Extração em fase sólida (SPE) e micro extração em fase sólida (SPME) de piretr��ides em ��gua

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.

Pr��-concentra����o de nitrosaminas a partir de amostras aquosas por extração em fase sólida e cromatografia capilar eletrocin��tica 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.

An��lise de praguicidas organofosforados em ��gua por extração em fase sólida (SPE) utilizando discos C18 e cromatografia em fase gasosa: avalia����o da contamina����o do reservat��rio de Furnas (MG-Brasil)

Solid phase extraction (SPE) in C18 disks has been optimized and validated for extraction of 5 organophosphorus (OP) pesticides in water. Extraction has been followed by separation and detection by gas chromatography/flame photometry. Excellent linearity was obtained for all compounds (r greater than 0.99), with CVs between 1.0-6.9%, recoveries between 73-95% and quantification limits between 2.5-5.0 ��g L-1. Samples from Furnas dam were analyzed monthly during one year and 10% showed OP pesticide residues.

Novos sorventes baseados em poli (metiloctilsiloxano) sobre s��lica para uso em extração em fase sólida

This paper presents an easy and practical procedure to obtain silica-based C-8 type sorbents for use in solid-phase extraction. The materials are prepared by depositing poly(methyloctylsiloxane), PMOS, on the silica support. Two different treatments for immobilization were used: thermal treatment or gamma irradiation. Suitable recoveries were obtained after pre-concentration of dilute solutions, at the ng/L level, of a mixture of pesticides, indicating the good performance of the materials.

Utiliza����o da extração em fase sólida (SPE) na determina����o de hidrocarbonetos polic��clicos arom��ticos em matrizes aquosas ambientais

Polycyclic aromatic hydrocarbons (PAHs) are a great environmental concern mainly because of their toxic, mutagenic and carcinogenic potential. This paper reports utilization of the solid-phase extraction (SPE) technique to determine PAHs in environmental aqueous matrices. The recovery from environmental aqueous matrices fortified with PAHs varied from 63.7 to 93.1% for atmospheric liquid precipitation, from 38.3 to 95.1% for superficial river water, and from 71.0 to 95.5% for marine water. No negative matrix effect was observed for the recovery of PAHs from atmospheric liquid precipitation and marine water, but was observed for superficial river water, particularly for PAHs possessing 5 and 6 aromatic rings.

Determina����o do coeficiente de atividade na dilui����o infinita (g¥) atrav��s da micro-extração em fase sólida (SPME)

In this study a new approach, solid phase micro extraction (SPME), is used in the evaluation of the infinite dilution activity coefficient of the solute in a given solvent. It is the purpose of the current work to demonstrate a different approach to obtain the data needed for studying the solution thermodynamics of binary liquid mixtures as well as for designing multi-component separations. The solutes investigated at the temperature 298.15 K were toluene, ethyl benzene and xylene in the solvent methanol.

Determina����o de metil-etil-cetona em amostras de urina com amostragem por micro extração em fase sólida (MEFS) em headspace associada �� cromatografia gasosa com detector de ioniza����o de chama (CG-DIC)

Methyl ethyl ketone (MEK) is a solvent commonly used in chemical, paint and shoe industry. The aim of this study was to develop and validate a method for urinary quantification of MEK, employing headspace solid phase micro extraction sampling (SPME) coupled to gas chromatography with flame ionization detection (GC-FID). The calibration curve (y=4.6851x-0.0011) presented good linearity with r��=0.9993. Accuracy (94-109%), intra-assay precision (4.07-5.91%) and inter-assay precision (3.03-5.62%) were acceptable. The quantification limit was 0.19 mg/L. This low cost method can be used routinely in the biological monitoring of occupational exposure to MEK, according to the requirements of the Brazilian legislation.

