Preconcentration Of Metals Research Articles

Ethylenediaminetetraacetate functionalized ordered Santa Barbara Amorphous‐15 mesoporous silica as an effective adsorbent for preconcentration of some heavy metals followed by inductively coupled plasma atomic emission spectrometry

AbstractA simple and sensitive method was developed for preconcentration of the several transition metal ions using Santa Barbara Amorphous‐15 mesoporous silica functionalized with the ethylenediaminetetraacetate functional group. The determination of the metal ions was performed by inductively coupled plasma atomic emission spectrometry. The effective parameters on the extraction efficiency of the ions were investigated. The optimized conditions were: the sample solution pH 4, adsorbent amount = 10 mg, adsorption time = 30 min, elution solvent = 1.5 M of HCl, and desorption time = 5 min. Under the optimum conditions, limits of detection of 50, 5, 10, 50, 10, and 500 ng/L were obtained for Co2+, Mn2+, Cu2+, Cd2+, Zn2+, and Fe3+ respectively. The relative standard deviations for determination of the selected metal ions at concentration level of 50 μg/L (n = 4) were in the range of 1.7–5.8%. Linear ranges for Co2+ and Cd2+ (0.1–250 μg/L), Cu2+ and Zn2+ (0.05–250 μg/L), Fe3+ (1–250 μg/L), and Mn2+ (0.01–25 and 50–500 μg/L) were obtained with perfect correlation coefficients (R = 0.9958–0.9996, n = 8). The applicability of the method was evaluated by the extraction and determination of the heavy metal ions in different water samples.

Ionic liquid-immobilized silica gel as a new sorbent for solid-phase extraction of heavy metal ions in water samples.

In the current study, we have developed a solid-phase extraction (SPE) method with novel C18-alkylimidazolium ionic liquid immobilized silica (SiO2–(CH2)3–Im–C18) for the preconcentration of trace heavy metals from aqueous samples as a prior step to their determination by inductively coupled plasma mass spectrometry (ICPMS). The material was characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Energy-Dispersive X-ray Spectroscopy (EDS), and Brunauer–Emmett–Teller (BET) analysis. A mini-column packed with SiO2–(CH2)3–Im–C18 sorbent was used for the extraction of the metal ions complexed with 1-(2-pyridylazo)-2-naphthol (PAN) from the water sample. The effects of pH, PAN concentration, length of the alkyl chain of the ionic liquid, eluent concentration, eluent volume, and breakthrough volume have been investigated. The SiO2–(CH2)3–Im–C18 allows the isolation and preconcentration of the heavy metal ions with enrichment factors of 150, 60, 80, 80, and 150 for Cr3+, Ni2+, Cu2+, Cd2+, and Pb2+, respectively. The limits of detection (LODs) for Cr3+, Ni2+, Cu2+, Cd2+, and Pb2+ were 0.724, 11.329, 4.571, 0.112, and 0.819 μg L−1, respectively with the relative standard deviation (RSD) in the range of 0.941–1.351%.

Novel thiol-functionalized covalent organic framework-enabled ICP-MS measurement of ultra-trace metals in complex matrices

Novel thiol-functionalized covalent organic frameworks for the quantitative preconcentration of heavy metals in environmental waters prior to ICP-MS analysis.

Metal preconcentration for gold mineralization in arcs: Geophysical observations from Western Junggar, NW China

