Metals and phosphorus determination in vegetable seeds used in the production of biodiesel by ICP OES and ICP-MS

Methods for the determination of 5 major (Ca, K, Mg, Na and P) and 14 minor elements (Al, Ba, Cd, Co, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Rb, Sr and Zn) in vegetable seeds by ICP OES and by ICP-MS, respectively, are proposed. After a common sample preparation consisting of smashing and homogenization in an agata mortar, followed by acid digestion in a microwave oven, the diluted sample solutions were measured in the spectrometers using conventional pneumatic nebulizers. External calibration with aqueous standard solutions was used for both techniques. Internal standard was not required, due to the absence of non-spectral interference. For the major elements, the detection limits were in the range of 0.01 (Mg) to 0.3 µg g^− 1 (Na and K) and for the minor elements they were in the range of 0.001 (several) to 0.4 µg g^− 1 (Fe). The detection limits were adequate for the seed analysis. The accuracy was validated by analyzing a botanical certified reference material (Pine Needles). Agreement of the concentrations with the certified or informed values was obtained, according to the t-test for a confidence level of 95%. The relative standard deviations were below 10% indicating an adequate precision. Seeds from seven different plants were analyzed: cotton seed, sunflower, castor bean, fodder turnip, curcas bean, soybean and tung. The element concentrations varied considerably in the different samples. The results were also evaluated using the principal component analysis.     

A new method for the chiral HRGC assay of L-2-hydroxyglutaric acid in urine

L -2-Hydroxyglutaric aciduria is a recently discovered inherited neurometabolic disease for which diagnostic identification of the right enantiomer is required. A method is described where alkyl esters of both L -and D -2-hydroxyglutaric acids are prepared without side lactonization. Esterification is achieved at room temperature by reaction with appropriate alkyl chloroformates. This method avoids lactonization, in contrast to esterification with alcohols in acidic media or with diazomethane. The identity of the derivatives is established by HRGC-FTIR and HRGC-MS. Chiral HRGC separation with capillaries coated with 1(R)-trans-N-N'-1,2-cyclohexylenebisbenzamideoligodimethyL-siloxane and with a cyclodextrin is compared. The method is adequate for quantitative determinations.     

Self‐Assembled Gold Arrays That Allow Rectification by Nanoscale Selectivity

The deposition of a monolayer nanoarray on the surface of a micrometer‐thick substrate is demonstrated, producing rectification characteristics at the nanoscale. The experimental results show that the heterogeneity of the structure and the charge density are the two key factors affecting rectification, which was confirmed with molecular dynamic (MD) and finite element simulations. Moreover, by altering the asymmetric electrolyte environment, the fabricated heterogeneous membrane can be used in energy conversion. This study provides insights into the mechanism underlying the generation of rectification and related factors, providing a theoretical basis for the characteristics of rectification.     

Hydroxypyridinone-Based Metal Chelators towards Ecotoxicity: Remediation and Biological Mechanisms

Hydroxypyridinones (HPs) are recognized as excellent chemical tools for engineering a diversity of metal chelating agents, with high affinity for hard metal ions, exhibiting a broad range of activities and applications, namely in medical, biological and environmental contexts. They are easily made and functionalizable towards the tuning of their pharmacokinetic properties or the improving of their metal complex thermodynamic stabilities. In this review, an analysis of the recently published works on hydroxypyridinone-based ligands, that have been mostly addressed for environmental applications, namely for remediation of hard metal ion ecotoxicity in living beings and other biological matrices is carried out. In particular, herein the most recent developments in the design of new chelating systems, from bidentate mono-HP to polydentate multi-HP derivatives, with a structural diversity of soluble or solid-supported backbones are outlined. Along with the ligand design, an analysis of the relationship between their structures and activities is presented and discussed, namely associated with the metal affinity and the thermodynamic stability of the corresponding metal complexes.     

Assessing cocaine use patterns in the Brazilian Capital by wastewater-based epidemiology

ABSTRACT

The levels of cocaine (COC) and its metabolites benzoylecgonine (BE) and cocaethylene (COE) in wastewater samples from Brasilia, Brazil, were determined using liquid chromatography coupled to hybrid quadrupole-time-of-flight mass spectrometry. The former metabolite was used to estimate cocaine consumption using a country-tuned correction factor that considers BE excretion rates for different routes of administration as well as the fraction of crack users in Brazil. A day-to-day analysis during a week indicates higher cocaine use in weekends with peaks on Sunday in both southern (7385 ± 121 mg day^?1 1000 inhab^?1) and northern (3566 ± 171 mg day^?1 1000 inhab^?1) areas of Brasilia. A significant high cocaine use was also observed in the Carnival Day of 2018 (6229 ± 219 mg day^?1 1000 inhab^?1). COE/BE ratios were used to assess COC and alcohol co-consumption since COE is produced during the co-consumption of both substances. Higher ratios were also observed during the weekend. However, higher ratios on Saturdays rather than Sundays may be explained by the decrease of BE excretion during the co-consumption with alcohol, which may lead to an underestimation of the cocaine use estimates on Saturdays, as well as by different patterns of co-consumption by powder and crack users, where the latter usually drink lower amounts of alcohol. Our data suggest that only 3% of cocaine was seized by the local Technical Police during the study.     

