Ultrasonic-assisted Cloud Point Extraction Research Articles

Ultrasound assisted-cloud point extraction coupled with spectrophotometry for determination of low levels of formaldehyde from milk-based products

In this study, a preconcentration method is proposed for the separation, extraction and spectrophotometric determination of free formaldehyde (FA) from milk-based products. The method is based on ion-pair formation between phenoxazine 3-one, resazurin, and hydroxymethanesulfonate (HMS), which is selectively formed by the reaction of FA with sulfite at pH 5.0, followed by its extraction into the micellar phase of Triton X-114. Resazurin was adopted as ion-pairing reagent for detection of low levels of FA at 610nm. The variables affecting the extraction efficiency were evaluated and optimized. A linear relationship was obtained in the range of 2–120μgL-1 with a detection limit of 0.501μgL-1. Under optimum conditions such as pH 5.0, 8 µmol L-1 Resazurin, 0.4mgL-1 sulfide, 0.03% (v/v) of Triton X-114, after applying ultrasonic assisted-cloud point extraction (UA-CPE), spectrophotometric determination was made at 610nm to measure the concentration of FA found in trace amounts in milk-based products such as liquid, semi-solid and solid-milk products including whole milk, semi-skimmed milk, cacao milk, banana flavored milk, strawberry flavored milk, goat milk, yogurt, fruit flavored yogurt, white cheese. The precision was in the range 2.5-4.8% (n: 5, for 5, 25 and 100μgL-1). After preconcentration of a 15mL sample, a sensitivity enhancement factor of 55.6 was obtained. To represent the sample matrix, the validation was checked by intra-day/inter-day accuracy and precision analysis of a spiked quality control sample and its recoveries at three concentration levels. Finally, the method was successfully applied to the determination of free FA in samples, and recoveries in the range 90.8-97.4% with RSD lower than 5.7% after spiking were obtained.

Determination of trace cobalt (II) in spices samples by ultrasonic assisted cloud point extraction with spectrophotometry

In this study, ultrasonic assisted cloud point extraction (UA-CPE) method was developed for the determination of Cobalt (II) (Co(II)) in spices. After extraction and preconcentration, the Co(II) contents of the samples were determined by UV–VIS. After complexing with Ponceau Xylidine (PX) and EDTA in the presence of cationic surfactant, CTAB at pH 4.0 with Britton–Robinson (BR) buffer, Co(II) ion was withdrawn the surfactant-rich phase of nonionic surfactant, Triton X-114 (TX-114). The concentrated surfactant-rich phase containing the analyte was diluted with ethanol to a volume of 1.0 mL and then analyzed by UV–VIS spectrophotometer. The various analytical parameters affecting the UA-CPE yield were investigated and optimized. Analytical data achieved after optimization: limits of detection (LOD) and: limits of quantification (LOQ) are 0.76 and 2.59 μg L−1, respectively; The calibration curve is rectilinear for Co(II) with changed calibration sensitivity in the range of 1–10 and 10-210 μg L−1. The precision (as RSD%) is 4.8. This optimized method was applied in the analysis of various spice samples.

Interference-free determination of carmine in food samples using ultrasonic assisted cloud point extraction coupled with spectrophotometry

In this study, a simple, green and cost effective method of extraction and preconcentration of carmine used as a food additive in some food samples was developed using ultrasonic assisted cloud point extraction (UA-CPE) before spectrophotometric determination. Carmine was extracted from the aqueous solution using polyoxyethylenesorbitan monolaurate (Tween 20) as the extraction solvent in presence of Ni(II) at pH 6.5. Variables such as pH, amount of metal, temperature, ultrasonic effect, solvent type, type and concentration of nanionic surfactant have been optimized in detail. Under the optimum conditions, the analytical characteristics of the method are as follows; linear working range 1.5-350 μg L-1; the detection limit, 0.4 μg L-1; and preconcentration factor, 80. The relative standard deviation (RSD%) obtained for the 10 μg L-1 concentration (n: 5) of carmine was 3.7%. Recovery values for two different concentration levels were in the range of 94.8-104.7%. The accuracy and precision of the method were evaluated by intra- and inter-day studies. Finally, the method has been successfully applied to the determination of carmine in various foods.

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.