Previous studies showed that metal preconcentration in fluids and/or magma is critical to the formation of gold deposit in arcs and is closely related to the segregation of sulfide phases. However, the depth range and the magnitude of and associated mechanism by which the deep crust controls the metal preconcentration of arc mineralization remain enigmatic. Here we present geophysical observations of the medium-scale Baogutu porphyry copper–gold deposit and the large-scale Hatu epithermal gold deposit from the late Paleozoic arc in the western Junggar, NW China. During the closure of Paleo-Asian Ocean, Baogutu deposit formed at ∼313 Ma relating to the adakitic intrusions driven by the ridge-related subduction, and Hatu deposit formed at ∼300 Ma just before the subduction termination. The transcrustal structures of resistivity and shear-wave velocity would show the signatures of metal preconcentration by reasoning the cause of low-resistivity anomaly to the persisting sulfide phases and the change of shear-wave velocity to the garnet proportion, respectively. Our results showed that the sulfide phases persisted in the entire deep crust and thus the metal preconcentration could occur in the base cumulates and mush reservoir beneath Hatu deposit, but the signatures were not fully reflected beneath the Baogutu deposit. These observations suggest that the reduced permeability of brittle-ductile transition and the water flux associated with magma likely affect the rising rate of melt, resulting in different efficiency of the metal preconcentration. Thus, the endowments of mineralization in arcs are controlled by crustal structures and contemporaneous arc magmatism during subduction.

Synthesis and Characterization of Poly(pyrrole-1-carboxylic acid) for Preconcentration and Determination of Rare Earth Elements and Heavy Metals in Water Matrices.

Pyrrole was N-functionalized with solid carbon dioxide followed by chemical polymerization to create a new air-stable, granular, and water-insoluble sorbent, poly(pyrrole-1-carboxylic acid) (PPy-CO2). PPy-CO2 exhibited enhanced affinity for the sorption of metal ions compared to unfunctionalized PPy due to the incorporation of carboxylate functional groups directly onto the polymer backbone. As a freestanding sorbent material, immobilization to an additional solid support is not needed. Sorption, and therefore preconcentration, occurs simultaneously to achieve efficient removal and recovery of metal ions by a pH-dependent sorption-desorption mechanism. PPy-CO2 was evaluated on the analytical scale for the solid-phase extraction of a range of metal ions and found to efficiently preconcentrate rare earth elements (REEs), Th, and heavy metals (Cr, Fe, Cd, and Pb), which allowed quantitation by inductively coupled plasma mass spectrometry (ICP-MS). The impact of sorption parameters, such as solution pH, amount of sorbent, and sorption time, and the effect of desorption flow rate for recovery were investigated and optimized using ultrasound-assisted dispersive solid-phase extraction (UAD-SPE) with ICP-MS analysis. Maximum efficiency for sorption and recovery of most metal ions was achieved at a solution pH of 6.0, 10 mg of sorbent, a sorption time of 5 min, and desorption conditions of 1 mL of 2 M nitric acid applied at a flow rate of 0.25 mL min-1. Detection limits for REEs and Th ranged from 0.2-3.4 ng L-1 for REEs and Th and 0.9-5.7 ng L-1 for heavy metals. Linear ranges from 0.1-1000 μg L-1 for REEs and 0.1-500 μg L-1 for heavy metals and Th were also observed. PPy-CO2 successfully preconcentrated and facilitated the determination of the targeted metal ions in water matrices of varying complexity, including tap water, well water, river water, and produced water samples. These results indicate the potential application of PPy-CO2 for larger-scale recovery and removal of valuable or hazardous metal ions.

Silicas Chemically Modified with Sulfur-Containing Groups for Separation and Preconcentration of Precious Metals Followed by Spectrometric Determination

Silicas chemically modified with a number of sulfur-containing groups (mercaptopropyl, mercaptophenyl, dipropyl disulfide, thiadiazole thiol, dithiocarbamate and thiourea derivatives) were proposed for the separation and preconcentration of precious metals. These adsorbents quantitatively extracted precious metals from 0.5 to 4 M solutions of hydrochloric acid. It allowed their separation from high concentrations of non-ferrous, alkaline earth, alkali and some other related metals. The selectivity of separation of kinetically labile precious metal ions in ligand substitution reactions from kinetically inert ones depended on the nature of sulfur atom within the functional group of adsorbents and increased when passing from thione to thiol sulfur. Approaches for the preconcentration of precious metals using silicas chemically modified with sulfur-containing groups prior to their AAS, ICP-OES, and ICP-MS determination in ores, concentrates and their processing products were proposed. The correctness of the developed methods was confirmed by the analysis of certified reference materials.

