Alkaloids Analysis of Habranthus cardenasianus (Amaryllidaceae), Anti-Cholinesterase Activity and Biomass Production by Propagation Strategies

Plants in the Amaryllidaceae family synthesize a diversity of bioactive alkaloids. Some of these plant species are not abundant and have a low natural multiplication rate. The aims of this work were the alkaloids analysis of a Habranthus cardenasianus bulbs extract, the evaluation of its inhibitory activity against cholinesterases, and to test several propagation strategies for biomass production. Eleven compounds were characterized by GC-MS in the alkaloid extract, which showed a relatively high proportion of tazettine. The known alkaloids tazettine, haemanthamine, and the epimer mixture haemanthidine/6-epi-haemanthidine were isolated and identified by spectroscopic methods. Inhibitory cholinesterases activity was not detected. Three forms of propagation were performed: bulb propagation from seed, cut-induced bulb division, and micropropagated bulbs. Finally, different imbibition and post-collection times were evaluated in seed germination assays. The best propagation method was cut-induced bulb division with longitudinal cuts into quarters (T1) while the best conditions for seed germination were 0-day of post-collection and two days of imbibition. The alkaloids analyses of the H. cardenasianus bulbs showed that they are a source of anti-tumoral alkaloids, especially pretazettine (tazettine) and T1 is a sustainable strategy for its propagation and domestication to produce bioactive alkaloids.     

Environmentally friendly synthesis of noble metal nanoparticles assisted by biodegradable dextran‐graft‐lactone copolymers

A simple “green synthesis” of noble metal nanoparticles by direct reaction between Dextran‐graft‐lactone copolymers and metal salts without the need to separately add reducing and stabilizing agents was carried out. The effects of the composition, molecular weights of copolymers and solvents on the characteristics of the nanoparticles were considered. The amphiphilic character of the copolymers seems to be an important factor in the results of the synthesis. According to the results, general correlations between experimental parameters of synthesis and characteristics of the obtained nanoparticles were established. Techniques such as, transmission electron microscopy, scanning electron microscopy, UV–visible spectroscopy, Zeta Potential, dynamic light scattering and Fourier transform Infrared Spectroscopy, were used for the characterization of the products. The results indicate the possibility of control of the characteristics of the nanostructured material. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of Pb in airborne particulate matter with a heavy matrix of silicon by SR-ETAAS

A study is undertaken to monitor Pb levels in airborne particulate matter collected on ash-free glass-fibre filters from urban and industrial areas of Argentina by electrothermal atomic absorption spectrometry with self-reversal background correction. For this sample with a heavy matrix of silicon, a simple acid treatment with aqua regia and HF is proposed aimed to minimize contamination and reduce sample treatment steps. Ultrasonic agitation was employed for sample homogenization. To overcome the problem of the high amounts of Si, main analytical variables including acid pretreatment conditions, temperature program of the graphite furnace and spectroscopic conditions were carefully studied and optimized. Continuum source and self-reversal methods for background correction were compared in order to avoid non-specific and spectral interferences due to the matrix. After optimization, synthetic acid solutions of Pb were employed for calibration. Calibration was linear within the range 1–40 µg L^{− 1} (correlation coefficient of 0.9995) when the 283.3 analytical line was used. Using optimized conditions limits of detection (3σ) of 0.6 µg L^{− 1} were achieved. The repeatability between injections (S_r%) was evaluated and was better than 4.2%. The precision (%RSD) for Pb determination in a single sample was estimated by analyzing three strips of the same filter. In all cases the RSD was better than 6.9%. For checking accuracy, an aliquot of a Standard Reference Material (NIST 2709, San Joaquin Soil) was subject to the same sample treatment and included in the overall analytical process. This method was successfully applied to the determination of Pb in airborne particulate matter collected in Buenos Aires city.     

Study of matrix effects and spectral interferences in the determination of lead in sediments, sludges and soils by SR-ETAAS using slurry sampling

An interference-free, fast, and simple method is proposed for Pb determination in environmental solid samples combining slurry sampling and electrothermal atomic absorption spectrometry. Samples were ground to an adequate particle size and slurries were prepared by weighing from 0.05 g to 0.20 g of dry sediment, adding nitric acid, and a solution containing 0.1% Triton X-100. Ultrasonic agitation was employed for slurries homogenization. Analytical variables including acid pre-treatment conditions, particle size, slurry stability, temperature program of the graphite furnace, and type and concentration of the chemical modifier were studied. The undesirable effects of potential non-specific and spectral interferences on Pb signal were also taken into account. Continuum source and self-reversal methods for background correction were evaluated and compared. For calibration, synthetic acid solutions of Pb were employed. Calibration was linear within the range 1-30 μg L⁻¹ and 5-30 μg L⁻¹ when the 217.0 nm and 283.3 nm analytical lines were used. Correlation coefficients of 0.9992 and 0.9997 were obtained. Using optimized conditions, limits of detection (3σ) of 0.025 μg g⁻¹ and 0.1 μg g⁻¹ were achieved for the 217.0 nm and 283.3 nm analytical lines, respectively. The method was successfully applied to the determination of lead in soil, contaminated soil, municipal sludge, and sediment samples. The accuracy was assessed by the analysis of two certified reference materials: municipal sludge (QC MUNICIPAL SLUDGE A) and lake sediment (TRAP-LRM from IJS).     

