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The combination of the extraction induced by microemulsion-breaking (EIMB) and preconcentration using the solid-phase extraction (SPE) using magnetic nanoparticles (MNP) for determination of Cd, Cr, Cu and Pb in gasoline samples by energy dispersive X-ray fluorescence spectrometry (EDXRF) is proposed. The procedure was based in the formation of a three components microemulsion: gasoline as organic phase, n-propyl alcohol as an emulsifier and 0.01 mol L−1 HNO3 as aqueous phase. After formation of the microemulsion, tris/nitric acid buffer (0.1 mol L−1, pH 8.5) was used for the microemulsion breaking and adjust the pH simultaneously. Subsequently, an amount of CoFe2O4 nanoferrite was added to the medium for the retention and preconcentration of the species of interest present in the aqueous phase of the broken emulsion. After a contact time between the nanoparticle and the mixture, the solid phase was separated from the supernatant with the aid of a magnet and, after drying, the determination of the analytes was performed directly on the solid support (nanoferrite) by EDXRF. To guarantee the better extraction conditions, some experimental variables were investigated. The recommended proportion for the microemulsion formation was 65% (v v−1) n-propyl alcohol, 20% (v v−1) gasoline, and 15% (v v−1) nitric acid solution. For the solid phase extraction, 100 mg of nanoferrite and a contact time of 10 min were recommended. Enrichment factors between 10 and 470 times were found for the analytes. The limits of detection obtained by the proposed method were 24, 2.8, 16 and 9.7 μg L−1 for Cd, Cr, Cu and Pb, respectively. The precisions for determination of each element were expressed as relative standard deviations (RSD) using standard solutions containing 0.2 and 0.4 mg L−1 of each analyte and were between 2.0 and 8.1%. The developed method was applied in the determination of Cd, Cr, Cu and Pb in gasoline samples.

In this study, multi-element determination in ethanol fuel samples using energy dispersive X-ray fluorescence spectrometry (EDXRF) combined with magnetic solid phase microextraction (MSPME) was explored. The extraction and preconcentration of Cd, Pb, Cu, V, Cr, and Mn from ethanol fuel samples using CoFe2O4 nanoparticles impregnated with 1-(2-pyridylazo)-naphthol (PAN) was carried out for posterior direct determination in the solid phase using EDXRF. Factors such as the concentration of PAN, pH value, time of extraction, and sample volume were optimized. Under the optimized conditions, linear calibration curves were obtained. The precisions for the determination of each element, expressed as relative standard deviations (RSD) of standard solutions containing 0.20 mg L−1 of Cu, Cd, Pb, Cr, V, and Mn and calculated from ten consecutive measurements, were 1.6, 2.8, 2.8, 4.0, 1.5, and 4.5%, respectively. The proposed method allowed the determination of metals with detection limits of 0.012, 0.013, 0.016, 0.012, 0.009, and 0.011 mg L−1 for Cu, Cd, Pb, Cr, V, and Mn, respectively. The method was successfully applied to the extraction and determination of Cd, Pb, Cu, V, Cr, and Mn in ethanol fuel samples.

The present article describes the development of an ultrasonic assisted extraction of phenolic compounds in Physalis angulata and determination of caffeic acid, rutin, catechin and trans-cinnamic acid by HPLC DAD. The mixtures were composed of extractor solvent and its ratio optimized using a mixture design. Doehlert matrix was used to optimize the extractor solvent volume and sonication time while using total phenolics as analytical response. The optimized conditions for the extractor solvent were the ratio of: 57% water, 35% ethanol and 8% methanol. The best experimental conditions for ultrasound were a sonication time of 10 min and extractor volume of 15 mL. The limit of detection varied from 5.0 to 30 μg L−1. The methods precision was expressed as relative standard deviation (RSD) and presented values lower than 3.0% for all analytes. The accuracy was evaluated using spike test with recoveries between 91% and 107%. The method was applied for the determination of caffeic acid, rutin, catechin and trans-cinnamic in four samples of Physalis angulata aerial parts and the concentration varied from 15.5 to 22.5 μg g−1 for catechin, from 25.0 to 32.5 μg g−1 for caffeic acid, 75.6 to 88.2 μg g−1 for rutin and varied from 23.5 to 110.7 μg g−1 for trans-cinnamic acid.

