Aline R. Borges

Determination of Cd and Cr in tannin samples by high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample sequential analysis (HR-CS SS-GF AAS)

A fast and reliable analytical method for the sequential determination of Cd and Cr in tannin samples by high-resolution continuum source graphite furnace atomic absorption spectrometry with direct solid sampling from the same sample aliquot (HR-CS SS-GF AAS) is proposed. A pyrolysis temperature of 400 °C and atomisation temperature of 1500 °C were used for the determination of Cd; no losses of Cr were observed at these temperatures. After the atomisation of Cd, the wavelength was changed and Cr was atomised at 2500 °C. Several studies with different modifiers were performed, but no chemical modifier was needed. Calibration was achieved using aqueous standards. The linearity of the response, performed by evaluating the absorbance value relative to the sample mass, was investigated as well. Relative standard deviation (RSD) values lower than 15% were found, which are acceptable for direct analysis. The parameters of merit were: a characteristic mass of 0.3 pg and 2.2 pg for Cd and Cr, respectively; the limit of detection (LOD) of 0.5 μg kg−1 and 17 μg kg−1 for Cd and Cr, respectively; the limit of quantification (LOQ) of 2 μg kg−1 and 57 μg kg−1 for Cd and Cr, respectively. The accuracy was validated by analysing three certified reference materials (tea, pine needles and bush branches). The results were not statistically different from the certified values at a 95% confidence level. Therefore, calibration using aqueous standards is suitable for this application. This method is simple, fast and suitable for routine analysis.

Determination of lead in biomass and products of the pyrolysis process by direct solid or liquid sample analysis using HR-CS GF AAS

A method has been developed for the determination of lead in biomass, bio-oil, pyrolysis aqueous phase, and biomass ashes by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) and direct solid or liquid sample analysis. All measurements were performed without chemical modifier and calibration could be carried out using aqueous standard solutions. A pyrolysis temperature of 800°C and an atomization temperature of 2200°C were applied. The limits of detection and quantification were, respectively, 0.5 µg kg(-1) and 2 µg kg(-1) using the analytical line at 217.001 nm and 6 µg kg(-1) and 19 µg kg(-1) at 283.306 nm. The precision, expressed as relative standard deviation, was between 3% and 10%, which is suitable for direct analysis. The lead concentrations found for the solid samples varied between 0.28 and 1.4 mg kg(-1) for biomass and between 0.25 and 2.3 mg kg(-1) for ashes, these values were much higher than those found for bio-oil (2.2-16.8 µg kg(-1)) and pyrolysis aqueous phase (3.2-18.5 µg kg(-1)). After the determination of lead in the samples, it was possible to estimate the relative distribution of this element in the fractions of the pyrolysis products, and it was observed that most of the lead present in the biomass was eliminated to the environment during the pyrolysis process, with a significant portion retained in the ashes.

Simultaneous determination of Mo and Ni in wine and soil amendments by HR-CS GF AAS

The use of high-resolution continuum-source graphite furnace atomic absorption spectrometry (HR-CS GF AAS), equipped with a linear charge-coupled device (CCD) array detector, makes simultaneous determination of more than one element possible. In this work, HR-CS GF AAS was used for the simultaneous determination of Mo (313.259 nm) and Ni (313.410 nm), for which two analytical methods were developed: direct solid sample analysis for soil amendments and direct sample injection for wine samples. For both these methods, a pyrolysis temperature of 1200 °C and an atomization temperature of 2650 °C were used. Aqueous standard solutions were used for calibration. The linear correlation coefficient was higher than 0.997 for the two analytes. Detection limits of 0.05 and 0.8 μg L−1 for wine samples and 0.04 and 0.60 mg kg−1 for soil amendments were found for Mo and Ni, respectively. To investigate the accuracy of the developed method, digested and undigested wine samples were evaluated with spike recovery values between 94% and 106%. For solid samples, three CRM were evaluated, and the values found for Mo were not significantly different from the certified ones; however, those for Ni were always too high. It was found that this was due to a direct line overlap of the Ni line with the Fe line. This effect was overcome by determining Fe using the unresolved analytical line doublet at 312.565/312.568 nm and subtracting this value from the total concentration (Ni + Fe) determined at 313.410 nm. Note that this interference was not observed in wine samples because of their low Fe concentration.

Determination of cadmium and lead in fresh meat by slurry sampling graphite furnace atomic absorption spectrometry

In this work a method for cadmium and lead determination in fresh meat based on slurry sampling graphite furnace atomic absorption spectrometry is proposed. The fresh meat samples were weighed directly into the autosampler cups of the spectrometer using a microbalance and the slurry was prepared using tetramethylammonium hydroxide (TMAH). The use of the response surface method for optimizing the slurry preparation has shown that it was possible to find the optimum zone in the experimental field of the variables under study. Calibration was performed against aqueous standards and a mixture of 0.05% v/v Pd + 0.03% v/v Mg + 0.05% v/v Triton X-100 was used as a modifier. The results obtained for cadmium and lead in two certified reference materials were statistically not different from the certified values on a 95% confidence level, indicating that calibration against aqueous standards is suitable for this application. A comparison of the results obtained by slurry sampling with the digestion method adopted by the Brazilian Ministry of Agriculture showed no significant differences between the results at the 95% confidence level. The positive results obtained in this work suggest that the application of this procedure in other element determinations is worthy of exploration.

