Development of dispersive liquid-liquid microextraction based on deep eutectic solvent using as complexing agent and extraction solvent: application for extraction of heavy metals

ABSTRACT

A green and efficient dispersive liquid-liquid microextraction method based on a new deep eutectic solvent has been developed for the preconcentration and extraction of cobalt and nickel ions. The deep eutectic solvent is formed by mixing choline chloride (hydrogen bond acceptor) and 4-aminophenol (hydrogen bond donor). Then, it is used as a chelating agent as well as extraction solvent. Under the optimum experimental conditions, the linear ranges for Ni(II) and Co(II) were 0.80–50 and 0.50–50 µgL^?1, respectively, by flame atomic absorption spectrometry. The obtained detection limits were 0.30 and 0.22 µg L^?1 for Ni(II) and Co(II), respectively.     

Solid Phase Extraction and Preconcentration of Trace Heavy Metal Ions in Natural Water with 2,2′‐Dithiobisaniline Modified Amberlite XAD‐2

Abstract

A solid phase extraction and preconcentration methodology utilizing a new chelating resin is described for the separation of Cd, Ni, Co, Cu, and Zn. The chelating resin matrix was prepared by covalently linking 2,2′‐dithiobisaniline synthesized from 2‐aminothiophenol with the benzene ring of polystyrene‐divinylbenzene resin Amberlite XAD‐2 through a –N?N– group. Its adsorption and preconcentration behavior for Cd, Ni, Co, Cu, and Zn in aqueous solution was studied using batch and column procedures in detail. The newly designed resin quantitatively adsorbs Cd, Ni, Co, Cu, and Zn above pH 5.0. Subsequent elution with 2 M HCl readily strips the sorbed metal ions from the resin. The sorption capacity is 360, 230, 170, 200, and 150 mol g^?1 for Cd, Ni, Co, Cu, and Zn, respectively. Their preconcentration factors are 80–200. The time for 80% sorption was less than 10 min for all five metal ions. The effects of electrolytes on the preconcentration were also investigated with the recoveries >95%. The procedure was validated by analysis of a standard reference river sediment material (GBW 08301 China). The developed method was successively utilized for the determination of Cd, Ni, Co, Cu, and Zn in tap water and river water by flame atomic absorption spectrometry (FAAS) after column SPE and preconcentration. The 3σ detection limits for these metal ions were found to be 0.10, 0.34, 0.42, 0.16, and 0.52 g L^?1, respectively. The relative standard deviation was <10% for the determination of 10 g each of Cd, Ni, Co, Cu, and Zn in a 100 mL water sample.     

Adsorption of Ni(II) and Co(II) Using Microballoons Containing Mg-Silicate and CYANEX923 Prepared by the Emulsion Liquid Membrane System

Abstract

The Mg-silicate microballoons containing CYANEX923 were prepared by W/O/W emulsion. The diameter of obtained micro-sphere particles was ～10 µm and shell thickness was 2 µm. The adsorption of Co(II) and Ni(II) from aqueous solutions using prepared micro-sphere particles was investigated. Experiments were carried out as a function of solute concentration and temperature (25–60°C). Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Equilibrium adsorption data were analyzed using Langmuir isotherm model. The results indicated that prepared micro-sphere particles can be used as an efficient adsorbent for the removal of Ni(II) and Co(II) from aqueous solution.     

Macromolecular Chelator‐Amberlite XAD‐16 Anchored with 2,3‐Dihydroxypyridine (DHP) for Enrichment of Metal Ions before their Determination by Flame Atomic Absorption Spectrometry

Abstract

2,3‐Dihydroxypyridine (DHP) was loaded onto Amberlite XAD‐16 via azo linker and the resulting resin AXAD‐16‐DHP explored for enrichment of Zn(II), Mn(II), Ni(II), Pb(II), Cd(II), Cu(II), Fe(III), and Co(II) in the pH range 4.0–6.5. The sorption capacity was found in the range 120–512 µmol g^?1 and the preconcentration factor from 200 to 300. Tolerance limits for foreign species are reported. The kinetics of sorption is fast, as t_1/2 is generally ≤2 min. The chelating resin can be reused for fifty cycles of sorption‐desorption without any significant change (≤2.0%) in its sorption capacity. The limit of detection values (blank + 3s) are 2.90, 3.80, 5.17, 7.02, 1.91, 1.63, 4.59, and 5.02 µg L^?1 for Zn, Mn, Ni, Pb, Cd, Cu, Fe, and Co respectively. The corresponding limit of quantification (blank + 10 s) values are 5.30, 6.20, 8.38, 9.54, 4.22, 4.17, 8.62, and 9.86 µg L^?1, respectively. The enrichment on AXAD‐16‐DHP coupled with monitoring by flame atomic absorption spectrometry (FAAS) is used to determine these metal ions in river and synthetic water samples, Co in vitamin tablets, and Zn in milk samples. AXAD‐16‐DHP has been found to perform better than DHP loaded cellulose and Amberlite XAD‐2.     