Ultrasensitive Electrochemical Immunoassay for Prostate Specific Antigen (PSA) Based Upon Silver-Functionalized Polyethyleneimine (PEI)–Silica Nanoparticles (NPs)

A novel sandwich-type electrochemical immunosensor was fabricated for the ultrasensitive electrochemical determination of prostate specific antigen (PSA) using silver-functionalized polyethyleneimine (PEI)-silica nanoparticles (NPs) (Ag+/PEI/SiO2 NPs) as electrochemical labels. First, the immunosensor platform was prepared by covalently immobilizing capture antibodies on a poly diallyldimethyl ammonium chloride/carboxylated-gold nanoparticles (PDDA/AuNPs) modified glassy carbon electrode (GCE). After sandwich-type immunoreactions, the detection antibody was labeled by the amino-containing Ag+/PEI/SiO2 NPs by strongly binding to carboxyl groups of protein. Next, many Ag+ with good complexing performance from each PEI/SiO2 nanoparticles released after hydrofluoric acid (HF) in situ etching. Here, the AuNPs acted as a catalyst to reduce Ag+ into metallic Ag using PEI as the reducing agent. Accordingly, an extremely sharp voltammetric peak of electro-oxidized metallic Ag can be determined directly through differential pulse voltammetry (DPV) without metal pre-concentration, and had a close relationship with the concentrations of PSA antigen. Under the optimized conditions, the immunoassay exhibited good sensitivity and selectivity for the determination of PSA with a linear range from 0.01 to 10 pg·mL−1 and a detection limit of 3.5 fg·mL−1. The new strategy provides a reliable, highly sensitive determination of the prostate cancer biomarker in biological samples with great potential for the fabrication of devices for clinical diagnostics.

Magnetic Fe3O4@Mg/Al-layered double hydroxide adsorbent for preconcentration of trace metals in water matrices

A magnetic Fe3O4@MgAl-layered double hydroxide (MLDH) nanocomposite was successfully synthesized and applied as an effective adsorbent for preconcentration of trace As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions from complex matrices. The quantification of the analytes was achieved using the inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The nanocomposite was then characterized using BET, FTIR, SEM, and EDS. Due to its high adsorption surface area, compared to traditional metal oxide-based adsorbents, MLDH nanocomposite exhibited high extraction efficiency. Several experimental parameters controlling the preconcentration of the trace metals were optimized using response surface methodology based on central composite design. Under optimum conditions, the linearity ranged from 0.1 to 500 µg L−1 and the correlation of coefficients (R2) were higher than 0.999. The limits of detection (LODs) and quantification (LOQs) were 0.11–0.22 µg L−1 and 0.35–0.73 µg L−1, respectively. The intra-day (n = 10) and inter-day precisions (n = 5 working days) expressed in the form of percent relative standard deviations (%RSDs) were below 5%. The proposed method was successfully applied for the analysis of the As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions in different environmental water samples.

Supramolecular solvent-based microextraction techniques for sampling and preconcentration of heavy metals: A review

Abstract Even very low concentrations of heavy metal pollutants have adverse effects on the environment and on human health. Thus, determining even trace concentrations of heavy metals in various samples has attracted a lot of attention. The conventional analytical methods used for the sampling and analysis of heavy metals have some limitations, including the effects of the matrix and their high detection limits. Thus, various methods are used for the pretreatment and concentration of the target analytes, and these methods are time-consuming, expensive, and require the use of toxic solvents. In recent years, supramolecular solvent-based microextraction (SSME), a green analytical strategy, has been used to determine low concentrations of heavy metals in various matrices. This method has unique features such as high enrichment factor, short extraction time, and rapid analysis. In addition, it is cost effective because it consumes less chemical reagents than other methods. Also, it is ecofriendly, and it has good sensitivity and selectivity. Herein, we presented a comprehensive review of the application of the SSME technique for the analysis of heavy metals in water, food, and biological samples. Also, we have provided the distinctive properties of the SSME technique, discussed the challenges that lie ahead, and addressed the potential future trend.

