Ultrasound-assisted Cloud Point Extraction Research Articles

Preconcentration and Determination of Trace Vanadium(V) in Beverages by Combination of Ultrasound Assisted-cloud Point Extraction with Spectrophotometry

A novel ultrasound assisted-cloud point extraction method was developed for preconcentration and determination of V(V) in beverage samples. After complexation by pyrogallol in presence of safranin T at pH 6.0, V(V) ions as ternary complex are extracted into the micellar phase of Triton X-114. The complex was monitored at 533 nm by spectrophotometry. The matrix effect on the recovery of V(V) from the spiked samples at 50 μg L-1 was evaluated. In optimized conditions, the limits of detection and quantification of the method, respectively, was 0.58 and 1.93 μg L-1 in linear range of 2-500 μg L-1 with sensitivity enhancement and preconcentration factors of 47.7 and 40 for preconcentration from 15 mL of sample solution. The recoveries from spiked samples were in range of 93.8-103.2% with a relative standard deviation ranging from 2.6% to 4.1% (25, 100 and 250 μg L-1, n: 5). The accuracy was verified by analysis of two certified samples, and the results were in a good agreement with the certified values. The intra-day and inter-day precision were tested by reproducibility (as 3.3-3.4%) and repeatability (as 3.4-4.1%) analysis for five replicate measurements of V(V) in quality control samples spiked with 5, 10 and 15 μg L-1. Trace V(V) contents of the selected beverage samples by the developed method were successfully determined.

A new method of UA_CPE coupled with spectrophotometry for the faster and cost-effective detection of proline in fruit juice, honey, and wine

The study developed a new method for proline detection in honey, wine and fruit juice using ultrasound assisted-cloud point extraction (UA-CPE) and spectrophotometry. Initially, a quaternary complex was built, containing proline, histamine, Cu(II), and fluorescein at pH 5.5. Samples were treated with ethanol–water mixture before extraction and preconcentration, using an ultrasonic bath for 10 min at 40 °C (40 kHz, 300 W). After the optimization of variables affecting extraction efficiency, good linearity was obtained between 15 and 600 µg L−1 with sensitivity enhancement factor of 105. The limits of detection and quantification were 5.7 and 19.0 µg L−1, respectively. The recovery percentage and relative standard deviations (RSD %) were between 95.3 and 103.3%, and 2.5 and 4.2%, respectively. The accuracy of the method was verified by the analysis of a standard reference material (SRM 2389a).

Utility of ultrasound assisted-cloud point extraction and spectophotometry as a preconcentration and determination tool for the sensitive quantification of mercury species in fish samples

The current study reports, for the first time, the development of a new analytical method employing ultrasound assisted-cloud point extraction (UA-CPE) for the extraction of CH3Hg+ and Hg2+ species from fish samples. Detection and quantification of mercury species were performed at 550nm by spectrophotometry. The analytical variables affecting complex formation and extraction efficiency were extensively evaluated and optimized by univariate method. Due to behave 14-fold more sensitive and selective of thiophene 2,5-dicarboxylic acid (H2TDC) to Hg2+ ions than CH3Hg+ in presence of mixed surfactant, Tween 20 and SDS at pH5.0, the amounts of free Hg2+ and total Hg were spectrophotometrically established at 550nm by monitoring Hg2+ in the pretreated- and extracted-fish samples in ultrasonic bath to speed up extraction using diluted acid mixture (1:1:1, v/v, 4molL−1 HNO3, 4molL−1 HCl, and 0.5molL−1 H2O2), before and after pre-oxidation with permanganate in acidic media. The amount of CH3Hg+ was calculated from difference between total Hg and Hg2+ amounts. The UA-CPE method showed to be suitable for the extraction and determination of mercury species in certified reference materials. The results were in a good agreement (with Student's t-test at 95% confidence limit) with the certified values, and the relative standard deviation was lower than 3.2%. The limits of detection have been 0.27 and 1.20μgL−1, for Hg2+ from aqueous calibration solutions and matrix-matched calibration solutions spiked before digestion, respectively, while it is 2.43μgL−1 for CH3Hg+ from matrix-matched calibration solutions. A significant matrix effect was not observed from comparison of slopes of both calibration curves, so as to represent the sample matrix. The method was applied to fish samples for speciation analysis of Hg2+ and CH3Hg+. In terms of speciation, while total Hg is detected in range of 2.42–32.08μgkg−1, the distribution of mercury in fish were in range of 0.7–11.06μgkg−1 for CH3Hg+ and in range of 1.72–24.56μgkg−1 for Hg2+.

