Matheus A.G. Nunes

Review of the applications of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to the analysis of biological samples

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has received significant attention over the last 10 years and has been widely used for the analysis of biological samples. The technique allows the determination of elements and isotopes in biological tissues and related materials with a spatial resolution typically ranging from 10 to 100 μm. When compared to other techniques usually employed to obtain bioimages, the greater advantage of LA-ICP-MS is its higher sensitivity. The literature survey over the last 10 years concerning the use of LA-ICP-MS for biological tissue analysis is reviewed in this article. Instrumentation, strategies of calibration for quantitative analysis, challenges and recent advances in this field are discussed. Applications of the isotope ratio (IR), including tracer experiments, and isotope dilution (ID), are reviewed for biological samples (briefly for proteins, in order to show the utility of LA-ICP-MS). Bioimaging methods, studies and applications for animal and plants tissues are emphasized, demonstrating the importance of bioimaging of metals and metalloids in biomedical research, bioaccumulation and bioavailability studies for ecological and toxicological risk assessment in humans, animals and plants. The usefulness of the IR associated with bioimaging for predicting geographical origin, habitat, movement of subjects, diet and lifestyle are also demonstrated.

Ultrasound-assisted oxidative process for sulfur removal from petroleum product feedstock

A procedure using ultrasonic irradiation is proposed for sulfur removal of a petroleum product feedstock. The procedure involves the combination of a peroxyacid and ultrasound-assisted treatment in order to comply with the required sulfur content recommended by the current regulations for fuels. The ultrasound-assisted oxidative desulfurization (UAOD) process was applied to a petroleum product feedstock using dibenzothiophene as a model sulfur compound. The influence of ultrasonic irradiation time, oxidizing reagents amount, kind of solvent for the extraction step and kind of organic acid were investigated. The use of ultrasonic irradiation allowed higher efficiency for sulfur removal in comparison to experiments performed without its application, under the same reactional conditions. Using the optimized conditions for UAOD, the sulfur removal was about 95% after 9min of ultrasonic irradiation (20kHz, 750W, run at 40%), using hydrogen peroxide and acetic acid, followed by extraction with methanol.

Determination of toxic elements in coal by ICP-MS after digestion using microwave-induced combustion.

A microwave-induced combustion (MIC) procedure was applied for coal digestion for subsequent determination of As, Cd and Pb by inductively coupled plasma mass spectrometry (ICP-MS) and Hg using cold vapor (CV) generation coupled to ICP-MS. Pellets of coal (500 mg) were combusted using 20 bar of oxygen and ammonium nitrate as aid for ignition. The use of nitric acid as absorbing solution (1.7, 3.5, 5.0, 7.0 and 14 mol L(-1)) was evaluated. For coal samples with higher ash content, better results were found using 7.0 mol L(-1) HNO(3) and an additional reflux step of 5 min after combustion step. For coal samples with ash content lower than 8%, 5.0 mol L(-1) nitric acid was suitable to the absorption of all analytes. Accuracy was evaluated using certified reference material (CRM) of coal and spikes. Agreement with certified values and recoveries was better than 95 and 97%, respectively, for all the analytes. For comparison of results, a procedure recommended by the American Society of Testing and Materials (ASTM) was used. Additionally, a conventional microwave-assisted digestion (MAD) in pressurized vessels was also performed. Using ASTM procedure, analyte losses were observed and a relatively long time was necessary for digestion (>6h). By comparison with MAD procedure, higher sample mass can be digested using MIC allowing better limits of detection. Additionally, the use of concentrated acids was not necessary that is an important aspect in order to obtain low blank levels and lower limits of detection, respectively. The residual carbon content in digests obtained by MAD and MIC was about 15% and <1%, respectively, showing the better digestion efficiency of MIC procedure. Using MIC it was possible to digest completely and simultaneously up to eight samples in only 25 min with relatively lower generation of laboratory effluents.

Quercetin protects the impairment of memory and anxiogenic-like behavior in rats exposed to cadmium: Possible involvement of the acetylcholinesterase and Na+,K+-ATPase activities

