Carbon-based materials applied to the development of chemically modified sensors: Trends to environmental applications**

Nowadays, carbon-based materials applied to the development of chemically modified sensors have been highlighted once they can generate methods with high sensitivity, stability, conductivity, accuracy and low cost. Hence, these sensors have been used in environmental monitoring in aneco-friendlyy, sensitive, fast, efficient, inexpensive and robust way. In this review, firstly we described about carbon-based materials and their derivatives, followed by the chemically modified carbon-based sensors manufacturing overview and their applications in environmental analytical chemistry related to inorganic and organic compounds determinations. Future perspectives on trends of the carbon-based materials applications in the sensor modifications are also described.     

Determination of mercury in gasoline diluted in ethanol by GF AAS after cold vapor generation, pre-concentration in gold column and trapping on graphite tube

A simple method for the determination of mercury in gasoline samples diluted with ethanol by graphite furnace atomic absorption spectrometry (GF AAS) after cold vapor (CV) generation, pre-concentration in a gold column and trapping on a graphite tube is proposed. The methodology is based upon conventional analytical processes that can be performed by any laboratory with a chemical generation and gold amalgamation systems coupled to the atomic absorption spectrometer. The GF AAS temperature was optimized, being the retention, pyrolysis and atomization temperatures, respectively, 100 °C, 150 °C and 800 °C. Gasoline samples were prepared simply by forming a 2-fold diluted solution in ethanol. The mercury formed vapors by reacting the sample with the reducing agent were pre-concentrated in a gold column and further retained on a graphite tube, coated with gold as permanent modifier. Five samples from different gas stations around the UFSC Campus (Florianópolis, Brazil) were analyzed and the Hg concentrations were found to be in the range from 0.40 µg L^− 1 to 0.90 µg L^− 1. Calibration against aqueous standard solutions in acidic medium was carried out. The standard solutions had about the same viscosity as the gasoline diluted in ethanol. The relative standard deviations were lower than 2.4% for the samples. The limits of detection in the samples were 0.08 and 0.14 µg L^− 1, with and without pre-concentration in the gold column, respectively. The accuracy of the method was estimated by applying the recovery test and recovery values between 92 and 100% were obtained. A sample throughput of 4 h^− 1 was achieved. Simplicity and high detection capability are some of the qualities of the method.     

Simple method for the determination of Cu and Fe by electrothermal atomic absorption spectrometry in biodiesel treated with tetramethylammonium hydroxide

A simple analytical procedure for the determination of Cu and Fe in biodiesel samples by electrothermal atomic absorption spectrometry is proposed. An aliquot of the sample is simply mixed with tetramethylammonium hydroxide (TMAH) and heated to 90 °C for 5 min. Pyrolysis and atomization temperatures were optimized through pyrolysis and atomization curves. The high pyrolysis temperature adopted, of 1000 °C, certainly helped minimizing potential interferences. Even though, calibration should be carried out with aqueous standard solutions in the presence of the TMAH. The detection limits (3 s, n = 10), in the sample, were quite low 15 ng g⁻¹ and 24 ng g⁻¹ for Cu and Fe, respectively. Seven biodiesel samples, produced from different raw materials, including vegetable seed, frying oil and animal fat were analyzed. Accuracy was validated by applying the recovery test to two samples, enriching the samples with two concentration levels (recoveries from 105% to 120%). The precision, expressed by the relative standard deviation was less than 3% for Cu and less than 7% for Fe. Copper could be quantified in two and Fe in three of the seven samples. The biodiesel sample from fodder turnip was especially rich in the analytes in comparison to the other samples.     

Eco-Friendly Synthesis of an Oxovanadium(IV)-bis(abietate) Complex with Antimicrobial Action

