European Journal of Chemistry
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Health risk assessment of heavy metals in sediment, shrimp (Parapenaeopsis atlantica), and periwinkles (Tympanotonus fuscatus) from Esuk Ibeno Beach, Akwa Ibom State, Nigeria
Full text linkBeaches play an important role in the survival of the world. They serve the purpose of water supply for domestic, industrial, agricultural, and power generation. Beaches are also used for the disposal of industrial and sewage waste, putting rivers under tremendous pressure due to human activities. This research assesses heavy metal contamination in sediments, shrimps (Parapenaeopsis atlantica) and periwinkles (Tympanotonus fuscatus) from Esuk Ibeno Beach, Akwa Ibom State, Nigeria, to ascertain their potential human health risks to consumers. Shrimp samples and periwinkle samples (at low tide) were obtained with the help of local fishermen from Esuk Ibeno beach. Sediment samples were collected at the same location as the periwinkles. Concentrations of chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), lead (Pb), and cadmium (Cd) were analyzed using atomic absorption spectrometry. The sediments indicated heavy metal concentrations of Cr (0.24-0.32 mg/kg), Fe (25.0-41.4 mg/kg), Ni (0.27-0.38 mg/kg), Cu (0.05-0.11 mg/kg) Pb (0.03-0.09 mg/kg), and Cd (0.01-0.02 mg/kg), all below the quality standards of marine sediments. In the biota, Fe concentrations in shrimps (8.80±0.25 mg/kg) and periwinkles (0.90±0.03 mg/kg) exceeded the FAO/WHO limit of 0.5 mg/kg, while Cr, Ni, Cu, Pb and Cd were within the permissible limits. Biomagnification was apparent for Cr (1.00) and Cd (2.00) in the periwinkles. Dietary exposure assessments showed ingestion rates for adults and children, with the Expdiet values for Cr, Fe, Ni, Cu, Pb and Cd being lower than the oral reference dose (RfD). The target hazard quotient (THQ) values were less than 1 for all metals, indicating that there were no significant health risks. The cumulative hazard indices for shrimps (1.56×10-2 in adults; 1.61×10-2 in children) and periwinkles (1.11×10-2 in adults; 1.15×10-3 in children) suggest potential long-term risks of bioaccumulation. Incremental lifetime cancer risk (ILCR) for all investigated metals were 1.0×10-6 and 1.0×10-4. This indicates that the consumption of Parapenaeopsis atlantica and Tympanostus fuscatus from the Esuk Ibeno beach was within the acceptable range. This study indicates a great impact of anthropogenic activities on Esuk Ibeno Beach and calls for sustainable industrial waste management to prevent environmental and public health hazards
Local structure and optical absorption of Mn2+ doped Cs2SO4 single crystals
Full text linkUsing perturbation theory and the superposition model, the splitting parameters for the zero field of Mn2+ doped crystals of Cs2SO4 are determined. When the local distortion is included in the computation, the estimated parameters match fairly well with the experimental ones. Theoretical evidence corroborates the experimental finding that the Mn2+ ion substitutes at the Cs+ site in Cs2SO4. The crystal's optical spectra are computed by the diagonalization of a complete Hamiltonian in the coupling scheme of the intermediate crystal-field, using the crystal field parameters obtained from the superposition model and the crystal field analysis program. The calculated and experimental band positions agree fairly well. Consequently, the results of the experiment are confirmed by theoretical analysis
Ibuprofen, a household pharmaceutical belonging to the racemic mimic class-chirality, diastereochemical details, packing and overlay of the pair within the (S)(+) crystals
