Solid-phase extraction of triazole fungicides from water samples using disks impregnated with carbon nanotubes followed by GC-MS analysis

Triazole fungicides are pesticides widely employed in the cultivation of fruits, vegetables and grains. However, their ability to change the steroid hormone biosynthesis may result in endocrine complications for mammals, as well as changes in cholesterol and triglyceride levels and hepatotoxicity. The analysis of the triazole fungicides in superficial waters is important in order to monitor the risk for the biota. However, the use of efficient extraction procedures has been necessary in order to concentrate these pesticides before the analysis. In-disk solid-phase extraction (SPE) can be highlighted as a potential pre-concentration technique, mainly because the possibility to extract the analytes from a large sample volume, increasing the method detectability. Carbon nanotubes (CNTs) have been often used as solid extraction phase due to their high sorption capacity, surface area and internal volume, as well as mechanical, chemical and thermal stability. In this paper, we proposed the preparation of a new SPE disk impregnated with CNTs for the extraction of triazole fungicides from environmental water samples. The disks were obtained by acid corrosion of a cellulose membrane followed by its impregnation with CNTs. The developed method was validated for the analysis of triadimenol, tebuconazole and epoxiconazole, according to international validation protocols. The limits of quantification obtained for triadimenol, tebuconazole and epoxiconazole were 0.1, 0.1 and 0.05 µg L^?1, respectively. The linearity ranged from 0.05 to 10.00 µg L^?1 for epoxiconazole and from 0.1 to 10.00 µg L^?1 for triadimenol and tebuconazole, with correlation coefficients higher than 0.999 for all of them. The precisions, expressed as relative standard deviation, were lower than 12%. The accuracies were within ?12.07% to 17.7% (expressed as relative error).     

Whiteness process of tile ceramics: using a synthetic flow as a modifier agent of color firing

Synthetic flow is proposed as a modifier agent of color firing in tile ceramic mass during the sinterization process, turning the red color firing into whiteness. Therefore, the ⁵⁷Fe Mössbauer spectroscopy was used to understand how the interaction of the iron element in the mechanism of color firing mass occurs in this system. The results suggest that the change of color firing can be alternatively due to two main factors: (i) diluting the hematite content in the sample because of the use of synthetic flow and (ii) part of the hematite is converted in other uncolored crystal structures, which makes the final color firing lighter.     

Design and Sensing Properties of a Self‐Assembled Supramolecular Oligomer

Supramolecular polymers are a class of macromolecules stabilized by weak non‐covalent interactions. These self‐assembled aggregates typically undergo stimuli‐induced reversible assembly and disassembly. They thus hold great promise as so‐called functional materials. In this work, we present the design, synthesis, and responsive behavior of a short supramolecular oligomeric system based on two hetero‐complementary subunits. These “monomers” consist of a tetrathiafulvalene‐functionalized calix[4]pyrrole (TTF‐C[4]P) and a glycol diester‐linked bis‐2,5,7‐trinitrodicyanomethylenefluorene‐4‐carboxylate (TNDCF), respectively. We show that when mixed in organic solvents, such as CHCl₃, CH₂ClCH₂Cl, and methylcyclohexane, supramolecular aggregation takes place to produce short oligomers stabilized by hydrogen bonding and donor–acceptor charge‐transfer (CT) interactions. The self‐associated materials were characterized by ¹H NMR and UV/Vis/NIR absorption spectroscopy, as well as by concentration‐ and temperature‐dependent absorption spectroscopy and dynamic light scattering (DLS) analyses of both the monomeric and oligomerized species. The self‐associated system produced from TTF‐C[4]P and TNDCF exhibits a concentration‐dependent aggregation behavior typical of supramolecular polymers. Further support for the proposed self‐assembly came from theoretical calculations. The fluorescence emitting properties of TNDCF are quenched under conditions that promote the formation of supramolecular aggregates containing TTF‐C[4]P and TNDCF. This quenching effect has been utilized as a probe for the detection of substrates in the form of anions (i.e., chloride) and nitroaromatic explosives (i.e., 1,3,5‐trinitrobenzene). Specifically, the addition of these substrates to mixtures of TTF‐C[4]P and TNDCF produced a fluorescence “turn‐on” response.     

Experimental NMR and MS study of benzoylguanidines. Investigation of E/Z isomerism

Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI‐MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (¹H‐¹³C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple‐Bond Correlation (HMBC), ¹H‐¹⁵N HMBC, ¹H‐¹H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p‐Cl and p‐Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p‐NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd.