Automatic determination of nickel in foods by flame atomic absorption spectrometry

Protective effect of resveratrol on nickel-refining fumes-induced inflammatory damage

Nickel (Ni), a ductile and hard silver-white transition metal, is commonly found in occupational environments and can harm the human body. Since it is a toxic compound, long-term Ni exposure can cause pneumonia, rhinitis, and other types of respiratory inflammatory diseases. Resveratrol (Res) is a plant antitoxin polyphenol, which also has anti-cancer and anti-inflammatory properties. In this report, the toxicity of Ni-refining fumes on the human lung bronchial epithelial (BEAS-2B) cells, as well as the protective effects of Res were investigated in vitro, and the specific mechanism of its anti-inflammatory effect was explained. The experimental observations of this study revealed that Ni-refining fumes induce BEAS-2B cell damage, increase reactive oxygen species (ROS) content, activate NLRP3 (LRR-, NOD-, and pyrin domain-containing 3) inflammasome, and promote the secretion of the cytokine Interleukin (IL)-1β, leading to cellular inflammation and reducing cell activity. Resveratrol (20 μmol/L) activated sirtuin 1 (SIRT1) in BEAS-2B cells to increase protein and mRNA expression. SIRT1 was observed to inhibit the transcriptional activity of nuclear factor-kappaB (NF-κB), reduced the expression of NLRP3 protein and mRNA, and inhibited NLRP3 inflammation. The level of inflammasome activation and IL-1β overexpression could reduce the inflammatory damage caused by the Ni-refining fume particles on the BEAS-2B cells and exert anti-inflammatory protective effects. In vivo experiments further confirmed that resveratrol could effectively alleviate the acute inflammatory injuries caused due to exposure to the Ni-refining fume particles in the lung tissues of the Wistar rats, and verified that resveratrol could exert its anti-inflammatory impact through the SIRT1-NF-κB-NLRP3 pathway. These results provide an important theoretical basis for developing novel protective drugs and investigating the mechanism of action for inflammatory injury in occupational populations caused by exposure to nickel and other heavy metals.

Electrochemical sensing platform based on Zeolite/Graphite/Dimethylglyoxime nanocomposite for highly selective and ultrasensitive determination of nickel

In this work, the fabrication and analytical application of a novel, unique, mercury-free, and user-friendly voltammetric sensor of Ni(II) based on glassy carbon electrode (GCE) modified with zeolite(MOR)/graphite(G)/dimethylglyoxime(DMG) composite (MOR/G/DMG-GCE) and the voltammetric procedure for highly selective, ultra-trace determination of nickel ions were reported for the first time. Deposition of a thin layer of the chemically active MOR/G/DMG nanocomposite enables the selective and effective accumulation of Ni(II) ions in the form of the DMG-Ni(II) complex. In 0.1 mol L^-1 ammonia buffer (pH 9.0), the MOR/G/DMG-GCE exhibited linear response in the Ni(II) ions concentration range of 0.86 - 19.61 µg L^-1 and 0.57 - 15.75 µg L^-1, for the accumulation time of 30 s and 60 s, respectively. For 60 s of accumulation time, the limit of detection (S/N = 3) was 0.18 µg L^-1 (3.04 nM), and sensitivity of 0.202 µA L µg^-1 was achieved. The developed protocol was validated by the analysis of wastewater certified reference materials. Its practical usefulness was confirmed by the determination of nickel released from metallic jewelry submerged in artificial sweat and stainless steel pot during water boiling. The obtained results were verified by electrothermal atomic absorption spectroscopy as a reference method.

Carbon-polymer dot-based UV absorption and fluorescence performances for heavy metal ion detection

In previous reports, carbon dots (CDs) were customarily used as fluorescent probes to detect heavy metal ions. However, scientists neglected to take advantage of the excellent UV absorption properties of CDs to detect heavy metal ions. Herein, we synthesized nitrogen-containing carbon polymer dots (N-CPDs) for the determination of Co²⁺ ions in water samples by a one-step hydrothermal method using l-histidine and ethylene imine polymer as raw materials. The N-CPDs were characterized by ultraviolet-visible spectrum (UV-vis), infrared spectrum (FT-IR), X-ray photoelectron spectrum (XPS) and transmission electron microscopy (TEM) techniques. They possess superior full-band UV absorption performance and the surface is rich in multifunctional groups such as -COOH, -CN-, -OH, etc. When Co²⁺ was added to N-CPDs solution, the color of the solution rapidly changed from colorless to yellow-brown, which was visible to the naked eye. The UV absorption intensity of N-CPDs changed, and the fluorescence was instantly quenched, due to the formation of chelate between Co²⁺ and N-CPDs, and the FRET process occurred. The detection of Co²⁺ showed good linearity for both fluorescence and UV absorption spectroscopy modes in the range of 0-200 μM, and the limit of detection were 1.0023 μM and 0.75 μM, respectively. These two methods have the advantages of simple operation, remarkable selectivity and small sample size, which can be applied to the field detection of Co²⁺ in water samples. It is possible to develop the UV absorption properties of CDs to detect the ions.