Full text linkWe have discovered that enantiopure and racemic Ibuprofen crystallize with nearly the same cell constants, the former in space group P21, the latter in P21/c. As expected from a pair that belongs to the racemic mimic class, the values of Z’ are 2.0 and 1.0, respectively. Interestingly, despite the fact that one is enantiopure and the other is a racemate, they form the classical dicarboxylate dimer one is familiar with in elemental chemistry and with nearly identical geometrical parameters, the enantiopure sitting at a true lattice inversion center, and the other one at a pseudo-inversion point located at 0.5000, 0.4458, and 0.5000. Packing diagrams are provided that show the remarkable degree to which they agree. Overlay diagrams generated with Mercury illustrate the extent to which the pair of enantiopure species resemble each other; the differences being largely small diastereoisomeric discrepancies and without a doubt the result of anisotropy in packing forces. Finally, within accepted limits for π-π bondings, there are no significant interactions between the phenyl rings in either crystalline form
New green HPLC and TLC methods for the determination of dapagliflozin, metformin hydrochloride, and its two official impurities, melamine and cyanoguanidine, in their quaternary mixture
Full text linkTwo environmentally friendly, simple, and accurate chromatographic methods were developed for the quantitative measurement of quaternary mixtures of dapagliflozin, metformin hydrochloride, melamine, and cyanoguanidine in both pure forms and pharmaceutical formulations. Recently, the development of new analytical methods requires taking into account green aspects. The principal objectives of green chemistry are the reduction and elimination of hazardous substances and their harmful effects on the environment and human health. The green HPLC method uses the C18 column (250 × 4.6 mm × 5 μm particle size) and a mobile phase consisting of methanol: water in a ratio of (90:10, by volume) with pH adjusted to 3.5 using o-phosphoric acid. The flow rate was 1.2 mL/min detected at 225 nm. Retention time (Rt) values were found to be 5.75, 2.06, 2.49 and 3.01 min for dapagliflozin, metformin hydrochloride, melamine, and cyanoguanidine, respectively, while the proposed green TLC method uses a silica gel plate 60F254 and ethanol: ethyl acetate (1:9, by volume) as a developing system detected at 225 nm. The Rf values were found to be 0.66, 0.74, 0.51 and 0.83 for the four components, respectively. Good linearity was shown through concentration ranges of 1-30, 2-70, 0.5-25, and 1-25 μg/mL for the four components, respectively, for the proposed HPLC method and 0.1-1.5, 0.2-3.0, 0.1-1.5 and 0.1-1.2 μg/band for the four components, respectively, for the proposed TLC method. The proposed methods were successfully applied to diaflozimet 10/1000® tablets containing dapagliflozin and metformin hydrochloride and the results were statistically compared to a published HPLC method and no significant differences were found
A re-examination of the crystal and molecular structure of azulene as is present in LADWEW = tris(1,2,4,5-tetrafluoro-3,6-diiodobenzene) bis(azulene), 2(C10H8), 3(C6F4I2) - a conglomerate in P1
Full text linkIn need of information on the precise structural data of the monomer of azulene, we were long frustrated by our inability to characterize it thus because the known specimens always contained its extremely stable head-to-tail dimer. Recently, a claim was made of having prepared such a monomeric species in the case of (tris(1,2,4,5-tetrafluoro-3,6-diiodobenzene)bis(azulene), whose REFCODE = LADWEW), which the authors used to “demonstrate how a highly robust C-I⋯π motif permits the systematic exchange of original co-crystal components with azobenzene and azulene, resulting in optically interesting dichroic or pleochroic materials.” We demonstrate that the structural data used in the theoretical treatment of the title compound were derived from an improper crystallographic analysis. The hkl values provided in the original report were used to obtain the correct structural solution in P1, (Z’ = 1) as opposed to the original centrosymmetric P-1, (Z’ = 0.5) interpretation. These new data have been deposited with the CCDC #2403565
Crystal structures, computational studies, and Hirshfeld surface analysis on 7-hydroxy-4-methyl-2H-chromen-2-one and 7-hydroxy-4-methyl-8-nitro-2H-chromen-2-one