Combined application of DP4+ and ANN-PRA to determine the relative configuration of natural products: The alpha-bisabol case study

The combination of computational methods and experimental data from Nuclear Magnetic Resonance (NMR) is a considerably valuable tool in the elucidation of new natural product structures and, also, in the structural revision of previously reported compounds. Until recently, only classical statistical parameters were used, for example, linear correlation coefficient (R²), mean absolute error (MAE), or root mean square deviation (RMSD), as a way to statistically “validate” the structure pointed out by experimental NMR spectra. Regarding the resolution of the relative configuration of organic molecules, novel tools were available in the last few years to assist in the NMR elucidation process. The most relevant are DP4+, which is based on a Bayesian probability, and ANN-PRA, which is based on artificial neural networks. The combined application of these tools has become the most accurate and important alternative to solve structural and stereochemical problems in natural product chemistry. Therefore, herein, in this case study, we intended to promote these novel tools, exploring the strengths and limitations of each approach in resolving the relative configuration of the sesquiterpene alpha-bisabol. We also highlighted the advantages of the complementary use of H- and C-DP4+ to obtain optimal results in the differentiation of the stereoisomers, validating the proposal with ANN-PRA method.     

Simultaneous quantification of lipopeptide isoforms by UPLC-MS in the fermentation broth from Bacillus subtilis CNPMS22

Analytical and Bioanalytical Chemistry - The rapid and accurate quantification of lipopeptide families in biological samples are challenging. We present the development and validation of a method...     

Adaptation of asexual populations in correlated environments

We introduce two computational models of subdivided populations of asexual organisms which present variability in selection pressure. In both models one can handle the level of environmental correlation among the subpopulations (demes), which is dependent on the length of the shortest path between the demes. This work mainly addresses how environmental heterogeneity can affect the rate at beneficial mutations fixes in a structured population, and the conditions under which clonal interference becomes significant. Although the fixation probability of beneficial mutations is roughly the same as in a panmitic population and so does not depend on the level of correlation among the demes, the simulation results show that fixation rates may be strongly influenced by environmental variability. Based on our simulations we conclude that an increased variability in selection leads to a smaller fixation rate. The effect of environmental heterogeneity on the adaptive process is enhanced as the flow of organisms between subpopulations is reduced. In extreme scenarios, the fixation rate decreases as the rate of beneficial mutations rises.     

Synergistic Approach to Elucidate the Incorporation of Magnesium Ions into Hydroxyapatite

Although the content of Mg²⁺ in hard tissues is very low (typically ≤1.5 wt %), its incorporation into synthetic hydroxyapatite (HAp) particles and its role in the mineral’s properties are still subject of intensive debate. A combined experimental–computational approach is used to answer many of the open questions. Mg²⁺‐enriched HAp particles are prepared using different synthetic approaches and considering different concentrations of Mg²⁺ in the reaction medium. The composition, morphology and structure of the resulting particles are investigated using X‐ray photoelectron spectroscopy, energy dispersive X‐ray spectroscopy, scanning and transmission electron microscopies, FTIR, and wide‐angle X‐ray diffraction. After this scrutiny, the role of the Mg²⁺ in the first nucleation stages, before HAp formation, is investigated using atomistic molecular dynamics simulations. Saturated solutions are simulated with and without the presence of DNA, which has been recently used as a soft template in the biomineralization process. This synergistic investigation provides a complete picture of how Mg²⁺ ions affect the mineralization from the first stages onwards.     

Lead in Hair of Children Exposed to Gross Environmental Pollution

Abstract

In the context of a cross-sectional study, concentrations of lead in hair (PbH) were determined by atomic absorption analysis among 263 children aged 1 to 9 years, living less than 900m from a lead smelter in Santo Amaro City, Bahia, Brazil. PbH levels ranged from 20 to 4933 ppm; the median was 349 and the geometric mean was 313 ppm. The mean PbH level was increased among individuals with the following characteristics: female; younger age; shorter distance between residence and smelter; longer residence time in the area; racial group Dark; curly hair; being a child of a lead worker; high lead content in peridomiciliar area. The mean PbH level did not vary markedly according to the child's nutritional status, iron status and the habit of pica. The marked variations in pbH levels point out the feasibility of its use as an epidemiological index in situations of heavy environment pollution.