Enriquecimento de compostos fen��licos de folhas de Inga edulis por extração em fase sólida: quantifica����o de seus compostos majorit��rios e avalia����o da capacidade antioxidante

A phenolic fraction was obtained from of the acetone-water-acetic acid extract of Inga edulis leaves, by liquid-liquid partition and SPE-C18 cartridges. This method provided an increase of 108, 66, 51, 50 and 36% of flavonols, proanthocyanidins, total polyphenols, gallotannins and flavanols, respectively. The major phenolics in purified fraction were procyanidin B2, catechin and myricetin-3-O-α-L-rhamnopyranoside, which achieved increases of 111, 47 and 45%, respectively, after SPE. Acid hydrolysis confirmed the presence of procyanidins, prodelphinidins and glycosylated flavonoids.

Sistema limpo em linha para extração em fase sólida de contaminantes emergentes em ��guas naturais

A solid-phase in-line extraction system for water samples containing low levels of emerging contaminants is described. The system was specially developed for large volume samples (up to 4 L) using commercial solid-phase extraction (SPE) cartridges. Four sets containing PTFE-made connectors, brass adapters and ball valves were used to fit SPE cartridges and sample bottles to a 4-port manifold attached to a 20 L carboy. A lab-made vacuum device was connected to the manifold cap. The apparatus is robust and less expensive than the typical available system. Its also provides less experimental handling, avoiding cross contamination and sample losses.

Determina����o de bifenilos policlorados em milho atrav��s de extração em fase sólida seguida de cromatografia a g��s acoplada �� espectrometria de massas

This paper describes an analytical method for analyzing polychlorinated biphenyls in corn samples using solid phase extraction (SPE) followed by determination by GC-MS. All calibration curves proved linear (r> 0.99). Recoveries ranged between 74.1 and 110.6% with relative standard deviation lower than 20% for all compounds. The limits of quantitation for the method were between 0.025 and 0.1 ng g-1. Of the 51 samples analyzed, PCB 180 showed the highest frequency, being detected in more than 39%, followed by PCB 138, detected in more than 33% of samples.

Res��duos de pesticidas em ��guas superficiais de ��rea de nascente do Rio S��o Louren��o-MT: valida����o de m��todo por extração em fase sólida e cromatografia l��quida

A multiresidue method using HPLC/DAD for the determination of fourteen pesticides in water based on SPE, using SDVB (styrene divynilbenzene copolymer) as adsorbent was validated. Recoveries from 61 to 120%, relative standard deviation between 2 and 15% and detection limits from 0.07 to 0.75 ��g L-1 were obtained. It was applied to 66 surface water samples collected in a degraded area at the headwaters of S��o Louren��o river, Mato Grosso, Brazil. Eight pesticides were detected in concentrations ranging from 0.15 to 35.25 ��g L-1. Considering ecotoxicological data, carbendazim and carbofuran may represent a risk to aquatic organisms. These results draw attention to the contamination of this vulnerable degraded area.

Equipamento de baixo custo para extração em fase sólida em amostras aquosas de grande volume utilizando press��o positiva de N

Extraction/concentration is a crucial step for the analysis of organic compounds at trace level concentrations and dispersed in complex matrices. Solid-phase extraction (SPE) is one of the techniques used for this purpose. In this work, a low cost apparatus for SPE was developed that uses nitrogen under positive pressure and ensures the maintenance of the sample flow, while also allows the simultaneous extraction of different samples without cross-contamination and sample contact with plastic materials. For the system set up, easily accessible materials were used such as hypodermic needles, stainless steel tubes, rubber stoppers, and 3-way valves from serum delivery apparatus.