Separation,Preconcentration, and Recovery of Pd(II) Ions using Newly Modified Silica Gel with Bis(3-Aminopropyl)Amine

Bis(3-aminopropyl)amine bonded silica gel (BAPA-SG) was synthesized and characterized by elemental analysis and FT-IR spectroscopy, and tested for adsorption, preconcentration, and recovery of Pd(II) ions. The effective parameters on the preconcentration of Pd(II) ions such as pH, volume, and flow rate of the Pd(II) solution, and the type and volume of eluent solution, and also matrix ions such as alkaline and heavy metals were investigated. Flame atomic absorption spectrometry was used for the determination of Pd(II) concentration. The modified silica gel could adsorb Pd(II) ions quantitatively from the solutions up to 400 mL at pH 1.0 by the flow rate of 5 mL/min. The retained Pd(II) ions could be easily eluted by using 5 mL of 1% (m/v) thiourea in 1.0 M HCl solution. The recovery of Pd(II) ions was 95 ± 2% at 95% confidence level. The analytical detection limit of Pd was found to be 0.36 µg L^?1 at the preconcentration factor of 80. Selective adsorption of Pd(II) ions over some base metal ions was also investigated. The developed method was applied to spent auto catalyst for palladium recovery, and a certified ore sample for the determination of palladium content.     

Determination of trace amounts of Co(II) after preconcentration with surface ion imprinted sorbent based on activated carbon

In this study, by using surface ion imprinting technique, Co(II)-imprinted activated carbon was synthesized as a new sorbent in order to use in solid phase extraction method. Several parameters were investigated and optimum experimental conditions were determined. Synthesized sorbent was characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Thermogravimetric Analysis and Brunaer, Emmet, and Teller techniques. The maximum adsorption capacity of imprinted and nonimprinted sorbents were found as 833.3 mg/g and 188.7 mg/g respectively. The limit of detection, the limit of quantification and relative standart deviation were found as 0.066 µg/L, 5.91 µg/L and 5.65% respectively.     

Adsorption of Cu(II) and Ni(II) using a Novel Xanthated Carboxymethyl Chitosan

Removal of Cu(II) and Ni(II) from aqueous solutions by a novel xanthated carboxymethyl chitosan (XCC) was investigated. XCC obtained was characterized by FTIR, SEM, EDX, and XRD. The adsorption ability of chitosan and XCC toward Cu(II) and Ni(II) was compared. The effect of pH (2.0–7.0), contact time (5–60 min), and adsorption isotherms on adsorption were also investigated. It was observed that the modified chitosan XCC showed a remarkable increase in Cu(II) and Ni(II) adsorption as compared to chitosan and displayed a quick adsorption performance. Further, The Langmuir isotherm was found to provide the best correlation of the experimental data and the adsorption capacity obtained from the Langmuir model was 174.2 mg/g and 128.4 mg/g for Cu(II) and Ni(II), respectively. FTIR and UV spectra suggested that the amino groups, carboxyl groups, and xanthate groups of XCC participated in the adsorption.     

Determination of Cd(II), Co(II), Cu(II), Ni(II), and Pb(II) Ions by FAAS after Separation/Preconcentration using Amberlite XAD‐1180 Chelating Resin Chemically Modified with o‐Aminophenol

Abstract

The use of a newly synthesized chelating resin with an o‐aminophenol–type functional groups and Amberlite XAD‐1180–type supporting material for separation/preconcentration of trace metal ions from various water samples was described. Amberlite XAD‐1180‐o‐aminophenol chelating resin (XAD‐o‐AP) was synthesized using Amberlite XAD‐1180 resin as solid support and o‐aminophenol as the chelating ligand. The determination of Cd(II), Co(II), Cu(II), Ni(II), and Pb(II) ions was made by flame atomic absorption spectrometry (FAAS). Studying with model solutions for the optimization of the method was based on the measurement of recovery values (between 92–106%) of the analyte elements. Some analytical parameters such as pH (6.0), volume of the sample (～250 mL), effect of matrix ions, flow rates of the sample (2.5 mL min^?1) and elution solutions (2.5 mL min^?1), concentration, type and volume of the eluent (4 mol L^?1 HNO₃, 20 mL) were investigated. The detection limit (3s/b, n=20) and the relative standard deviation (n=7) of the method were found to be in the range 0.9–4.3 µg L^?1 and 4.4–5.5%, respectively. The proposed method was successfully applied to the real samples such as wastewater, boiler feeding water and a certified reference material (Estuarine water, LGC 6016).     