The present study investigated the effects of quercetin in the impairment of memory and anxiogenic-like behavior induced by cadmium (Cd) exposure. We also investigated possible alterations in acetylcholinesterase (AChE), Na(+),K(+)-ATPase and δ-aminolevulinate dehydratase (δ-ALA-D) activities as well as in oxidative stress parameters in the CNS. Rats were exposed to Cd (2.5mg/kg) and quercetin (5, 25 or 50mg/kg) by gavage for 45days. Animals were divided into eight groups (n=10-14): saline/control, saline/Querc 5mg/kg, saline/Querc 25mg/kg, saline/Querc 50mg/kg, Cd/ethanol, Cd/Querc 5mg/kg, Cd/Querc 25mg/kg and Cd/Querc 50mg/kg. Results demonstrated that Cd impaired memory has an anxiogenic effect. Quercetin prevented these harmful effects induced by Cd. AChE activity decreased in the cerebral cortex and hippocampus and increased in the hypothalamus of Cd-exposed rats. The Na(+),K(+)-ATPase activity decreased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin prevented these effects in AChE and Na(+),K(+)-ATPase activities. Reactive oxygen species production, thiobarbituric acid reactive substance levels, protein carbonyl content and double-stranded DNA fractions increased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin totally or partially prevents these effects caused by Cd. Total thiols (T-SHs), reduced glutathione (GSH), and reductase glutathione (GR) activities decreased and glutathione S-transferase (GST) activity increased in Cd exposed rats. Co-treatment with quercetin prevented reduction in T-SH, GSH, and GR activities and the rise of GST activity. The present findings show that quercetin prevents alterations in oxidative stress parameters as well as AChE and Na(+),K(+)-ATPase activities, consequently preventing memory impairment and anxiogenic-like behavior displayed by Cd exposure. These results may contribute to a better understanding of the neuroprotective role of quercetin, emphasizing the influence of this flavonoid in the diet for human health, possibly preventing brain injury associated with Cd intoxication.

Determination of metal impurities in carbon nanotubes by direct solid sampling electrothermal atomic absorption spectrometry

A determinacao de Al, Cd, Co, Cr, Cu, Mg, Mn e Pb em nanotubos de carbono (CNTs) foi realizada por espectrometria de absorcao atomica com atomizacao eletrotermica e amostragem direta de solidos (DSS-ET AAS, corretor de fundo com fonte de deuterio). Foram avaliados os parâmetros de aquecimento, uso de Pd como modificador quimico, possibilidade de calibracao com solucoes aquosas e massa maxima de amostra. Para comparacao dos resultados as amostras foram analisadas por espectrometria de massa com plasma indutivamente acoplado (ICP-MS) e espectrometria de emissao optica com plasma indutivamente acoplado (ICP OES) apos decomposicao por via umida em sistema de alta pressao assistida por micro-ondas e tambem por combustao iniciada por micro-ondas. Nao foram observadas diferencas significativas entre os resultados obtidos pelo metodo proposto e pelas outras tecnicas. A exatidao tambem foi avaliada por comparacao com resultados de analise por ativacao neutronica (NAA). A calibracao foi possivel com solucoes de referencia aquosas. Os sinais de fundo foram sempre inferiores a 0,02 (altura de pico) e o uso de modificador quimico nao foi necessario. O metodo proposto possibilitou a determinacao de todos os analitos, com menores limites de deteccao quando comparados com as outras tecnicas.

Imazethapyr and imazapic, bispyribac-sodium and penoxsulam: zooplankton and dissipation in subtropical rice paddy water.

Herbicides are very effective at eliminating weed and are largely used in rice paddy around the world, playing a fundamental role in maximizing yield. Therefore, considering the flooded environment of rice paddies, it is necessary to understand the side effects on non-target species. Field experiment studies were carried out during two rice growing seasons in order to address how the commonly-used herbicides imazethapyr and imazapic, bispyribac-sodium and penoxsulam, used at recommended dosage, affect water quality and the non-target zooplankton community using outdoor rice field microcosm set-up. The shortest (4.9 days) and longest (12.2 days) herbicide half-life mean, estimated of the dissipation rate (k) is shown for imazethapyr and bispyribac-sodium, respectively. Some water quality parameters (pH, conductivity, hardness, BOD5, boron, potassium, magnesium, phosphorus and chlorides) achieved slightly higher values at the herbicide treatment. Zooplankton community usually quickly recovered from the tested herbicide impact. Generally, herbicides led to an increase of cladocera, copepods and nauplius population, while rotifer population decreased, with recovery at the end of the experiment (88 days after herbicide treatment).

Fast TiO2-catalyzed direct amidation of neat carboxylic acids under mild dielectric heating

The development of green protocols for amide bond formation is a major socioeconomic goal for chemical and pharmaceutical industries and an important challenge for academic research. We herein report a protocol for the quantitative conversion of carboxylic acids and amines to form amides at 100 °C in the presence of a TiO2 powder catalyst, under monomodal microwave irradiation. The sustainability of the process appears to be augmented by the ease with which the catalyst is recycled.

