Bruno M. Soares

Assessment of Modified Matrix Solid-Phase Dispersion as Sample Preparation for the Determination of CH3Hg+ and Hg2+ in Fish

This paper reports, for the first time, the development of an analytical method employing modified matrix solid-phase dispersion (MSPD) for the extraction of CH3Hg(+) and Hg(2+) species from fish samples. Separation and determination of mercury species were performed by gas chromatography coupled to mass spectrometry (GC/MS). Important MSPD parameters, such as sample mass, type and mass of solid support, concentration of extraction solution (HCl and NaCl), and stirring time, were investigated by the response surface methodology. The derivatization step and the separation of mercury species were also evaluated for the determination by GC/MS. Quantitative recoveries were obtained with 0.2 g of fish sample, 0.5 g of SiO2 as the solid support, 0.5 mol L(-1) NaCl and 4.2 mol L(-1) HCl as the extraction solution, and 1 min stirring time. The MSPD method showed to be suitable for the extraction and determination of mercury species in certified reference materials of dogfish liver (DOLT-3) and dogfish muscle (DORM-2). It had good agreement (about 99%) with the certified values, and the relative standard deviation was lower than 9.5%. The limits of detection were 0.06 and 0.12 μg g(-1), for CH3Hg(+) and Hg(2+), respectively. A matrix effect was observed, and the quantification was carried out by the matrix-matched calibration. The method was applied to tuna fish ( Thunnus thynnus ), angel shark ( Squatina squatina ), and guitarfish ( Rhinobatos percellens ) samples. The results of the mercury speciation by MPSD and GC/MS were compared to the total mercury concentration determined by flow injection cold vapor generation inductively coupled plasma mass spectrometry, after microwave-assisted digestion. Agreement ranged from 102% to 105%.

Investigation of major and trace element distribution in the extraction-transesterification process of fatty acid methyl esters from microalgae Chlorella sp.

This work reports, for the first time, the determination of major and trace elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Sn, Sr, Ti, Tl, U, V, and Zn) in the fractions of the synthesis of fatty acid methyl esters (FAMEs). These include fresh microalgae, residual biomass, lipid fraction, crude FAMEs, insoluble fraction and purified FAMEs from microalgae Chlorella sp. A microwave-assisted digestion procedure in closed vessels was applied for sample digestion and subsequent element determination by inductively coupled plasma-based techniques. The proposed method was suitable for the multielement determination in FAMEs and its fractions obtained from microalgae. The element concentration was compared with results found in the literature and a careful discussion about the use of residual biomass for different applications was performed.

Determination of cadmium and lead at sub-ppt level in soft drinks: An efficient combination between dispersive liquid-liquid microextraction and graphite furnace atomic absorption spectrometry

A DLLME method for extraction and preconcentration of Cd and Pb from soft drinks and further determination by GF AAS was developed. Important parameters of DLLME such as the type and volume of dispersive and extraction solvents, concentration of DDTC (complexing agent) and pH were evaluated. Better results were obtained using 500μL of acetone for Cd and 700μL of acetonitrile for Pb as dispersive solvents, 60μL of CCl4 as extraction solvent for both analytes and 500μL of 1.5% DDTC solution. Accuracy was evaluated by recovery assays and ranged from 91 to 113% for Cd and from 95 to 108% for Pb, with RSD below 10 and 7%, respectively. The LODs were 0.006 and 0.072ngL-1 for Cd and Pb, respectively. The optimized method was applied for the determination of Cd and Pb in soft drinks with different brands and flavours.

Quantification of pharmaceuticals and personal care product residues in surface and drinking water samples by SPE and LC-ESI-MS/MS

Currently, industrialized nations have faced a new problem, the contamination of water by emerging contaminants, such as pharmaceuticals and personal care products (PPCPs). A method based on solid-phase extraction (SPE) and liquid chromatography with electrospray ionization source tandem mass spectrometry was developed and validated for the determination of nimesulide, amitriptyline, enalapril, glibenclamide, haloperidol and methylparaben in water samples. In the study of SPE, a 2v5-1 fractional factorial design was used as a tool for the selection of the most significant variables in the extraction efficiency of the analytes under study. The limits of detection and quantification ranged from 0.01 to 0.2 µg L-1 and 0.05 to 1.0 µg L-1, respectively. Good linearity was obtained by a correlation coefficient (r) > 0.99 for all compounds. Recoveries ranged from 65 and 120% with relative standard deviation (RSD) lower than 20%. The method was applied to the determination of PPCPs in samples of surface and drinking water for three months. PPCPs were detected at µg L-1 levels.

Assessment of dispersive liquid–liquid microextraction for the simultaneous extraction, preconcentration, and derivatization of Hg2+ and CH3Hg+ for further determination by GC–MS

This work reports the development of a dispersive liquid-liquid microextraction method for the simultaneous extraction, preconcentration, and derivatization of Hg(2+) and CH3Hg(+) species from water samples for further determination by GC-MS. Some parameters of the proposed method, such as volume and type of disperser and extraction solvent, and Na[B(C6H5)4] concentration were investigated using response surface methodology. Suitable recoveries were obtained using 80 μL C2 Cl4 (as extraction solvent), 1000 μL ethanol (as disperser solvent), and 300 μL 2.1 mmol/L Na[B(C6H5)4] (as derivatizing agent). Accuracy was evaluated in terms of recovery and ranged from 87 to 99% with RSD values <7%. In addition, a certified reference material of water (NIST 1641d) was analyzed and agreed with the certified value about 107% (for Hg(2+)), with RSD values <8.5%. LODs were 0.3 and 0.2 μg/L, with enrichment factors of 112 and 115 for Hg(2+) and CH3Hg(+), respectively. The optimized method was applied for the determination of Hg(2+) and CH3Hg(+) in tap, well, and lake water samples.