Cleaner Pre-concentration of Metals from Printed Circuit Board Waste Using Novel Dense Liquid Medium Based on Sodium Silicate

Printed circuit boards (PCBs) are present in most electrical and electronic equipment and contain valuable metals such as Cu, Au, Ag, and Pd, being considered attractive sources of metals. In order to recover those metals from PCBs by metallurgical processes, a pre-concentration step is needed. In this study, the metallic components from waste PCBs have been pre-concentrated using a separation process with dense liquid medium based on sodium silicate, as an alternative to toxic chloroform, which is commonly used. After grinding, the waste PCBs presented a mean particle size of less than 0.56 mm. After dense medium separation, similar concentrations of Cu and precious metals were obtained using either sodium silicate solution or chloroform. Therefore, sodium silicate has a high potential to be applied as a cleaner dense liquid medium in gravity separation processes.

Influence of grade heterogeneity and gangue mineralogy on the efficacy of high voltage pulse enabled ore pre-concentration

Variations in the amenability of different ores to high voltage pulse (HVP) enabled pre-concentration has been observed, yet it is unclear which intrinsic properties of the ores caused the variation in HVP efficacy. The objective of this study is to investigate the influence of grade heterogeneity and gangue mineralogy on the efficacy of HVP enabled ore pre-concentration. Two ore samples with different mineralisation were treated with HVP and mechanical impact breakage, respectively. The results showed that Sample A with an intrusive vein-like mineralisation structure exhibited better pre-concentration efficacies for gold and copper after HVP pretreatment compared to Sample B, which had a finely disseminated copper mineralisation structure. Pretreatment by mechanical impact breakage presented negligible metal pre-concentration potential for both ore samples. The Constitution Heterogeneity determined from assaying randomly selected feed particles, showed that Sample A had a significantly greater grade heterogeneity than SampleB. It was found that the gold and copper grade heterogeneities of the two ore samples exhibited a positive linear correlation with the efficacy of HVP enabled pre-concentration. This is a consequence of heterogeneity resulting in distinct populations of mineralised and barren particles, a requirement necessary to achieve selective breakage. It is also proposed that the presence of conductive gangue minerals can play a role on the efficacy of HVP enabled pre-concentration, with the effect being positive or negative depending on whether or not the gangue has an association with the valuable minerals of interest.

Preconcentration of noble metals on alumina prior to analysis by inductively coupled plasma mass spectrometry: Application to geological samples

A preconcentration method for the determination of noble metals (Ag, Au, Ir, Os, Pd, Pt, Re, Rh, Ru) was developed using alumina as a sorbent. The method involves an off-line preconcentration analytical procedure: the formation of chloro-complexes of these elements with HCl, loading of the chloro-complexes on alumina followed by elution of analytes and analysis by inductively coupled plasma mass spectrometry. The effects of HCl/HNO3 concentration in the sample digest, mass of alumina, and concentration of eluents (HCl and HNO3)/thiourea were studied using multivariate experimental designs. Using 2 M HCl as eluent, detection limits were improved by a factor of 10–20 for Ag, Ir, Os, Pd, Pt, and Ru, and 3–5 for Re and Rh compared to those achieved by direct nebulization (i.e. without preconcentration). Accuracy was verified through analysis of CDN-PGMS-19 ore reference material. Using 2 M HCl for elution, the results for Ag, Pd and Pt agreed with the reference values obtained based on aqua regia digestion (which does not achieve total dissolution). For the determination of Au, evaporation of HNO3 and elution with thiourea were required.

