Ultrasound-assisted Cloud Point Extraction Research Articles

Rapid preconcentration and determination of Co (II) ions in aqueous medium using ultrasound assisted cloud point extraction method

A flame atomic absorption spectrophotometric technique was studied for the preconcentration and determination of of Co2+ ions in trace amounts after ultrasound enhanced enrichment of its 1-(2-pyridylazo)-2-naphthol (PAN) complexes by cloud point extraction. The Co2+ ions were firstly complexed with PAN molecules at pH 4 and the complex transferred to a surfactant (Tergitol NP-7) rich phase with a very small volume under ultrasound waves. The surfactant rich phase was separated and dissolved by 1 mL, 1.0 M HNO3 in ethanol prior to determination of Co2+ concentration by flame atomic absorption spectrophotometry. The optimization steps of ultrasound interaction time, solution pH and surfactant volumes were achieved by response surface methodology (RSM) which is a combination of statistical approaches. Sample volume, PAN concentration and and possible interfering ions were optimized conventionally. The Co2+ ions were extracted only in 150 s at pH 4 quantitatively under optimum conditions (˃95%). The accuracy and validity of developed UA-CPE was granted by employing a certified reference material wastewater UME CRM 1204. The technique was applied to wastewater and natural water with satisfactory results.

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.

Application of ultrasound assisted-cloud point extraction coupled with spectrophotometry for the selective extraction/pre-concentration of low levels of inorganic Hg (as Hg2 2+/Hg2+) from liquid matrices

ABSTRACT This study presents the analytical characterisation of a low-cost, selective and sensitive method for inorganic Hg (as Hg2 2+/Hg2+) determination in liquid matrices based on spectrophotometry. The novelty of the study lies in combining the pre-concentration of i-Hg with spectrophotometry after chelation with the 2-aminobenzimidazole modified amidic copolymer to increase the selectivity and sensitivity of the method. The method involves ultrasonic extraction of the samples in a dilute acid mixture of HClO4-HCl-CH3COOH and mixture of Cu(II)-oxalic acid-KCl adjusted to pH 5.0 in parallel, pre-con centration using UA-CPE process on modified amide copolymer, and absorbance measurement at 332 nm using a micro-volume UV-spectrophotometer. The figures of merit were discussed in relation with the demands in the national/international regulations and standards on the determination of toxic i-Hg in water intended for human consumption. After a pre-concentration of 62.5-fold, the limits of detection and quantification (LODs, LOQs) were 0.24 and 0.22 μg L−1 allowing the use of the method for i-Hg determination in liquid matrices such as cold-/hot-spring waters, plain soda, bottled drinking waters, and carbonated soft drinks. For concentrations of Hg2 2+, Hg2+ and total Hg in the range of <LOD, 0.35–4.20, and 0.40–4.50 μg L−1, the precision was 3.3–8.3%, below and little above the maximum limits of 1.0 µg L−1 set in the mentioned legislation. The recovery of 92–96.4% and the precision in the range of 4.1–5.4% in the analysis of two certified waters were found to be satisfactory, so as to validate the method. The method developed is cost-effective and enables us to achieve i-Hg determination in liquid matrices complying with European legislation. The system has a good potential for the future and analytical perspectives.

Novel amide- and imide-co-polymers modified with sulfathiazole as efficient chelator for selective extraction, pre-concentration and determination of trace inorganic antimony (as Sb(III)) from edible vegetable oils by ultrasound assisted-cloud point extraction coupled to micro-volume UV-spectrophotometry