Using Safranin T as a Charge Transfer-Sensitive Ion-Pairing Reagent in Ultrasound-Assisted Cloud Point Extraction: Determination of Bisphenol A in Selected Beverages.

In this study, a new ultrasonic-assisted cloud point extraction method coupled with spectrophotometry was developed to extract from and determine bisphenol A (BPA) in a sample matrix. The method is based on charge transfer-sensitive ion-pairing complex formation between BPA and Safranin T in the presence of nitrate in a micellar interface at pH 5.0. The variables affecting extraction efficiency were optimized. A good linear relationship with a significant sensitivity difference was obtained in the ranges of 2-40 and 2-120 µg/L with LODs of 0.54 and 0.38 µg/L after preconcentration with two different extractants, respectively. From a preconcentration of a 15 mL sample, a preconcentration factor of 60 was obtained. Due to the lack of a certified material compatible with the sample matrix, the method was validated by conducting intraday and interday accuracy and precision studies based on two spiked QC samples (with a recovery rate greater than 94% and an RSD ranging from 3.8 to 5.9%). Moreover, the beverage samples were analyzed by the standard addition method to control for possible matrix effects. BPA was detected in the range of 1.8-7.2 µg/L in beverages with Triton X-114, whereas the levels changed to a range of 1.8-7.3 µg/L with Triton X-45. In such a way not to create a threat, these levels were considerably lower than the specific migration limit set by the European Union.

Indirect determination of the flavor enhancer maltol in foods and beverages through flame atomic absorption spectrometry after ultrasound assisted-cloud point extraction

A simple ultrasound assisted-cloud point extraction (UA-CPE) method was developed and combined with flame atomic absorption spectrometry (FAAS) for pre-concentration and indirect determination of the flavor enhancer maltol in foods and beverages. The method is based on reduction of Cu(II) to Cu(I) by maltol at pH 6.5, and subsequent selective interaction of Cu(I) with bathocuproine (BCP) to form a ternary complex in presence of sodium dodecyl sulfate (SDS). Under the optimized conditions, pre-concentration of a 35mL sample solution allowed detection of 1.24µgL−1 maltol in a linear range of 4–230µgL−1. The method was validated by intra- and inter-day precision studies ranging from 2.1 to 3.4%, and recoveries ranged from 93.3% to 104.4% using standard addition method. After pretreatment with two different sample preparation steps assisted by ultrasound energy, the proposed method was applied successfully for determination of maltol in selected foods and beverages.

A New Ultrasound Assisted-Cloud Point Extraction Method for the Determination of Trace Levels of Tin and Antimony in Food and Beverages by Flame Atomic Absorption Spectrometry

In the current study, a new ultrasonic-assisted cloud-point extraction (UA-CPE) method for the preconcentration and determination of antimony and tin in the selected food and beverages was developed by flame atomic absorption spectrometry (FAAS). The method is based on the fact that formation of the stable ternary complexes of Sb(III) and Sn(IV) with 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one (morin) in presence of cetyltrimethylammoniumbromide (CTAB) as both sensitivity improvement auxiliary ligand and counter ion, and then extraction into the micellar phase of poly(ethylene glycol-mono-p-nonylphenylether (PONPE 7.5) as extracting agent at pH 8.5. Under the optimized conditions, the calibration curves for Sb(III) and Sn(IV) were rectilinear with changing calibration sensitivities in ranges of 0.1–140 and 0.1–225 μg L−1, respectively. The limit of detection for both Sb(III) and Sn(IV) was 0.03 μg L−1 with sensitivity enhancement factor of 114.5 and 110.6, respectively. The precision as a relative standard deviation (RSD) for Sb(III) and Sn(IV) is in range of 2.3–5.2 and 2.6–5.4 %, respectively. The trueness of the method was verified by analysis of certified reference materials (CRMs). The method was successfully applied to determination of antimony and tin in the selected food and beverage matrices.

