A new tunable dispersive liquid-liquid micro extraction method developed for the simultaneous preconcentration of lead and cadmium from lakes water: a multivariate study

Modified Polysulfone Nanofibers for the Extraction and Preconcentration of Lead from Aqueous Solutions

Since lead is a highly toxic metal, it is necessary to detect its presence in different samples; unfortunately, analysis can be complicated if the samples contain concentrations below the detection limit of conventional analytical techniques. Solid phase extraction is a technique that allows the carrying out of a pre-concentration process and thus makes it easy to quantify analytes. This work studied the efficiency of sorption and preconcentration of lead utilizing polysulfone (PSf) fibers grafted with acrylic acid (AA). The best conditions for Pb(II) extraction were: pH 5, 0.1 mol L^-1 of ionic strength, and 40 mg of sorbent (70% of removal). The sorbed Pb(II) was pre-concentrated by using an HNO₃ solution and quantified using flame atomic absorption spectrometry. The described procedure was used to obtain a correlation curve between initial concentrations and those obtained after the preconcentration process. This curve and the developed methodology were applied to the determination of Pb(II) concentration in a water sample contained in a handmade glazed clay vessel. With the implementation of the developed method, it was possible to pre-concentrate and determine a leached Pb(II) concentration of 258 µg L^-1.

Miniaturized point discharge optical emission spectrometry coupling with solid phase extraction: A robust approach for sensitive quantification of total mercury in mung bean sprout growth

In this work, a portable chemical vapor generation point discharge optical emission spectrometry (CVG-PD-OES) system was designed for trace Hg²⁺ monitoring in mung bean sprout samples. The system incorporated selective solid phase extraction (SPE) to enhance the detection sensitivity. Gold nanoparticles (AuNPs) were prepared and utilized to extract trace amounts of Hg²⁺ by forming gold amalgam. Subsequently, the amalgam was desorbed using 5% HCl and introduced into a low-power PD-OES system analysis via CVG. A low limit of detection (LOD) of 0.16 ng mL^-1 was obtained with a linear range of 0.5-6 ng mL^-1. The well-designed system was successfully utilized for monitoring trace Hg²⁺ in the growth of mung beans. The results indicated that the Hg²⁺ in mung bean sprouts was continuously decreased during growth based on the metabolism. Furthermore, the risk assessment conducted implied a negligible hazard quotient, suggesting that the observed levels of exposure posed minimal risk.

Assessment of Health Risk and Presence of Metals in Water and Fish Samples from Doce River, Brazil, After Fundão Dam Collapse

The rupture of the Fundão dam released about 50 million m³ of mining tailings in the Doce river basin. To assess the potential for environmental contamination and the risks of residual exposure of the human population generated by these tailings, water and fish samples from the Doce river were collected 25 days after the accident and analyzed the physicochemical parameters of the water and levels of metals by ICP-MS, in addition to the temporal variability of the concentration of these elements through other studies. This was the first study to carry out an assessment of the health risk associated with the consumption of fish contaminated by metals from the areas affected by the disaster. The values of turbidity (5460 NTU), electrical conductivity (74.8 μS cm^-1), total dissolved solids (892 mg L^-1) and total suspended solids (772 mg L^-1) were above the maximum limit allowed by Brazilian legislation, due to the presence of large amounts of solid materials released after the dam rupture. The analysis of metals in water samples indicated high concentrations of Al (1,906.71 μg L^-1), Mn (370.32 μg L^-1), Fe (8,503.50 μg L^-1) and Hg (34.25 μg L^-1), while for the fish samples, only As (1,033.98 μg kg^-1) and Hg (herbivorous: 505.32 μg kg^-1; predatory: 1,184.09 μg kg^-1) presented levels above those established by Brazilian legislation. The health risk assessment showed that the estimated daily intake for Hg was higher than the reference dose, reinforcing the need for monitoring the area affected by the disaster.

Simultaneous enrichment of inorganic and organic species of lead and mercury in pg L-1 levels by solid phase extraction online combined with high performance liquid chromatography and inductively coupled plasma mass spectrometry

