Extraction of Organochlorine Pesticides from Porous Membrane Packed Dried Fish Samples: Method Development and Greenness Evaluation

In this work, ultrasound-assisted solvent extraction was utilized for extraction of organochlorine pesticides from membrane-protected dried fish samples. The dried fish samples were packed inside a porous membrane bag which was immersed in a solvent and subjected to ultrasonication. After the extraction process, the sample-containing bag was separated from the extract. Since samples were packed inside the membrane, their separation did not require centrifugation or filtration. Moreover, the complex components of the biota matrix may also retain inside the porous membrane bag, alleviating the requirement of extract cleanup before analysis. The parameters that can affect the ultrasound-assisted solvent extraction of membrane-protected dried fish samples were suitably optimized. These parameters include the extraction solvent and its volume, the sample amount, ultrasound intensity and extraction time. Under the optimum extraction conditions, good linearity was achieved for all the tested organochlorine pesticides, with the coefficients of determination (R2) higher than 0.9922 for the linear ranges from 5–1000, 10–1000 and 20–1000 ng/g. The values of intra-day and inter-day relative standard deviations were ≤13.8%. The limit of detection ranged from 1.5 to 6.8 ng/g. The spiked relative recoveries were in the range of 87.3–104.2%. This method demonstrated excellent figures of merit and could find potential applications in routine analytical laboratories. Finally, the greenness of this method was evaluated using the green analytical procedure index and analytical greenness calculator metrics

Total and soluble fluoride concentration present in various commercial brands of children toothpastes available in Saudi Arabia – A pilot study

Objective: The aim of this pilot study was to perform chemical analysis and investigate the total and soluble fluoride concentrations in various brands of children toothpastes. Materials and methods: Three samples of five different commercial brands of children toothpastes were collected and divided into five groups; group A – Biorepair Oral Care toothpaste containing no fluoride (control), group B – Signal Kids Strawberry toothpaste having 500 ppm fluoride, group C – Aquafresh Milk Teeth toothpaste having 500 ppm fluoride, group D – Aquafresh Little Teeth toothpaste having 500 ppm fluoride, and group E – Siwak F Junior having 400 ppm F. The total fluoride (TF) and total soluble fluoride (TSF) concentration of the toothpastes was determined using fluoride ion selective electrode. Data were analysed using Paired sample t-test. Results: The measured TF values were inconsistent with that of the declared concentrations by the manufacturers. Mean TF found in the toothpastes ranged between 2.37 and 515.74 ppm whereas, the mean TSF ranged between 2.00 and 503.4 ppm. For two groups, TF was more than the declared TF whereas for the other three groups, it was less than the declared concentration. All the differences between the declared and observed TF concentration were statistically significant (p < .05) except for one group. All the toothpastes demonstrated mean TSF slightly lower than their respective observed mean TF concentrations. Conclusion: The analysis of TF and TSF concentrations revealed variations from the labelled claims. Therefore, some of the toothpastes may have doubtful anti-caries effectiveness owing to deficiency of total and soluble fluoride. Keywords: Fluoride, Fluoride ion electrode, Total fluoride, Total soluble fluoride, Toothpaste

Determination of N-nitrosamines by automated dispersive liquid-liquid microextraction integrated with gas chromatography and mass spectrometry

10.1002/jssc.201401043Journal of Separation Science38101741-174

Mechanistic study of polyepoxy succinic acid (PESA) as green corrosion inhibitor on carbon steel in aerated NaCl Solution

The inhibition mechanism of mild steel corrosion in aerated aqueous 3% NaCl medium was studied using Polyepoxy succinic acid (PESA) as a green inhibitor. The study utilized electrochemical, thermodynamic, and surface microscopic techniques. Computational methods supported the empirical results of the inhibition mechanism at the molecular level. Results showed inhibition efficiency of PESA exceeding 60% at 2 g/l at 25 °C through the formation of a protection layer on mild steel surface. An addition of 2 mg/l of zinc cations to 2 g/l of PESA at 25 °C enhanced the inhibition efficiency reaching 90%. SEM and AFM scans revealed an efficient coverage of an adsorbed layer on mild steel surface. Quantum chemical, Monte Carlo computation and simulation provided mechanistic insights of the reactivity sites and PESA's adsorption strength on metal surface

Modulating the electrocatalytic reduction of CO2 to CO via surface reconstruction of ZnO nanoshapes

