Fabiane G. Antes

N-acetylcysteine prevents memory deficits, the decrease in acetylcholinesterase activity and oxidative stress in rats exposed to cadmium

The present study investigated the effect of the administration of N-acetylcysteine (NAC), on memory, on acetylcholinesterase (AChE) activity and on lipid peroxidation in different brain structures in cadmium (Cd)-exposed rats. The rats received Cd (2 mg/kg) and NAC (150 mg/kg) by gavage every other day for 30 days. The animals were divided into four groups (n=12-13): control/saline, NAC, Cd, and Cd/NAC. The results showed a decrease in step-down latency in the Cd-group, but NAC reversed the impairment of memory induced by Cd intoxication. Rats exposed to Cd and/or treated with NAC did not demonstrate altered shock sensitivity. Decreased AChE activity was found in hippocampus, cerebellum and hypothalamus in the Cd-group but NAC reversed this effect totally or partially while in cortex synaptosomes and striatum there was no alteration in AChE activity. An increase in TBARS levels was found in hippocampus, cerebellum and hypothalamus in the Cd-group and NAC abolished this effect while in striatum there was no alteration in TBARS levels. Urea and creatinine levels were increased in serum of Cd-intoxicated rats, but NAC was able to abolish these undesirable effects. The present findings show that treatment with NAC prevented the Cd-mediated decrease in AChE activity, as well as oxidative stress and consequent memory impairment in Cd-exposed rats, demonstrating that this compound may modulate cholinergic neurotransmission and consequently improve cognition. However, it is necessary to note that the mild renal failure may be a contributor to the behavioral impairment found in this investigation.

Cadmium and mineral nutrient accumulation in potato plantlets grown under cadmium stress in two different experimental culture conditions

In order to evaluate the effect of cadmium (Cd(2+)) toxicity on mineral nutrient accumulation in potato (Solanum tuberosum L.), two cultivars named Asterix and Macaca were cultivated both in vitro and in hydroponic experiments under increasing levels of Cd(2+) (0, 100, 200, 300, 400 and 500 microM in vitro and 0, 50, 100, 150 and 200 microM in hydroponic culture). At 22 and 7 days of exposure to Cd(2+), for the in vitro and hydroponic experiment, respectively, the plantlets were separated into roots and shoot, which were analyzed for biomass as well as Cd(2+), and macro (Ca(2+), K(+) and Mg(2+)) and micronutrient (Cu(2+), Fe(2+), Mn(2+) and Zn(2+)) contents. In the hydroponic experiment, there was no reduction in shoot and root dry weight for any Cd(2+) level, regardless of the potato cultivar. In contrast, in the in vitro experiment, there was an increase in biomass at low Cd(2+) levels, while higher Cd(2+) levels caused a decrease. In general, Cd(2+) decreased the macronutrient and micronutrient contents in the in vitro cultured plantlets in both roots and shoot of cultivars. In contrast, the macronutrient and micronutrient contents in the hydroponically grown plantlets were generally not affected by Cd(2+). Our data suggest that the influence of Cd(2+) on nutrient content in potato was related to the level of Cd(2+) in the substrate, potato cultivar, plant organ, essential element, growth medium and exposure time.

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.

Microwave-induced combustion of carbon nanotubes for further halogen determination

A procedure for single and multi-walled carbon nanotubes digestion by microwave-induced combustion (MIC) is proposed for the first time for further halogens (Cl, Br and I) determination by inductively coupled plasma mass spectrometry (ICPMS) and ion chromatography (F, C, Br and I). Samples of carbon nanotubes (up to 500 mg) were pressed as pellets and combusted using 20 bar of oxygen and 50 μl of 6 mol l−1 of ammonium nitrate as igniter. The following absorbing solutions were evaluated: H2O, (NH4)2CO3, NH4OH, tetramethylammonium hydroxide (TMAH) and water-soluble tertiary amines (CFA-C). A reflux step was applied after combustion (5 min of microwave irradiation at 1400 W) in order to achieve better analyte recoveries. For Cl determination by ICPMS, a dynamic reaction cell was used with ammonia as reaction gas. The accuracy was evaluated using certified reference materials (CRM) of coal, spiked samples and also by comparison of results with neutron activation analysis. In spite of 1% (v/v) of TMAH or CFA-C being used as absorbing solution, 100 mmol l−1 NH4OH was preferred in view of lower blank values and quantitative recoveries (better than 97%). Agreement with CRM values for NIST 1632b, NIST 1632c and SARM 19 was higher than 96% for Cl and Br (ICPMS) and for F (IC). The limit of detection (LOD, 3σ) for Cl, Br and I obtained by ICPMS was 1.3, 0.02 and 0.002 μg g−1, respectively. The LOD for F, Cl, Br and I determined by IC was 0.3, 1.1, 2.4 and 4.2 μg g−1, respectively. The residual carbon content for MIC digests was always below 1%. As an advantage over conventional procedures, using MIC it was possible to digest up to eight samples in only 25 min, obtaining a single solution suitable for determination of all halogens by different techniques. According to the authors’ knowledge this is the first application for halogen determination in this kind of material.