Simultaneous determination of iron and nickel in fluoropolymers by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry.

This paper reports the development of a method of simultaneous determination of iron and nickel in fluoropolymers by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) with direct solid sampling. In order to carry out simultaneous measurements, both the main resonance line of nickel (232.003nm) and the adjacent secondary line of iron (232.036nm) were monitored in the same spectral window. The proposed method was optimized with a perfluoroalkoxy (PFA) sample and was applied to the determination of iron and nickel in fluorinated ethylene propylene (FEP) and modified polytetrafluoroethylene (PTFE-TFM) samples. Pyrolysis and atomization temperatures, as well as the use of Pd and H2 (during pyrolysis) as chemical modifiers, were carefully investigated. Compromise temperatures for pyrolysis and atomization of both analytes were achieved at 800 and 2300°C, respectively, using only 0.5Lmin(-1) H2 as chemical modifier during pyrolysis. Calibration curves were performed with aqueous standards by using a single solution which contained both analytes. Limits of detection were 221 and 9.6ngg(-1) for iron and nickel, respectively. Analyte concentrations in all samples ranged from 3.53 to 12.4µgg(-1) for iron and from 37 to 78ngg(-1) for nickel, with relative standard deviation less than 19%. Accuracy was evaluated by comparing these results with those obtained by inductively coupled plasma mass spectrometry after sample digestion by microwave-induced combustion and no significant statistical difference was observed.

Development of a dispersive liquid–liquid microextraction method for iron extraction and preconcentration in water samples with different salinities

A new, efficient, fast and simple method for iron determination in environmental water samples with different salinities by a dispersive liquid–liquid microextraction method, followed by UV-Vis spectrophotometric determination, was developed. In this study, Fe was complexed with ammonium pyrrolidinedithiocarbamate and extracted into 1,2-dichlorobenzene droplets after the injection of a mixture composed of 1,2-dichlorobenzene (extraction solvent) and ethanol (dispersive solvent) into the sample solution. Factors which affected the efficiency of Fe extraction and its subsequent spectrophotometric determination were studied and optimized. Under optimized conditions, the calibration curve was linear and ranged from 0.02 to 2.5 mg L−1 (r = 0.999). The limits of method detection and quantification were 6.1 and 18.3 μg L−1, respectively, with a preconcentration factor of 3.3. The accuracy evaluated in terms of recovery was between 90 and 100% with RSD lower than 12%. In addition, a certified reference material (SRM 1643e, Trace Elements in Water) was analyzed with agreement of 104% and RSD about 5%. The method was applied to total Fe determination in environmental water samples with different salinities and satisfactory results were obtained.

Assessment of inorganic contaminants in golden mussel (Limnoperna fortunei) in Southern Brazil

Major and trace element content was determined in golden mussel (Limnoperna fortunei) collected in the Sao Goncalo Channel (Rio Grande City, Brazil). A microwave-assisted digestion procedure in closed vessels was applied to mussel decomposition and subsequent determination of elements by spectrometric techniques. Results showed that the mussel tissue contains Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn, Mo, P, Pb, S, Sn, Sr, Ti, V and Zn, while the same elements (except Ag and Hg) were quantified in its shell, demonstrating its potential as a biomarker. In this sense, these results can be used to establish an initial view and to contribute to further studies related to element contamination in the area under study.

Simple and fast method for iron determination in white and red wines using dispersive liquid-liquid microextraction and ultraviolet-visible spectrophotometry.

This work reports the development of a method for Fe extraction in white and red wines using dispersive liquid-liquid microextraction (DLLME) and determination by ultraviolet-visible spectrophotometry. For optimization of the DLLME method, the following parameters were evaluated: type and volume of dispersive (1300 μL of acetonitrile) and extraction (80 μL of C(2)Cl(4)) solvents, pH (3.0), concentration of ammonium pyrrolidinedithiocarbamate (APDC, 500 μL of 1% m/v APDC solution), NaCl concentration (not added), and extraction time. The calibration curve was performed using the analyte addition method, and the limit of detection and relative standard deviation were 0.2 mg L(-1) and below 7%, respectively. The accuracy was evaluated by comparison of results obtained after Fe determination by graphite furnace atomic absorption spectrometry, with agreement ranging from 94 to 105%. The proposed method was applied for Fe determination in white and red wines with concentrations ranging from 1.3 to 4.7 mg L(-1).

A vortex-assisted MSPD method for triclosan extraction from fish tissues with determination by LC-MS/MS

In this study, a simple, rapid and sensitive analytical method for the detection of TCS from Poecilia vivipara tissues (muscle, gills, brain, liver, gonads and whole fish) was developed. A matrix solid phase dispersion (MSPD) extraction method followed by analysis with a liquid chromatography tandem mass spectrometry (LC-MS/MS) system was developed and the multivariate statistical approach (experimental design) was applied to optimize the extraction conditions. The results showed that the method is accurate, robust and highly reproducible, since high recoveries were achieved. The analytical method showed high extraction yields for the determination of this compound in a complex matrix such as tissue. Moreover, the extraction procedure is very fast and it is possible to perform on a small sample aliquot. Besides, extraction and cleanup are performed in a single step. The LOQ value in fish tissue was 0.083 μg g−1 and the LOD was 0.016 μg g−1. The RSDs for repeatability and intermediate precision studies were in the range of 1.1 to 8.9% and from 0.2% to 8.9%, respectively. Adequate linearity with correlation coefficients (r) higher than 0.99 was obtained for the range of 0.005 to 0.25 mg L−1. Quantitative recoveries (≥80%) and satisfactory precision (average 9%) were obtained. The application of the vortex-assisted MSPD method to the analysis of real samples shows TCS in some fish liver and fish gill samples at trace levels.