Full text link7-Hydroxy-4-methyl-2H-chromen-2-one and 7-hydroxy-4-methyl-8-nitro-2H-chromen-2-one have been synthesized. The compounds have been characterized using IR, NMR, GC-MS, and elemental analysis. The single-crystal X-ray structure of the compounds showed that compound 1 was crystallized in the orthorhombic space group P212121 while compound 2 crystalized in the monoclinic space group P21/c. A comparison of the computed and experimental bond lengths and bond angles showed good agreement among the data. A Hirshfeld surface analysis showed that the H∙∙∙O/O∙∙∙H interaction was the most prominent molecular interaction for both compound 1 H∙∙∙O/O∙∙∙H (34.4%) and compound 2 H∙∙∙O/O∙∙∙H (48.6%)
Preparation and properties of physically plasticized chitosan films
Full text linkFood packaging prevents conditions that can reduce food quality and shelf life. This leads to environmental pollution because it does not degrade naturally. The food packaging industry is increasingly adopting biodegradable polymer films as an alternative to plastic packaging. They are receiving great attention and are more suitable for food applications because they do not need to be eliminated as solid waste, which is why the industry has recently begun to pay more attention to food packaging films derived from natural chitosan polymers to replace traditional synthetic polymers. Shrimp cortex was used to extract the chitosan using the casting procedure; It was plasticized with different ratios of polyvinyl alcohol (PVC), namely 1:1, 1:2, 1:3, and 1:4 to create plasticized chitosan films from its solution in 2% acetic acid by casting technique. All films prepared were examined by infrared spectroscopy (FT-IR) and were found to be comparable to the original chitosan spectrum, indicating that the basic composition of the basic polymeric chitosan chains was not affected by the addition of various ratios of PVC plasticizer. Unlike unplasticized chitosan films. The results of the mechanical tensile strength measurements of plasticized chitosan films showed an improvement in tensile strength, % elongation at breakage, and a decrease in the Young modulus, which means that less rigid films were obtained, with an enhancement in their optical properties accompanying this by decreasing the opacity from 85 for unplasticized chitosan to about 3 for plasticized chitosan films. The addition of plasticizer to chitosan was also found to increase the solubility of prepared plasticized chitosan films in water and reached 100% for 1:3 chitosan:PVA in contrast to the unplasticized chitosan polymer, which is insoluble in water
Effects of solvents on the aromaticity and thermodynamic properties of azacalix[2]arene[2]pyrimidines: A computational study
Full text linkThe Harmonic Oscillator Model of Aromaticity (HOMA) indexes for the 2,4,6,8-tetraaza-1(2,4),5(4,2)-dipyrimidina-3,7(1,3)-dibenzenacyclooctaphane (TPB) molecule were calculated in gas, ethanol, n-octanol and water phase. Solvent effects were analyzed with the use of the Integral Equation Formalism Polarizable Continuum Model (IEFPCM) as the default in the self-consistent reaction field (SCRF) method in Gaussian09. The HOMA indexes indicate the presence of highly aromatic pyrimidine and benzyl rings while the parameters for pyrimidine rings slightly decrease and those for the benzyl ring slightly increase with increasing dielectric constant. According to the results, the pyrimidine ring shows the highest aromaticity in the gas phase and a slight decrease in more polar solvents. In contrast, the benzene ring shows an increase in aromaticity as the solvent polarity increases. The HOMO energy of the TPB shifts downward in more polar solvents and the most significant shift occurs in the water phase. The HOMO-LUMO energy gap increases in polar solvents, indicating higher chemical stability and decreased reactivity in these solvents. These findings provide insight into the stability and reactivity of TPB in different phases for potential applications. In addition, apparent thermodynamic properties such as the heat capacity, entropy, enthalpy, and Gibbs free energy of TBP in various solvents were calculated. Using computational simulations, we derive heat capacity equations that exhibit similar quadratic and linear terms in both phases, differing only in their constants. The negative quadratic term leads to a decrease in heat capacity at very low temperatures