Cloud point extraction, preconcentration and simultaneous spectrophotometric determination of nickel and cobalt in water samples

Cloud point extraction has been used for the preconcentration and simultaneous spectrophotometric determination of nickel and cobalt after the formation of a complex with 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA), and latter analysis by spectrophotometer using Triton X-114 as surfactant. The parameters affecting the separation phase and detection process were optimized. Under the optimum experimental conditions (i.e. pH=5, 0.07 mM ACDA, Triton X-114=0.25% (w/v)), calibration graphs were linear in the range of 20-500 and 20-200 microg l(-1) with detection limits of 10 and 7.5 microg l(-1) for Ni and Co, respectively. The method was applied to the determination of Ni and Co in natural and waste water samples with satisfactory results.     

Simultaneous spectrophotometric determination of uranium and zirconium using cloud point extraction and multivariate methods

A cloud point extraction (CPE) process using the nonionic surfactant Triton X-114 to simultaneous extraction and spectrophotometric determination of uranium and zirconium from aqueous solution using partial least squares (PLS) regression is investigated. The method is based on the complexation reaction of these cations with Alizarin Red S (ARS) and subsequent micelle-mediated extraction of products. The chemical parameters affecting the separation phase and detection process were studied and optimized. Under the optimum experimental conditions (i.e. pH 5.2, Triton X-114?=?0.20%, equilibrium time 10?min and cloud point 45?°C), calibration graphs were linear in the range of 0.01?C3?mg?L^?1 with detection limits of 2.0 and 0.80???g L^?1 for U and Zr, respectively. The experimental calibration set was composed of 16 sample solutions using an orthogonal design for two component mixtures. The root mean square error of predictions (RMSEPs) for U and Zr were 0.0907 and 0.1117, respectively. The interference effect of some anions and cations was also tested. The method was applied to the simultaneous determination of U and Zr in water samples.     

Cloud point extraction and simultaneous determination of zirconium and hafnium using ICP-OES

In the present study a simple versatile separation method using cloud point procedure for extraction of trace levels of zirconium and hafnium is proposed. The extraction of analytes from aqueous samples was performed in the presence of quinalizarine as chelating agent and Triton X-114 as a non-ionic surfactant. After phase separation, the surfactant-rich phase was diluted with 30% (v/v) propanol solution containing 1 mol l(-1) HNO3. Then, the enriched analytes in the surfactant-rich phase were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The different variables affecting the complexation and extraction conditions were optimized. Under the optimum conditions (i.e. 3.4 x 10(-5) mol l(-1) quinalizarine, 0.1% (w/v) Triton X-114, 55 degrees C equilibrium temperature) the calibration graphs were linear in the range of 0.5-1000 mug l(-1) with detection limits (DLs) of 0.26 and 0.31 microg l(-1) for Zr and Hf, respectively. Under the presence of foreign ions no significant interference was observed. The precision (%RSD) for 8 replicate determinations at 200 microg l(-1) of Zr and Hf was better than 2.9% and the enrichment factors were obtained as 38.9 and 35.8 for Zr and Hf, respectively. Finally, the proposed method was successfully utilized for the determination of these cations in water and alloy samples.     

Determination of nitroanilines in hair dye using polymer monolith microextraction coupled with HPLC

In this study, a novel method for the determination of nitroanilines in hair dye samples has been developed based on poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith microextraction (PMME) and high-performance liquid chromatography (HPLC) analysis. Four nitroanilines, p-nitroaniline (PNAL), m-nitroaniline (MNAL), o-nitroaniline (ONAL), and 2,4-dinitroaniline (DNAL), are studied as representatives. To obtain optimum extraction efficiency, several experimental parameters including sample flow rate, sample volume, sample pH, and eluent flow rate have been investigated. Under the optimal experimental conditions, the linear regression coefficients of the standard curves are greater than 0.9990. The limits of detection for p-nitroaniline, m-nitroaniline, o-nitroaniline, and 2,4-dinitroaniline are 0.012, 0.008, 0.018, and 0.005 μg/mL, respectively. The intraday and interday relative standard deviations are less than 3.1 and 5.4%, respectively. The proposed method is simple, rapid, sensitive, and competent when used for the determination of nitroanilines in hair dye samples and the accuracy is assessed through recovery experiments.     

Application of vortex-assisted supramolecular solvent liquid–liquid microextraction for trace determination of nitroaniline isomers

A novel, fast and efficient method for the analysis of nitroaniline isomers as model compounds was developed using vortex-assisted supramolecular solvent liquid–liquid microextraction (VA-SMS-LLME). A vortex mixer was used as the mixer in supramolecular solvent liquid–liquid microextraction, and it decreased the extraction time greatly. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, salt effect and extraction time, were optimised in detail. Under the optimal conditions, the enrichment factor was 133 for p-nitroaniline, 98 for m-nitroaniline and 115 for o-nitroaniline, and the limits of detection by HPLC were 0.3, 1.0 and 0.5 μg L^?1, respectively. Linearity with determination coefficient from 0.9981 to 0.9993 was evaluated using water samples spiked with the nitroanilines at fourteen different concentration ranging from 4 to 1000 μg L^?1. The ranges of intra-day and inter-day precision (n = 5) at 10 μg L^?1 of nitroanilines were 1.67–7.05% and 9.4–11.6%, respectively. The VA-SMS-LLME method was successfully applied for preconcentration of nitroanilines in environmental water samples.     

The application of cloud point preconcentration for the determination of Cu in real samples by flame atomic absorption spectrometry

A simple and practical preconcentration method using cloud point approach is proposed for the extraction and preconcentration of Cu (II). The analyte in the initial aqueous solution, acidified with HCl, is complexed with O,O-diethyldithiophosphate and Triton X-100 is added as a surfactant. After phase separation at 40°C based on cloud point of the mixture and dilution of the surfactant-rich phase with methanol, the enriched analyte is determined by flame atomic absorption spectrometry using conventional nebulization and the analytical wavelength used is 324.8 nm. The variables affecting the complexation and extraction steps were optimized. Under optimum conditions, preconcentration of 10 ml of sample in the presence of 0.1% (v/v) Triton X-100 permitted the detection of 0.94 ng ml⁻¹ of Cu. Analytical graphs were rectilinear in the concentration range of 5-200 ng ml⁻¹ and relative standard deviations were lower than 3%. The method affords recoveries in the range 97-101%. The method was successfully applied to the determination of Cu in drinking and rainwater, serum and human hair samples.     

浊点萃取-火焰原子吸收光谱法测定淡水鱼中痕量铅

采用以双硫腙为络合剂、Triton X-100为表面活性剂的新型浊点萃取体系富集淡水鱼中的痕量铅,并用火焰原子吸收光谱法对其进行测定。探讨了溶液pH、表面活性剂浓度、络合剂用量、平衡温度、平衡时间等对浊点萃取及测定灵敏度的影响,优化了实验条件。在最佳条件下测得铅的检出限为0.090μg/L,校准曲线相关系数为0.9999。该方法已用于淡水鱼中痕量铅的测定。     

Pre-concentration procedure for determination of copper and zinc in food samples by sequential multi-element flame atomic absorption spectrometry

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box-Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3sigma(b)/S, LOD) of 0.1 microg L(-1), precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% (N=10), for copper concentrations of 10 and 50 microg L(-1), respectively. Zinc is determined with a LOD of 0.15 microg L(-1) and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 microg L(-1), respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a - Wheat Flour and SRM 8433 - Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 microg g(-1) and zinc from 8.7 to 22.9 microg g(-1).     

Spectrophotometric determination of paracetamol in urine with tetrahydroxycalix[4]arene as a coupling reagent and preconcentration with triton X-114 using cloud point extraction

