Ionization by pH and Anionic Surfactant Binding Gives the Same Thickening Effects of Crosslinked Polyacrylic Acid Derivatives

Physical properties of aqueous solutions of hydrophobically modified crosslinked polyacrylic acids change quite extensively as the polymer is charged up. A study is carried out concerning the similarities between two polymer ionization processes, that is, by pH increment and anionic surfactant addition. The two processes charge the polymer by distinctly different mechanisms. At sufficiently high pH the carboxylic groups of the polymer are virtually all ionized and the polymer is, therefore, fully charged. The effective repulsion among the charged groups due to the entropy of the counterions promotes an increased stiffness as well as an expansion of the polymer particles. We investigate here how the ionization and swelling will be if, instead of high pH, the polymer is at low pH conditions but associated to ionic surfactants. Surfactants associate to the polymer both in a noncooperative way by the binding of individual surfactant molecules and in a cooperative way as micelles since the polymer promotes surfactant self-assembly. This binding leads to a highly charged polymer-surfactant complex and leads to an osmotic swelling as well. The swelling and the gelation were monitored by rheology and dynamic light scattering, of polymer solutions by varying the pHs and adding ionic surfactants at low pH. The results show that ionization by surfactants and by pH lead to approximately the same gelation degree, as can be seen by similar viscosity values. Both processes result in dramatic viscosity increases, up to 8 orders of magnitude. More hydrophobic surfactants, with longer alkyl chain, are shown to be more efficient as enhancers of swelling and gelation. The network that is formed at high pH or at sufficiently high concentration of surfactant can be weakened or even disrupted if monovalent or divalent salts are added, demonstrating the role of counterion entropy.     

Radiolabeling of low molecular weight d-galactose-based glycodendrimer with technetium-99m and biodistribution studies

Glycodendrimers are neoglycoconjugates that can be considered as bioisosters of glycoproteins, since they can mimic the multivalent interactions of lectin-carbohydrate. The ability of glycodendrimers to present multivalent interactions with lectins as compared to a monovalent ligand is referred to as “cluster effect”. It is expected that, because of the cluster effect, glycodendrimers would result in a better association with lectins than mono-carbohydrate anchored systems. Radioisotopes are useful to evaluate biodistribution of molecules. This study is important to obtain information about molecule–receptor interactions. Indeed, such study can provide an exquisite tool to evaluate the affinity of certain molecules to specific areas in the body, leading to the development of new radiopharmaceuticals and/or drug delivery systems. Herein, we describe a d-galactose coated low molecular weight PAMAM G0 dendrimer that was successfully radiolabeled with technetium-99m. Biodistribution studies and scintigraphic images were performed in healthy mice. It was observed high liver uptake which was significantly reduced in blocking studies, indicating hepatic specificity. Therefore, low molecular weight glycodendrimer can be considered as useful platform for selective targeting of drugs to the liver and to assess hepatic function.     

Analysis of PCBs in soils and sediments by microwave-assisted extraction,headspace-SPME and high resolution gas chromatography with ion-trap tandem mass spectrometry

A procedure for the determination of seven indicator PCBs in soils and sediments using microwave-assisted extraction (MAE) and headspace solid-phase microextraction (HS-SPME) prior to GC-MS/MS is described. Optimization of the HS-SPME was carried out for the most important parameters such as extraction time, sample volume and temperature. The adopted methodology has reduced consumption of organic solvents and analysis runtime. Under the optimized conditions, the method detection limit ranged from 0.6 to 1?ng/g when 5?g of sample was extracted, the precision on real samples ranged from 4 to 21% and the recovery from 69 to 104%. The proposed method, which included the analysis of a certified reference material in its validation procedure, can be extended to several other PCBs and used in the monitoring of soil or sediments for the presence of PCBs.     

Amoxicillin removal from aqueous matrices by sorption with almond shell ashes

The adsorption of the antibiotic amoxicillin at low concentration levels (µg?L^?1 order) from aqueous solution on almond shell ashes has been investigated, either by kinetic or equilibrium assays. The effect of the adsorbent amount, initial concentration of the antibiotic, particle diameter (d_p) and temperature were considered to evaluate the adsorption capacity of the adsorbent. The results showed that amoxicillin sorption is dependent on these four factors. The adsorption process was relatively fast and equilibrium was established in about 12 hours. The optimum parameters for an initial concentration of 450?µg?L^?1 were 50?mg of adsorbent, 303?K and d_p?<?600?µm. A comparison of kinetic models showed that pseudo-second order kinetics provides the best correlation of the experimental data. Isotherm data adjusted better to Langmuir equation, with an adsorption capacity of 2.5?±?0.1?mg?g^?1 at 303?K. The desorption process was also evaluated (maximum efficiency of 5%). Thermodynamic parameters were calculated and the negative value of ΔH⁰ and ΔG⁰ showed that adsorption was exothermic and a spontaneous process.     

Synthesis of (Z)-N-alkenyl-β-arylselanyl imidazoles via additive-free nucleophilic addition of imidazole to arylselanylalkynes

We present herein our results on the nucleophilic addition of imidazole to a range of arylselanylalkynes by simple heating in DMF without any additives to give (Z)-1-(1-organyl-(2-arylselanyl)vinyl)-1H-imidazoles. The reactions were performed under mild conditions with a range of arylselanylalkynes in good yields and with high regio- and stereoselectivity to give the respective (Z)-arylselanyl alkene as the only isomer.     

Correlation study of air pollution and cardio-respiratory diseases through NAA of an atmospheric pollutant biomonitor

In this study neutron activation analysis was applied to analyze lichen samples used as atmospheric pollutant biomonitors in order to verify if there is correlation between air pollution and its effects on the cardio respiratory system. Canoparmelia texana lichenized fungii species was chosen for passive biomonitoring of atmospheric pollutants. The population group selected for this study was adults over 45 years. Lichen samples collected in São Paulo city were cleaned, freeze-dried and ground for the analyses. Aliquots of samples were irradiated at the IEA-R1 nuclear research reactor for short and long periods along with synthetic element standards. The induced gamma activities of the samples and standards were measured using a gamma ray spectrometer with an HPGe detector and the concentrations of As, Ba, Br, Ca, Cd, Cl, Co, Cr, Cs, Fe, Hf, K, Mg, Mn, Na, Rb, Sb, Sc, Se,Th, V, Zn and lanthanides were determined. For quality control of the results, certified reference materials were analyzed together. Mortality data for the population due to cardio-respiratory diseases were obtained from the database of the Secretariat of Health of the São Paulo Municipality for the years 2005–2009. Results obtained point to vehicular and industrial emissions as the origins of pollutants in São Paulo city. The statistical treatment of Pearson’s correlation applied to the results of lichen element concentrations and mortality rates indicated significant positive correlation for the elements Co, Mn and Zn for adults.     

Human biomonitoring of emerging pollutants through non-invasive matrices: state of the art and future potential

Human biomonitoring (HBM) is a scientific technique that allows us to assess whether and to what extent environmental pollutants enter humans. We review here the current HBM efforts for organophosphate esters, emerging flame retardants, perfluoroalkyl substances, and phthalate esters. Use of some of these chemicals has already been banned or restricted; they are regularly detected in the environment, wildlife, and human matrices. Traditionally, blood and urine collection have been widely used as sampling methods. New non-invasive approaches (e.g., saliva, hair, nails) are emerging as valid alternatives since they offer advantages with respect to sampling, handling, and ethical aspects, while ensuring similar reliability and sensitivity. Nevertheless, the identification of biomarkers of exposure is often difficult because chemicals may be metabolized in the human body. For many of the above-mentioned compounds, the mechanisms of the favorable metabolization pathways have not been unraveled, but research on important metabolites that could be used as biomarkers of exposure is growing. This review summarizes the state of the art regarding human exposure to, (non-invasive) HBM of, and metabolism of major organophosphate esters, emerging flame retardants, perfluoroalkyl substances, and phthalate esters currently detected in the environment.

Using Design of Experiments to Optimize a Screening Analytical Methodology Based on Solid-Phase Microextraction/Gas Chromatography for the Determination of Volatile Methylsiloxanes in Water

Volatile methylsiloxanes (VMSs) constitute a group of compounds used in a great variety of products, particularly personal care products. Due to their massive use, they are continually discharged into wastewater treatment plants and are increasingly being detected in wastewater and in the environment at low concentrations. The aim of this work was to develop and validate a fast and reliable methodology to screen seven VMSs in water samples, by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography with flame ionization detection (GC-FID). The influence of several factors affecting the extraction efficiency was investigated using a design of experiments approach. The main factors were selected (fiber type, sample volume, ionic strength, extraction and desorption time, extraction and desorption temperature) and optimized, employing a central composite design. The optimal conditions were: 65 µm PDMS/Divinylbenzene fiber, 10 mL sample, 19.5% NaCl, 39 min extraction time, 10 min desorption time, and 33 °C and 240 °C as extraction and desorption temperature, respectively. The methodology was successfully validated, showing low detection limits (up to 24 ng/L), good precision (relative standard deviations below 15%), and accuracy ranging from 62% to 104% in wastewater, tap, and river water samples.     

Antimicrobial Activity of Pyrazinamide Coordination Frameworks Synthesized by Mechanochemistry

The urge for the development of a more efficient antibiotic crystalline forms led us to the disclosure of new antibiotic coordination frameworks of pyrazinamide, a well-known drug used for the treatment of tuberculosis, with some of the novel compounds unravelling improved antimycobacterial activity. Mechanochemistry was the preferred synthetic technique to yield novel compounds, allowing the reproduction of a 1D zinc framework, the synthesis of a novel hydrogen bonding manganese framework, and three new compounds with silver. The structural characterization of the novel forms is presented along with stability studies. The increased antimicrobial activity of the new silver-based frameworks against Escherichia coli, Staphylococcus aureus, and Mycobacterium smegmatis is particularly relevant.