In the present work, a method was developed, optimized, and validated for the determination of aluminum, manganese, lead, copper, cadmium, and zinc by microwave-induced plasma optical emission spectrometry of wine samples from the Sao Francisco Valley, northeastern Brazil. The samples were subjected to a sonochemical treatment aiming at the degradation of the sample matrix. To optimize the analytical procedure, initially, a two-level fractional factorial design was used to study five experimental variables and determine which ones significantly affected the analytical response. In a second step, the significant variables were optimized using the Doehlert matrix as the response surface methodology and the desirability function as a strategy to optimize multiple responses. The optimum conditions established were concentrations of nitric acid (2.3 mol L−1) and hydrogen peroxide (9%). The developed method is simple, fast, and precise, has a low operational cost and low limits of detection and quantification. The accuracy confirmed by spike tests with recoveries ranging from 104 to 118% and comparative analysis of the results obtained using the proposed method and digestion total procedure. The method was applied for multi-element determination in three wine samples.

A bamboo fiber mini-column impregnated with bathocuproine is proposed as an off-line pre-concentration system for determination of copper speciation in food samples using flame atomic absorption spectrometry (FAAS). Sampling flow rate, elution flow rate, pH and buffer concentration were evaluated for their importance in the solid-phase extraction using a 2 4 full factorial design and were all found to be significant. Afterward, a Doehlert matrix was used to optimize the pre-concentration process. The experimental conditions established with this design were: 8.0 mL min − 1 sampling flow rate, 10.0 mL min − 1 elution flow rate and 0.02 mol L − 1 buffer at pH 5.5. This system allowed the determination of copper with a limit of detection (LOD) of 0.5 μg L − 1 , a limit of quantification (LOQ) of 1.66 μg L − 1 and a precision expressed as relative standard deviation (RSD) of 2.70 and 2.79% for copper concentrations of 5.0 and 20 μg L − 1 , respectively. A pre-concentration factor of 33 was achieved using a 50.0-mL sample volume. The accuracy was confirmed by analysis of a certified reference material (NIST SRM 1573a Tomato Leaves). Spike/recovery tests were performed with results ranging from 93 to 100%. The developed method was applied to determine copper in corn flour, cassava root flour, oregano leaves and cumin. In addition, a speciation strategy was used for wine samples, in which free copper was evaluated in 40.00-mL aliquots of undigested samples and total copper assessed in samples digested before the pre-concentration step.

A dispersive liquid-liquid microextraction assisted by ultrasound (USADLLME) with 5-(4-Dimethylaminobenzylidene)Rhodanine procedure has been developed for preconcentration of cadmium in water and sediment samples by flame atomic absorption spectrometry (FAAS). The proportions of mixture composed of disperser, extractor solvents and complexing reagent was optimized using a constrained mixture design. The variables pH, concentration of NaCl and sonication time were optimized using a Doehlert matrix. The precision of method expressed as relative standard deviation (RSD) of 2.92 and 3.38% for 50 and 20 μg L − 1 , respectively, the detection limit was 0.23 μg L − 1 and the limit of quantification of 0.76 μg L − 1 . The accuracy was confirmed by the analysis of certified reference materials (Drinking Water Standard APS 1071, Fresh Water Sediment 3 RTC 016, Oyster Tissue NIST 1566b, Tomato Leaves NIST 1773a), the Spike test showed recoveries between 90 and 110%. The method was applied to river water, drinking water and sediment, the concentration of cadmium ranged from 1.46–4.60 μg L − 1 for water samples and from 0.90 to 1.23 μg g − 1 for sediment samples.

