human serum by HPLC

A new fully automated method for the determination of metabolites of Vitamin D(3) and Vitamins A and E has been developed. A robotic station for liquid-liquid extraction, connected on line with an automatic system for solid-phase extraction (Prospekt) and a liquid chromatograph were used and the complexity of the overall method was overcome by full automation. The eluate from the chromatograph was monitored by a photodiode-array detector at three wavelengths, namely, 265 nm for Vitamin D(3) metabolites, 291 nm for Vitamin E and 325 nm for Vitamin A-which are the maximum absorption wavelengths for the analytes. The time required per sample analysis was 35 min because of the overlapping development of the steps. The linearity obtained for serum samples (standard addition method) gives correlation coefficients (r(2)) ranging between 0.996 and 0.989, with standard deviation of the slope between 4.0 and 4.9%. The repeatability was between 4.0 and 6.0% and the within-laboratory reproducibility was lower than 10.1% in all cases-both expressed as relative standard deviation-for low concentrations of the analytes, namely, 3 ng/ml for 24,25(OH)(2) dihydroxyvitamin D(3), 10 ng/ml for 25(OH) hydroxyvitamin D(3), 100 ng/ml for Vitamin A and 2 microg/ml for Vitamin E. The method has been validated using a CRM (NIST, SRM968c).