A New Ultrasonic Assisted Cloud Point Extraction and Preconcentration Procedure for the Spectrophotometric Oxalate Determination in Beverages

A New Ultrasonic Assisted Cloud Point Extraction and Preconcentration Procedure for the Spectrophotometric Oxalate Determination in Beverages

Development of a New Methodology for Determination of Vitamin B9 at Trace Levels by Ultrasonic-Assisted Cloud Point Extraction Prior to HPLC

A new analytic methodology based on ultrasonic-assisted cloud point extraction coupled with high-performance liquid chromatography (UA-CPE-HPLC) was developed and successfully applied to determine vitamin B9 in food samples. Polyethylene glycol 6000 (PEG-6000) was used as nonionic surfactant due to its chemical properties and trade availability. All parameters such as surfactant concentration, ionic strength, and the other conditions were also investigated and optimized. The optimal conditions for UA-CPE method were presented with 2.4 % w/v PEG-6000, 14.6 % w/v Na2SO4, and ultrasonic heating assistance at 40 °C for 20 min. The calibration curve for vitamin B9 was linear ranging from 20 to 800 μg L−1, with correlation coefficients being 0.9944 determined by a HPLC-diode array detector (DAD) detector. Relative standard deviation for 150 μg L−1 was calculated as 2.87 %. Recovery values in different concentration levels were in the range of 95.6–104.2 %. The obtained results demonstrate that the proposed method can be applied for determination of vitamin B9 in real samples.

A preconcentration method for indirect determination of acrylamide from chips, crackers and cereal-based baby foods using flame atomic absorption spectrometry

Acrylamide is a toxic species for human health, and is a Maillard reaction product which forms spontaneously in heat treatment process of foods. Therefore, a simple, fast and cost-effective method was developed for the indirect determination of acrylamide in processed foods particularly consumed by children. The method is based on ion–pairing of acrylamide with fluorescein (F2−) in presence of Ni(II) ions at pH 9.0, and then extraction of the formed ternary complex into micellar phase of poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) before analysis by flame atomic absorption spectrometry (FAAS). The ultrasonic-assisted cloud point extraction (UA-CPE) has been used for the preconcentration of acrylamide in the samples prior to its FAAS detection. The matrix matched calibration curve is linear in range of 0.3–150µgkg−1 under optimal reagent conditions (1.75mL of 0.1molL−1 ammonia buffer at pH 9.0, 2.2mgL−1 Ni(II), 4.0×10−4molL−1 F2−, 0.4% (w/v) NH4Cl and 0.7% (v/v) PONPE 7.5) with sensitivity enhancement of 160-fold. The proposed method has been validated by assessment of the following parameters; the limits of detection (LOD) and quantification (LOQ) (0.08µgkg−1 and 0.28µgkg−1, respectively) with a relative standard deviation (RSD%) lower than 6.3%, and extractive recovery higher than 95% for acrylamide spiked at levels of 5 and 25µgkg−1. The method was successfully applied to the indirect determination of acrylamide in the processed foods and two CRMs with satisfactory results.

Separation/preconcentration of ultra-trace levels of inorganic Sb and Se from different sample matrices by charge transfer sensitized ion-pairing using ultrasonic-assisted cloud point extraction prior to their speciation and determination by hydride generation AAS

In the existing study, a new, simple and low cost process for separation/preconcentration of ultra-trace level of inorganic Sb and Se from natural waters, beverages and foods using ultrasonic-assisted cloud point extraction (UA-CPE) prior to their speciation and determination by hydride generation AAS, is proposed. The process is based on charge transfer sensitized complex formations of Sb(III) and Se(IV) with 3-amino-7-dimethylamino-2-methylphenazine hydrochloride (Neutral red, NRH+) in presence of pyrogallol and cetyltrimethylammonium bromide (CTAB) as both sensitivity enhancement and counter ion at pH 6.0. Under the optimized reagent conditions, the calibration curves were highly linear in the ranges of 8–300ngL−1 and 12–250ngL−1 (r2≥0.993) for Se(IV) and Sb(III), respectively. The limits of detection were 2.45 and 3.60ngL−1 with sensitivity enhancement factors of 155 and 120, respectively. The recovery rate was higher than 96% with a relative standard deviation lower than 5.3% for five replicate measurements of 25, 75 and 150ngL−1 Se(IV) and Sb(III), respectively. The method was validated by analysis of two certified reference materials (CRMs), and was successfully applied to the accurate and reliable speciation and determination of the contents of total Sb/Sb(III), and total Se/Se(IV) after UA-CPE of the pretreated sample matrices with and without pre-reduction with a mixture of l-cysteine and tartaric acid. Their Sb(V) and Se(VI) contents were calculated from the differences between total Sb and Sb(III) and/or total Se and Se(IV) levels.