The study described the synthesis, characterization, and application of newly prepared sulfathiazole-modified amide/imide co-polymers for the extraction of trace Sb(III) from edible vegetable oils. The method was based on the pH-dependent complexation between Sb(III) and chelators as a result of charge transfer via tautomerization in presence of the mixed ionic surfactants in 5%(v/v) 2-propanol, 1:1, v/v) at pH 2.0 and 8.0, respectively for amide and imide copolymers and then selectively ultrasound assisted-cloud point extraction of the Sb(III)-complexes into the micellar phase of extractant. The separated micellar phase by centrifugation was diluted to 0.4 mL with tetrahydrofuran, and detected at 269 nm by micro-volume UV-spectrophotometry. The parameters affecting extraction efficiency were optimized. The optimal extraction conditions were found to be: 0.6/0.8 mmol L−1 of McIlvaine buffer, 30 µmol L−1 of the mixed-ionic surfactant mixture, 120 µmol L−1 KCl, 0.1/0.06% (v/v) of the nonionic surfactant and (0.4/0.2)× 10−3%(w/v) of sulfathiazole-modified amide/imide copolymers at pH 2.0 and 8.0 for 7 min at 40 °C in an ultrasonic bath (40 kHz, 300 W). From preconcentration of 20-mL sample, the good linear relationships (r2 ≥0.995) between absorbance and Sb(III) concentration were obtained from calibration curves prepared in solvent in range of 1–40 and 1–62.5 µg L−1 with the method detection limits of 0.30/0.47 and 0.51/0.51 µg L−1 at 269 nm by spectrophotometer after 50-fold pre-concentration. The accuracy was statistically verified by analysis of a non-certified sample with and without spiking where the precision and relative recoveries are within 5–12% and 83–92%, respectively. Also, the matrix effect was evaluated by triplicate measurements of 25 µg L−1 Sb(III) (n: 3) under optimal conditions. The method was successfully applied into the analysis of total iSb levels of edible vegetable oils. The results shown that the STZ-modified amide/imide co-polymers were efficient selective chelators even in presence of 50-fold excess Sb(V), and exhibited great potential as alternative binding chelators for the extraction of Sb(III) from edible vegetable oils.

PH-controlled charge transfer sensitive 2-aminobenzimidazole modified poly(styrene-co-maleic anhydride) copolymer for selective extraction, pre-concentration and determination of trace Hg2+ and CH3Hg+ in vinegar by combination of ultrasound assisted-cloud point extraction with UV–VIS spectrophotometry

In this study, a separation/pre-concentration procedure, ultrasound assisted-cloud point extraction with modified 2-aminobenzimidazole (2-ABzI), was developed for the extraction of trace Hg2+ and CH3Hg+ and from vinegar samples- modified copolymer coupled with Hg-binding chelator, 2-ABzI. The imidic copolymer was characterized, and used for detection of the enriched Hg species by spectrophotometer at 332 nm. The method is based on their pH-induced charge transfer sensitive complexation with copolymer matrix via 2-AmBzI moiety at pH 6.0 and 4.5, and their extraction into the mixed micellar phase of the mixed non-ionic/ionic surfactants as extractant/sensitivity enhancer. The variables influencing the extraction efficiency were optimized. From pre-concentration of 25-mL sample, with a changing calibration sensitivity and pre-concentration factor of 62.5, a good rectilinear relationship between absorbance and concentrations of Hg species in ranges of 1–15, 15–150 µg L−1 was obtained. The detection limits are 0.30 and 0.31 µg L−1, respectively. Its precision/accuracy were in range of 3.1–7.6 % and 90.5–96 % after spiking (n: 5, for measurements of 5, 25 and 100 µg L−1 in same day and three consecutive days). The matrix effect was also studied (n: 3, 100 µg L−1). The method is simple, cost-effective, fast, accurate, safe, highly stable and selective, which has successfully been applied to the speciation of mercury in vinegar.

A magnetic nanocomposite based on amine-functionalized pH-sensitive functional poly(styrene-co-maleic anhydride) copolymer for selective extraction, pre-concentration and determination of sub-trace Ag+ and Cu2+ ions from edible vegetable oils by a combination of spectrophotometry and ultrasound-assisted cloud point extraction

A magnetic nanocomposite based on amine-functionalized pH-sensitive functional poly(styrene-co-maleic anhydride) copolymer for selective extraction, pre-concentration and determination of sub-trace Ag+ and Cu2+ ions from edible vegetable oils by a combination of spectrophotometry and ultrasound-assisted cloud point extraction

Eco-friendly trace analysis of silver in beer/wine samples using a new co-polymeric nanocomposite based-ultrasound assisted-cloud point extraction combined with spectrophotometry