Determination of Cadmium(II) in Water and Soil Samples after Preconcentration with a New Solid Phase Extractor

Abstract

A new simple and reliable method has been developed to separate and preconcentrate trace cadmium ion from water and soil samples for subsequent measurement by flame atomic absorption spectrometry (FAAS). Cadmium ions adsorbed quantitatively on Amberlyst 36 cation exchange resin were eluted with a 5 mL of 3 mol/L hydrochloric acid solution. Different factors and matrix effects for the preconcentration step were examined. The analytical figures of merit for the determination of cadmium are as follows: analytical detection limit, 0.51 µg/L; precision (RSD), 2.9%; enrichment factor, 200; capacity of resin 192 mg/g. The method was applied for cadmium determination in tap water, natural drinking water, soil, and roadside dust samples. The accuracy of the method is confirmed by analyzing standard reference material (Montana Soil, SRM 2711).     

Preconcentration of Heavy Metals and Matrix Elimination using Silica Gel Chemically Modified with 2,3‐Dihydroxybenzaldehyde

Abstract

Many direct methods cannot easily be used to measure analytes such as Cd(II), Cu(II), Ni(II), Pb(II), and Zn(II) ions in sea and river water since these elements are present at very low concentration and the sample has a very complex matrix. In this study a method was developed to preconcentrate these ions by solid phase extraction within a column system using a newly synthesised 2,3‐dihydroxy benzaldehyde modified silica gel (SGDHB). Different parameters, such as pH, resin amount, eluent type, eluent volume, sample flow rate, preconcentration factors, and resin capacity were determined for the preconcentration of metal ions with the resin. Samples (125–500 ml) containing metal ions were passed through the column filled with SGDHB resin so that metal ions were retained on the column. The preconcentrated analytes were then eluted with 15 mL of 0.1 M HCl. The metal concentrations in the eluate were measured by FAAS. A sample and eluent flow rate of 1.12 and 0.56 ml/min respectively was used. Estimates of accuracy, precision, and detection limits were determined. In addition, analysis of the CRM LGC 6156 harbor sediment was undertaken, using the resin to isolate the analytes from potential interferences. Good agreement with certified values was obtained, indicating that the method is equally applicable to the analysis of water samples and to digests of solid materials.     

In situ solvent formation microextraction based on a new ionic liquid for green preconcentration of trace amount of Cu (II) ions in water samples

A simple, fast, and effective analytical technique known as in situ solvent formation microextraction was used to preconcentrate/separate trace amounts of Cu(II) ions in water samples prior to determination by flame atomic absorption spectroscopy. In the present method, 6,6′-(1Z,1′Z)(butane-1,4-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis-3-bromophenol (Schiff base ligand) as the complexing agent and 1-methyl-3-pentylimidazolium bromide (ionic liquid) as an extracting agent were successfully synthesized and characterized by FTIR, C-NMR, and H-NMR spectroscopies. The effects of several analytical parameters on the method were studied and optimized, and the merits of the method, such as LDR (0.2–1000 µg L^?1), LOD (0.12 µg L^?1), RSD (4.1%), and preconcentration factor (70) were evaluated.     

Solid Phase Extraction and Determination of Ultra Trace Amounts of Copper using Activated Carbon Modified by N,N′‐Bis(Salicylidene)‐1,2‐Phenylenediamine

Abstract

N,N′‐bis(salicylidene)‐1,2‐phenylenediamine(salophen) modified activated carbon was prepared and used as an effective sorbent for solid phase extraction of Cu(II) ions from aqueous solutions. The salophen modified activated carbon showed a high sorption affinity for Cu(II). In this method a column mode was used for preconcentration of copper(II) in the pH range 3.5–6.5. The retained copper was eluted with 0.1 mol l^?1 EDTA and determined by atomic absorption spectrometry. The calibration graph was linear over the copper concentration in the range 0.05–1.5 µg ml ^?1. Five replicate determination of 0.4 µg ml^?1 of copper(II) gave a mean absorbance of 0.385 with a relative standard deviation of 1.35%. The detection limit was 0.0133 µg ml^?1. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for determination of copper in various real samples.     