Food safety of the green tiger shrimp Penaeus semisulcatus from the Persian Gulf

Seafood is a rich source of essential compounds for human health, but the consumption of aquatic products that are exposed to environmental pollutants, especially trace metals, comes with risk. Therefore, in this study, the levels of nickel, zinc, and lead in the muscle of shrimp Penaeus semisulcatus caught from the north of the Persian Gulf as a polluted environment were measured, and the health risks were assessed. The results showed that the level of Zn (300.88 ± 2.76 µg/g) in the muscle of shrimp was higher than Ni (6.82 ± 0.10) and Pb (1.10 ± 0.09 µg/g), and the amount of accumulation of all three metals is higher than the allowable limit proposed by the FAO/WHO. According to values of estimated daily intake (EDI) and target hazard quotient (THQ), the consumption of shrimp has no or minimal risk for health. However, the target cancer risk (TR) of Ni (adult, 0.00294; child, 0.00196) indicated that Ni accumulation is associated with carcinogenic risks. These findings may be helpful in the proper management of seafood quality and public health in the Persian Gulf.

Nickel sulfate exposure induces ovarian inflammation and fibrosis and decreases oocyte quality in mice

Nickel is a heavy metal element extensively distributed in the environment and widely used in modern life. Divalent nickel is one of the most widespread forms of nickel and has been reported as toxic to various tissues. However, whether exposure to divalent nickel negatively affects ovarian homeostasis and oocyte quality remains unclear. In this study, we found that 3 weeks of nickel sulfate exposure affected body growth and decreased the weight and coefficient of the ovary, and increased atretic follicles exhibiting enhanced apoptosis in granulosa cells. Further studies have found that nickel sulfate triggered ovarian fibrosis and inflammation via transforming growth factor-β1 and nuclear factor-κB pathways, and reduced oocyte development ability. In addition, nickel sulfate increased the level of reactive oxygen species, which induced DNA damage and early apoptosis. Moreover, it was found that nickel sulfate caused damage to the mitochondria showing aberrant morphology, distribution and membrane potential while decreased levels of histone methylation. To summarize, our results indicated that nickel sulfate exposure triggered ovarian fibrosis and inflammation and caused structural and functional disorders of mitochondria in oocytes, which consequently disturbed ovarian homeostasis and follicle development and decreased oocyte quality.

Polymer/BiOBr-Modified Gauze as a Dual-Functional Membrane for Heavy Metal Removal and Photocatalytic Dye Decolorization

It is crucial to remove heavy metals and dyes before discharging industrial effluents. Gauze substrate was surface-modified by coating with a polymeric adsorbent and a spray coating of BiOBr photocatalyst to develop a novel dual-functional membrane, polymer/BiOBr-modified gauze, for water remediation. The polymeric adsorbent was crosslinked to prevent the dissolving of the adsorbent during operation in contaminated water. The morphology and surface chemistry of the modified gauze were characterized before and after the adsorption of Ni²⁺. The surface wettability, isotherms, and kinetics of Ni²⁺ adsorption were studied. We also studied the effect of pH, initial Ni²⁺ concentration, monomer molar ratio, and monomer chemical structure on the Ni²⁺ adsorption capacity. To achieve a high Ni²⁺ adsorption capacity and good photocatalytic decolorization activity, the amount of decorated BiOBr was tuned by changing the spray-coating time to optimize the exposed BiOBr and polymer on the surface. The optimized dual-functional membrane PB20 possesses excellent adsorption capacity (650 mg g^-1) for Ni²⁺ ions and photocatalytic decolorization activity (100% degradation of RhB within 7 min). Decorating the optimized amount of BiOBr on the surface can introduce photocatalytic decolorization activity without sacrificing the adsorption capacity for Ni²⁺.

Resveratrol protects human bronchial epithelial cells against nickel-induced toxicity via suppressing p38 MAPK, NF-κB signaling, and NLRP3 inflammasome activation

Nickel is a common environmental pollutant that can impair the lung, but the underlying mechanisms have not yet been fully elucidated. Furthermore, natural products are generally used to inhibit cell damage induced by heavy metal. Resveratrol possesses wide biological activities, including anti-inflammation and antioxidative stress. This study was conducted to explore the toxicity of nickel on human bronchial epithelial (BEAS-2B) cells and evaluate the protective effect of resveratrol. The results showed that nickel could induce cell apoptosis, increase oxidative stress, and promote the expression of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8, C-reaction protein. Western blot analysis showed that nickel activated p38 mitogen-activated protein kinase (MAPK), nuclear factor-kappa B, and nucleotide-binding oligomerization domain-like receptor pyrin-domain-containing protein 3 pathways, while resveratrol could reverse these effects. Our results suggested that resveratrol could protect BEAS-2B cells from nickel-induced cytotoxicity. Therefore, resveratrol is a potential chemopreventive agent against nickel-induced lung disease.

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 0.7 mL 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 0.78 μg/L; sensitivity enhancement factors are 48.6 and 53.9; the calibration curves were linear 3-180 and 2-160 μg/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 100 μg/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.