In this present work, an ultrasound-assisted extraction was developed and optimized to the extraction of bioactive phenolic compounds in leaves of Croton heliotropiifolius plants. A factorial design (24) was performed to screen the most significant variables. Subsequently, the Doehlert matrix was used to optimize the percentage of the solvent, extractor volume, temperature, and extraction time. Through HPLC DAD, phenolic compounds were determined in the samples of the C. heliotropiifolius extract, catechin, gallic acid, quercetin, vanillic acid, ellagic acid, trans-cinnamic acid, p-coumaric acid, syringic acid, acid ferulic and chlorogenic acid. The accuracy of the analytical method used was assessed, the results of the recovery ranged from 88 to 94%. The optimum conditions found were 11.4 mL of 37.5% v/v ethanol at a temperature of 54.8 °C for 39.5 min in an ultrasonic bath. The procedure developed for the extraction of bioactive compounds is efficient, fast, simple, and following the principles of green chemistry.

In the present work, a method based on the Ultrasound-dispersive liquid-liquid microextraction (US-DLLME) for the preconcentration of melatonin in Brazilian and Argentinian wine samples prior to the determination by reverse phase high performance liquid chromatography with diode array detector HPLC-DAD was developed. Sample prep optimization was carried out in two stages. First, a full factorial design was executed to evaluate the variables significance. The second step consisted of significant variables optimization (pH, extraction volume, sonication time, centrifugation time) using a Doehlert matrix to determine the critical values. Optimal US-DLLME extraction conditions were as follows: pH of 4.5, sonication time of 6.8 min, centrifugation time of 2.5 min, extractor volume of 250 µL and 5.0 mL of sample. The organic phase was retrieved with a microsyringe to a glass tube, dried and diluted with the mobile phase prior injection. The method presented a limit of detection (LOD) of 0.23 μg L-1 and a limit of quantification (LOQ) of 0.70 μg L-1. The precision expressed as relative standard deviation (R.S.D.) was 0.8 % and 1.9 % at 10.0 and 1.0 μg L-1, respectively. Accuracy was confirmed by comparison of the results found by the proposed methods with an alternative method, and spike tests with recuperations ranging from 92 to 103%. the analyzed samples showed concentrations varying from 2.2 to 5.0 μg L−1.

This study aimed to determine ellagic acid, vanillic acid, syringic acid, quercetin, and melatonin in samples of wines from Brazil, the São Francisco Valley region, and Argentina. The phenolic compounds and melatonin were determined by UPLC MS/MS. Quercetin was the compound found in major quantities in Argentine wines. In some bottles of Brazilian wines, vanillic acid and ellagic acid were found in higher bottles compared to Argentine wines. As for syringic acid, as selected filters in Brazilian wines, they were inferior in samples in Argentine wines. PCA and HCA were carried out to group the data obtained according to the region of origin of the wines. Fil: Carneiro, Candice N.. Universidade Federal do Recôncavo da Bahia; Brasil Fil: Gomez, Federico Jose Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Spisso, Adrián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Silva, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Azcarate, Silvana Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: De S. Dias, Fabio. Universidade Federal da Bahia; Brasil

A nanostructured immunosensor based on carbon nanotubes supported by a conductive polymer film was developed for detection of cardiac Troponin T (cTnT), an important cardiac marker for acute myocardial infarction. Carboxylated carbon nanotubes were covalently bound to the electrode surface via polyethyleneimine. The functionalized nanostructured surface was used to bind anti-cTnT monoclonal antibodies. Stepwise modification of the electrode was characterized by cyclic voltammetry studies. The immunosensor achieved a low limit of detection (0.033 ng mL − 1 ) and a linear range between 0.1 and 10 ng mL − 1 cTnT), significant for acute myocardial infarction diagnosis. Good reproducibility and repeatability were obtained by the proposed immunosensor supported by a coefficient of variation of 3.7% and 2.6%, respectively.