A new approach to calibration and determination of selected trace elements in food contact polymers by LA-ICP-MS

A calibration strategy using porous nylon disks and reference solutions is proposed for the first time for matrix matching and determination of As, Ba, Cd, Cr, Pb, Sr and Zn in polymers by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Polymer samples commonly used in contact with food were analyzed. The procedure consists on the use of porous nylon disks as support for a dried droplet reference solution. Calibration in the range of 0.50-190μgg-1 for Ba, Cd, Cr, Pb, Sr and Zn and from 0.30-9.0μgg-1 for As was used. Laser and ICP-MS instrument conditions were evaluated in order to achieve the best signal-to-background ratio. The radiofrequency power and carrier gas flow rate were fixed at 1300W and 1.25Lmin-1, respectively. Spot size, repetition rate, scan line speed and laser fluency were set to 100µm, 20Hz, 100µms-1 and 17.9Jcm-2, respectively, as the established conditions for analysis of standards and samples. By using these conditions, limits of detection, estimated considering B+3s (where B is the value of the blank and s is the standard deviation of 10 measurements of the blank), ranged from 0.09μgg-1 (208Pb) to 1.09 (53Cr) and 0.05μgg-1 (208Pb) to 2.10 (53Cr) for calibration with and without 13C as internal standard (IS). In spite to the use of nylon for matrix matching of different polymeric matrices, the normalization with 13C as IS was also evaluated. The precision of the method is relatively good (RSD<20%), and the accuracy of the method, evaluated by analysis of certified reference materials (CRM) and by comparison with results obtained from solution analysis by ICP-MS after sample decomposition by microwave induced combustion (MIC) is relatively good. The suitability of the proposed method resulted in direct and reliable analyses of polymer samples with a simplified or unnecessary sample preparation step. In addition, the calibration with dried droplet reference solutions may be considered a promising procedure in view of its advantages to other forms of calibration, as the use of CRM or the preparation of synthetic standards. The use of porous nylon disks spiked with reference solutions for calibration is the main advantage of the present work.

Delta-aminolevulinate dehydratase activity in red blood cells of rats infected with Trypanosoma evansi

The aim of this study was to evaluate the activity of delta-aminolevulinate dehydratase (δ-ALA-D) in red blood cells of rats infected with Trypanosoma evansi and establish its association with haematocrit, serum levels of iron and zinc and lipid peroxidation. Thirty-six male rats (Wistar) were divided into 2 groups with 18 animals each. Group A was non-infected while Group B was intraperitoneally infected, receiving 7·5×106 trypomastigotes per animal. Each group was divided into 3 subgroups of 6 rats and blood was collected during different periods post-infection (p.i.) as follows: day 5 (A1 and B1), day 15 (A2 and B2) and day 30 PI (A3 and B3). Blood samples were collected by cardiac puncture to estimate red blood cell parameters (RBC), δ-ALA-D activity and serum levels of iron, zinc and thiobarbituric acid reactive substances (TBARS). Rats in group B showed a significant (P<0·05) reduction of RBC count, haemoglobin concentration and haematocrit at days 5 and 15 p.i. The activity of δ-ALA-D in blood was significantly (P<0·001) increased at days 15 and 30 p.i. δ-ALA-D activity in blood had a significant (P<0·05) negative correlation with haematocrit (r=-0·61) and haemoglobin (r=-0·70) at day 15 p.i. There was a significant (P<0·05) decrease in serum iron and zinc levels and an increase in TBARS levels (P<0·05) during infection. The δ-ALA-D activity in blood was negatively correlated with the levels of iron (r=-0·68) and zinc (r=-0·57) on day 30 p.i. It was concluded that the increased activity of δ-ALA-D in blood might have occurred in response to the anaemia in remission as heme synthesis was enhanced.

Characterization of three main degradation products from novel oral anticoagulant rivaroxaban under stress conditions by UPLC-Q-TOF-MS/MS

Drugs of long-term use may cause the accumulation of chemical compounds in human body. Therefore, the evaluation and structure characterization of synthesis and degradation impurities is substantial to guarantee drug safety and successful pharmaceutical therapy. The present work evaluated the anticoagulant rivaroxabana (RIV) under stress conditions in order to elucidate the chemical structure of major degradation products (DPs) formed after drug exposition to acid and alkaline hydrolysis, and UVC radiation. Analyses were performed in UPLC coupled to quadrupole time-of-flight MS. ESI was applied in positive mode, and C18 Agilent(®) column (2.1×50 mm, 1.8 μm) used for separation of compounds. RIV molecular íon [M+H](+) (m/z 436.07) was fragmented under 20 kV, best energetic condition to obtain clear and reproducible fragmentation pattern, assisting identification of RIV DPs. With support from UPLC separation and specific detection by MS/MS, three main degradation products (DP-1, DP-2, and DP-3) formed under stress conditions were successfully characterized. Presented study agrees with requirements for analytical assessment of impurities in pharmaceutical formulations, ensuring quality of pharmaceutical substances.