Review on the Risk Assessment of Heavy Metals in Malaysian Clams

The current review discusses the levels of six heavy metals in different clam species from 34 sites of Malaysian coasts. The concentrations (µg/g dry weight) of these heavy metals ranged around 0.18-8.51, 0.13-17.20, 2.17-7.80, 0.84-36.00, 24.13-368.00, and 177.82-1912.00 for Cd, Pb, Ni, Cu, Zn, and Fe, respectively. It was observed that the concentrations of metals slightly depend on different clam species but mostly depend on site locations. According to Malaysian Food Regulation (1985), about 30% and more than 50% sites are safe from Cd and Pb contamination, respectively, and also the clam species from the other populations studied were safe for consumption.

Sensitive determination of cadmium in brown rice and spinach by flame atomic absorption spectrometry with solid-phase extraction

A sensitive flame atomic absorption spectrometry (FAAS) method was developed for the determination of cadmium (Cd) in brown rice and spinach. The method involves extraction with 1 M hydrochloric acid (HCl), followed by a selective pre-concentration by solid-phase extraction (SPE). The pH of the loading sample solution was adjusted to 4.0 for the brown rice and to 5.0 for the spinach. The masking agents, tartrate and citrate, were required for the spinach before pH adjustment. The SPE step achieved a 20-fold enrichment of the sample solution. The limits of quantification (LOQs) were 0.0054 mg kg⁻¹ for the brown rice and 0.0022 mg kg⁻¹ for the spinach, being more sensitive than those of AOAC Official method 999.10. A single-laboratory validation was performed by testing spiked samples at 0.04 and 0.08 mg kg⁻¹ for the brown rice, and 0.02 and 0.04 mg kg⁻¹ for the spinach. The average recoveries were 93.3-96.9% with relative standard deviations (RSDs) of 4.1-8.2% for brown rice, and 90.5-91.9% with RSDs of 5.8-10.0% for spinach.

Analytical sonochemistry; developments, applications, and hyphenations of ultrasound in sample preparation and analytical techniques

Ultrasonic assistance is one of the great successes of modern analytical chemistry, which uses this energy for a variety of purposes in relation to sample preparation and development of methods for the analysis of numerous contaminants including organic and inorganic compounds. This review will attempt to provide an overview of more recent applications of ultrasound in different environmental and biological samples such as food, soil and water as well as a brief description of the theoretical understanding of this method. Also, the possibility of coupling ultrasound with other analytical techniques will be discussed.

A green analytical method using ultrasound in sample preparation for the flow injection determination of iron, manganese, and zinc in soluble solid samples by flame atomic absorption spectrometry

A simple and rapid analytical method was developed for the determination of iron, manganese, and zinc in soluble solid samples. The method is based on continuous ultrasonic water dissolution of the sample (5-30 mg) at room temperature followed by flow injection flame atomic absorption spectrometric determination. A good precision of the whole procedure (1.2-4.6%) and a sample throughput of ca. 25 samples h(-1) were obtained. The proposed green analytical method has been successfully applied for the determination of iron, manganese, and zinc in soluble solid food samples (soluble cocoa and soluble coffee) and pharmaceutical preparations (multivitamin tablets). The ranges of concentrations found were 21.4-25.61 μg g(-1) for iron, 5.74-18.30 μg g(-1) for manganese, and 33.27-57.90 μg g(-1) for zinc in soluble solid food samples and 3.75-9.90 μg g(-1) for iron, 0.47-5.05 μg g(-1) for manganese, and 1.55-15.12 μg g(-1) for zinc in multivitamin tablets. The accuracy of the proposed method was established by a comparison with the conventional wet acid digestion method using a paired t-test, indicating the absence of systematic errors.

Application of quartz crystal nanobalance and principal component analysis for detection and determination of nickel in solution

Quartz crystal nanobalance (QCN) sensors are considered as powerful mass sensitive sensors to determine materials in the sub-nanogram level. In the first part of this study, a single piezoelectric QCN modified with polypyrrole (PPy) has been tested for detection and determination of nickel ions in the solution at room temperature. The developed method was successfully applied for detection of total nickel in samples taken from several hot springs located at the Northwest of Iran. The frequency shifts were linear with respect to the concentration of nickel in solution. Using this method, nickel can be measured in the range of 3-20 mg L(-1). A lower limit of detection of 0.79 mg L(-1) and a sensitivity factor of 4.429 Hz/mg L(-1) were obtained. Some possible interference such as heavy metal ions (lead, mercury, and cadmium) was checked. No major interference was observed with the performance of the sensor except for mercury. To evaluate the ability of the PPy-modified QCN in discriminating between nickel ions and interfering mercury ions, a principal component analysis (PCA) was carried out. PCA was utilized to process the frequency response data of the single piezoelectric crystal at different times, considering different adsorption-desorption dynamics of nickel and interfering mercury ions on electrode. Using PCA, it was found that about 97.90% of the data variance could still be explained by two principal components (PC1 and PC2). The score plot of the data for the first two PCs showed that the PPy-modified QCN yields favorable identification and quantification performances for nickel ions. The accuracy of method for hot spring samples was evaluated and RSD of 4.10% was obtained.