In this study, a new magnetic nanocomposite based on the tris(2-hydroxymethyl)aminomethane-modified poly(styrene-co-N-maleimide) copolymer and Fe3O4 nanoparticles were prepared as a new micellar interface for pre-concentration of trace levels of silver from aqueous solutions by ultrasound assisted-cloud point extraction (UA-CPE). The structure of the nanocomposite was characterized by using some instrumental tools in detail. The method is selectively based on charge transfer among silver and reagents at pH 5.0, and detection by micro-volume UV–vis spectrophotometry at 346 nm. The main variables affecting extraction efficiency were evaluated and optimized in detail. Under the optimized conditions, the method shows good linear relationships in ranges of 2.5−125 μg L−1 and 4−160 μg L−1 by two calibration curves (established in solvent and beer/wine matrices) with a better determination coefficient (r2) than 0.992. The limits of detection, repeatability/intermediate precision (as RSDs%, 5, 25 and 100 μg L-1, n: 5) and recovery percentages were 0.85/1.21 μg L-1, 3.5–7.1% and 91.5–98.5%, respectively. From pre-concentration of 25-mL sample solution, a pre-concentration factor was found to be 62.5 with sensitivity enhancement of 23.2-fold in calibration. A matrix effect was not observed for the triplicate measurements of 100 μg L−1 Ag+ in the presence of various interfering species. The method accuracy was validated with the outcome of validation that was carried out. The method after two sample preparation procedures was successfully applied to reliable determination of total Ag in beer and wine samples. The total Ag levels were in range of 2.5–4.2 and 2.7–5.5 μg L−1 in beer and wine samples, respectively.

Coupling of ion pair ultrasound assisted-cloud point extraction to microvolume UV-Vis spectrophotometry for speciation analysis of ionic NO2-,NO3- and total NO2-/NO3- without and with reduction in the selected beverage and food matrices

ABSTRACT This study proposes a simple, low-cost, easy to use, fast, accurate and reliable ultrasound assisted-cloud point extraction (UA-CPE) method for the enrichment and speciation analysis of low levels of ionic NO2 −, NO3 − and total NO2 −/NO3 − without and with reduction by micro-volume UV-vis spectrophotometry. The method relies on the reaction of NO2 − with excess iodide at pH 5.5 to form triiodide, and then the extraction of the oxidation product formed by charge transfer into micellar phase of Triton X-114 using cationic redox-sensitive phenazine dye, neutral red (NRH+) as ion-pairing in absence and presence of 1.5 mL of 1.0 × 10−3 mol L−1 Br− ions. The main variables affecting extraction efficiency were studied and optimised in detail. Under the optimal conditions, the calibration curves in solvent were linear over the ranges of 5–100 and 100–1280 µg L−1 with a detection limit of 1.32 µg L−1 while the matrix-matched calibration curves prepared from sample extracts were linear over the ranges of 5–125 and 125–1350 µg L−1 with a detection limit ranging from 1.15 to 1.50 µg L−1 for sample matrices. From pre-concentration of 25-mL sample, pre-concentration and sensitivity enhancement folds of 62.5 and 76.5 were obtained. The accuracy/precision studies after spiking were performed, and observed to be in range of 96.5–99.6% and 1.9–5.7% (15, 75 and 250 µg L−1, n: 5). The speciation analysis of ionic NO2 −, NO3 − and total NO2 −/NO3 − was performed from artificially prepared binary mixtures after reduction with a mixture of Zn and NaCl in acidic media. The free NO3 − contents of samples were calculated from difference between free NO2 − and total NO2 −/NO3 − contents. After validation by analysis of a certified sample, the method was successfully applied to the speciation analysis of the beverage, cured meat, vegetable and milk samples. After pre-treatment with two sample preparation steps, it was observed that the results obtained were also compatible with each other, statistically validating the method.

Selective extraction of Cu+ and Cu2+ ions from mushroom and lichen samples prior to analysis by micro-volume UV-Vis spectrophotometry: Application of a novel poly (SMIm)-Tris-Fe3O4 nanocomposite

In this study, a novel poly (SMIm)-Tris-Fe3O4 nanocomposite was prepared for selective extraction of Cu+ and Cu2+ ions by ultrasound assisted-cloud point extraction (UA-CPE). The nanocomposite was characterized by analysis of ATR-FT-IR, 1H NMR and XRD. After optimization of the extraction conditions, the copper ions were independently detected against sample blank at 347 nm by micro-volume UV–vis spectrophotometer. Under the optimal conditions, good linear relationship was obtained in the ranges of 0.3−150 and 10−350 μg L−1 for each ion at pH 7.0 and pH 5.0, respectively, with a better regression coefficient than 0.992. The method detection limits, accuracy and precision were 0.095 and 3.03 μg L−1, 91.5−96.0 % and 93.0−98.5 %, and 2.5–4.5 and 3.8–7.1 % (n:5, 25 and 100 μg L−1) for Cu+ and Cu2+ ions, respectively. A preconcentration of 70-fold was obtained from 35-mL of sample. After validation, the method was successfully applied to determination of total Cu levels in lichen and mushroom samples after pre-reduction at pH 7.0, and the recoveries in the range of 90−96 % were obtained by two calibration approaches after spiking with 10 μg L−1. The results were also statistically compared with those obtained by FAAS analysis to ensure accuracy and precision.

