Recuperação de sílica-gel utilizando processos oxidativos avançados: uma alternativa simples e de baixo custo

Silica gel is widely used as adsorbent for isolating and purifying natural compounds. Intensive use and high cost make this process expensive and generate solid residues contaminated with many different organic compounds. In the present work a simple method for recycling silica was investigated, by using Advanced Oxidative Processes. Silica gel was treated with H2O2/solar light and compared with a sample treated by conventional methods (high temperature and oxidation with KMnO4). High temperature treatment changes the structure of the silica and, consequently, the separation efficiency. Oxidation by using KMnO4 requires multiple steps and produces residues, including manganese and oxalic acid. The method using H2O2/solar light to recuperate silica gel does not modify its separation efficiency and is less expensive than the traditional methods. Additionally, HPLC and GC-MS analysis indicate that H2O2/solar light eliminates all residues of the silica gel.

Teor e composição do óleo essencial de cinco acessos de mentrasto

This study aimed to analyse the content and the composition of the essential oil of five accesses of mentrasto (Ageratum conyzoides). Five accesses of mentrasto with three repetitions were used. The accesses were obtained in Mariana-MG (AMA), Piranga-MG (API), Visconde do Rio Branco (ARB) and Viçosa-MG (AVB and AVP). The essential oil was obtained by hydrodistillation and the identification of the oil components by CG and GC/MS. The ARB access presented the higher essential oil content, that is 0.70% (P < 0.05). Eleven chemical compounds were identified. The precocene I was the main constituent in the access API, and the precocene II was the main constituent in the accesses AMA, ARB, AVB and AVP.

Lignanas de Strychnos guianensis (Aublet) Mart.

The present communication reports the isolation and identification of three lignans from metanolic root extracts of Strychnos guianensis (Aublet) Mart.: olivil (1), cycloolivil (2) and the unknown derivative cycloolivil carbonate (3). From hexane extracts was identified a long chain fatty acid mixture and the triterpene lupeol. The analyses were based on chromatographic and spectroscopy techniques (IR, MS, GC/MS, ¹H-NMR and 13C-NMR, 1D (BB, DEPT 135) and 2D (¹H, ¹ H-COSY, ¹H, 13C-COSY, ¹H, 13C-COSY-LR, HMQC, HMBC and NOESY) and comparison with literature data.

Quantitative analysis of phenol and alkylphenols in Brazilian coal tar

The main purpose of this work is the identification and quantification of phenolic compounds in coal tar samples from a ceramics factory in Cocal (SC), Brazil. The samples were subjected to preparative scale liquid chromatography, using Amberlyst A-27TM ion-exchange resin as stationary phase. The fractions obtained were classified as "acids" and "BN" (bases and neutrals). The identification and quantification of phenols, in the acid fraction, was made by gas chromatography coupled to mass spectrometry (GC/MS). Nearly twenty-five phenols were identified in the samples and nine of them were also quantified. The results showed that coal tar has large quantities of phenolic compounds of industrial interest.

Análise química quantitativa para a padronização do óleo de copaíba por cromatografia em fase gasosa de alta resolução

Quantitative GC-FID was evaluated for analysis of methylated copaiba oils, using trans-(-)-caryophyllene or methyl copalate as external standards. Analytical curves showed good linearity and reproducibility in terms of correlation coefficients (0.9992 and 0.996, respectively) and relative standard deviation (< 3%). Quantification of sesquiterpenes and diterpenic acids were performed with each standard, separately. When compared with the integrator response normalization, the standardization was statistically similar for the case of methyl copalate, but the response of trans-(-)-caryophyllene was statistically (P < 0.05) different. This method showed to be suitable for classification and quality control of commercial samples of the oils.