Nanomaterials-based solid phase extraction and solid phase microextraction for heavy metals food toxicity

In the last few years, nanomaterials are widely used sorbents for the extraction of heavy metals in food samples. The nanomaterials have a larger surface area and show high selectivity, fast adsorption capability, and high efficiency for food contaminants (heavy metals). Carbon nanomaterials (CNMs), magnetic nanoparticles (MNPs), nano-imprinted polymers (NIPs), nano-based metal-organic frameworks (N-MOFs), and silica nanoparticles (SiNPs) are most prominent nanomaterials used in the preconcentration and determination of heavy metals. The most popular sorbent-based techniques for the extraction of heavy metals are solid phase extraction (SPE) and solid phase microextraction (SPME). The use of these nanomaterial sorbents increases the extraction efficiency of both techniques. This review summarizes the nanomaterial sorbents (published 2015 to May-2020) used in solid phase extraction (SPE) and solid phase microextraction (SPME) for heavy metals extraction in food.

Friendly and Resource-Saving Methods of Underground Ore Mining in Disturbed Rock Masses

One of the most problematic aspects in underground ore extraction in mining-disturbed rock masses is backfilling of man-made voids, which affect origination and redistribution of stress-strain state of the rock mass. Their existence in the earth's crust provokes subsidence/collapse of the day surface and also contributes to arising geomechanical and seismic phenomena. The purpose of the study is to substantiate environmental-friendly and resource-saving methods for backfilling of voids in underground ore mining based on revealing the features of rock integrity of the day surface and life-sustaining activity of the population living in the mining-affected area. The main negative consequences of the impact of mining on the environment and humans are high costs for conserving day surface and ensuring life-sustaining activity of the population living in the mining-affected area, as well as removing large areas of land from human activity, etc. Based on the study of a rock mass stress-strain state using geophysical and surveying methods, an environment-friendly method for backfilling of man-made voids in disturbed rock masses is proposed. It enables ensuring the integrity of the day surface and life-sustaining activity of the population living in the mining-affected area (in the vicinity of mines, dumps, sites of backfilling complexes, preconcentration and heap leaching of metals from substandard ores, tailings storage facilities, etc.). Combined geotechnologies are proposed for backfilling of voids during the development of ore deposits by underground block leaching, and scientific and methodological and technical support was provided for drilling and blasting preparation of hard ores and underground leaching of pilot blocks at the Michurinsky deposit of GP VostGOK, Ukraine. The research findings can be used in underground mining of ore deposits of complicated structure.

Preconcentration and Test Determination of Heavy Metal Ions Using a Modified Nanofiber Based on Polyacrylonitrile

New test systems made of nanofibers based on polyacrylonitrile and modified by NaOH are obtained for the chemisorption preconcentration of heavy metal (HM) ions and the subsequent colorimetric determination of their total amount . The kinetics of the adsorption of HM ions is studied, and corresponding adsorption isotherms are obtained. The adsorption capacities of nanofiber adsorbents for Mn2+, Co2+, Cu2+, Pb2+, and Fe3+ equal 52, 87, 126, 153, and 162 mg/g, respectively. The distribution and concentration coefficients of HM ions are calculated. The hydrophilic–hydrophobic properties of the nanofibers are estimated from the calculated values of limiting wetting angles and water resistance. Examples of the quantitative assessment of the total of ultra-small amounts of HM ions in model solutions and real samples (natural and drinking water) by the mathematical processing of digital images of colored areas of test facilities are given. It is shown that the developed color scale ensures the determination of the excess of total HM ions in natural water over the maximum permissible concentration (>20 μg/L), which was confirmed by the results of determination by atomic absorption spectrometry.

Advanced core-shell EDTA-functionalized magnetite nanoparticles for rapid and efficient magnetic solid phase extraction of heavy metals from water samples prior to the multi-element determination by ICP-OES.