Determination of trace metals in vegetables and water samples using dispersive ultrasound-assisted cloud point-dispersive µ-solid phase extraction coupled with inductively coupled plasma optical emission spectrometry

A simple method combining ultrasound assisted cloud point extraction (UA-CPE) and dispersive μ-solid phase extraction (D-μ-SPE) was developed for preconcentration of As, Cd, Cr, Co, Sb, Pb and Tl to inductively coupled plasma optical emission spectrometric (ICP-OES). At optimum conditions, the linearity, limits of detection and limits of quantification were 0.20–1000 µg L−1, 90–150 ng L−1 and 200–500 ng L−1, respectively. The intraday (n = 20) and intraday (n = 5) precisions reported as the relative standard deviation ranged from 1.5 to 3.5% and 1.9–4.5%. The trueness of the method was investigated using CRM BCR679, NIST SRM 1573a, and SRM 1640a, as well as spiked recovery experiments. Satisfactory recoveries and relative errors ranging from 97 to 99.3% and −4.0 to 2.4% were obtained. The proposed UA-CPE-D-µ-SPE/ICP-OES method was successfully applied for various real samples such as groundwater, bottled mineral water, river water and borehole water and food samples.

Application of Ultrasound-assisted Cloud-point Extraction and Spectrophotometry for Preconcentration and Determination of Trace Amounts of Copper(II) in Beverages

A new method for preconcentration of trace Cu(II) in beverages before determination by spectrophotometry is presented. The method is based on the ternary complex formation of Cu(II) with Safranin T in presence of pyrogallol at pH 5.5 followed by its extraction into the micellar phase of Triton X-114. The ternary complex was monitored by spectrophotometry at 532 nm. Variables affecting extraction efficiency were evaluated and optimized. Under the optimal conditions, the detection limit was 0.6 µg/L in the range of 2–300 µg/L with sensitivity enhancement of 55 after preconcentration from 15 mL of the sample, and precision was in the range of 2.5–3.9%. The accuracy was verified by the analysis of two certified samples and recovery studies of the spiked samples. The intra- and inter-day precision varied in the ranges of 3.7–4.6 and 3.9–5.2%, respectively. The method was successfully applied to determination of trace Cu(II) in beverages.

Use of new polymeric composites for preconcentration of trace Ag+ ions from the selected mushroom/vegetables by ultrasound-assisted cloud-point extraction coupled to microvolume UV-Vis spectrophotometry

ABSTRACT The magnetic nano-composites based on the tris(hydroxymethlmethyl)aminomethane-modified maleic anhydride-co-styrene copolymers and Fe3O4 nano-particles were prepared as new potential chelating agents for ultrasound-assisted-cloud point extraction (UA-CPE) and pre-concentration of trace levels of Ag+ ions from aqueous solutions. The structures of the nano-composites were characterised via FT-IR, 1H-NMR and XRD analysis. After structural characterisation of composites, Ag+ ions were detected by micro-volume UV-vis spectrophotometry at 347 nm. The variables affecting complex formation and extraction efficiency for separation/pre-concentration of the Ag+ ions from various food matrices were evaluated and optimised in detail. Under the optimised conditions, the method shows a good sensitivity with linearity range from 10 to 350 µg L−1 and 4 to 160 µg L−1 for amidic and imidic composites, respectively, with a better correlation coefficient than 0.9825. The limits of detection, intra- and inter-day precision (as RSDs%) and recovery rates for six replicate determinations of Ag+ ions at levels of 25 and 100 μg L−1 were 4.28/1.21 μg L−1, 2.4–4.1% and 92–98% for the modified copolymers, respectively. The pre-concentration factor for Ag+ ion from pre-concentration of 35-mL sample was 70. A significant matrix effect was not observed for the triplicate measurements of 100 µg L−1 Ag+ in the presence of various interfering species below their maximum concentrations allowed in this method, for Ag+ ions. The accuracy of the method was confirmed by analysis of the two certified samples. The method was successfully applied to determine low levels of Ag+ ions in mushroom and vegetable samples, and satisfactory recoveries were obtained in the range of 91-97% with lower RSD than 5.1% for the spiked samples.