Dimethacrylate derivatives of dimer acid

Dimethacrylate monomers are used in a wide variety of crosslinked polymer applications, including adhesives, coatings, dental restoratives, and stereolithography. The advantages of rapid curing and good mechanical properties offered by these materials are countered by problems with dimensional changes during polymerization and long‐term physical instability resulting from water sorption and loss of residual unreacted monomer. In this work, several examples of hydrophobic monomers based on a dimer acid structure were synthesized, and their monomeric and homopolymer properties were evaluated. The photopolymerization reactivity and conversion were investigated with near‐infrared spectroscopy. Studies of the volumetric shrinkage, water sorption, and water contact angle and three‐point‐bend testing of the homopolymers were also carried out, with the results compared with those of commonly used dimethacrylate monomers. The new monomers produced higher degrees of conversion combined with lower polymerization shrinkage and water sorption values in comparison with conventional monomers. The relatively low crosslink density of dimethacrylates constructed from dimer acid produced polymers with high flexibility and low modulus, as expected; however, changes in the functionality of the group linking the dimer acid core with the methacrylate end groups induced significant property differences. On the basis of the properties demonstrated by the dimer acid monomers and their homopolymers, these new materials appear well suited for applications such as coatings and adhesives. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3921–3929, 2006     

Study of carbon nanotubes and functionalized-carbon nanotubes as substrates for flow injection solid phase extraction associated to inductively coupled plasma with ultrasonic nebulization: Application to Cd monitoring in solid environmental samples

A research was performed to evaluate the capabilities of carbon nanotubes (CNTs) and modified CNTs to serve as sorbents for preconcentrating Cd together with on-line ultrasonic nebulization (USN)-inductively coupled plasma optical emission spectrometry (ICPOES). Three different carbon nanotubes sustrates namely, carbon nanotubes (CNTs), oxidized-carbon nanotubes (ox-CNTs) and l-alanine-carbon nanotubes (ala-CNTs) were studied systematically and the main factors influencing the preconcentration and determination of Cd were examined thoroughly. The CNTs evaluated showed dissimilar adsorption behaviors leading to increasing preconcentration factors when used in the proposed on-line solid phase extraction (SPE) system as follows: CNT < ala-CNT < ox-CNT. Aiming to achieve the best analytical performance, ox-CNTs were used as they enable quantitative retention of Cd at pH 7.0 and instantaneous elution of the analyte with 10% HNO₃. Under optimal conditions, the adsorption capacity on ox-CNTs was found to be 130 μmol g^?1 and the detection limit (3σ) achieved was 1.03 μg L^? 1. The precision of the method expressed as the relative standard deviation (RSD) turned to be 3.0%. The flow injection method involving use of ox-CNTs as sorbent and USN-ICPOES for detection was successfully applied to the determination of Cd in different kinds of environmental samples.     

On-line solid phase extraction of Ni and Pb using carbon nanotubes and modified carbon nanotubes coupled to ETAAS

A study about the capabilities of three kinds of nanomaterials namely, carbon nanotubes (CNT), oxidized carbon nanotubes (ox-CNT) and l-alanine immobilized on carbon nanotubes (ala-CNT) to serve as sorbents for preconcentrating Ni and Pb using an on-line system coupled to electrothermal atomic absorption spectroscopy (ETAAS) technique, was accomplished. The solid phase extraction was performed in a conical minicolumn used as sorbent holder. After loading a fixed volume of the analytes, they were eluted with a discrete volume (50 μL) of nitric acid, placed directly into the platform of a L’Vov tube. After that, each analyte was determined individually. Ni and Pb retention was strongly influenced by pH but exhibiting different behaviors. The study demonstrated that the sorbent based on ox-CNTs was the one that exhibited the highest capacity and linearity for both analytes when compared with CNT or ala-CNT. The analytical performance was evaluated for the three sorbents to establish the best conditions regarding sensitivity, reproducibility and accuracy. The precision expressed as relative standard deviations (n = 6) were 3.9 and 0.5% for Ni²⁺ and Pb²⁺, respectively The limit of detection (LOD), calculated as the concentration required to yield a net peak equal to three times the standard deviation of the background signal (3σ) was 30 and 10 ng L⁻¹ for Ni²⁺ and Pb²⁺ respectively. Alternatively, the limit of quantification (10σ) was calculated and resulted to be 0.79 and 0.07 μg L⁻¹ for Ni²⁺ and Pb²⁺ respectively. After optimization, the method that involved the use of ox-CNT associated to an on-line preconcentration was tested in samples of relevant environmental importance. Accuracy was evaluated analyzing a certified reference material namely, Municipal Sludge (QC MUNICIPAL SLUDGE A) and a reference sample of Lake Sediment (TRAP-LRM from IJS).     

A new hybrid organic–inorganic chain: [(phen)Cu–μ‐(κ2O:O′‐VP2O10H3)2–Cu(phen)]n

The structure of the title compound, poly[(dihydrogenphosphato‐κO)(μ₃‐hydrogenphosphato)di‐μ‐oxido‐(1,10‐phenanthroline)copper(II)vanadium(V)], [CuV(HPO₄)(H₂PO₄)O₂(C₁₂H₈N₂)]_n, is defined by [(phen)Cu–μ‐(κ²O:O′‐VP₂O₁₀H₃)₂–Cu(phen)] units (phen is 1,10‐phenanthroline), which are connected to neighbouring units through vanadyl bridges. Neighbouring chains have no covalent bonds between them, although they interdigitate through the phen groups viaπ–π interactions.