Direct Method for Determination of Al, Cd, Cu, and Pb in Beers In Situ Digested by GF AAS Using Permanent Modifiers

The object of the present study was to development of safe, reliable fast, and efficient methodologies for the direct determination of Al, Pb, Cu, and Cd in non-digested beer samples of widely consumed brand name beers sold in Brazil, using graphite furnace absorption spectrometry (GF AAS). Pyrolysis and atomization temperature curves of selected chemical modifiers (iridium, rhodium, ruthenium, zirconium, and non-modifier use) were used to stabilize each metal and sensitivity in a beer sample was diluted to 1:1 with 0.2 % v/v nitric acid after degasification. The best modifier for aluminum was permanent zirconium, with a characteristic mass of 4.2 pg (recommended is 10 pg), demonstrating a symmetrical peak with a corrected background using a deuterium arc lamp. For cadmium and copper, the best modifier was permanent ruthenium with characteristic masses of 0.3 and 7 pg (recommended are 0.35 and 4 pg, respectively, for Cd and Cu), respectively. The best condition for lead was using a non-modifier, with a characteristic mass of 6.9 pg (recommended is 10 pg). The limits of detection and mean recoveries, done over three consecutive days for aluminum, copper, lead, and cadmium, were 1.9, 2.9, 0.8, and 0.6 pg and 105, 104, 101, and 102 %, respectively. From the observed results, we may conclude that some metals, such as Al, Cd, Cu, and Pb, can be determined easily with graphite furnace atomic absorption spectrometry without sample digestion using a dilute nitric acid solution.

Direct electrothermal atomic spectrometric determination of Ag in aqua regia extracts of soils, sediments, and sewage sludge with matrix modification

Silver is subject to significant interferences caused by high chloride concentrations in electrothermal atomic absorption spectrometry, thus its direct determination in aqua regia leaches from soils, sediments, and sludges is very difficult, especially when using instrumentation equipped with deuterium-lamp background correction (D2). In this study, the interference of the aqua regia medium was successfully eliminated using Pd-citric acid chemical modifier. This chemical modifier was found to be the most advantageous in comparison with Pd mixture with ascorbic acid, tartaric acid, or citric acid-Li based on its ability to suppress the interference originating from different chloride matrix. Palladium increases the analyte stability; citric acid serves as a reducing reagent, and furthermore, it helps to remove the interfering chlorides by forming HCl, in the drying step of the electrothermal program. In the presence of the modifier, the pyrolysis temperature can be adjusted up to 1,000 °C with no loss of the analyte. The obtained limit of detection and characteristic mass were 5 ng g(-1) and 1.7 pg, respectively. The accuracy of the method was verified by means of six different reference samples and by comparing the results of the analysis of real samples with those obtained by inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometer. The proposed method was applied to the Ag determination in soils, sediments, and sewage sludge samples from the Pardubice region in Czech Republic.

Determination of Manganese in Urine and Whole Blood Samples by Electrothermal Atomic Absorption Spectrometry: Comparison of Chemical Modifiers

In this work, methodologies to determine manganese (Mn) in urine and whole blood by electrothermal atomic absorption spectrometry were developed. The use of Ru, Rh, and Zr as permanent modifiers, Pd as a modifier in solution, and the condition without modifier were investigated for the direct determination of Mn in urine and whole blood samples. The best results for Mn in urine and in whole blood were obtained without modifier use. The analytical characteristic, such as accuracy, precision and limit of detection of the proposed methodology were adequate.

Direct determination of selenium in urine samples by electrothermal atomic absorption spectrometry using a Zr plus Rh-treated graphite tube and co-injection of Rh as chemical modifier