Determination of cadmium, chromium and copper in vegetables of the Solanaceae family using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Three methods have been developed for the determination of cadmium, chromium and copper in vegetables of the Solanaceae family, such as bell pepper, physalis, eggplant, potato, tomato and red pepper, cultivated in conventional and organic farming systems. The samples were lyophilized, milled and the particle size was controlled using a 200 μm polyester sieve. The determination was established using a high-resolution continuum source graphite furnace atomic absorption spectrometer and direct solid sample analysis. The analytical lines at 228.802 nm, 357.869 nm and 327.396 nm were used for Cd, Cr and Cu, respectively. Pyrolysis and atomization temperatures were optimized for all target elements. The calibration curves were obtained with aqueous standard solutions. The characteristic masses obtained were 0.42 pg, 2.7 pg and 19 pg for Cd, Cr and Cu, respectively. The trueness of the methods was confirmed by the analysis of certified reference materials. The concentrations in the vegetables were between 0.78–300 μg kg−1 for Cd, 0.063–1.05 μg g−1 for Cr and 4.5–18.4 μg g−1 for Cu. Some samples presented analyte concentrations above the maximum permitted by legislation. The proposed methods were accurate, simple, fast and sensitive; only a minimum sample preparation was necessary, reducing considerably the sample manipulation and/or dilution.

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30 µg L−1 and 2.6 µg L−1, respectively. A precision expressed as relative standard deviation (RSD, n = 10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10 µg L−1 and 30 µg L−1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10 µg L−1 and 30 µg L−1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.

Transformation of Tributyltin in Zebrafish Eleutheroembryos (Danio rerio)

Organotin compounds are highly versatile group of organometallic chemicals used in industrial and agricultural applications. Their endocrine-disrupting effects are well known and their extensive uses as biocide materials, e.g., in antifouling paints, for many years have led to serious environmental problems. So far, attention has mainly been given to tributyltin pollution in water, sediments, and marine organisms because of its highly toxic effects and high accumulation levels at very low concentrations. In this study, we will focus on the conversion of tributyltin after it is absorbed by zebrafish eleutheroembryos, presented here as an alternative model to adult fish for describing bioconcentration. A simplified analytical extraction procedure based on the use of an assisted ultrasonic probe and derivatization by ethylation, followed by gas chromatography with a flame photometric detector (GC-FPD) is proposed. This classical methodology for organotin determination has been validated by inductively coupled plasma mass spectrometry (ICP-MS) and Zeeman graphite furnace atomic absorption spectrometry (ZGF-AAS) in terms of total tin content. The speciation analysis results show that zebrafish eleutheroembryos absorb high amounts of tributyltin and convert it into monobutyltin and likely in inorganic tin.

GEOCHEMICAL CORRELATIONS BETWEEN PETROLEUM SAMPLES FROM THE POTIGUAR BASIN AND DEFINITION OF THEIR POSSIBLE GENERATING ROCKS

Jeferson Cavalcante Alvesa, Rennan Geovanny Oliveira Araujoa,b,*,#, Eliane Soares de Souzac, Sarah Adriana Rocha Soaresa, José Roberto Cerqueiraa, Karina Santos Garciaa, Antonio Fernando de Souza Queiroza, Maria Goreti Rodrigues Valed e Aline Rocha Borgese Núcleo de Estudos Ambientais, Instituto de Geociências, Universidade Federal da Bahia, Campus de Ondina, Rua Barão de Jeremoabo, s/n – Ondina, 40170-110 Salvador – BA, Brasil Departamento de Química Analítica, Instituto de Química, Universidade Federal da Bahia, Campus Ondina, Rua Barão de Jeremoabo, 147 – Ondina, 40170-115 Salvador – BA, Brasil Laboratório de Engenharia e Exploração de Petróleo, Centro de Ciências e Tecnologia, Universidade Estadual do Norte Fluminense, Rodovia Amaral Peixoto Km 163, Avenida Brennand s/n – Imboacica, 27925-310 Macaé – RJ, Brasil Instituto de Química, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 91501-790 Porto Alegre – RS, Brasil Instituto Federal do Paraná, Campus Palmas, 85555-000, Palmas – PR, Brasil

False-positive results in screening for metallo-β-lactamase are observed in isolates of Acinetobacter baumannii due to production of oxacilinases

Carbapenemases production, either metallo-lactamases (MBLs), KPC or oxacillinases (OXA), is the main resistance mechanism responsible for resistance phenotype to carbapenems in Acinetobacter.1 While for MBLs and KPCs there are some screening tests for their detection,2,3 the same is not true for oxacillinases. During the investigation of a large outbreak, we analyzed 584 carbapenem-resistant Acinetobacter spp. isolates from seven hospitals. Isolates were identified using the API 20NE system (Biomerieux, Basingstoke, United Kingdom). PCR for the blaOXA-51 gene was performed as a marker of Acinetobacter baumannii at species level.1 The MIC for imipenem was performed by Etest® (AB BIODISK, Solna, Sweden) and was ≥8 g/mL in all isolates. A total of 562 (96.3%) and 553 (95%) isolates proved to be OXA-51 and OXA-23 producers respectively, by a multiplex PCR, which included primers for the blaOXA-23-like, blaOXA-24-like, blaOXA-51, blaOXA-58, blaOXA-143 genes. 4 Among the 553 OXA-23-like A. baumannii producing isolates, we observed 86 (15.5%) positive isolates in the screening test for MBLs either by the disk-approximation test using a ceftazidime (CAZ) and a 2-mercaptopropionic acid (MPA) or by the Etest MBL (Imipenem/Imipenem + EDTA − AB BIODISK, Solna, Sweden).2,5 The modified Hodge Test was performed in these isolates and only nine (1.5%) were positive.6 PCR using blaIMP-1-like, blaVIM-2-like blaSPM-1, blaNDM-1, blaKPC-1,2 primers 2–4,7