Quantification of ultra-trace inorganic and organic species of lead and mercury in unpolluted environmental water is crucial to estimate the mobility, toxicity and bioavailability and interactions. Simultaneous pre-concentration of Pb and Hg species in pg L^-1 levels followed by multi-elemental speciation analysis makes great sense to a large set of unstable samples because of time advantages. Herein simultaneous enrichment and speciation analysis of ultra-trace lead and mercury in water was developed by online solid-phase extraction coupled with high performance liquid chromatography and inductively coupled plasma mass spectrometry (SPE-HPLC-ICP-MS) for this aim. Pb(II), trimethyl lead (TML), triethyl lead (TEL), Hg(II), methylmercury (MeHg) and ethylmercury (EtHg) were baseline separated in 11 min under gradient elution using 5 mM l-cysteine (Cys) at pH 2.5 in the 0-1 and 4-15 min and 5 mM Cys + 0.5 mM tetrabutyl ammonium hydroxide solution at pH 2.5 in the 1-4 min. Lead and mercury species in 10 mL intact water samples were adsorbed on a 1 cm C₁₈ enrichment column pre-conditioned with 10 mL of 1 mM 2-mercaptoethanol at 10 mL min^-1, and then directly desorbed by the mobile phases. High enrichment factors (459 for Pb(II), 1248 for TML, 1627 for TEL, 2485 for Hg(II), 1984 for MeHg and 1866 for EtHg) were obtained with good relative standard deviations (<5%), leading to low LODs (0.001-0.011 ng L^-1) and LOQs (0.004-0.036 ng L^-1). Good accuracy of this method was validated by two certified reference materials of total lead in water (GBW08601) and total mercury in water (GBW08603) along with spiked recoveries (89-93%). The method was applied to analyze trace lead and mercury species in river, lake, tap and rain water, and purified and mineral water. Inorganic lead of 13-68 ng L^-1 and inorganic mercury of 21-49 ng L^-1 were measured in the nine water samples whereas TML, TEL and MeHg were not detected with 2-5 ng L^-1 EtHg presented only in one river water and tap water.

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.

Determination of trace levels of selenium in natural water, agriculture soil and food samples by vortex assisted liquid-liquid microextraction method: Multivariate techniques

A green vortex assisted based liquid-liquid microextraction (VA-LLME) method was developed for preconcentration of selenium. Ammonium pyrrolidine dithiocarbamate (APDC) was used to form a hydrophobic complex with selenium in natural water, agricultural soil and food samples by GFAAS. Whereas Triton X-114, a nonionic surfactant and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid were used for Se extraction as a dispersing medium. The conical flasks contents were shack on a vortex mixer to increase the extraction efficiency. Multivariate techniques were used to evaluate extraction parameters; pH, vortex time, APDC amount, volume of ionic liquid and Triton X-114 and centrifugation rate on the recovery of Se. The central composite design (CCD) was used for further optimization of the essential extraction parameters. The enhancement factor and limit of detection were obtained as 98.7 and 0.07 µg L^-1. The certified reference materials was used for accuracy of method and the related standard deviation was found to be 3.51%. The resulted data indicated that concentrations of Se in all types of water samples were below the permissible limit recommended by WHO.

Recent Advances in Nanomaterials for Analysis of Trace Heavy Metals

In an effort to achieve high sensitivity analysis methods for ultra-trace levels of heavy metals, numerous new nanomaterials are explored for the application in preconcentration processes and sensing systems. Nanomaterial-based methods have proven to be effective for selective analysis and speciation of heavy metals in combination with spectrometric techniques. This review outlined the different types of nanomaterials applied in the field of heavy metal analysis, and concentrated on the latest developments in various new materials. In particular, the functionalization of traditional materials and the exploitation of bio-functional materials could increase the specificity to target metals. The hybridization of multiple materials could improve material properties, to build novel sensor system or achieve detection-removal integration. Finally, we discussed the future perspectives of nanomaterials in the heavy metal preconcentration and sensor design, as well as their respective advantages and challenges. Despite impressive progress and widespread attention, the development of new nanomaterials and nanotechnology is still hampered by numerous challenges, particularly in the specificity to the target and the anti-interference performance in complex matrices.

A rapid ultrasonic energy assisted preconcentration method for simultaneous extraction of lead and cadmium in various cosmetic brands using deep eutectic solvent: A multivariate study

An innovative ultrasonic assisted microextraction method using a deep eutectic solvent for entrapping the organ metallic complexes was developed to pre-concentrate the trace quantities of cadmium (Cd) and lead (Pb) in lipsticks and eye shadows of different brands prior to flame atomic absorption spectrometry analysis. A deep eutectic solvent (DES) was used in this study, prepared by mixing metal salt (ZnCl₂) and hydrogen bond donors such as (acetamide) in different ratio. The different branded cosmetic items, lipstick and eye shadows, obtained from local market and subjected to acid digestion prior to application of proposed ultrasonic assisted microextraction method based on deep eutectic solvent (UAµE-DES) with the aid of mechanical and ultrasound energies. Ammonium pyrrolidine dithiocarbamate was used as a ligand to made hydrophobic complexes of Cd and Pb, entrapped in DES in the presence of aprotic solvent. The seven variables, mixing ratio of ZnCl₂ and Acetamide, DES volume, Ultrasound and Conventional shaking time, pH, tetrahydrofuran and complexing reagent volume were optimized by multivariate approach for the optimum recovery of Cd and Pb from real cosmetic items. The resulted data indicates that ultrasound energy assisted extraction time, volume of DES and pH were most significant variables. The precision and validity of developed procedure were checked by the spiked known certified standards in real samples. The resulted data indicated that the lipsticks have different glittering colors contains high contents of Pb and Cd, whereas dark colors of eye shadows contain high level of both elements.