Different chemical modifiers for use with electrothermal atomic absorption spectrometry (ET AAS) were investigated in relation to determining the selenium in human urine samples. The samples were diluted in a solution containing 1% v/v HNO3 and 0.02% m/v cetyltrimethylammonium chloride (CTAC). Studying the modifiers showed that the use of either Ru or Ir as the permanent modifier gave low sensitivity to Se and the peak shape was very noisy, while Zr or Rh gave no peak at all. The same occurred when Zr was used in solution. For mixtures of permanent modifiers, Ir plus Rh or Zr plus Rh gave very low sensitivity, Zr plus Rh with co-injection of Ir in solution was also not efficient, Zr plus Rh in solution gave good sensitivity, but the best results were obtained with a mixture of Zr and Rh as the permanent modifier and co-injection of Rh in solution. Using this last modifier, the following dilutions with the HNO3 and CTAC were studied: 1:1, 1:2, 1:3 and 1:4. The best dilution was 1:1, which promoted good sensitivity and a more defined peak shape and made it possible to correct for the background using a deuterium arc lamp. Under these conditions, a characteristic mass of 26+/-0.2 pg was obtained for Se in aqueous solution. Six certified urine samples were analyzed using matrix matching calibration and the measured concentrations were in agreement with the certified values, according to a t-test at the 95% confidence level. Recovery tests were carried out and the recoveries were in the range 100-103%, with relative standard deviation better than 9%. The limit of detection (LOD, 3 sd, n = 10) was 3.0 microg L(-1) in the sample. The treated graphite tube could be used for at least 600 atomization cycles without significant alteration of the analytical signal.

Oral delivery of meglumine antimoniate-beta-cyclodextrin complex for treatment of leishmaniasis

The need for daily parenteral administration represents one of the most serious limitations in the clinical use of pentavalent antimonials against leishmaniasis. In this work, we investigated the ability of beta-cyclodextrin to enhance the oral absorption of antimony and to promote the oral efficacy of meglumine antimoniate against experimental cutaneous leishmaniasis. The occurrence of interactions between beta-cyclodextrin and meglumine antimoniate was demonstrated through the changes induced in the spin lattice relaxation times of protons in both compounds. When free and complexed meglumine antimoniate were given orally to Swiss mice, plasma antimony levels were found to be about three times higher for the meglumine antimoniate-beta-cyclodextrin complex than for the free drug. Antileishmanial efficacy was evaluated in BALB/c mice experimentally infected with Leishmania amazonensis. Animals treated daily with the complex (32 mg of Sb/kg of body weight) by the oral route developed significantly smaller lesions than those treated with meglumine antimoniate (120 mg of Sb/kg) and control animals (treated with saline). The effectiveness of the complex given orally was equivalent to that of meglumine antimoniate given intraperitoneally at a twofold-higher antimony dose. The antileishmanial efficacy of the complex was confirmed by the significantly lower parasite load in the lesions of treated animals than in saline-treated controls. This work reports for the first time the effectiveness of an oral formulation for pentavalent antimonials.

Lead stimulates ERK1/2 and p38MAPK phosphorylation in the hippocampus of immature rats

Lead (Pb(2+)) is widely recognized as a neurotoxicant whose mechanisms of action are not completely established. We have previously demonstrated that Pb(2+) can activate the p38(MAPK) pathway and increase the phosphorylation of Hsp27 in bovine adrenal chromaffin cells and human SH SY5Y cells over a short incubation period (1 h). In the present work we analyzed the effects of Pb(2+) administered in vivo on the level and the phosphorylation state of ERK1/2 and p38(MAPK) in the hippocampus of immature rats. Rats were treated with lead acetate (2, 8 or 12 mg/kg, i.p.) or saline (control) over the 8th to 12th postnatal days, and hippocampal slices were prepared on the 14th day. The Pb(2+) level in the lead-treated animals increased 2.5-6-fold in the blood (3.0-6.0 microg/dl) and 2.0-3.0-fold in the forebrain (78-103 ng/g wet weight), compared to control (saline). The phosphorylation of both ERK1/2 and p38(MAPK) was significantly increased by prior exposure to Pb(2+) in vivo. In in vitro experiments, hippocampal slices from 14-day-old rats were exposed to Pb(2+) (1-10 microM) for 1 and 3 h. There were no changes in the phosphorylation state of ERK and p38(MAPK) for 1-h incubation, whereas a significant increase of ERK1/2 and p38(MAPK) phosphorylation by Pb(2+) (5 microM) was observed for the 3-h incubation. Cell viability measured using MTT was not modified in any of the conditions tested. These results indicate that the phosphorylation of hippocampal ERK1/2 and p38(MAPK) is stimulated by lead in a period of rapid brain development, an effect that may underlie, at least in part, the neurotoxicty elicited by this metal.