A Cost-Effective Spectrophotometric Method Based on Enzymatic Analysis of Jackfruit Latex Peroxidase for the Determination of Carbaryl and Its Metabolite 1-Napthol Residues in Organic and Chemical-Free Vegetables

Carbaryl is a member of the carbamate family and commonly used as an insecticide. A cost-effective and reliable method to determine carbaryl and its metabolite 1-naphthol was developed based on alkaline hydrolysis of carbaryl into 1-naphthol followed by enzymatic reaction with peroxidase, extracted from jackfruit latex in the presence of 4-aminoantipyrine and hydrogen peroxide under pH 6.0. The reaction product was pre-concentrated using ultrasound-assisted cloud-point extraction (UA-CPE) of Triton X-114 as surfactant prior to spectrophotometry at 500 nm. UA-CPE of jackfruit latex peroxidase achieved a calibration curve of carbaryl standard between 0.025 and 0.20 mg L−1 with r2 > 0.99. Detection and quantification limits were 9 and 24 μg L−1, respectively. Intra- and inter-day assay %RSDs were 5.15% (n = 7) and 7.24% (n = 4), respectively. An UA-QuEChERS technique was employed to ameliorate extraction performance of sample preparation. Recoveries between 81.9 and 102.4% were achieved. The proposed method was applied to determine carbaryl residues in organic and chemical-free vegetable samples. HPLC with UV detection was also performed for comparison and confirmation of measurements obtained by the proposed method.

A new ion-pair ultrasound assisted-cloud point extraction approach for determination of trace V(V) and V(IV) in edible vegetal oils and vinegar by spectrophotometry

A new ion-pair ultrasound-assisted-cloud point extraction (UA-CPE) procedure for the preconcentration and determination of V(V) and V(IV) in edible vegetal oils and vinegar by spectrophotometry at 530 nm was developed. The method is based on selective and sensitive anionic chelation of V(V) and V(IV) with EDTA, and then a stable ion-pair formation of the formed chelate complexes with cationic phenazine dye, Safranin T, at pH 4.0 and/or pH 5.0 respectively, which can be easily extracted into the micellar phase of Triton X-114 with the help of ultrasound energy. The variables affecting ion-pair formation and extraction efficiency were evaluated and optimized. Under the optimized conditions, there was a linear relationship in range of 1–40 μg/L for V(IV) at pH 5.0 with higher calibration sensitivity while it obtained a rectilinear behavior in the range of 2–180 μg/L for V(V) at pH 4.0. The limits of detection and quantification for V(IV) were 0.26 and 0.85 μg/L with a sensitivity enhancement of 83.6 from preconcentration of 35-mL sample, respectively where these values are 0.53 and 1.77 μg/L, respectively, for V(V). The recovery rate and precision for five replicate measurements of 5, 25 and 100 μg/L V(V) and V(IV) were in range of 98–101%, 3.1–4.2% and 3.2–4.5%, respectively. The accuracy was statistically verified by analysis of a certified oil sample with both the developed method and independent comparison method, and the method was successfully applied to the analysis of total V contents of edible vegetal oils and vinegar samples after preconcentration.

Manganese sensitised-indirect determination of melamine in milk-based samples by flame atomic absorption spectrometry coupled with ultrasound assisted-cloud point extraction

ABSTRACTIn the current study, a simple and low- cost method of UA-CPE in combination with flame atomic absorption spectrometry (FAAS) was developed for pre-concentration and indirect determination of melamine in milk-based samples. The method is based on the formation of charge transfer sensitive ternary complex among melamine, Mn(II) and Eosin Yin presence of sensitivity enhancer, ionic surfactant cetyltrimethylammonium bromide at pH 4.5, and then extraction of the formed complex into the micellar phase of nonionic surfactant, Triton X-114. After extraction, the surfactant-rich phase was diluted with 1.0 mol L−1 HNO3 in methanol and aspirated into the nebuliser of FAAS for indirect analysis. For optimisation of the variables affecting the ion-pair formation and extraction efficiency, the univariate method was adopted due to its simplicity and ease of use. Under optimal conditions, a good linear relationship was observed from 0.8 to 130 µg L−1 with a detection limit of 0.23 µg L−1. From pre-concentration of 35-mL sample, a pre-concentration factor of 70-fold was obtained with a good sensitivity enhancement (88.5). The accuracy and precision were evaluated as repeatability and intermediate precision with RSD of less than 6.5% with a recovery varied from 92.5% to 98.6%. (n: 5, 5, 25 and 100 µg L−1). The performance of the method from the accuracy and precision studies of two quality control samples was highly good with the precision (4.2–6.0%) and relative recoveries (91.4–96.0%) obtained for spiking levels, 5 and 10 µg L−1. The accuracy, according to two-way ANOVA analysis, was also controlled by two calibrations approaches without any matrix effect in analysis step of samples.