Análise de ácidos graxos não-esterificados de plasma humano por cromatografia gasosa capilar com injeção sem divisão de fluxo

The aim of the present work was to test the combination of non-esterified fatty acid (NEFA) isolation using fumed silicon dioxide with capillary gas-chromatography (C-GC) with splitless injection for the analysis of NEFAs in human plasma. Injection volume, solvent re-condensation and split purge flow-rate were the parameters evaluated for the analysis of fatty acid methyl esters by C-GC. The use of a solvent re-condensation technique, associated with 1.0 µL injection and a split purge flow rate of 80 mL/min resulted in satisfactory analysis of NEFAs. Fourteen fatty acids were identified in plasma samples, ranging from 2.03 to 184.0 µmol/L. The combination of both techniques proved useful for routine analyses of plasma NEFAs.

Métodos para análise de ácido clorogênico

This paper describes the analytical methods for determination of total chlorogenic acid (CGA) and their individual isomers. Spectrofotometric methods are adequate for total CGA analysis in green coffee but they can provide inflated results for coffee products. High pressure liquid chromatography (HPLC) with gel permeation column and ultraviolet (UV) monitoring is adequate for the simultaneous analysis of total CGA, alkaloids and sugars in coffee products. HPLC-UV-reversed phase is a simple, rapid and precise method for the determination of the individual isomers of CGA. Gas chromatography (GC) also is applied to the analysis of the individual isomers but phenolic acids need to be derivatized before analysis. Both HPLC- and GC-mass spectrometry provide an unequivocal identification of the individual isomers. The capillary electrophoresis method is simple, rapid and adequate to the simultaneous analysis of polyphenols and xanthines. Advantages and limitations of each method are discussed throughout the text.

Otimização dos parâmetros de extração para determinação multiresíduo de pesticidas em amostras de água empregando microextração em fase sólida

In this study the factors that affect the extraction of pesticide residues from water samples for their determination by solid-phase micro-extraction (SPME) and GC/MS were optimized. The fiber polymer, the extraction mode, the ionic strength, the stirring rate, the pH and the extraction time were the most significant parameters evaluated. The recovery obtained with the proposed method ranged from 94 to 110% and the sensitivity of the method, determined by calculating the detection limit (DL), ranged from 0.004 to 0.1 mug l-1. The results obtained with spiked real samples, at the 0.1 mug l-1 level, showed acceptable conformity with the expected values.

Validação em métodos cromatográficos e eletroforéticos

The validation of an analytical method is fundamental to implementing a quality control system in any analytical laboratory. As the separation techniques, GC, HPLC and CE, are often the principal tools used in such determinations, procedure validation is a necessity. The objective of this review is to describe the main aspects of validation in chromatographic and electrophoretic analysis, showing, in a general way, the similarities and differences between the guidelines established by the different Brazilian and international regulatory agencies.

Aplicação da técnica de dispersão da matriz em fase sólida (DMFS) na análise de pesticidas em quiabo por CG-EM

A matrix solid phase dispersion and gas chromatography-mass selective detection method for the simultaneous determination of monocrotophos, methyl parathion, cypermethrin and deltamethrin in okra is described. Analyses of 2 g of fortified okra (0.05-0.75 mg kg-1) showed an average recovery of 96.2% (71.4-128.4%) and average relative standard deviation of 11.7% (1.4-37.1%). The cypermethrin recovery at the lower level was above 130%. The limit of detection ranged from 0.02 to 0.15 mg kg-1. The procedure was applied to the okra samples and has found 0.56 mg kg-1 of cypermethrin-cis, 0.75 mg kg-1 of cypermethrin-trans and 2.71 mg kg-1 of deltamethrin.

