Determination of Aldehydes and Ketones in Fuel Ethanol by High-Performance Liquid Chromatography with Electrochemical Detection

A new methodology was developed for analysis of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography (HPLC) coupled to electrochemical detection. The electrochemical oxidation of 5-hydroxymethylfurfural, 2-furfuraldehyde, butyraldehyde, acetone and methyl ethyl ketone derivatized with 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode present a well defined wave at +0.94 V; +0.99 V; +1.29 V; +1.15 V and +1.18 V, respectively which are the basis for its determination on electrochemical detector. The carbonyl compounds derivatized were separated by a reverse-phase column under isocratic conditions with a mobile phase containing a binary mixture of methanol / LiClO_4(aq) at a concentration of 1.0 × 10⁻³ mol L⁻¹ (80:20 v/v) and a flow-rate of 1.1mL min⁻¹ . The optimum potential for the electrochemical detection of aldehydes-DNPH and ketones-DNPH was +1.0 V vs. Ag/AgCl. The analytical curve of aldehydes-DNPH and ketones-DNPH presented linearity over the range 5.0 to 400.0 ng mL⁻¹, with detection limits of 1.7 to 2.0 ng mL⁻¹ and quantification limits from 5.0 to 6.2 ng mL⁻¹, using injection volume of 20 μL. The proposed methodology was simple, low time-consuming (15 min/analysis) and presented analytical recovery higher than 95%.     

Development of a rapid and specific assay for detection of busulfan in human plasma by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

A sensitive and specific assay for detection of busulfan in human plasma was developed. The assay is based on rapid isolation of busulfan by liquid-liquid extraction with ethyl acetate, and detection by high-performance liquid chromatography with electrospray ionization and tandem mass spectrometry. 1,6-Bis(methanesulfonyloxy)hexane, a synthesized analogue of busulfan, was used as the internal standard (IS). The acquisition was performed in the multiple reaction monitoring mode; busulfan and the IS were detected with no interferences from plasma matrix. The method was linear over the range 5-2500 ng mL(-1), with r2 > 0.99 and a run time of only 3.5 min. The intra- and inter-assay precisions were in the ranges 2.1-11.9% and 3.2-10.1%, respectively, and the intra- and inter-assay accuracies were 92.2-107.6% and 94.7-104.1%, respectively. The absolute recoveries were 82.0% (20 ng mL(-1)), 90.6% (1000 ng mL(-1)) and 80.0% (2000 ng mL(-1)) for busulfan, and 89.1% for the IS (1000 ng mL(-1)). The limits of detection and quantification were 2 and 5 ng mL(-1), respectively. The validated method was successfully applied to analyze plasma samples obtained from six adults receiving doses of 1 mg kg(-1) in a conditioning regimen prior to bone marrow transplantation. A marked intra-patient variation in busulfan concentrations during the steady state was observed, which limits the application of pharmacokinetic modeling and suggests that continuous therapeutic monitoring is necessary for adequate individualized dosing. In this regard, the present assay brings important advantages relative to other methods described in the literature, i.e., it is highly specific and simple to perform, with a rapid chromatographic run time (3.5 min), and the whole procedure can be completed in 4-5 h, which would permit dose corrections after the third dose allowing earlier and better dosing adjustments towards the target level of busulfan.     

Determination of trace elements in tree rings ofPinus by neutron activation analysis

The elemental composition of pine trees as a function of age was achieved by the tree-ring method. By using instrumental neutron activation analysis, trace elements were determined in individual rings ofPinus elliottii var.elliottii of 32, 14 and 9 years, from an implanted forest ofPinus sp., Buri, São Paulo, far away from industrial pollution. Different components of the system such as needles, pith, bark, soil and litter were also analyzed for 18 elements (As, Br, Ce, Co, Cs, Eu, Fe, Hf, K, La, Mn, Na, Rb, Sc, Sm, Yb, Zn, and Zr). Al, B, Ba, Ca, Fe, K, Mg, and P concentrations were determined by atomic absorption and/or emission spectrometry (AAS; ICP-AES). Some elements have showed similar radial distribution of the concentration for the three ages. Abrupt concentration changes in the pith and ring-bark boundary corresponding to the first and last growth rings were observed.     

Morphological and structural characteristics of diazo dyes at the air-water interface: in situ Brewster angle microscopy and polarized UV/vis analysis

A morphological analysis is presented for Langmuir films of the diazo dyes Sudan 4 (S4), Sudan 3 (S3), and Sudan red (SR), using Brewster angle microscopy. Stable nonmonomolecular structures are formed at the air-water interface denoted as a plateau in the pressure-area isotherms. Monolayer domains are evident by the contrastless image even before the pressure onset, which grow in size until it reached a condensed monolayer. This behavior resembles that of Langmuir films from simple aromatic fatty acids. Films from all the azo dyes display similar features, according to the surface potential isotherms and in situ polarized UV/vis spectroscopy except for the larger area per molecule occupied by S4 and SR. This is attributed to the presence of CH(3) groups that cause steric hindrance modifying the organization of diazo dye molecules at the air-water interface. UV/vis polarized absorption spectroscopy showed preferential orientation of S4 and S3 on the water surface, while SR molecules lie isotropically. For these three diazo dyes, film absorption was negligible at very large areas per molecule, becoming nonzero only at a critical area coinciding with the onset of surface potential. The critical area is ascribed to the formation of a H-bonded network between water molecules and diazo dye headgroups.     