In the present paper, conventional spectrophotometry in conjunction with cloud point extraction-preconcentration were investigated as alternative methods for paracetamol (PCT) assay in urine samples. Cloud point extraction (CPE) was employed for the preconcentration of p-aminophenol (PAP) prior to spectrophotometric determination using the non-ionic surfactant Triton X-114 (TX-114) as an extractant. The developed methods were based on acidic hydrolysis of PCT to PAP, which reacted at room temperature with 25,26,27,28-tetrahydroxycalix[4]arene (CAL4) in the presence of an oxidant (KIO(4)) to form an blue colored product. The PAP-CAL4 blue dye formed was subsequently entrapped in the surfactant micelles of Triton X-114. Cloud point phase separation with the aid of Triton X-114 induced by addition of Na(2)SO(4) solution was performed at room temperature as an advantage over other CPE assays requiring elevated temperatures. The 580 nm-absorbance maximum of the formed product was shifted bathochromically to 590 nm with CPE. The working range of 1.5-12 mug ml(-1) achieved by conventional spectrophotometry was reduced down to 0.14-1.5 mug ml(-1) with cloud point extraction, which was lower than those of most literature flow-through assays that also suffer from nonspecific absorption in the UV region. By preconcentrating 10 ml sample solution, a detection limit as low as 40.0 ng ml(-1) was obtained after a single-step extraction, achieving a preconcentration factor of 10. The stoichiometric composition of the dye was found to be 1 : 4 (PAP : CAL4). The impact of a number of parameters such as concentrations of CAL4, KIO(4), Triton X-100 (TX-100), and TX-114, extraction temperature, time periods for incubation and centrifugation, and sample volume were investigated in detail. The determination of PAP in the presence of paracetamol in micellar systems under these conditions is limited. The established procedures were successfully adopted for the determination of PCT in urine samples. Since the drug is rapidly absorbed and excreted largely in urine and its high doses have been associated with lethal hepatic necrosis and renal failure, development of a rapid, sensitive and selective assay of PCT is of vital importance for fast urinary screening and antidote administration before applying more sophisticated, but costly and laborious hyphenated instrumental techniques of HPLC-SPE-NMR-MS.     

Micro-cloud point extraction for preconcentration of Aspirin in commercial tablets prior to spectrophotometric determination

A fast, simple, inexpensive and effective method is developed for spectrophotometric determination of Aspirin in commercial tablets based on micro-cloud point extraction (MCPE). The proposed MCPE is essentially a miniaturized form of traditional cloud point extraction (CPE) in which only a few microliters of micellar extracting phase is sufficient for spectrophotometric determination. For comparison with MCPE, cloud point extraction was examined for Aspirin extraction. Triton X-114 was employed as a non-ionic surfactant for extraction/preconcentration of aspirin. Factors influencing the extraction efficiency, such as concentration of Triton, effect of pH, type of dilution solvent, etc. were investigated and optimized. Under the optimized condition, linear calibration curve for MCPE was in the range of 0.05–2 mg/L and limit of detection of 0.05 mg/L was obtained, whereas linear part for CPE calibration curve was 0.9 to 11 mg/L with a limit of detection of 0.5 mg/L.     

Determination of Sn(II) and Sn(IV) after mixed micelle-mediated cloud point extraction using alpha-polyoxometalate as a complexing agent by flame atomic absorption spectrometry

The cloud point extraction behavior of Sn(II) and Sn(IV) using alpha-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with alpha-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5x10(-5) mol L(-1) CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 microg L(-1) of Sn(II) and 46-750 microg L(-1) of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 microg L(-1) for Sn(IV) and 8.4 microg L(-1) for Sn(II). The relative standard deviation of seven replicate determination of 100 microg L(-1) both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.     

H-point standard addition method for simultaneous spectrophotometric determination of Co(II) and Ni(II) by 1-(2-pyridylazo)2-naphthol in micellar media

A very simple and selective spectrophotometric method for simultaneous determination of Co(II) and Ni(II) by 1-(2-pyridylazo) 2-naphthol (PAN), in micellar media, using H-point standard addition method (HPSAM) is described. The ligand and its metal complexes (Co(II)-PAN and Ni(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. Formation of both the complexes was complete within 10 min at pH 9 (adjusted by ammonia buffer). The linear range was 0.10-2.00 microg ml(-1) for Co(II) and 0.05-1.50 microg ml(-1) for Ni(II). The relative standard deviation (R.S.D.) for the simultaneous determination of 0.50 microg ml(-1) each of Co(II) and Ni(II) was 2.32 and 3.13%, respectively. Interference effects of common anions and cations were studied and the method was applied to simultaneous determination of Co(II) and Ni(II) in alloy samples. The method was compared with derivative spectrophotometric method.     