Determination of toxic elements in tricyclic active pharmaceutical ingredients by ICP-MS: a critical study of digestion methods

The determination of As, Cd, Hg and Pb in tricyclic active pharmaceutical ingredients (APIs) was performed by ICP-MS after digestion by both combustion and wet digestion methods. Carbamazepine was digested using the dry ashing method recommended in United States Pharmacopeia 35th edition and significant losses of analytes were observed in recovery tests (38.0 ± 8.9, 99.5 ± 7.1, and 89.4 ± 6.3% of recovery for As, Cd and Pb, respectively). Mercury was completely lost by volatilization during digestion. The digestion of carbamazepine, amitriptyline hydrochloride and imipramine hydrochloride by microwave-assisted wet digestion in closed vessels (MW-AD) was not effective and a yellow-orange solid residue was observed for all substances. 1H NMR of the carbamazepine residue indicated the nitration of carbamazepine aromatic rings forming stable nitro compounds. High pressure asher digestion systems were also used and solid residues were observed for carbamazepine and amitriptyline hydrochloride even under drastic digestion conditions (280 °C, 120 min). A complete digestion of all substances was obtained only by the use of high temperature and long time of digestion and reduction of sample mass to 0.08 g (320 °C, 180 min). The microwave-induced combustion (MIC) method for digestion of tricyclic APIs allowed the digestion of 0.5 g of all substances with high efficiency (RCC lower than 1%) using diluted nitric acid as absorbing solution (7 mol l−1). The recoveries using this method were between 94 and 103% for the evaluated elements. The low RCC and acidity of digests obtained using MIC allowed the compatibility with ICP-MS and makes MIC a promising alternative as a sample preparation method for subsequent determination of toxic elements in APIs by ICP-MS.

Speciation and degradation of triphenyltin in typical paddy fields and its uptake into rice plants.

Triphenyltin (TPhT) is a biocide used worldwide in agriculture, especially in rice crop farming. The distribution and dissipation of TPhT in rice fields, as well as uptake of TPhT and other phenyltin compounds (monophenyltin, MPhT, and diphenyltin, DPhT) is still unknown at present. In this study, speciation analysis of phenyltin compounds was carried out in soil and water from a rice field where TPhT was applied during rice seeding according to legal application rates in Brazil. The results indicate the degradation of biocide and distribution of tin species into soil and water. To evaluate whether TPhT is taken up by plants, rice plants were exposed to three different TPhT application rates in a controlled mesocosm during 7 weeks. After this period, tin speciation was determined in soil, roots, leaves, and grains of rice. Degradation of TPhT was observed in soil, where DPhT and MPhT were detected. MPhT, DPhT, and TPhT were also detected in the roots of plants exposed to all TPhT application rates. Only TPhT was detected in leaves and at relatively low concentration, suggesting selective transport of TPhT in the xylem, in contrast to DPhT and MPhT. Concentration of phenyltin species in rice grains was lower than the limit of detection, suggesting that rice plants do not have the capability to take up TPhT from soil and transport it to the grains.

Determination of bromine, fluorine and iodine in mineral supplements using pyrohydrolysis for sample preparation

Pyrohydrolysis was employed for mineral supplements decomposition prior to F, Br and I determination. Fluoride determination was carried out by potentiometry using a fluoride-ion selective electrode, whereas Br and I were determined by inductively coupled plasma mass spectrometry. The main parameters that influence on pyrohydrolysis were investigated. After evaluation, the following conditions were established: reactor temperature of 1000 oC during 10 min; sample plus accelerator mass ratio of 1 + 5 and carrier gas (air) flow rate of 200 mL min-1. The accuracy of the proposed method was evaluated by analyte recovery tests and analysis of certified reference materials of phosphate rock and soil. Commercial mineral supplement samples were analyzed. The limits of quantification were 16, 0.3 and 0.07 µg g-1 for F, Br and I, respectively. By using a relatively simple and low cost pyrohydrolysis system up to 5 samples can be processed per hour. The developed sample preparation procedure can be routinely employed for F, Br and I determination in mineral supplements.

Preparo de amostras de combustíveis fósseis por piroidrólise para a determinação de flúor e cloro

Pyrohydrolysis is proposed for fossil fuels sample preparation for further fluorine and chlorine determination. Samples were heated during 10 min at temperatures up to 1000 °C. Water vapor was passed through the reactor and the volatile products were condensed and collected in NH4OH solution. Fluoride was determined by potentiometry using an ion selective electrode (ISE) and Cl by ICP OES and DRC-ICP-MS. The results are in good agreement with certified values and the precision is better than 10% (n = 4). Sample preparation by means of pyrohydrolysis is relatively simple, whereas chlorine and fluorine can be determined at low concentrations.

Separation of Heavy Crude Oil Emulsions Using Microwave Radiation for Further Crude Oil Analysis

Microwave radiation in closed vessels was used for the separation of heavy crude oil emulsions for further oil characterization. Operational conditions were studied and the following parameters were evaluated: water content, density, viscosity, N, S, V, Ni, and Cl. Using the proposed procedure it was possible to reduce the water and Cl content in crude oil to values lower than 1% and 300 µg g−1, respectively. It was possible to determine important crude oil properties without interferences caused by excessive water and salt concentrations. The proposed procedure is relatively fast and it was possible to obtain a suitable condition for water and salt removal from heavy crude oil emulsions without using demulsifiers or toxic reagents.

Fluoride Determination in Carbon Nanotubes by Ion Selective Electrode

Fluoride determination by ion selective electrode (ISE) in carbon nanotubes (CNTs) is proposed after pyrohydrolysis decomposition. Up to 1 g of CNTs could be decomposed improving the limit of detection (1.5 μg g-1), precision (RSD < 5%) and accuracy (agreement higher than 95% with values of certified reference materials (CRMs) and microwave-induced combustion (MIC)). Fluoride could be absorbed in water and the resulting solution can be analyzed by ISE. Pyrohydrolysis is easy to be performed and does not require any sophisticated instrumentation, which is attractive for routine fluoride control in CNTs.