Removal of divalent nickel from aqueous solution using blue-green marine algae: adsorption modeling and applicability of various isotherm models

Adsorption of Ni(II) onto blue-green marine algae (BGMA) is investigated under batch condition. Under optimum experimental conditions, the initial Ni(II) metal ion concentration is varied from 25 to 250 ppm and the maximum adsorption capacity of BGMA is found to be 42.056 mg/g. The optimum pH, biomass loading, and an agitation rate on maximum removal of Cu(II) ion are found to be 6, 2 g, and 120 rpm, respectively. 24 h of contact time is allowed to achieve equilibrium condition. All the experiments are carried out at room temperature. The equilibrium experimental data infer that the isotherm is L-shaped. It is the indication of no strong competition between solvent and Ni(II) to occupy the active sites of BGMA. Also, it indicates that the BGMA has a limited sorption capacity for adsorption of Ni(II). The experimental data are tested with various isotherm models; subsequently, the mechanism of adsorption is identified and the characteristic parameters for process design are established. Fritz–Schlunder-V isotherm model is highly significant in establishing the mechanism of adsorption of Ni(II) under the conditions employed in this investigation followed by Freundlich. The q_max of 41.89 mg/g obtained by this model indicates its relevance more precisely with experimental data.     

Structure Elucidation and Evaluation of Antioxidant and Tyrosinase Inhibitory Effect and Mechanism of Proanthocyanidins from Leaf and Fruit of Leucaena Leucocephala

This study aimed to investigate the structural features, antioxidant activity, tyrosinase inhibitory effect, and mechanism of proanthocyanidins from leaf and fruit of Leucaena leucocephala. MALDI-TOF-MS, thiolysis coupled with HPLC-ESI-MS, and ¹³C-NMR confirmed that these proanthocyanidins were complex mixtures of propelargonidins, procyanidins, and prodelphinidins. (Epi)catechin, (epi)gallocatechin, (epi)catechin gallate, and (epi)gallocatechin gallate were the main constitutive units. The findings obtained from enzyme analysis revealed that the proanthocyanidins had inhibitory effects on both monophenolase and diphenolase of tyrosinase. The IC₅₀ values of leaf and fruit proanthocyanidins were 73.5?±?2.7 and 52.3?±?3.5 µg/mL for monophenolase activity, and 27.2?±?1.4 and 16.1?±?1.1 µg/mL for diphenolase activity, respectively. The inhibition of diphenolase by proanthocyanidins were proved to be reversible and mixed type. In addition, it was also found from various antioxidant methods that the proanthocyanidins in leaf and fruit possessed potent DPPH radical scavenging activity with IC₅₀ values of 103.4?±?0.8 and 87.8?±?1.1 µg/mL, ABTS radical scavenging activity with IC₅₀ values of 72.9?±?0.4 and 65.7?±?0.9 µg/mL, and ferric reducing antioxidant power with FRAP values of 3.74?±?0.03 and 4.02?±?0.15?mmol AAE/g, respectively. The results obtained suggested that the proanthocyanidins from leaf and fruit of L. leucocephala might have the potential to be exploited as natural tyrosinase inhibitors and antioxidants.     

气相色谱法测定6种邻苯二甲酸酯痕量组分的固相萃取条件研究

利用固相萃取技术富集了水中6种邻苯二甲酸酯类:邻苯二甲酸二(2-乙基己基)酯(DEHP)、邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二辛酯(DOP)、邻苯二甲酸丁基苄基酯(BBP)。借助均匀设计法及计算机回归建模优化技术对6种邻苯二甲酸酯类的固相萃取条件进行了设计与优化,得到最佳固相萃取条件为:洗脱剂配比(正己烷与丙酮的体积比)30∶1,洗脱体积2 mL,洗脱速率为4 mL/min,上样速率8 mL/min。富集后的样品用带电子捕获器的毛细管气相色谱检测,方法的线性范围为1~1 000μg/L(DMP、DEP、DOP),0.2~100μg/L(DBP、DEHP),0.1~100μg/L(BBP);线性回归方程的相关系数为0.997 0~1.000,检测限为0.01~0.4μg/L,方法回收率为69.0%~117.0%,相对标准偏差为2.2%~9.5%。     

Nanometer-sized cerium oxide particles for solid phase extraction of trace amounts of mercury in real samples prior to cold vapor atomic adsorption spectrometry

Ceria (CeO₂) nanoparticles were synthesized using the microwave-assisted heating technique and employed as a sorbent for preconcentration of trace amounts of Hg(II) ions from aqueous solutions for the first time. The analysis of mercury was performed by cold vapor atomic absorption spectrometry (CV-AAS). The characteristics of nanoparticles were assessed using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Experimental parameters influencing the extraction procedure recovery were thoroughly investigated. Under the optimized experimental conditions, the calibration curve was linear in the range of 0.035–0.8 µg/L of mercury. The method was validated by analysis of a certified reference material.     