The electrocatalytic conversion of carbon dioxide (CO2) into valuable chemicals presents a promising strategy for closing the carbon cycle. In this study, we synthesized zinc (Zn) catalysts through hydrothermal methods using either polyvinylpyrrolidone (PVP) or cetyltrimethylammonium bromide (CTAB) as stabilizing agents. These catalysts proved highly efficient in converting CO2 into carbon monoxide (CO). Our findings revealed that ZnO, synthesized with different morphologies—namely, nanoneedles (ZnO-NN) and nanorods (ZnO-NR)—underwent significant electro-reconstruction, ultimately leading to the formation of hexagonal metallic Zn crystals, regardless of their initial characteristics. Utilizing ex-situ operando techniques, we elucidated that metallic Zn serves as the active phase for the CO2-to-CO conversion process. In a comparison, ZnO-NN catalysts demonstrated superior selectivity and stability, achieving 91.3% CO selectivity at a potential of −0.88 V vs. RHE (Reversible Hydrogen Electrode) due to the facile transformation of ZnO to metallic Zn. Remarkably, these catalysts maintained this level of performance for more than 17 h. Conversely, ZnO-NR catalysts exhibited a lower CO selectivity of 62.5% at a relatively higher potential of −0.98 V vs RHE

A First-Principles Study on the Multilayer Graphene Nanosheets Anode Performance for Boron-Ion Battery

Advanced battery materials are urgently desirable to meet the rapidly growing demand for portable electronics and power. The development of a high-energy-density anode is essential for the practical application of B3+ batteries as an alternative to Li-ion batteries. Herein, we have investigated the performance of B3+ on monolayer (MG), bilayer (BG), trilayer (TG), and tetralayer (TTG) graphene sheets using first-principles calculations. The findings reveal significant stabilization of the HOMO and the LUMO frontier orbitals of the graphene sheets upon adsorption of B3+ by shifting the energies from &minus;5.085 and &minus;2.242 eV in MG to &minus;20.08 and &minus;19.84 eV in 2B3+@TTG. Similarly, increasing the layers to tetralayer graphitic carbon B3+@TTG_asym and B3+@TTG_sym produced the most favorable and deeper van der Waals interactions. The cell voltages obtained were considerably enhanced, and B3+/B@TTG showed the highest cell voltage of 16.5 V. Our results suggest a novel avenue to engineer graphene anode performance by increasing the number of graphene layers

A First-Principles Study on the Multilayer Graphene Nanosheets Anode Performance for Boron-Ion Battery

Advanced battery materials are urgently desirable to meet the rapidly growing demand for portable electronics and power. The development of a high-energy-density anode is essential for the practical application of B3+ batteries as an alternative to Li-ion batteries. Herein, we have investigated the performance of B3+ on monolayer (MG), bilayer (BG), trilayer (TG), and tetralayer (TTG) graphene sheets using first-principles calculations. The findings reveal significant stabilization of the HOMO and the LUMO frontier orbitals of the graphene sheets upon adsorption of B3+ by shifting the energies from −5.085 and −2.242 eV in MG to −20.08 and −19.84 eV in 2B3+@TTG. Similarly, increasing the layers to tetralayer graphitic carbon B3+@TTG_asym and B3+@TTG_sym produced the most favorable and deeper van der Waals interactions. The cell voltages obtained were considerably enhanced, and B3+/B@TTG showed the highest cell voltage of 16.5 V. Our results suggest a novel avenue to engineer graphene anode performance by increasing the number of graphene layers

Highly Efficient and Selective Oxidation of Aromatic Alcohols Photocatalyzed by Nanoporous Hierarchical Pt/Bi₂WO₆ in Organic Solvent-Free Environment

Selective conversion of aromatic alcohols into corresponding aldehydes is important from energy and environmental stance. Here, we describe highly selective (>99%) and efficient conversion (>99%) of aromatic alcohols (e.g., 4-methoxybenzyl alcohol and 4-nitrobenzyl alcohol) into their corresponding aldehydes in the presence of Pt-modified nanoporous hierarchical Bi₂WO₆ spheres in water under simulated sunlight at ambient conditions. Overoxidation of <i>p</i>-anisaldehyde, formed during photooxidation process, was not observed until comprehensive alcohol oxidation was attained. Furthermore, the catalyst showed substantial oxidation under dark and course of conversion was different than that of under light. Dependency of alcohol oxidation on substrate concentration, photocatalyst amount, and Pt loading was studied. The effect of various radical scavengers was investigated, and the rate-determining step was elucidated. It has been envisaged that the reduction site of semiconductor photocatalysts plays more decisive role in determining the selectivity as alcohol preferably get oxidized over that of water. Furthermore, the chemical stability and recyclability of the photocatalyst were investigated