A method for preconcentration and simultaneous determination of trace heavy metals in water media by core-shell superparamagnetic nanoparticles with the immobilized derivative of ethylenediaminetriacetic acid (referred to as MNPs/SiO2-EDTA) is proposed. The specific layer-by-layer covering of magnetite endowed the new material with essentially increased chemical stability of MNPs including acidic media and improved the affinity toward traces of toxic metal ions. The initial and modified materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, elemental analysis, and vibrating sample magnetometry. The obtained particles were nanodimensional with a7-12-nm magnetic core and a4-6-nm silica shell. The MNPs/SiO2-EDTA quantitatively removes heavy metals from contaminated media at pH ≥ 3.5 within 15min. The adsorption data were successfully fitted to the pseudo-second-order kinetic model. The preconcentration factor was 150 and maximum adsorption capacity was 36.9mgg-1 for Cu(II), 108.8mgg-1 for Pb(II), 30.9mgg-1 for Zn(II), 34.32mgg-1 for Cr(III), and 59.5mgg-1 for Cd(II). Due to high stability in the wide range of pH, the magnetic adsorbent can be regenerated at least six times using0.1M HNO3. Following adsorption/desorption, determinationof metal ions isprovided by inductively coupled plasma optical emission spectrometry (ICP-OES) . The linear range of theproposed method is 0.1 - 200μgL-1. The limits of detection (LOD) are 0.12μgL-1 for Zn(II); 0.06μgL-1 for Cd(II); 0.39 for Cu(II); 0.15μgL-1 for Cr(III); and 0.76μgL-1 for Pb(II). The method performance was evaluated in the analysis of environmental, tap, and wastewater samples with recoveries in the range of 94.0-104.0%.

Evaluate the exposure of toxic metals via drinking water and smoking nonbranded cigarette in malnourished women by modified single/two-step cloud point extraction.

Presently, the exposure of heavy metals (cadmium and lead) was determined in biological sample (serum) of women (pregnant and nonpregnant) who belong to low socioeconomic group (malnutrition). The cadmium (Cd) and lead (Pb) were determined in drinking water and locally produced cigarette (bidi), smoking by women of childbearing age. The preconcentration of heavy metals in serum, water, and tobacco of bidi were carried out by cloud point extraction at single and two-step methods before determination by atomic absorption spectrometry with flame mode. The Cd and Pb in the water- and acid-digested serum and tobacco samples were treated with a complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN). The hydrophobic complex of Cd and Pb was entrapped in Triton X-114. For the first step, the entrapped analytes in Triton X-114 was diluted with alcoholic acid (0.2mol/L of HNO3) and subjected to FAAS, whereas for the second step of CPE, the surfactant-rich analyte was subjected to the second round of enrichment method. Lastly, the analyte was back-extracted in acidic solution (0.2mol/L) and analyzed by FAAS. The all significant variable was optimized for optimal recovery of Cd and Pb. The recommended single/two-step cloud point extraction method was validated by simultaneously evaluated matrices matched certified reference materials of water, serum, and tobacco. The resulted data indicated that the groundwater samples contained elevated concentrations of Cd and Pb than recommended values for drinking water by WHO, while the contents of Cd and Pb were observed about two-fold higher in nonbranded cigarette (bidi) than branded cigarette. It was observed that there were about 3 to 4 times higher concentrations of both toxic metals in blood serum of smoker malnourished women group than in referent nonsmoker women. Graphical abstract.

Silica Gel‐Immobilized 5‐aminoisophthalohydrazide: A novel sorbent for solid phase extraction of Cu, Zn and Pb from natural water samples