Ultrasound-assisted cloud point extraction of manganese, zinc and tin from digested food samples for their determination by FAAS

The current study is focused on the determination of the trace levels of manganese, zinc and tin in wet acid digested foods by flame atomic absorption spectrometry (FAAS) after preconcentration with ultrasound assisted-cloud point extraction (UA-CPE).

Comparison of ultrasound-assisted cloud point extraction and ultrasound-assisted dispersive liquid liquid microextraction for copper coupled with spectrophotometric determination

In this work, ultrasound-assisted cloud point extraction (UA-CPE) and ultrasound-assisted dispersive liquid liquid microextraction (UA-DLLME) were investigated and compared firstly as ultrasound-assisted liquid phase microextraction methods, which were coupled with spectrophotometer for copper preconcentration and detection. Compared to conventional CPE and DLLME, the extraction patterns were changed and improved by the effect of ultrasound. As novel methods, their applications were expanded and the analytical performance of spectrophotometric determination for copper was considerably improved. The influence factors of UA-CPE and UA-DLLME were studied in detail. Under the optimal conditions, the limits of detection (LODs) for copper were 0.7μgL−1 of UA-CPE and 0.8μgL−1 of UA-DLLME with sensitivity enhancement factors (EFs) of 17 and 16. The developed methods were applied to the determination of trace copper in real water samples with satisfactory analytical results.

Determination of trace vanadium in sea cucumbers by ultrasound-assisted cloud point extraction and graphite furnace atomic absorption spectrometry

An ultrasound-assisted cloud point extraction (CPE) procedure was used for preconcentration and determination of vanadium by graphite furnace atomic absorption spectrometry. The vanadyl(IV) complex with ascorbic acid form a hydrophobic complex with 4-(2-pyridylazo) resorcinol (PAR) in a micelle medium, which is stable under our working conditions, and followed by its extraction into Triton X-100 surfactant-rich phase. The main factors affecting CPE efficiency, such as pH, concentrations of PAR, ascorbic acid and Triton X-100, incubation temperature, frequency and equilibration time of ultrasonic bath were investigated in detail. Under the optimum conditions, preconcentration of 10 mL sample gave a preconcentration factor of 36.4 and a detection limit of 4.0 µg kg−1. The proposed method was successfully applied to determination of vanadium in sea cucumbers with satisfactory results.

Ultrasound assisted-cloud point extraction combined with flame atomic absorption spectrometry for selective preconcentration and determination of As(v) in selected water and beverage samples

A new UA-CPE method was efficiently combined with FAAS for detection of As(v). The method is based on the ion-association of As(v) with NRH+ in the presence of pyrogallol. A detection limit of 0.45 μg L-1 for As(v) was achieved.

Ultrasound-assisted cloud point extraction coupled with flame atomic absorption spectrometry for the determination of lead and cadmium in water samples

A new method based on ultrasound-assisted cloud point extraction (UA-CPE) using the mixture of non-ionic surfactant alkylphenol ethoxylate NP-7 and alkylphenol ethoxylate NP-9 for the preconcentration of trace amounts of lead (Pb) and cadmium (Cd) in water samples prior to determination by FAAS has been developed.

Comparison of rapidly synergistic cloud point extraction and ultrasound-assisted cloud point extraction for trace selenium coupled with spectrophotometric determination

In this work, rapidly synergistic cloud point extraction (RS-CPE) and ultrasound-assisted cloud point extraction (UA-CPE) were firstly compared and coupled with spectrophotometer for selenium preconcentration and detection. The established RS-CPE pretreatment was simple, rapid and high effective. The extraction time was only 1min without heating process. Under the effect of ultrasound, UA-CPE accomplished extraction efficiently although the extraction procedure was relatively time-consuming. In this study, RS-CPE and UA-CPE were firstly applied for selenium preconcentration and coupled with conventional spectrophotometer. Their applications were expanded and the analytical performance of spectrophotometric determination for selenium was considerably improved. The influence factors relevant to RS-CPE and UA-CPE were studied in detail. Under the optimal conditions, the limits of detection (LODs) for selenium were respectively 0.2μgL−1 of RS-CPE and 0.3μgL−1 of UA-CPE with sensitivity enhancement factors (EFs) of 124 and 103. The developed methods were applied to the determination of trace selenium in real water samples with satisfactory analytical results.