Application of ultrasonic-assisted cloud point extraction/flame atomic absorption spectrometry (UA-CPE/FAAS) for preconcentration and determination of low levels of antimony in some beverage samples

Due to be able to migrate or leach from food packaging materials into the foods and/or beverages, development of a new, sensitive and selective analytical methods for low levels of antimony as a food contaminant is of great importance in terms of food safety. In this context, an ultrasonic-assisted cloud point extraction method was developed for the preconcentration and determination of antimony as Sb(III) using 4-(2-thiazolylazo)resorcinol (TAR) and 2-(2-thiazolylazo)-p-cresol (TAC) as chelating agents and sodium dodecyl sulfate as signal enhancing agent at pH 6.0 and mediated by nonionic surfactant, t-octylphenoxypolyethoxyethanol by flame atomic absorption spectrometry. Using the optimized conditions, the calibration curves obtained from Sb(III) with TAR and TAC were linear in the concentration ranges of 0.5–180 and 1–180 μg L−1 with detection limits of 0.13 and 0.28 μg L−1, respectively. The precision (as relative standard deviations, RSDs) was lower than 3.9 % (25 and 100 μg L−1, n: 6). The method accuracy was validated by the analysis of two standard reference materials. The results obtained were statistically in a good agreement with the certified values at 95 % confidence limit. The method has successfully been applied to the determination of Sb(III) and total Sb in selected beverages, milk and fruit-flavored milk products before and after pre-reduction of Sb(V) to Sb(III) with a mixture of KI/ascorbic acid in acidic media. The Sb(V) contents of samples were quantitatively calculated from analytical difference between total Sb and Sb(III) levels.

Combination of Ultrasonic-Assisted Cloud Point Extraction with Flame AAS for Preconcentration and Determination of Trace Amounts of Silver and Cadmium in Dried Nut and Vegetable Samples

In this article, ultrasonic-assisted cloud point extraction (UA-CPE) was used to the preconcentration of trace Ag(I) and Cd(II) in dried nut and vegetable samples. After ion association of Ag(I) and Cd(II) ions with 3,7-diamino-2,8-dimethyl-5-phenyl-phenaziniumchlorid (Safranin T) in the presence of excess potassium iodide (KI) at pH 6.0, the ternary complexes formed were quantitatively extracted into a micellar phase of poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) and then determined by flame atomic absorption spectrometry (FAAS). The matrix effects of possible some interfering ions on the method recovery and tolerance limits were also investigated. Under the optimized reagent conditions, the method was linearly dependent on the analyte concentrations in the range of 0.08–90 and 3–250 μg L−1 with limits of detection of 0.02 and 0.9 μg L−1 for Ag(I) and Cd(II), respectively. The reproducibility as the percent relative standard deviations (RSDs %) (0.5, 5.0, and 25 μg L−1 for Ag(I) and 15, 30, and 100 μg L−1 for Cd(II), n = 6) was lower than 3.6 % for both analytes. The accuracy of the method was controlled by analysis of two certified samples (SRM 1573a Tomato leaves and SRM 1643e Trace elements in waters) as well as recovery studies from spiked samples. It has been observed that the results obtained are in a good agreement with the certified values at confidence interval of 95 %. The method was successfully applied to determination of Ag(I) and Cd(II) in several dried nut and vegetable samples by FAAS after separation/preconcentration with UA-CPE.

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.