Texto completo. Acesso restrito. p. 363–367 Submitted by Santiago Fabio (fabio.ssantiago@hotmail.com) on 2013-07-10T18:43:09Z No. of bitstreams: 1 2222222222222222.pdf: 472268 bytes, checksum: 56f1bc38c1719aa0bf4579b0047cbb1a (MD5) Made available in DSpace on 2013-07-10T18:43:10Z (GMT). No. of bitstreams: 1 2222222222222222.pdf: 472268 bytes, checksum: 56f1bc38c1719aa0bf4579b0047cbb1a (MD5) Previous issue date: 2013 In the present work, a minicolumn of sisal fiber loaded with tiazolylazo-Resorsinol (TAR) is proposed a preconcentration system for cadmium determination in drinking water samples by flame atomic absorption spectrometry. In the optimizationwas first of all a full factorial design of two levels (24)was used for preliminary evaluation of four factors, involving the variables: sampling flow rate, elution flow rate, buffer concentration and pH. This design has showed that, for the studied levels, buffer concentration and pH are significant factors. Using the established experimental conditions in the optimization step of: pH 7.0, buffer concentration of 0.009 mol L−1 for elution utilized HCl at 2.0 mol L−1, this system allows the determination of cadmium with a detection limit (LD) (3σ/S) of 0.05 μg L−1 and a quantification limit (LQ) (10σ/S) of 0.17 μg L−1, precision expressed as a relative standard deviation (R.S.D.) of 2.9 and 3.4% for a cadmium concentration of 10.0 and 20.0 μg L−1, respectively, and a preconcentration factor of 30 for a sample volume of 50.0 mL. The accuracy was confirmed by cadmium with spike tests with recuperations varying from 92% to 103%, procedure was applied for cadmium determination in drinking water samples collected from Salvador City, Bahia, Brazil. From the five samples analyzed, the achieved concentrations varied from 0.10 to 0.54 μg L−1. Salvador

The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ions Pb(II) and Cd(II) biosorption from natural waters. The flame atomic absorption spectrometry was used for quantitative determination and study of the ions Pb(II) and Cd(II) adsorption on the solid phase. The Fourier transform infrared spectroscopy (FT IR) was used to investigate the sisal structure and the specific BET surface area was analyzed. The biosorption potential of sisal as biosorbent for the removal of the ions Pb(II) and Cd(II) from aqueous solution was investigate considering the followings parameters: pH, biomass amount and contact time. Langmuir and Freundlich isotherms were used to evaluate adsorption behavior of the ions on this solid phase. The results showed that sisal has a surface area to adsorption of 0.0233 m2 g− 1, and the OH and CO functional groups are the main involved in the biosorption. The best interpretation for the experimental data was given by Freundlich isotherm that proposes a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interactions between sorbed molecules. The maximum monolayer biosorption capacity was found to be 1.85 mg g− 1 for Cd (II) and 1.34 mg g− 1 for Pb (II) at pH 7 and 296 K. This phase solid can be used for biosorption of cadmium and lead in polluted natural waters.

The present paper describes a direct procedure for the determination of catechin and epicatechin concentrations in red wines employing reverse-phase high performance liquid chromatography (RP HPLC) and detection by fluorescence. The method was performed using a sample volume of 10 µL without dilution. The separation process employed a Chromolith performance RP-18e (100 mm × 4.6 mm) column, and the mobile phase was composed of solvent A: methanol–acetic acid–water (90:8:2) and solvent B: water–acetic acid–methanol (10:2:88) at a flow rate of 1.0 mL min − 1 . Linearity was observed in the range of 1 to 30 mg L − 1 , with limits of detection and quantification of 0.27 and 0.89 mg L − 1 , respectively, for catechin and 0.33 and 1.01 mg L − 1 , respectively, for epicatechin. The precisions estimated by the relative standard deviation were 3.34 and 1.09% for catechin concentrations of 0.5 and 20 mg L − 1 respectively and 2.82 and 0.49% for epicatechin concentrations of 0.5 and 20 mg L − 1 , respectively. The evaluation of the accuracy was done using an addition/recovery assay. Four wine samples were used, and the recoveries varied from 105 to 108% for catechin and from 97 to 119% for epicatechin. The method was applied to the analysis of red wine samples collected from the Sao Francisco region, Bahia State, Brazil. Nine samples were analyzed, and the catechin and epicatechin concentrations varied from 7.51 to 73.20 and from 5.08 to 43.32 mg L − 1 , respectively. The concentrations found agree with data reported in the literature.