Óleos voláteis de espécies de Myrcia nativas do Rio Grande do Sul

Essential oils from M. richardiana, M. arborescens, M. selloi, M. oligantha, M. rostrata, M. lajeana, M. obtecta, M. pubipetala and M. hatschbachii were obtained by hydrodistillation and analyzed by GC and GC/MS. Sixty-seven compounds have been identified ranging from 90-99% of the oil contents. All analyzed species were rich in cyclic sesquiterpenes (66-99%), mainly those from the cadinane, caryophyllane and germacrane cyclization pathway, among them b-caryophyllene, germacrene D, bicyclogermacrene, d-cadinene, spathulenol, caryophyllene oxide, globulol and a-cadinol. The acyclic sesquiterpene series was well represented by M. lajeana (32.1%), with 25,3% of (E)-nerolidyl acetate.

Constituintes químicos voláteis e não-voláteis de Cochlospermum vitifolium (Willdenow) Sprengel

The essential oils from leaves, root bark and root wood of Cochlospermum vitifolium were investigated for the first time. The oils were obtained by hydrodistillation and analyzed by GC/MS. The main volatile constituents were beta-caryophyllene (8.2 - 46.5%), beta-bisabolene (11.5 - 29.3%), gamma-muurolene (28.4%), alpha-humulene (26.0%), 1-hydroxy-3-hexadecanone (16.2 - 19.5%) and beta-pinene (10.6%). Phytochemical analysis of the root bark and root wood extracts yielded excelsin, pinoresinol, narigenin, aromadendrin, galic acid and a triacylbenzene, along with beta-sitosterol and stigmasterol and their D-glucosides. The structures of all compounds were determined by analyses of the spectroscopic data (NMR and MS), and comparison with the literature.

A destilação simulada na indústria do petróleo

One of the most widely used physico-chemical characterizations of hydrocarbon mixtures is the determination of their boiling point distribution. Knowledge of the boiling range of crude oils and petroleum products is essential to ensure the correct specification of final products and to control refinery processes. Simulated distillation, a GC based process, has been playing this role for the past decades in the petroleum industry. The main purpose of this work is to show the fundamentals of this technique as well as its present trends.

Sesquiterpenos do caule de Pilocarpus riedelianus e atividades sobre microorganismos

Pilocarpus riedelianus was studied in order to obtain compounds with activity against fungi and bacteria. The dichloromethane extract, the most active one, was chromatographed yielding hexane and dichloromethane fractions. Six known sesquiterpenes, alpha-calacorene, beta-calacorene, gamma-calacorene, cadalene, sesquichamaenol and 1-hydroxy-1,3,5-bisabolatrien-10-one were identified in the hexane fractions. The identification of these compound was done by NMR and GC/MS analyses. The hexane fraction from the dichloromethane extract showed activity against several fungi and bacteria.

Resultados de la implantación de la norma ISO 9000 y el modelo EFQM: conclusiones de un estudio tipo Delphi

Desde el ámbito académico el auge de la Gestión de la Calidad (GC) ha sido analizadoextensamente a través de numerosos estudios de carácter empírico. Una parte importante de estos estudios han tratado de analizar cuáles han sido los principales efectos de laimplantación de estos modelos sobre los resultados o el desempeño (performance) empresarial. Hay que señalar que la mayor parte de dichos estudios son de tipo cuantitativo, basados en la utilización de encuestas dirigidas a los directivos de las empresas que han participado en el proceso de implantación. Ahora bien, el análisis de los efectos de la GC realizado de esta forma, cuenta, a nuestro entender, con una posible debilidad y distorsión metodológica al tomar sólo como base las opiniones de los directivos de las empresas involucradas en el proceso de implantación sobre los efectos del propio proceso y los resultados pueden tener cierto sesgo, tal y como ha sido subrayado por diversos investigadores (ver, por ejemplo, Wayhan et al, 2002 y Heras et al, 2002). Por estos motivos, en el estudio que aquí presentamos hemos considerado necesario utilizar una metodología que tenga en cuenta la opinión de expertos de diversa índole que tienen distintas funciones en la implantación de modelos de GC, de forma que se pueda obtener una información de interés para contrastarla y triangularizarla con la obtenida en estudios empíricos previos llevados a cabo con la metodología tradicional