A simple and efficient approach for preconcentration of some heavy metals in cosmetic products before their determinations by flame atomic absorption spectrometry

In the current study, a simple and efficient analytical method for preconcentration and determination of Cd(II), Pb(II), and Sn(II) in some cosmetic samples, using ultrasonic assisted-cloud point extraction and flame atomic absorption spectrometry, was developed. The method is based on the ternary complex formations of Sn(II), Pb(II), and Cd(II), which are available in the form of neutral and/or anionic hydroxo complexes (Sn(OH)$_{3}^{-}$, Pb(OH)$_{3}^{-}$, Cd(OH)$_{2}$, and/or Cd(OH)$_{3}^{-})$, with Victoria Pure Blue BO (VPB$^{+})$ in the presence of cetylpyridinium chloride at pH 8.5, and then extraction of the formed ternary complexes into the micellar phase of polyoxyethylene sorbitan monostearate (Tween 60). Using the optimized conditions, a linear relationship was observed in the ranges of 12-330 $\mu $g L$^{-1}$ for Cd(II), 4-200 $\mu $g L$^{-1}$ for Pb(II), and 1-275 $\mu $g L$^{-1}$ for Sn(II). The detection limits for Cd(II), Pb(II), and Sn(II), respectively, were 3.70, 1.35, and 0.45 $\mu $g L$^{-1}$, with a preconcentration factor of 50, and the precision as relative standard deviations was lower than 4.2% for each analyte. The validity was verified by analysis of two certified reference materials. Finally, the method was successfully applied to the determination of these metals in various cosmetic samples.

A new ultrasonic-assisted cloud-point-extraction procedure for pre-concentration and determination of ultra-trace levels of copper in selected beverages and foods by flame atomic absorption spectrometry

A new ultrasonic-assisted cloud-point-extraction (UA-CPE) method was developed for the pre-concentration of Cu(II) in selected beverage and food samples prior to flame atomic absorption spectrometric (FAAS) analysis. For this purpose, Safranin T was used as an ion-pairing reagent based on charge transfer in the presence of oxalate as the primary chelating agent at pH 10. Non-ionic surfactant, poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) was used as an extracting agent in the presence of NH4Cl as the salting out agent. The variables affecting UA-CPE efficiency were optimised in detail. The linear range for Cu(II) at pH 10 was 0.02–70 µg l–1 with a very low detection limit of 6.10 ng l–1, while the linear range for Cu(I) at pH 8.5 was 0.08–125 µg l–1 with a detection limit of 24.4 ng l–1. The relative standard deviation (RSD %) was in the range of 2.15–4.80% (n = 5). The method was successfully applied to the quantification of Cu(II), Cu(I) and total Cu in selected beverage and food samples. The accuracy of the developed method was demonstrated by the analysis of two standard reference materials (SRMs) as well as recoveries of spiked samples.

Quantification of 5-hydroxymethylfurfural in honey samples and acidic beverages using spectrophotometry coupled with ultrasonic-assisted cloud point extraction

The simple, cost-effective and fast preconcentration method using ultrasonic-assisted cloud point extraction (UA-CPE) has been developed for determination of 5-hydroxymethylfurfural (5-HMF) by means of spectrophotometry. The method is based on selective complex formation of 5-HMF with p-nitrophenylhydrazine (p-NPH) in presence of sodium dodecyl sulfate (SDS) as auxiliary ligand with counter charge at pH 4.0,and then extracted into the non-ionic surfactant, polyethylene glycol 4-tert-octylphenyl ether (Triton X-45). Under the optimized conditions, the calibration graph was rectilinear in the range of 6.5–275μgL−1 with two different calibration slopes in two linear regions with changing sensitivity. The limits of detection and quantification (LOD and LOQ) (3σblank/m and 10σblank/m) was 1.96 and 6.50μgL−1, and the precision (as RSD) for determination of 25, 75 and 150μgL−1 of 5-HMF was in range of 2.10–3.65%. The method was successfully applied to the accurate and reliable determination of 5-HMF as an indicator of honey quality in different honey and acidic beverage samples. The accuracy of the method was statistically established by recoveries of spiked samples. The results of analysis by the developed method were found to be in good agreement with those obtained by the modified spectrophotometric White method.