NOVO SORVENTE DE HIDROFOBICIDADE REDUZIDA PARA EXTRA����O EM FASE S��LIDA: PREPARA����O E CARACTERIZA����O

C18 chemically bonded sorbents have been the main materials used in solid phase extraction (SPE). However, due their high hydrophobicity some hydrophobic solutes are strongly retained leading to the consumption of larger quantities of organic solvent for efficient recoveries. This work presents a sorbent with lower hydrophobicity but similar selectivity to the C18 sorbent, prepared by thermal immobilization of poly(dimethylsiloxane-co-alkylmethylsiloxane) (PDAS) on silica. PDAS has organic chains with methyl groups alternating with octadecyl or hexadecyl groups in its monomeric unities. For the Si(PDAS) sorbent presented, the polymeric layer was physically adsorbed on the silica surface with 12% carbon load. Although the coating of silica with the polymeric layer was incomplete, the PDAS provided better protection for the silica surface groups, promoting mostly hydrophobic interactions between analytes and the sorbent. Sorption isotherm studies revealed that the retention of hydrophobic solutes on Si(PDAS) was less intense than on conventional sorbents, confirming the lower hydrophobicity of the lab-made sorbent. Additional advantages of Si(PDAS) include simplicity and low cost of preparation, making this material a potential sorbent for the analysis of highly hydrophobic solutes.

Potencialidades anal��ticas do dietilditiofosfato de am��nio em espectrometria de massas com plasma indutivamente acoplado empregando extração em fase sólida e sistemas de inje����o em fluxo

Um sistema de inje����o em fluxo envolvendo complexa����o com dietilditiofosfato de am��nio e sor����o de complexos met��licos em minicolunas de s��lica gel modificada por grupos octadecil C18 �� proposto para determina����es multielementares em espectrometria de massa com plasma indutivamente acoplado. Influ��ncia da concentra����o de reagentes, natureza do ��cido, tempo de rea����o, tempos de comuta����o, vaz��es e interfer��ncia de s��dio foram investigadas. ��gua ou solu����o 2% v/v HNO3 podem ser utilizadas para lavar a coluna antes da elui����o dos analitos com etanol. Amostras contendo 5000 mg Na L-1 e analisadas diretamente com o sistema proposto produzem uma concentra����o aparente de 63Cu de 0,45 ��g L-1; por outro lado n��o foi observada interfer��ncia para As, Pb, Bi, Se, In, Tl, Cd, Hg e 65Cu. Para 0,25 % w/v NH4DTP e 3 mL de solu����o de amostra, curvas anal��ticas para Bi, Cu, Pb, As, Se, In, Tl, Cd, Hg no intervalo de 0,10 a 2,00 ��g L-1 podem ser constru��das com boas correla����es (r2 > 0.998). A velocidade anal��tica e sensibilidade podem ser melhoradas pois dependem das condi����es de pr��-concentra����o e elui����o selecionadas. Com os par��metros acima fixados, limites de detec����o de 0.014 (Cu), 0.027 (As), 0.06 (Se), 0.02 (Cd), 0.029 (In), 0.043 (Hg), 0.02 (Tl), 0.06 (Pb) e 0.002 ��g L-1 (Bi) foram obtidos.

Estr��genos em ��gua: otimiza����o da extração em fase sólida utilizando ferramentas quimiom��tricas

Muitos m��todos anal��ticos est��o sendo desenvolvidos visando �� determina����o de contaminantes org��nicos, especialmente alteradores end��crinos. Tais m��todos baseiam-se geralmente na extração em fase sólida (SPE) seguida por determina����o cromatogr��fica (CG ou HPLC). No presente trabalho utilizou-se ferramentas quimiom��tricas no processo de SPE para avaliar os principais fatores que influenciam tal processo e as intera����es entre os mesmos. Foram analisadas matrizes de ��gua subterr��nea fortificada com horm��nios (17 b estradiol, estrona e 17 b etinilestradiol) e a determina����o anal��tica foi feita por HPLC/Fluoresc��ncia. Um planejamento fatorial completo foi utilizado. Os fatores escolhidos inclu��ram: condicionamento da fase sólida, concentra����o dos analitos, volume da amostra e solvente de elui����o. As melhores condi����es obtidas foram: 500 mL da amostra, condicionamento da fase sólida (C18) com acetona (4mL), metanol (6 mL) e ��gua pH 3(10 mL), e elui����o dos analitos com 4 mL de acetona.