In this study, a highly sensitive and reliable microextraction method, known as in tube ultrasonic and air assisted liquid-liquid microextraction (IT-UAA-LLME), was developed for the preconcentration of some phthalate esters, such as dimethyl phthalate, diethyl phthalate (DEP), di-butyl-phthalate (DBP), bis(2-ethylhexyl) phthalate (BEHP), butyl benzyl phthalate (BBP), and di n-octyl-phthalate (DNOP), prior to their determination using gas chromatography-mass spectrometry (GC-MS). In this technique, the extraction solvent was dispersed into the aqueous sample solution using an ultrasonic bath. The effects of solvent type, aeration time and salt concentration were investigated. After extraction, an organic solvent was injected into the GC-MS instrument for quantification. Under optimum conditions, the enrichment factors ranged from 100 to 330. The calibration curves showed good linearity (r2 > 0.99) and limit of detections were obtained in the range of 0.1-2.1 ng mL-1 in the working concentration ranges. The method was successfully applied for determination of six phthalate esters in real samples with complex matrices with relative standard deviation less than 8%, recovery 88-112% and thus, satisfactory results were obtained.

An on-line solid phase extraction (SPE) method using mini column packed with natural sorbent based on cotton roll dyed by quinalizarin was developed for simultaneously pre-concentration of rare earth elements and uranium at trace levels in environmental samples followed by inductively coupled plasma optical emission spectrometry (ICP OES) determination. Various parameters such as sample and eluent flow rate, sample volume and matrix ions on the method efficiency have been investigated. Under the optimized conditions, the limits of detection (LODs, 3σ) for rare earth elements were in the range of 0.002-0.300 µg L-1 and 0.420 µg L-1 for uranium. The relative standard deviation (n = 5) were lower than 6% except for samarium and uranium. The method was successfully applied for determination of trace rare earth elements and uranium in lake, well, tap water and carbonate mineral samples. The accuracy of the proposed method was validated by add-found method and direct analysis by ICP OES. This method has some advantages such as simplicity, rapidity, green chemistry and high sensitivity.

Foi desenvolvido um método sensível baseado na pré-concentração de urânio em papel de filtro modificado (filme fino) para a determinação deste elemento em amostras de águas e de solos, usando a técnica de fluorescência de raios-X de comprimento de onda dispersivo. Para a extração de urânio (VI), 100 mL de amostra reagiram com tri-octil fosfina (TOPO) em presença de ácido nítrico. O efeito da concentração de ácido nítrico e de TOPO, bem como da retenção do metal em função do volume de amostra foram avaliados neste estudo. O método proposto mostrou boa linearidade entre 7 e 1000 µg de urânio (VI) e o limite de detecção (LOD), calculado com a relação sinal-ruído (S/N) igual a 3 foi de 2,5 µg.

A sensitive method based on the preconcentration of uranium on modified filter paper (thin film) has been developed to determinate this element in water and soil samples by wavelength dispersive X-ray fluorescence. Uranium (VI) extraction from nitric acid medium by trioctyl phosphine (TOPO) from 100 mL of sample was carried out. The effects of nitric acid concentration, TOPO concentration and sample breakthrough on uranium extraction were investigated in this study. The proposed method provided good linearity from 7 to 1000 µg and the limit of detection (LOD), based on a signal-to noise ratio (S/N) of 3, was 2.5 µg.

No presente trabalho, uma técnica de pré-tratamento de amostra simples, rápida e econômica, extração líquido-líquido homogênea miniaturizada de baixa densidade (LDMHLLE), foi desenvolvida para a determinação de hidrocarbonetos policíclicos aromáticos (PAH) e hidrocarbonetos totais de petróleo (TPH) em amostras de sedimentos. O método LDMHLLE é baseado na extração líquido-líquido homogêneo com metanol, contendo n-hexano como solvente de densidade inferior à da água que imediatamente após adição de água forma uma fase distinta imiscível em água na parte superior do frasco. Esta fase pode ser facilmente separada e injetada no cromatógrafo gasoso com detector de ionização de chama (GC-FID) para quantificação. A linearidade foi obtida no intervalo de concentração de 0,100-100,00 e 0,030-100,00 µg g-1 para PAH e TPH, respectivamente. Os coeficientes de correlação foram melhores do que 0,99 para PAH e TPH. O limite de detecção (LOD), com base na razão sinal-ruído (S/N), foi de 0,010-0,060 µg g-1 para os PAH e 0,008 µg g-1 para TPH. As recuperações relativas de PAH e TPH para amostras de sedimento de nível fortificado de 10,0 µg g-1 foram 57-92 e 91%, respectivamente. O método foi aplicado com sucesso em material de referência certificado, CRM372-100 para TPH e CRM CNS391-050 para PAH.

In the present work, a simple, rapid and economic sample pre-treatment technique, low density miniaturized homogeneous liquid-liquid extraction (LDMHLLE), was developed for determination of polycyclic aromatic hydrocarbons (PAH) and total petroleum hydrocarbons (TPH) in sediment samples. The LDMHLLE method is based on the homogeneous liquid-liquid extraction with methanol containing n-hexane as a solvent of lower density than water that after addition of water forms a distinct water immiscible phase at the top of the vial. This phase can be easily separated and injected to the gas chromatography with flame ionization detector (GC-FID) instrument for quantification. The linearity was obtained in the concentration range of 0.100-100.00 and 0.030-100.00 mg g-1 for PAH and TPH, respectively. Correlation coefficients were better than 0.99 to for PAH and TPH. The limit of detection (LOD), based on the signal-to-noise ratio (S/N), was 0.010-0.060 mg g-1 for PAH and 0.008 mg g-1 for TPH. The relative recoveries of PAH and TPH for sediment samples at spiking level of 10.0 mg g-1 were 57-92 and 91%, respectively. The method was successfully applied to corresponding standard reference material, CRM372-100 for TPH and CRM CNS391-050 for PAH.