Flaviano Oliveira Silvério

Determination of Eucalyptus spp lignin S/G ratio: A comparison between methods

The syringyl/guaiacyl ratio was determined for six different Eucalyptus spp. wood clones cultivated in four regions in Brazil. The determinants were made by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and the results were compared with those obtained by alkaline nitrobenzene oxidation method. The S/G ratios were obtained considering all the identified lignin derivatives in the pyrograms and also using two groups of markers. The first group of markers consisted of guaiacol, 4-methylguaiacol, 4-vinylguaiacol, trans-isoeugenol, syringol, 4-methylsyringol, 4-vinylsyringol and trans-4-propenylsyringol compounds as markers. The second group included guaiacol, 4-methylguaiacol, 4-vinylguaiacol, vanillin, 4-ethylsyringol, 4-vinylsyringol, syringaldehyde, syringylacetone and trans-4-propenylsyringol. It was observed from the statistical analysis that the values of S/G obtained by Py-GC-MS using the two groups of markers did not differ significantly from those obtained by nitrobenzene oxidation method.

Efeito de matriz na quantificação de agrotóxicos por cromatografia gasosa

The lack of accuracy of a chromatographic method can be associated with the matrix effect. This effect is observed in pesticide quantification by gas chromatography when the chromatographic signals of standards prepared in solvents are compared with those of the analyte in extracts of complex matrices. In the competition between the matrix components and the pesticides for the active sites of the liner, a larger amount of pesticides is transferred to the column, giving apparent extractions above 100%. In this work, we discuss factors that contribute to the matrix effect and present some attempts to overcome the problem.

Determination of Sugarcane Bagasse Lignin S/G/H Ratio by Pyrolysis GC/MS

Abstract In this work, analytical pyrolysis (Py-GC-MS) was employed to identify lignin markers derived from H, S, and G phenylpropanoid units in sugarcane bagasse. Temperatures of 450 and 500°C allowed the detection of key products that were informative on the bagasse lignin composition. The method was validated by comparing the S/G ratio as determined by the nitrobenzene oxidation (NBO) standard method for five sugarcane varieties. The S/G ratio as determined by Py-GC-MS, taking into consideration all known lignin markers in the analysis, resulted in a correlation coefficient of 0.85 with a linear regression coefficient of 0.74. When a group of selected markers (M2) was used, the correlation coefficient between methods was improved to 0.95 and the linear regression coefficient was adjusted to 0.92. M2 markers consisted of five syringyl markers (syringol, 4-methylsyringol, 4-ethylsyringol, 4-vinylsyringol, and trans-4-propenylsyringol) and four guaiacyl markers (guaiacol, 4-vinylguaiacol, 4-methylguaiacol, and vanillin). Importantly, Py-GC-MS allowed for the study of lignin composition in sugarcane bagasse without the need to remove the extractives, minimizing the work with sample preparations.

Synthesis and insecticidal activity of new pyrethroids.

BACKGROUND Pyrethroids are among the most potent pesticides known, with great potential for structural variation with retention or enhancement of potency. The simple methyl ester is easier to prepare (at least one step shorter) than the more complex pyrethroids modified on the alcohol moiety. The objective was to synthesise methyl esters of pyrethroid acids containing an aromatic ring on the acid moiety and evaluate their biological activity against Ascia monuste orseis Latr., Tuta absoluta Meyrick, Periplaneta americana (L.), Musca domestica L. and Sitophilus zeamais (Motsch.). RESULTS The synthetic sequence required seven steps: protection of the hydroxyl groups of D-mannitol, diol oxidative cleavage with sodium metaperiodate, alkene formation by Wittig reaction with methoxycarbonylmethylidene(triphenyl)phosphorane, cyclopropanation, acetal hydrolysis with perchloric acid and oxidative cleavage with sodium metaperiodate gave methyl (1S, 3S)-3-formyl-2,2-dimethylcyclopropane-1-carboxylate. The final step comprised reaction of the aldehyde with five different aromatic phosphorus ylides to give the pyrethroids. CONCLUSION An efficient and versatile synthesis of ten new pyrethroid methyl esters has been accomplished from the readily available D-mannitol in seven steps. All compounds showed insecticidal activity, and methyl (1S, 3S)-3-[(Z)-2-(4-chlorophenyl)vinyl]-2,2-dimethylcyclopropane-1-carboxylate was the most active, killing 90% of A. monuste orseis and 100% of T. absoluta and P. americana.

A pirólise como técnica analítica

In this paper historical aspects of analytical pyrolysis, the equipment used, the fundamentals and the mechanisms of pyrolysis of different polymeric materials are discussed. The latest work on analytical pyrolysis applied to various types of synthetic and natural samples is reviewed. Current applications of this technique that are discussed include identification of microorganisms, analysis of trace compounds by forensic laboratories, investigation of food and agricultural products, study of the chemical composition of wood, authentication and conservation of artworks, and the study of environmental and geochemical samples.