Synthesis of pyrrolidine-substituted benzamides via iodocyclization of β-enaminoesters

Novel 2-, and N-substituted 5-methylene-pyrrolidine benzamides and 2-, 3-, and N-substituted 5-methylene-2-pyrroline benzamides were synthesized for the first time in a straightforward manner and in good yields via iodocyclization of γ- and α-alkenyl-β-enaminoesters, respectively. The key step in the process is the synthesis of the methylene-pyrrolidine iodide and methylene-2-pyrroline iodide intermediates. Functional group inter-conversion of these iodides to their amino analogs, and their subsequent coupling to benzoic acids via EDC, afforded the above pyrrolidine/2-pyrroline-substituted benzamides in yields of around 75%.     

Optimization of acid hydrolysis of sugarcane bagasse and investigations on its fermentability for the production of xylitol by Candida guilliermondii

The dilute-acid hydrolysis of sugarcane bagasse was optimized using a statistical experimental design resulting in hydrolysates containing 57.25 g/L of xylose, which were fermented with a high inoculum concentration (10 g/L of the yeast Candida guilliermondii IM/UFRJ 50088). The addition of urea reduced the time of conversion (t _C) to 75 h (without nitrogen source addition t _C>127 h), and, consequently, improving the rates of xylitol bioproduction. Fermentator experiments, using the optimized conditions, resulted in enhanced conversion rates, reducing t _C to 30 h. The stability of the yeast in the hydrolysate was also verified in a 480-h cultivation.     

Complex Tellurium Salts with Supramolecular Bidimensional Lattices: Synthesis and X‐ray Characterization of (2‐Br‐C5NH5)2[TeX6] (X = Cl,Br)

The reaction of tellurium(IV) tetrahalides with hydrochloric and hydrobromic acid leads to the formation of (H₃O)₂[TeX₆], which reacts subsequently with (2‐Br‐C₅NH₅)⁺X^‐ to afford (2‐Br‐C₅NH₅)₂[TeCl₆] ( 1 ) and (2‐Br‐C₅NH₅)₂[TeBr₆] ( 2 ). The structure of the complex salts were analysed by X‐ray diffractometry affording the centrosymmetric space groups P2₁/n (monoclinic, 1 ) and P1¯ (triclinic, 2 ). Interionic hydrogen bondings hold their lattices in bidimensional supramolecular arrays not yet described in the literature. The lone electron pair of the AX₆E‐system of the hexahalotellurates [TeX₆]^2‐ (X = Cl, Br) seems to be fully delocalized since only small octahedral deviations were observed for the anionic species. The structures of the title compounds were refined with the Te atoms occupying sites with full point symmetry, approximately m3¯m. In both cases the Te atoms enclose centers of inversion and the octahedrally dynamic structures are enforced and stabilized along the supramolecular lattices by the crystal field of the 2‐Br‐pyridinium cations.     

The glucocorticoid derivative with the phthalimide group cationic nanocrystal for ophthalmic application: a design space development approach

The glucocorticoid derivative of budesonide with a phthalimide group is a drug candidate to treat inflammatory eye diseases; nevertheless, it presents low water solubility. Drug nanocrystals have been proposed to overcome this hurdle. The development of an innovative ophthalmic anti-inflammatory nanosuspension was performed using a design space approach. We obtained the particle size reduction of this glucocorticoid derivative on a nanometer scale (approximately 165.0 nm), applying wet bead milling on a super reduced scale. The design of experiment supported the optimization of the formula evaluating the parameters that influence reducing the particle size and also allowed determining the design space. Considering the two statistical models developed and the size range obtained, we proposed that the optimized formulation for the glucocorticoid derivative nanosuspension may be 1.0 wt% glucocorticoid derivative and 0.092 wt% cetylpyridinium chloride. This formulation was characterized by the morphological, physical–chemical, and mucoadhesive in vitro test and showed potential for ophthalmic use with reduced frequency of product application, improved efficiency, and safety, which may promote better patient compliance.     

Biotransformation of (−)β-pinene by Aspergillus niger ATCC 9642

The main objective of this work was to investigate the biotransformations of (−)α-pinene, (−)β-pinene, and (+) limonene by Aspergillus niger ATCC 9642. The culture conditions involved—concentration of cosolvent (EtOH), substrate applied, and sequential addition of substrates—were investigated. Adaptation of the precultures with small amounts of substrate was also studied. The experiments were performed in conical flasks with liquid cultures. This strain of A. niger was able to convert only (−)β-pinene into α-terpineol. An optimum conversion of (−)β-pinene into α-terpineol of about 4% was obtained when the substrate was applied as a diluted solution in EtOH and sequential addition of substrate was used.     

Molecular-level control of the photoluminescence from PPV nanostructured films

The fabrication of varied molecular architectures in layer-by-layer (LbL) films is exploited to control the photoluminescence (PL) of poly(p-phenylene vinylene) (PPV) in an unprecedented way. This was achieved by controlling the F?rster energy transfer between PPV layers (donors) and layers of a commercial azodye, Brilliant Yellow (BY) (acceptors). Energy transfer was controlled by inserting spacer layers of inert polymers between PPV and BY layers and by photoaligning the BY molecules via trans-cis-trans isomerization. The PPV/BY LbL films displayed polarized PL whose intensity could be varied almost continuously by changing the time of photoalignment, which was carried out by impinging a linearly polarized laser light simultaneously to the PL experiments. For PPV/BY films with no spacer layers, PL was completely quenched, but its intensity increased with the number of spacing layers. Further increase in PL was obtained by photoaligning the BY molecules perpendicularly to the PPV molecules. This minimizes energy transfer, since F?rster processes are directional, dipole-dependent resonant transfers. Energy transfer is also controlled by imparting a preferential orientation of the PPV chains on PPV/BY LbL films deposited onto flexible Teflon substrates that may be stretched.