The search for less expensive and viable products is always one of the challenges for research development. Commonly, the synthesis of coordination compounds involves expensive ligands, through expensive and low-yield routes, in addition to generating toxic and unusable residues. In this work, the organic ligand used is derived from the resin of a reforestation tree, Pinus elliottii var. elliottii. The synthesis method used Pinus resin and an aqueous solution of vanadium(III) chloride at a temperature of 80 °C. The procedure does not involve organic solvents and does not generate toxic residues, thus imparting the complex formation reaction a green chemistry character. The synthesis resulted in an unprecedented oxovanadium(IV)-bis(abietate) complex, which was characterized by mass spectrometry (MS), chemical analysis (CHN), vibrational (FTIR) and electronic spectra (VISIBLE), X-ray diffraction (XRD), and thermal analysis (TG/DTA). Colorimetric studies were performed according to the CIELAB color space. The structural formula found, consisted of a complex containing two abietate ligands, [VO(C₂₀H₂₉O₂)₂]. The VO(IV)-bis(abietate) complex was applied against microorganisms and showed promising results in antibacterial and antifungal activity. The best result of inhibitory action was against the strains of Gram-positive bacteria S. aureus and L. monocytogenes, with minimum inhibitory concentration (MIC) values of 62.5 and 125 μmol L⁻¹, respectively. For Gram-negative strains the results were 500 μmol L⁻¹ for E. coli; and 1000 μmol L⁻¹ for Salmonella enterica Typhimurium. Antifungal activity was performed against Candida albicans, where the MIC was 15.62 μmol L⁻¹, and for C. tropicalis it was 62.5 μmol L⁻¹. According to the MFC analysis, the complex presented, in addition to the fungistatic action, a fungicidal action, as there was no growth of fungi on the plates tested. The results found for the tests demonstrate that the VO(IV)-bis(abietate) complex has great potential as an antimicrobial and mainly antifungal agent. In this way, the pigmented ink with antimicrobial activity could be used in environments with a potential risk of contamination, preventing the spread of microorganisms harmful to health.     

Pharmacological and Therapeutic Potential of Myristicin: A Literature Review

Natural products have been used by humanity for many centuries to treat various illnesses and with the advancement of technology, it became possible to isolate the substances responsible for the beneficial effects of these products, as well as to understand their mechanisms. In this context, myristicin, a substance of natural origin, has shown several promising activities in a large number of in vitro and in vivo studies carried out. This molecule is found in plants such as nutmeg, parsley, carrots, peppers, and several species endemic to the Asian continent. The purpose of this review article is to discuss data published in the last 10 years at Pubmed, Lilacs and Scielo databases, reporting beneficial effects, toxicity and promising data of myristicin for its future use in medicine. From 94 articles found in the literature, 68 were included. Exclusion criteria took into account articles whose tested extracts did not have myristicin as one of the major compounds.     

A new enantioselective synthesis of the four stereoisomers of pallantione,the male-produced sex pheromone of Pallantia macunaima (Heteroptera: Pentatomidae)

In a previous study we reported the identification of the first ketone found in the Pentatomidae family, the sex attractant pheromone of the male stink bug Pallantia macunaima, (6R,10S)-6,10,13-trimethyltetradecan-2-one. Here we describe an efficient enantioselective route for the synthesis of the four stereoisomers of this pheromone. The synthesis was conceived as the connection of two chiral building blocks, employing (R)- or (S)-citronellol and methyl (S)-3-hydroxy-2-methylpropionate as the source of chirality.     

Voltammetric Determination of Low‐Molecular‐Weight Sulfur Compounds in Hydrothermal Vent Fluids – Studies with Hydrogen Sulfide,Methanethiol, Ethanethiol and Propanethiol

Determination of sulfide compounds in hydrothermal vent fluid samples was performed by DPCSV. The methodology was applied to speciate sulfides via primitive and first‐derivative curve interpretation. Hydrogen sulfide, methanethiol, and propanethiol were simultaneously assayed in samples containing no ethanethiol. In the presence of ethanethiol, the organic sulfides were determined without speciation. Sulfides were determined in an acidic electrolyte, and detection limits ranging from 0.1 to 1.1 μmol L^?1 were calculated. The method was tested in real hydrothermal vent fluid samples, with recoveries ranging from 86.9% (R–SH) to 115.3% (H₂S). Interference of the metallic species present in seawater was investigated.     

Tandem reduction + cyclization of ortho-substituted cinnamic esters

Conjugate reduction of ortho-substituted cinnamic esters by Stryker’s reagent to form copper enolates, followed by intramolecular aldol-type cyclization, successfully generated indane and tetralin rings in one pot efficiently. This tandem reaction is generally diastereoselective and provides good yields.     

Biomimetic synthesis of diversifolin

The conversion of a germacranolide structure (tagitinin C) into a furanoheliangolide one (diversifolin) was achieved by hydride conjugate addition using Stryker’s reagent.     

One-step biomimetic conversion of a furanoheliangolide into an eremantholide using Stryker’s reagent

The conversion of a furanoheliangolide structure (15-deoxygoyazensolide) into an eremantholide one (eremantholide C) was achieved by tandem hydride conjugate addition–intramolecular carbanion addition using Stryker’s reagent.