Use of cloud point extraction with derivatizing reagent for the extraction and determination of isoniazid

A simple and sensitive cloud point extraction high-performance liquid chromatography method is proposed for the determination of isoniazid in blood. The procedure is based on the product of the reaction of isoniazid with benzaldehyde. It can be validated that there is a linear relationship between the signal of isonicotinyl hydrazone and the concentration of isoniazid. A cloud point extraction system of nonionic surfactant Triton X-100 is applied for preconcentration of isonicotinyl hydrazone. Then the analytes in surfactant-rich phase are detected with HPLC-UV system. calibration graph was obtained in the range of 2.0 × 10(-3)-0.5 mg/L, the detection limit was 5.0 × 10(-4) mg/L. Method validation is performed on serum samples spiked at two levels, the recoveries ranging from 82.17-83.81%, with relative standard deviations from 2.45% to 3.89%.     

Simultaneous cloud point extraction and spectrophotometric determination of carmoisine and brilliant blue FCF in food samples

A novel simultaneous cloud point extraction method for the determination of carmoisine and brilliant blue FCF by spectrophotometry has been developed. The method is based on the cloud point extraction of carmoisine and brilliant blue FCF from aqueous solution using Triton X-100, diluting the extracted surfactant rich phase with water and measuring the absorbance at 522 and 640 nm for carmoisine and brilliant blue FCF, respectively. The effects of different parameters such as pH, concentration of surfactant and temperature on the cloud point extraction of both dyes were investigated and optimum conditions were established. Linear calibration curves were obtained in the range of 0.02-3.50 μg mL⁻¹ for carmoisine and 0.05-3.50 μg mL⁻¹ for brilliant blue FCF under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.017 and 0.016 μg mL⁻¹ (n = 10) for carmoisine and brilliant blue FCF, respectively. The relative standard deviation (RSD) for 0.1 μg mL⁻¹ was 4.14 and 3.30% (n = 10), for carmoisine and brilliant blue FCF, respectively. The method was applied to the simultaneous determination of the dyes in different food samples.     

浊点萃取-火焰原子吸收光谱法测定样品中的痕量钴

研究了基于表面活性剂Triton X-114和络合剂吡咯烷二硫代氨基甲酸铵（APDC）浊点萃取钴的样品前处理方法.优化了浊点萃取条件参数,包括pH值、Triton X-114用量、APDC浓度、平衡温度及时间等,建立了浊点萃取-火焰原子吸收光谱法测定痕量钴的方法.该法的检测限（3σ）为2.6μg/L,相对标准偏差RSD为6.2%（n=7,c=200μg/L）.该法成功地应用于海带、维生素B12注射液等样品中钴的测定.     

Flame atomic absorption spectrometric determination of trace amounts of palladium,gold and nickel after cloud point extraction

In this article, a sensitive cloud point extraction procedure for the preconcentration of trace amounts of palladium, gold and nickel prior to their determination by flame atomic absorption spectrometry has been developed. The cloud point extraction method is based on the complexation of Pd(II), Au(II), and Ni(II) ions with 1-(2-pyridylazo)-2-naphthol and entrapping in non-ionic surfactant Triton X-114. The main factors affecting cloud point extraction efficiency, such as pH of sample solution, concentration of 1-(2-pyridylazo)-2-naphthol and Triton X-114, equilibration temperature and time, were investigated in detail. Under the optimized conditions, calibration curves were constructed for the determination of palladium, gold and nickel according to the general procedure. Linearity was maintained from 0.01 to 1.0 μg/mL for palladium, 10.0 μg/mL to 1.5 μg/mL for gold, and 10.0 μg/mL to 0.5 μg/mL for nickel. Detection limits based on three times the standard deviation of the blank divided by the slope of analytical curve (3Sb/m) for Pd(II), Au(III), and Ni(11) ions were 3.4, 3.9, and 2.4 μg/mL, respectively. Seven replicate determination of a mixture of 0.5 μg/mL palladium and gold and 0.2 μg/mL nickel gave a mean absorbance of 0.174, 0.150, and 0.201 with relative standard deviation ±1.5, ±1.3, and ±1.8%, respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method has been applied for determination of trace amount of palladium, gold and nickel in certified reference material and water samples with satisfactory results.     

