Métodos de extração e/ou concentração de compostos encontrados em fluidos biológicos para posterior determinação cromatográfica

When organic compounds present in biological fluids are analysed by chromatographic methods, it is generally necessary to carry out a prior sample preparation due the high complexity of this type of sample, especially when the compounds to be determinated are found in very low concentrations. This article describes some of the principal methods for sample preparation in analyses of substances present in biological fluids. The methods include liquid-liquid extraction, solid phase extraction, supercritical fluid extraction and extraction using solid and liquid membranes. The advantages and disadvantages of these methods are discussed.

Extração em fase sólida (SPE) e micro extração em fase sólida (SPME) de piretróides em água

The pyrethroids bifenthrin, permethrin, cypermethrin and deltamethrin were extracted by solid phase extraction (SPE) and solid phase microextraction (SPME). The analysis were performed on a gas chromatograph with electron capture detection (GC-ECD). Octadecil Silano-C18, Florisil and Silica stationary phases were studied for SPE. Better results were obtained for Florisil which gave recoveries from 80% to 108%. Pyrethroids extraction by SPME showed a linear response and a detection limit of 10 pg ml-1. Although the data showed that the two extraction methods were able to isolate the pesticide residues from water samples, the best results were obtained by using SPME which is more sensitive, faster, cheeper, being a more useful technique for the analysis of pyrethroids in drinking water.

Extração por fluido supercrítico de alguns inseticidas carbamatos em amostras de batata, com determinação por HPLC/fluorescência e confirmação por HPLC/espectrometria de massas

Six supercritical fluid extraction (SFE) methods were tested, by varying the following operational parameters: CO2 pressure, time and temperature of extraction, type and proportion of static modifier, and Hydromatrix®/sample rate into cell. Firstly, insecticide carbamates were extracted from spiked potatoes samples (fortification level of 0,5 mg.Kg-1) by using SPE procedures, and then final extracts were analyzed HPLC/fluorescence. Good performance was observed with SFE methods that operated with values of temperature and CO2 pressure of 50 ºC and 350 bar, respectively. Best efficiency was obtained when it was used acetonitrile as a modifier (3% on the cell volume), and Hydromatrix®/sample rate of 2:1. Static time was of 1 min; total extraction time was of 35 min; dynamic extraction was performed with 15 mL of CO2, and it was used methanol (2 mL) for the dissolution of the final residue. In such conditions, pesticide recoveries varied from 72 to 94%, depending on the analyzed compound. In higher extraction temperatures, a rapid degradation was observed for some compounds, such as aldicarb and carbaryl; presence of their metabolites was further confirmed by HPLC-APCI/MS in positive mode. Detection limits for chromatographic analysis varied from 0,2 to 1,3 ng.

Métodos de extração e determinação do herbicida glifosato: breve revisão

This paper supplies a compact revision about the main extraction, clean-up and pre-concentration methods of the herbicide glyphosate for water and soil samples, as well as methods for its determination and quantification.

Pré-concentração de chumbo e cádmio em um sistema de micro extração líquido-líquido e determinação por espectrometria de absorção atômica com chama

A method for determination of lead and cadmium in aqueous samples using solvent microextraction and dithizone as complexing agent with FAAS was developed. Solvent microextraction parameters were optimized. The effect of foreign ions on the extraction yields was studied. The extraction was carried out until the aqueous to organic phase ratio achieved a 250 fold preconcentration of metals. For preconcentration times of 4 min the 3sigma detection limits, relative standard deviations (n=7) and linear calibration ranges were 1.6 mug L-1, 5.8% and 10.0 -- 80.0 mug L-1 for lead and 11.1 ng L-1, 5.9% and 0.3 -- 3.0 mug L-1 for cadmium, respectively. The solvent microextraction procedure presented here was applied to the determination of lead and cadmium in natural waters.

Uso de métodos analíticos convencionados no estudo da autenticidade do óleo de copaíba

The acidity and ester index are suggested, as simple and cheap methods, adequate to be employed in the study of the authenticity of copaíba oil by small drugstores and export firms. The acidity index permits both the detection and the evaluation of the content of adulteration of copaíba oil. The ester index permits to know if the adulterant either contain ester compounds,as the case of fatty oils, or contain only non saponifiable compounds as is the case of ethyl alchool or mineral oil. The results of the aplication of the methods to eight commercial samples, of copaiba oil, where three samples were adultered, are coherent with those obtained by more sophisticated instrumental methods.

A extração de cafeína em bebidas estimulantes: uma nova abordagem para um experimento clássico em química orgânica

Caffeine extraction procedures from water soluble and water insoluble materials for preparing stimulating beverages are described. Water soluble materials used were instant tea and coffee and water insoluble materials were, among others, guaraná powder and maté leaves. The extraction of caffeine from water soluble materials, especially instant tea, is more suitable for an organic chemistry teaching laboratory than the classic experiment using tea leaves, due to the economy of time and a larger amount of extracted caffeine. The procedure is time-saving and requires only a four-hour period. The experiments illustrate the extraction process as used in undergraduate organic chemistry laboratories.