Comparative study on the chemical composition of lipophilic fractions from three wood tissues of Eucalyptus species by gas chromatography-mass spectrometry analysis

Abstract The chemical compositions of lipophilic fractions from Eucalyptus urograndis and Eucalyptus urophylla cultivated in Brazil and Eucalyptus camaldulensis from Mexico were determined by gas chromatography-mass spectrometry (GC-MS) before and after alkaline hydrolysis followed by derivatization. In all fractions, fatty acids (including small amounts of α-and ω-hydroxy fatty acids) and sterols were the most abundant components followed by smaller amounts of long-chain aliphatic alcohols, phenolic acids, and hydrocarbons. The presence of steroid esters and triacylglycerols in all three species was indirectly confirmed by the increased amount of fatty acids and sterols (manly β-sitosterol) in the hydrolyzed fractions compared with the corresponding nonhydrolyzed fractions. The amount of liphophilic compounds (mainly fatty acids and sterols) identified in hydrolyzed fractions of E. urograndis, E. camaldulensis, and E. urophylla corresponded to 1921, 1915, and 634 mg kg−1 of dry matter, respectively. The lower abundance of fatty acids and sterols in the fractions from E. urophylla indicates that problems related to pitch formation will be less severe for this species than for the other two.

Metodologia de extração e determinaçao do teor de extrativos em madeiras de eucalipto

The extractives content in eucalypt woods were evaluated using direct extractions with acetone, mixture of toluene:ethanol (2:1), chloroform and dichloromethane. The largest percentages of extractives were obtained using acetone as solvent. The extracts obtained in acetone and toluene:ethanol were dissolved in dichloromethane to establish the percentage of lipophilic extractives. The percentages of these extractives were similar to those obtained with dichloromethane or chloroform by direct extractions. The extracts were analyzed by infrared spectroscopy to identify the main functional groups.

Influência dos constituintes químicos dos extratos de diferentes matrizes na resposta cromatográfica de agrotóxicos

Multiresidue methods for pesticides monitoring by GC are commonly employed, however, it is well known that the presence of compounds of the matrix introduces errors during the quantiucation. The main consequence of matrix effect is an increasing or decreasing analyte signal after the GC saturation with extracts of matrix. In this paper, the influence of constituents of nine matrices on the quantification of the four pesticides by GC-ECD was studied. Variation of signal was evaluated by PCA and HCA, and results showed that the constituents of tomato increased the signal (until 300%), while extracts of apple decreased (until -20%). Variation the analyte signal in the presence of the matrix in respect to the same analyte in solvent (standard solution) also was observed, mainly for liver extract (until 270%).

Evaluation of Chemical Composition of Eucalyptus Wood Extracts after Different Storage Times Using Principal Component Analysis

Abstract Deposits of wood extractives, commonly referred to as pitch, cause significant problems for the pulp and paper industries. The reduction of these extractives is an important strategy aspect used to minimize problems. The present work studied the effects of wood storage time on the amount and variation of chemical composition of extracts, before and after alkaline hydrolysis. Fatty acids, sterols, long-chain aliphatic alcohols, and aromatic compounds were the main chemical classes of substances found in all analyzed extractives, before and after hydrolysis. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to confirm the similarity of wood samples using groups directly correlated with the chemical composition. PC1 explains approximately 99% of the total variance, and β-sitosterol was the major compound responsible for the groupings. The exploratory analysis of the extract samples after 20, 40, 60, 100, 140, and 180 days of storage, before and after alkaline hydrolysis, showed that they were affected by the strong influence of β-sitosterol, which is derived from glucosteroids degradation by water present in the wood was the compound present in the largest amount in the extracts, before and after hydrolysis, as well as octadec-9-enoic acid can be oxidized at the double bond becoming more soluble in water and 3,4,5-trihydroxybenzoic acid, derived from lignin degradation by water present in the wood or microorganism attack, which were responsible for differentiating and clustering the storage time. These studies demonstrate that the best period of storage of the wood in the field is 60 days, because the reduction of the main compounds present in extracts (mainly β-sitosterol and octadec-9-enoic acid) was more significant.

A simple and efficient method for derivatization of glyphosate and AMPA using 9-fluorenylmethyl chloroformate and spectrophotometric analysis

This work presents the confirmation and optimization of the method for derivatization of glyphosate and aminomethylphosphonic acid (AMPA) using 9-fluorenylmethyl chloroformate (FMOC-Cl) evaluating the parameters: concentration of borate buffer and FMOC-Cl, homogenization time and of reaction, wavelength and solvent washing. The reaction was successfully promoted and the method is simple and easy to perform because it uses five minutes of homogenization and allows ultraviolet analysis immediately after the end of the reaction.