Preparation and Application of Inorganic Microballoons Membrane

Abstract

The primary emulsification to form the microballoons was studied. The effects of preparation conditions against the formation of microballoons were examined. The factors examined were metal species in the external aqueous phase, the concentrations of sodium silicate in the internal phase and Cyanex 923 as carrier. The particle size and shell thickness were found 10 µm and 2 µm, respectively. Since the penetration of metal species through the oil phase was promoted by the increase of carrier concentration. The formation of microballoons was completed in a short time of less than 30 min. The formation of microballoons of Co(II), Ni(II), Zn(II), Sr(II), and Cu(II) were used for removal of these metal ions.     

Removal of arsenic from aqueous media using zeolite/chitosan nanocomposite membrane

In this work, the removal of arsenic (III) using zeolite/chitosan nanocomposite membranes was studied and characterized using scanning electron microscopy (SEM), atomic force microscope (AFM), etc. The water contact angle of the membrane decreased from 74.2 to 59.2° and the porosity of the prepared membranes increased from 20.38 to 45.81% with an increase in the concentration of zeolite. The rejection of arsenic (III) increases with increase in the zeolite loading for 500 and 1000 µg/L; but at 100 and 150 µg/L, the trend was opposite. The membrane with 1.0 [Chi-Z (1.0)] and 1.25 [Chi-Z (1.25)] wt% zeolite showed the highest rejection (>94%) for 1000 µg/L concentration of arsenic trioxide aqueous solution.     

Synthesis,Characterization, and Applications of a New Chelating Resin Containing 4-2-(Thiazolylazo) Resorcinol (TAR)

A new phenol–formaldehyde based chelating resin containing 4-(2-thiazolylazo) resorcinol (TAR) functional groups has been synthesized and characterized by Fourier transform infrared spectroscopy and elemental analysis. Its adsorption behavior for Cu(II), Pb(II), Ni(II), Co(II), Cd(II), and Mn(II) has been investigated by batch and column experiments. The chelating resin is highly selective for Cu(II) in the pH range 2 ～ 3, whereas alkali metal and alkaline earth metal ions such as Na(I), Mg(II), and Ca(II) are not adsorbed even at pH 6. Quantitative recovery of most metal ions studied in this work except Co(II) is achieved by elution with 2M HNO₃ at a flow rate of 0.2 mL min^?1. A similar trend is observed for distribution coefficient values. The quantitative separations achieved on a mini-column of chelating resin include Cd(II) – Cu(II), Mn(II) – Pb(II), Co(II) – Cu(II), Mn(II) – Ni(II), and Mn(II) – Co(II) – Cu(II). The recovery of copper(II) is quantitative (98.0–99.0%) from test solutions (10–50 mg/L) by 1 mol/L HNO₃-0.01 mol/L EDTA. The chelating resin is stable in acidic solutions below 2.5 M HNO₃ or HCl as well as in alkaline solution below pH 11. The adsorption behavior of the resin towards Cu(II) was found to follow Langmuir isotherm and second order rate.     

Development of an ultrasonic-assisted restricted access supramolecular solvent-based liquid phase microextraction (UA-RAS-LPME) method for separation-preconcentration and UV-VIS spectrophotometric detection of curcumin

ABSTRACT

Environment-responsive long chain acid (C7–C14)-based supramolecular solvents (SUPRAs) were produced and their potential usage for microextraction of curcumin was assessed in the presented work. The SUPRAs were prepared by mixing of decanoic acid with tetrahydrofuran. The ultrasonic-assisted restricted access supramolecular solvent liquid phase microextraction of curcumin was achieved at pH 6 by 200 µL of using SUPRAs. Various parameters including pH, solvent volume, ultrasonication time, and sample volume were optimized. The limit of detection, limit of quantification, relative standard deviation %, and preconcentration factor were 5.3 µg L^?1, 17.5 µg L^?1, 2.2%, and 50, respectively. The accuracy of method was checked by additional-recovery experiments.