Development of a new analytical method for Pb preconcentration and its further determination in water and foodstuffs using relatively low-sensitivity flame atomic absorption spectrometry

ABSTRACTThe present study describes chelation of Pb(II) with ascorbic acid and formation of a charge-transfer sensitive ion-pair in the presence of Rhodamine 6G at pH 5.5, and then its extraction to the micellar phase of non-ionic surfactant, PONPE 7.5 by an ultrasound-assisted cloud point extraction method before analysis by FAAS. The various variables affecting ion-pair formation and extraction efficiency were studied and optimised. Under the optimised conditions, the good linear relationships in the ranges of 0.4–150 μg L−1 and 0.8–120 μg L−1 for solvent-based calibration and matrix-matched calibration curves, respectively, were achieved with a pre-concentration factor of 71.4 from pre-concentration of 50-mL sample. Moreover, the limits of detection with good sensitivity enhancements of 124 and 114.5 were 0.13 and 0.24 μg L−1, respectively, while the intra-day and inter-day precision (as RSD%, for five replicate measurements of 5 and 100 μg L−1 in the same day and three succeed days) were in range of 2.8–5.4% and 3.7–6.3%, respectively. The matrix effect on triplicate determination of 50 µg L−1 Pb(II) was also investigated. The accuracy of the method was statistically verified by the analysis of two certified reference materials (CRMs) after digestion with acid mixtures (HNO3-H2O2-HF and HNO3-H2O2) and dilution at suitable ratios. It has been observed that there is statistically not a significant difference between the certified- and found-values. The accuracy was also controlled using the pre-treated sample solutions spiked at different concentration levels, and the good spiked recoveries were obtained in range of 90–102.8%. The method was successfully applied to the determination of trace amounts of lead in water and food matrices with satisfactory results.

Use of 2-Hydrazinobenzothiazole-Modified Copolymer(s) as Potential Chelating Agent for Sensitive and Selective Determination of Low Levels of Mercury in Seafood by Ultrasound-Assisted Cloud-Point Extraction Combined with Spectrophotometry.

In this study, a new method was developed for the pre-concentration of trace mercury from seafood samples prior to analysis by spectrophotometry. The method is based on the complexation between 2-hydrazinobenzothiazole (2-HBT)-modified copolymer(s) and Hg(II) in the presence of an ionic surfactant, cetyltrimethylammonium bromide (CTAB), as sensitivity enhancer at pH4.5 and the extraction of the complex into the surfactant-rich phase of polyethylene glycol tert-octylphenyl ether (Triton X-114) as the extractant. The variables affecting extraction efficiency were evaluated and optimized. Due to the observation that the modified copolymers are 2.5-fold more sensitive and selective to the Hg2+ ions than the CH3Hg+, the amounts of free Hg2+ and total Hg were determined at 325nm by spectrophotometric detection of free Hg2+ and total Hg in the pre-treated and extracted fish samples using dilute acid mixture containing Triton X-114 and K2Cr2O7, before and after oxidation of CH3Hg+ to Hg2+ with mixture of KBr and KBrO3 in the acidic media. The amount of CH3Hg+ was calculated from the difference between total Hg and free Hg2+ amounts. The accuracy was tested by analysis of two certified samples. The results were statistically in good agreement with the certified values, and the precision was lower than 6.4%. The limits of detection were 1.40 (1.58) and 1.91 (2.11)μgL-1 for Hg2+ from the two calibration solutions spiked before the pre-treatment, respectively. It has been observed that there is no significant matrix effect by comparison of slopes of the calibration curves. The method was applied to seafood samples for speciation analysis of free Hg2+ and CH3Hg+. In terms of speciation, while total Hg is detected in the range of 12.6-143.8μgkg-1, the distribution of mercury in seafood was in the range of 7.4-53.3μgkg-1 for CH3Hg+ and in 8.3-90.5μgkg-1 for free Hg2+.