Indirect Determination of Free, Total, and Reversibly Bound Sulfite in Selected Beverages by Spectrophotometry Using Ultrasonic-Assisted Cloud Point Extraction as a Preconcentration Step

A new indirect ultrasonic-assisted cloud point extraction (UA-CPE) method has been developed for the determination of trace sulfite species by means of spectrophotometry. The method is based on either directly imide–bisulfite adducts formation or ion-pairing complexation of enolate–bisulfite adducts produced by the oxidation of pyrogallol with sulfite at pH 10 with 3-amino-7-diethylamino-8,9-benzo-2-phenoxazine chloride (Nile blue A) and CPE of ion-pairing complex formed from aqueous solution using Triton X-114. Under the optimized conditions, the calibration graphs with and without bromide were highly linear in the ranges of 6–180 and 7.5–180 μg L−1 with changing sensitivity. The limits of detection and quantification (LOD and LOQ) (3σblank/m and 10σblank/m) with bromide was 1.75 and 5.83 μg L−1 (n = 6) and the precision, the relative standard deviations (RSDs), for determination of 25, 75, and 150 μg L−1 of sulfite was in range of 2.40–5.20 % (n = 10). The method showed good selectivity, and was successfully applied to the speciative determination of trace sulfite in selected beverages with and without alcohol. The results were compared with those of the standard 5,5′-dithio-bis(2-nitrobenzoic acid (DTNB) method, and the two paired t test was used to determine whether the results obtained by the two methods differ significantly.

Optimization of an analytical method for the spectrophotometric determination of copper in tea and water samples after ultrasonic assisted cloud point extraction using a benzothiazole fluorescein derivative complexing agent

BTF is exists with spirolactone species with adding Cu2+, which leads to the absorbance intensity is decreased gradually and the decrease of the absorbance value is linear for Cu2+.

Ultrasonic-assisted cloud point extraction for determination of nickel in water samples by flame atomic absorption spectrometry

A novel method for the determination of nickel was established by ultrasonic-assisted cloud point extraction (UA-CPE) prior to flame atomic absorption spectrometry (FAAS) analysis. The nickel reacted with N,N'-bis(salicylidene)-1,2-ethanediamine (BSE) to form hydrophobic chelates, which were extracted into the micelles of alpha-[3,5-dimethyl-1-(2-methylpropyl)hexyl]-omega- poly(oxy-2-ethanediyl) (Tergitol TMN-6). Tergitol TMN-6 was used as green nonionic surfactant. BSE was synthesized and checked by nuclear magnetic resonance (NMR) spectra. The phase diagrams of the binary system, water-surfactant (Tergitol TMN-6), and the ternary systems, water-surfactant-salt, were determined. The effects of experimental conditions including pH of sample solution, concentration of chelating agent and surfactant, ultrasonic power, equilibration temperature and incubation time were evaluated in order to enhance sensitivity of the method. Under the optimal conditions, the calibration graph was linear in the range of 10-500 μg L(-1). The values obtained for the limit of detection and enrichment factor were 1.0 μg L(-1) and 30, respectively. The method was successfully applied to the analysis of nickel in water samples.

Pilot‐scale Ultrasonic Assisted Cloud Point Extraction of Polycyclic Aromatic Hydrocarbons from Polluted Water

Cloud point extraction (CPE) has been proved to be an efficient and environment‐friendly separation technology for polycyclic aromatic hydrocarbons from polluted water in many related researches. However, its traditional phase separation process, based on throughput‐limited centrifugation or low‐efficient heating, limited the scaling up and continuous operation of CPE process to a large extent. In our previous study, an efficient and easy‐scaling up CPE process, namely ultrasonic assisted cloud point extraction (Us‐CPE), was developed by performing the CPE process in an ultrasonic environment. The introduction of an ultrasonic environment successfully accelerated the phase separation; and due to that the ultrasonic effect was free from throughput limitation, the process was of a good potential in the scaling up and continuous operation. In this paper, a pilot‐scale Us‐CPE process of three polycyclic aromatic hydrocarbons (PAHs), anthracene, phenanthrene, and pyrene from polluted water was performed in a pilot‐scale extraction column with a volume up to 500 mL, and the treatment was operated continuously with pumps. The steady state time of the continuous system was determined, and the influence of operation parameters including ultrasonic power, temperature, extraction column volume, flow rate, and PAHs initial concentration, were evaluated by determining the PAHs concentrations in the treated water and the corresponding distribution coefficients. Comparing with the batch operation in our previous study, a comparable high performance was able to be obtained by the continuous process in a PAHs initial concentration range lower than 20 mg/L, which means that the continuous process was feasible in the treatment of common PAHs polluted water. And the results that the extractability of the system increased with the ultrasonic power and system volume indicated that a high performance was expectable in a further scaling up process with a higher column volume, given a suitable ultrasonic power.