Pré-concentração de nitrosaminas a partir de amostras aquosas por extração em fase sólida e cromatografia capilar eletrocinética micelar

This paper describes the development of a methodology for solid phase extraction (SPE) and pre-concentration of nitrosamines from aqueous samples using granular activated charcoal as stationary phase. micelar electrokinetic capillary Chromatography (MEKC) was used for the separation and identification of the nitrosamines in the extracts. Using a sample with 50 µg l-1 of each nitrosamines standards (dimethylnitrosamine, DMN; diethylnitrosamine, DEN; N-nitrosopyrrolidine, NPYR; N-nitrosopiperidine, NPIP; N-nitrosomorpholine, NMOR), the methodology showed a range of recuperation from 29 to 107% with a linear zone between 10 and 500 µg l-1. The developed methodology can be applicable to the determination of these analytes in different aqueous samples.

Extração de matéria orgânica aquática por abaixamento de temperatura: uma metodologia alternativa para manter a identidade da amostra

In this work was developed an alternative methodology to separation of aquatic organic matter (AOM) present in natural river waters. The process is based in temperature decreasing of the aqueous sample under controlled conditions that provoke the freezing of the sample and separation of the dark extract, not frozen and rich in organic matter. The results showed that speed of temperature decreasing exerts strongly influence in relative recovery of organic carbon, enrichment and time separation of the organic matter present in water samples. Elemental composition, infrared spectra and thermal analysis results showed that the alternative methodology is less aggressive possible in the attempt of maintaining the integrity of the sample.

Avaliação dos métodos de extração sequencial de Tessier, Keller e Miller na determinação de ferro nativo em três tipos de solos: orgânico, brunizem e latossolo

Sequential extraction is not totally effective to dissolve distinct forms of trace elements. The extractive solution, for example, can dissolve less of the target fraction and more than another not wished fraction. The goal of this work is to compare the extraction of native iron with three sequential extraction methods of the heavy metals, using three soils with different physical chemistry characteristics: a histosol, an oxisol, and a mollisol. The results obtained in this work demonstrate that a smaller relation soil/extractor results in a larger extraction in almost all phases. The use of many stages of the sequential extraction, with the purpose of more association of the metal with different components of the soil, can result, among other things, in modification of the substratum by the action of the reagents used, besides reducing the selectivity of the more specific extractors. Readsorption and redistribution of the heavy metals could have happened with larger intensity in the fraction where hidroxilamine was used with higher temperature. Sequential extraction of iron, without enrichment of soil samples, in the respective fractions in each method, it was important to better understand the behavior of the reagents considered specific to each form of the metal in soil.

Quantificação do linalol no óleo essencial da Aniba duckei Korstermans utilizando uma nova coluna capilar POLYH4-MD em Cromatografia Gasosa

In the present work a polyurethane polymer derived from castor oil was used as stationary phase for capillary gas chromatography. The polymer was obtained by reaction of hydroxylated compound and isocynate (NCO), forming urethane. Columns of 7 m x 0,25 mm were then coated with this stationary phase (film thickness of 0,25 µm) using static coating method. The Grob test was also performed. Samples of essential oil of the Aniba duckei Korstermans was then analysed in POLYH4-MD capillary column in order to evaluate its chromatographic perfomance. The linalool was found to be the major component and has been used as compound of departure for many important syntheses. Results show that the experimental columns give higher resolution and can be employed for analysis of essentials oils.

Extração de esteróides em frutos de Ottonia martiana Miq., Piperaceae, com gás liqüefeito

A new extraction method for sterols was tested in fruits of Ottonia martiana Miq., a shrub belonging to the family Piperaceae, popularly known as "anestésica" due to the use of its roots and aerial parts, in alcoholic preparations, in treatment of odontological problems. For this purpose, a portable extraction equipment was developed, to operate with liquified gases, which showed to be practical, fast and effective, besides being economical and ecological. In the chromatographic analysis of the extracts obtained in this equipment, it was demonstrated the presence of two sterols, isomers of b-sitosterol and stigmasterol.

Produtos naturais para o controle da transmissão da dengue: atividade larvicida de Myroxylon balsamum (óleo vermelho) e de terpenóides e fenilpropanóides

The bioassay-guided fractionation of the hexane extract obtained from the medicinal plant Myroxylon balsamum (red oil) was conducted in preparative thin layer chromatography on silica gel. The obtained fractions and some terpenoids and phenylpropanoids were assayed as larvicidal on third instar Aedes aegypti larvae, NPPN colony. The results indicate that the sesquiterpene nerolidol was the active constituent in the extract and that the sesquiterpenes were more active than the monoterpenes and phenylpropanoids utilized in this study. Lipophilicity seems to be an important property for the activity since the compounds with hydroxyl, carbonyl and methoxyl groups were less active. The results confirm also that essential oils can be a good tool for the control of dengue.

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.

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.