Application of ultrasound-assisted cloud point extraction for preconcentration of antimony, tin and thallium in food and water samples prior to ICP-OES determination

This study reports a simple, rapid and greener method based on ultrasound assisted-cloud point extraction coupled with inductively coupled plasma-optical emission spectroscopy (ICP-OES) for preconcentration and determination of antimony (Sb), tin (Sn) and thallium (Tl) in food and water samples. Factors affecting the preconcentration procedure were optimized using fractional factorial design and response surface methodology based on Box-Behnken design. Under optimum conditions, the calibration graphs were linear over the concentration range of 0.023–700 μg L−1 with correlation coefficients up to 0.9994, the limits of detection ranged from 0.007–0.010 μg L−1, the limits of quantification were from 0.023 to 0.033 μg L−1 and the relative standard deviations (n = 15) were between 1.3% and 4.1%. In addition, the preconcentration factors were found to be 150, 145 and 160 for Sb, Sn and Tl, respectively. Finally, the developed method was successfully applied in various food and water samples as well as certified reference materials for rapid determination of Sb, Sn and Tl.

Combination of Ultrasound-Assisted Cloud-Point Extraction with Spectrophotometry for Extraction, Preconcentration, and Determination of Low Levels of Free Formaldehyde from Cosmetic Products.

In the present study, a new preconcentration method was developed to quantify the free formaldehyde (FA) in hair cosmetics by combining ultrasound-assisted cloud-point extraction with spectrophotometry. The method is based on the ion association of FA with cationic phenothiazine group dye, toluidine blue in presence of sulfite at pH 5.0, and then extraction of the formed complex into the micellar phase of nonionic surfactant, Triton X-114. The analyte extracted into the micellar phase was diluted with ethanol, and then detected at 630nm by spectrophotometer. Under optimal conditions, a good linear relationship was obtained in the range of 2-120μg/L with a detection limit of 0.38μg/L. By preconcentration of 15 mL sample, the calibration sensitivity increased by 74-fold. The intra- and inter-day precisions expressed as RSDs are lower than 4.7 and 5.2%, respectively. Compared with other techniques, the study shown here provides a simple, fast, accurate, and reliable method for the analysis of FA in cosmetic products. The contents of FA of the samples are in the range of 3.4-25.1mg/kg with an RSD lower than 4.6%. The results were statistically in good agreement with those obtained by an independent comparison method. Highlights: A new method was developed for the preconcentration of free formaldehyde from hair cosmetics. The method is simple, fast, precise, selective, and sensitive to detect trace formaldehyde. The precision is lower than 5.2% with recovery higher than 95% after spiking. The method was validated by comparing the results with those of independent method. The formaldehyde levels of hair cosmetics were reliably monitored and determined.

Preconcentration and Determination of Trace Nickel and Cobalt in Milk-Based Samples by Ultrasound-Assisted Cloud Point Extraction Coupled with Flame Atomic Absorption Spectrometry.

In this study, ultrasound-assisted cloud point extraction (UA-CPE) method was developed for the determination of Ni(II) and Co(II) in milk-based products. After extraction and preconcentration, the Ni(II) and Co(II) contents of samples were determined by flame atomic absorption spectrometry (FAAS). After their complexation with hydroxy naphthol blue (HNB) in the presence of cationic surfactant, CTAB at pH 4.0, the Ni(II) and Co(II) were taken within the micellar phase of nonionic surfactant, TX-114. The micellar phase containing the analytes were diluted to a volume of 0.7mL with 1.0-mol/L HNO3 in ethanol to reduce its viscosity and to facilitate sample treatment and then was analyzed by FAAS. The various analytical parameters affecting UA-CPE efficiency were investigated. The analytical features obtained after optimization are as follows: limits of detection are 0.56 and 0.78μg/L; sensitivity enhancement factors are 48.6 and 53.9; the calibration curves were linear 3-180 and 2-160μg/L for Co(II) and Ni(II), respectively, after preconcentration of 50-fold. The precision (as RSD%) between 1.8-3.6% and 2.2-3.8% (25 and 100μg/L, n = 5) for Ni(II) and Co(II), respectively. The accuracy was statistically verified by analysis of two certified reference material samples (CRMs), including recovery studies after spiking. The method was applied to the analysis of milk-based samples with satisfied results.