Development of a cloud point extraction and preconcentration method for silver prior to flame atomic absorption spectrometry

The possibility was investigated of using 2-mercaptobenzothiazole (MBT) for Ag(I) concentration by micellar extraction at cloud point (CP) temperature and subsequent determination by flame atomic absorption spectrometry (FAAS). The method is based on the complexation of Ag(I) with 2-mercaptobenzothiazole (MBT) in the presence of non-ionic micelles of Triton X-114. The effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. Under the optimum conditions, the preconcentration of 10 mL of water sample in the presence of 0.1% Triton X-114 and 2 × 10⁻⁴ mol L⁻¹ 2-mercaptobenzothiazole permitted the detection of 2.2 ng mL⁻¹ silver. The calibration graph was linear in the range of 10–200 ng mL⁻¹, and the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Ag(I) in water samples.     

Cloud point extraction and spectrophotometric determination of Cu(II) in saturated saline solutions using 4-ethyl-1-(pyridin-2-yl)thiosemicarbazide

4-Ethyl-1-(pyridin-2-yl)thiosemicarbazide (HEPTS) has been used as a new complexing agent in cloud point extraction (CPE) for preconcentration and determination of trace amounts of copper in saturated saline medium. The chemical variables affecting the separation and determination processes were optimized. Copper(II) is preconcentrated using 0.05% (w/v) Triton X-114 and 10⁻⁴ M HEPTS at pH 6. The surfactant rich phase containing the complex was dissolved in 2 mL MeOH and determined spectrophotometrically. The calibration curve is linear in the 0.1–25 ng/mL copper range. The proposed method was applied successfully in the determination of copper in water and saturated saline samples. The reaction between CuSO₄ and HEPTS yields a deep-blue solid complex which is characterized by analytical and spectroscopic analyses.     

Separation, preconcentration and measurement of inorganic iron species by cloud point extraction and flow injection flame atomic absorption spectrometry

A sensitive and simple method for determination of iron species after separation/preconcentration by cloud point extraction (CPE) has been developed. When the temperature is higher than the cloud point extraction temperature (60 °C), the complexes of iron(II) and iron(III) species with ferron enter the surfactant-rich phase. Total amount of iron in the surfactant-rich phase was analyzed by FI-AAS, whereas, Fe(II) concentration was determined by a spectrophotometric method using mathematical equation to overcome the interference of Fe(III), when they are both present in the same solution. In this way the time-consuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) were eliminated. The parameters affecting could point extraction, such as concentrations of ferron and Triton X-114, pH, and equilibrium temperature were systematically investigated. Under the optimum conditions, the calibration curves were linear over the range of 10-250 and 5-150 μg l^-1 for 20 and 40 ml preconcentration volume, respectively. The detection limit was 1.7 μg l^-1, and relative standard deviation (RSD) was 2.1% for 20 ml preconcentration volume. The method was applied to the determination of iron species in water samples and total iron in milk. The accuracy was determined by recovery experiment, independent analysis by furnace atomic absorption spectrometry and analysis of certified reference water.     

Cloud point extraction and preconcentration for the gas chromatography of phenothiazine tranquilizers in spiked human serum.

Cloud point extraction was successfully applied to the preconcentration of phenothiazine derivatives, such as pericyazine (PC), chlorpromazine (CP) and fluphenazine (FUL), for gas chromatography (GC). Phenothiazine derivatives were separated from surfactants by passing the surfactant-rich phase through a cation exchange column after cloud point extraction, permitting the determination of the phenothiazine derivatives extracted in the surfactant-rich phase by GC. The optimal condition for the cloud point extraction of phenothiazine derivatives was also investigated using Triton X-100, Triton X-114, and PONPE10. Triton X-114 provided the most efficient recovery of phenothiazine derivatives among the surfactants used. The addition of sodium chloride and excess ammonia to the sample solution resulted in a decrement of the recovery of the phenothiazine derivatives. The proposed method was applied to the determination of phenothiazine derivatives in spiked human serum by GC. The recoveries of PC, CP, and FUL in spiked human serum were 95.1%, 87.1%, and 84.7%, respectively.