Development of a Precolumn Derivatization Procedure Prior to Ultrasound-Assisted Cloud Point Extraction for Sensitive Determination of Fluoroquinolones in Eggs by High-Performance Liquid Chromatography with Fluorescence Detection

In this work, a 4-chloro-7-nitrobenzodioxazole (NBD-Cl) derivatization coupled with the ultrasound-assisted cloud point extraction (UACPE) method prior to high-performance liquid chromatography with fluorescence detection (HPLC-FLD) analysis was developed for the determination of four widely used fluoroquinolones (FQs) including norfloxacin (NOR), ciprofloxacin (CIP), sarafloxacin (SAR), and gatifloxacin (GAT) in eggs. The derivatives of FQs with NBD-Cl were extracted into the Triton X-114 surfactant-rich phase, which was analyzed by reversed-phase HPLC-FLD. Ultrasound was applied to accelerate the phase separation in extraction and enhance the extraction efficiency of target analytes. Variable parameters affecting the derivatization and UACPE procedure were systematically evaluated and optimized. Under the optimum conditions, four FQs were successfully separated within 30 min through an Agilent TC-C18 column. Good recoveries of 86.2–103.5 %, which were calculated using a range of spiked samples at three concentrations, were obtained by UACPE. The calibration graphs were linear over the range of 1.2–73.0 μg kg−1 for four FQs with correlation coefficients (R) no less than 0.9957. The limits of detection were 0.2, 0.5, 0.3, and 0.4 μg kg−1 for NOR, CIP, SAR, and GAT, respectively. The precisions indicated by relative standard deviations ranged from 0.6 to 4.3 % for both intraday and interday analysis. The proposed method proved to be a selective, sensitive, and eco-friendly approach which was successfully applied to analyze FQs in eggs at the local farmers market, and none of the target analytes were detected in these samples.

Ultrasound-assisted cloud point extraction for the determination of sulfonamides in honey samples by fluorescence spectrophotometry

An ultrasound-assisted cloud point extraction (UA-CPE) method using nonionic surfactant nonylphenol ethoxylate (NP-7) as the extractant was developed for determination of two sulfonamides (SAs, sulfadiazine sodium and sulfamerazine) in honey samples. The procedure was based on the derivatization SAs in honey with fluorescamine yielding fluorescent complexes, which were extracted into the surfactant-rich phase and analyzed by molecular fluorescence spectrophotometry. The polar of SAs of derivatives was reduced and strong fluorescence was produced at λex = 410 nm. Variable parameters affecting the derivatization and UA-CPE procedure were evaluated and optimized. The calibration graph was linear from 10 to 10 000 ng mL−1 with coefficient of determination more than 0.9991. The limits of detection (LOD) were 0.5 ng mL−1 for sulfadiazine sodium and 5.0 ng mL−1 for sulfamerazine with the relative standard deviations of the method ranging from 2.2% to 4.1%. Recoveries of the compounds on spiked honey samples at fortified level of 1 μg mL−1 were 92.2% for sulfadiazine sodium and 84.1% for sulfamerazine, respectively. Therefore, the developed method is practical and reliable, with potential application to determine the content of SAs in honey samples.

Development of a cloud point extraction method for the determination of phenolic compounds in environmental water samples coupled with high‐performance liquid chromatography

A method based on ultrasound-assisted cloud point extraction (CPE) was developed for the determination of phenolic compounds in water samples by high-performance liquid chromatography coupled with diode array detection (DAD) (HPLC-DAD). A nonionic surfactant, Tergitol 15-S-7, was chosen as the surfactant. The parameters affecting the CPE efficiency, such as Tergitol 15-S-7 concentration, salt concentration, extraction temperature, incubation time, centrifugation time, ultrasonic time, sample pH, and dilution solvent were systematically evaluated and optimized. Under the optimum experimental conditions, the linear regression coefficients of the standard curves were greater than 0.9986 and the limits of detection were in the range of 1.7-6.0 μg/L. The method was shown to be reproducible and reliable with intraday and interday relative standard deviations lower than 4.0 and 5.8%, respectively. The recoveries for the addition of different concentrations of phenolic compounds to water samples were in the range of 81.1-109.4%.