A novel silica sorbent, silica gel‐immobilized 5‐aminoisophthalohydrazide (SiO2‐APH), was prepared by the condensation of 3‐chloropropyl‐functionalized silica gel with 5‐aminoisophthalohydrazide (APH) derived from dimethyl 5‐aminoisophthalate as a starting material and used for separation and preconcentration of Cu, Zn, and Pb metals in water samples using Flame Atomic Absorption Spectrometry (FAAS). The characterization of the new sorbent was carried out by Elemental Analysis, Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). Important analytical parameters including as pH, amount of sorbent, type and amount of eluting solvent, sample volume, vortex and ultrasonic bath time, matrix ions that effect the developed SiO2‐APH‐solid phase extraction (SPE) method were investigated and optimum parameters were detected. Recoveries of examined metals were obtained as 98% for Cu and Pb and 101% for Zn. The relative standard deviation (RSD, n = 8) of Cu, Zn and Pb metals were 3.2, 2.8 and 1.6%, respectively. Limit of detections (LODs) (n = 10) were found as 2.7 μg L−1 for Cu, 7.4 μg L−1 for Zn and 3.5 μg L−1 for Pb μg L−1. The accuracy of the new method was assessed by analyzing of TMDA‐51.4 and TMDA‐70.2 certified reference materials. The results obtained for metals were in a good agreement with certified values. Addition/recovery test was applied to the real well, river, dam and stream water samples to check the accuracy of the method. The results showed that the developed SiO2‐APH‐SPE method can be effectively used as an alternative method for determination of Cu, Zn, and Pb metals in water samples.

Ligandless, deep eutectic solvent-based ultrasound-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase for preconcentration of lead, cadmium, cobalt and nickel in water samples.

A green and efficient sample preparation method using a deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase followed by high performance liquid chromatography analysis was developed for preconcentration and determination of heavy metals in environmental samples. In the proposed method, a novel, low density deep eutectic solvent was prepared by mixing trihexyl(tetradecyl)phosphonium chloride and thiosalicylic acid at a molar ratio of 1:2 and used both as an extractant and complexing agent. Ultrasound was used to disperse the extractant in the aqueous phase of the sample. Then, the phases were separated by centrifugation, after which the aqueous phase was frozen and the surface extractant phase was dissolved in a small volume of acetonitrile and subjected to liquid chromatographic analysis. The proposed method provided precisions (relative standard deviation, n=5) in the range of 2.6-4.7%. The limit of detection were 0.05, 0.13, 0.06, and 0.11µg/L for Pb(II), Cd(II), Co(II), Ni(II), respectively. The enhancement factors were equal to 154, 159, 162, and 158 for lead(II), cadmium(II), cobalt(II), and nickel(II), respectively. The accuracy of the proposed method was evaluated using certified reference materials (CA011b - hard drinking water, NIST 1643e - trace elements in water, TMRAIN-04 - simulated rain sample).

CO2-effervescence assisted dispersive micro solid-phase extraction based on a magnetic layered double hydroxide modified with polyaniline and a surfactant for efficient pre-concentration of heavy metals in cosmetic samples.

In this paper, a CO2-effervescence assisted dispersive micro solid-phase extraction procedure (CO2-EA-DμSPE) using a magnetic layered double hydroxide modified with polyaniline and a surfactant (Zn-Al-LDH-PA-DBSNa-Fe3O4) was applied for the pre-concentration of heavy metals (Ni2+, Pb2+, Co2+, and Cd2+). The final analysis of the analytes was carried out by atomic absorption spectroscopy. XRD, FTIR, and SEM studies were used for the characterization of the synthesized nanoadsorbent. For the maximum extraction efficiency, effective factors (including pH, nanoadsorbent dosage, and volume of the eluent) were investigated using the central composite design (CCD) method. Under the optimum conditions, the preconcentration factor was more than 20. The linear ranges for Ni2+, Pb2+, Co2+, and Cd2+ were obtained as (5-550), (7-750), (5-500), and (3-100) ng mL-1, respectively. The proposed method provided low detection limits (1.4, 2.1, 1.5, and 0.9 ng mL-1 for Ni2+, Pb2+, Co2+, and Cd2+, respectively) and suitable repeatability (relative standard deviation values (RSDs) below 6.1%, n = 6). Finally, the current method was successfully used for the extraction of heavy metals from cosmetic samples.