Ultrasound-assisted cloud point extraction for speciation and indirect spectrophotometric determination of chromium(III) and (VI) in water samples

Ultrasound-assisted cloud point extraction (UACPE) procedure was developed for speciation and indirect spectrophotometric determination of chromium(III) and (VI) in environmental water samples. The method is based on the reduction of Cr(VI) by iodide in acidic media and subsequently formation of I3− anion. The I3− formed can further react with cetyltrimethylammonium bromide (CTAB) and induce its clouding due to formation of an ion-association complex. The formed complex was separated from solution and dissolved in ethanol for spectrophotometric measurement. Cerium(IV) ammonium sulphate was chosen as an oxidizing reagent for pre-oxidation step of Cr(III) to Cr(VI) species before the addition of iodide to the system, up to chromium in trivalent can be determined by the procedure. Experimental parameters for both spectrophotometric reaction and extraction procedure have been optimized. Under optimized conditions Cr(VI) can be determined in the range 20–400ngmL−1 (R2=0.999). Detection limit, preconcentration factor and relative standard deviation were 12ngmL−1, 20.0 and 2.2% (n=5), respectively with 10mL sample volumes. The proposed method has been successfully applied for determination of chromium(V) in spiked water, synthetic seawater and electroplating wastewater samples with average recoveries of 100.1, 99.4 and 99.1%, respectively.

A simplified ultrasound-assisted cloud-point extraction method coupled with high performance liquid chromatography for residue analysis of benzimidazole anthelmintics in water and milk samples

A simple ultrasound-assisted cloud point extraction (UA-CPE) method combined with high performance liquid chromatography-photodiode array (PDA) detection has been developed for the extraction, preconcentration and determination of benzimidazole anthelmintics (e.g., thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) residues in water and milk samples. Parameters affecting the extraction efficiency, such as concentration of surfactant, content of salt additive, incubation temperature and time, and centrifugation were investigated and optimized. The optimum conditions of UA-CPE were 0.75% (w/v) Triton X-114, 7% (w/v) sodium acetate, 2 min ultrasonication, and 10 min centrifugation. The surfactant-rich phase (SRP) was analyzed by subjecting it to HPLC under gradient condition of 1% (v/v) acetic acid and methanol, an Inertsil ODS column (4.6 × 150 mm, 5 μm), a flow rate of 1.0 mL min−1, and photodiode array detection at 296 nm. Under the optimum conditions, linearity was obtained in the range of 0.1–100 μg L−1 with the correlation coefficients (r2) higher than 0.996. A high preconcentration factor of up to 164 was obtained, corresponding to limits of detection (LOD) in the range of 0.005–0.1 μg L−1. Intra-day (n = 5) and inter-day (n = 3 × 3) precisions were obtained with relative standard deviation (RSD) for retention time and peak area lower than 2.0 and 7.0%, respectively. The recoveries for the spiked target anthelmintics at different concentrations in water (3, 10, and 70 μg L−1) and milk (20, 50 and 100 μg L−1) were in the ranges 81.6–111.4% and 75.3–111.4%, respectively. The proposed UA-CPE method has been demonstrated to be simple, effective, and reliable for the analysis of analytes in the samples studied. In addition, the developed method can be used as an alternative technique to the conventional CPE.

Determination of estrogens in human urine by high-performance liquid chromatography/diode array detection with ultrasound-assisted cloud-point extraction

A novel and efficient analytical methodology is proposed for extracting and preconcentrating three kinds of estrogens (17β-estradiol (βE2), estrone (E1), and diethylstilbestrol (DES)) in human urine prior to high-performance liquid chromatography (HPLC) analysis. It is based on the induction of micellar organized medium by using a nonionic surfactant (Tergitol TMN-6) to extract the target estrogens. Ultrasound was applied to enhance the extraction efficiency. Parameters affecting the extraction of target analytes including the concentration of surfactant, temperature, extraction time, sample pH, ionic strength, and centrifuging time were investigated. Under the optimum conditions, the linear range of βE2, E1, and DES was from 5.0 to 1000ng/ml. All correlation coefficients of the calibration curves were higher than 0.997. The relative standard deviations (RSD, n=5) were 2.36–5.27% and the limits of detection (LOD) were 0.1, 0.2, and 0.1ng/ml for βE2, E1, and DES in human urine, respectively. The results indicated that the method was successfully applied for analyzing βE2, E1, and DES in human urine.