Determination of Arsenic Species in Water and Grape-Based Beverages

Arsenic is a human carcinogen that has been found in various waters and wines throughout the world. Therefore, close examination of these liquids is necessary to prevent the intoxication of animals and humans. Wines and waters often contain significant amounts of toxic arsenic species. The source of arsenic in wines and waters is generally believed to be the result of arsenic-based pesticides and herbicides. Recent studies have also shown that toxic arsenic may be used in the cultivation and acceleration of the ripening process of fruit, ultimately contaminating fruit-based beverages. The determination of total arsenic can be found by using several methods, including AFS or ICP/MS. No pretreatment of water is necessary, except for filtering by means of a Fisherbrand PTFE 0.45 connected to a Becton-Dickinson 10 mL syringe to filter particles from water. The pretreatment of the wine includes ethanol evaporation and an addition of 0.1% nitric acid. A number of commercial drinking waters and regional lake water were analyzed. Since we have confirmed the presence of arsenic in a variety of waters and wines from different countries, we decided to test a number of commercially available beverages for the presence of arsenic. The focus ofthis project is to establish the presence of arsenic in various commercially available beverages. ICP-MS was used to determine total arsenic using certified standards. Internal standards Indium and Yttrium were also used to verify the concentration readings, which varied from 0- 20 ppb.

Selenium Distribution in the Human Retina

Selenium is known to occur in the enzyme, glutathione peroxidase, and plays an important role as an antioxidant. The objective of this investigation was to determine if amounts of selenium are selectively accumulated in different regions of the retina or uniformly distributed with eccentricity. 20 human retinas were analyzed for selenium. 18 of these were sectioned into a disc and two concentric annuli centered on the fovea using trephines having diameters of 3, 11, and 21 mm. The sections had areas of7.1, 93, and 343 mm2, respectively. Corresponding sections of these retinas were combined and analyzed together in sets of n = 5 and n = 11. For two donors, the whole retina of one eye was analyzed for selenium and the other retina was sectioned for analysis as described above. Selenium was determined using atomic fluorescence spectroscopy after digestion of the retinal tissues in nitric acid. The two whole retinas were found to have an average of 0.89 ± 0.49 pmoles/mm2 of selenium as compared to the companion which had 0.84 ± 0.28 pmoles/mm2 as determined from the sum of the selenium amounts measured in the individual sections. The inner, medial, and outer portions of these two sectioned retinas were found to contain an average of5.28 ± 1.1, 1.28 ± 0.44, 0.63 ± 0.22 pmoles/mm2, respectively. The five retinas that were sectioned and pooled for analysis were found to have average amounts of3.64, 1.26, and 0.56 pmoles/mm2 • The 11-sectioned retinas were found to have 1.16, 0.61, and 0.38 pmoles/mm2 respectively in the same three sections. This limited data set indicates that selenium is not uniformly distributed within the human retina but rather concentrated to a greater extent within the macula. If confirmed, these data would support the hypothesis that selenium may be an important antioxidant involved in protection of the macula from radical oxidants.

Advanced oxidation of arsenic species in aqueous solutions

Ingestion of arsenic from contaminated water is a serious problem and affects the health of more than 100 million people worldwide. Traditional water purification technologies are generally not effective or cost prohibitive for the removal of arsenic to acceptable levels (≤10 ppb). Current multi-step arsenic removal processes involve oxidation, precipitation and/or adsorption. Advanced Oxidation Technologies (AOTs) may be attractive alternatives to existing treatments. The reactions of inorganic and organic arsenic species with reactive oxygen species were studied to develop a fundamental mechanistic understanding of these reactions, which is critical in identifying an effective and economical technology for treatment of arsenic contaminated water. ^ Detailed studies on the conversion of arsenite in aqueous media by ultrasonic irradiation and TiO2 photocatalytic oxidation (PCO) were conducted, focusing on the roles of hydroxyl radical and superoxide anion radical formed during the irradiation. ·OH plays the key role, while O2 -· has little or no role in the conversion of arsenite during ultrasonic irradiation. The reaction of O2-· does not contribute in the rapid conversion of As(III) when compared to the reaction of As(III) with ·OH radical during TiO2 PCO. Monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) are readily degraded upon TiO2 PCO. DMA is oxidized to MMA as the intermediate and arsenate as the final product. For dilute solutions, TiO2 also may be applicable as an adsorbent for direct removal of arsenic species, namely As(III), As(V), MMA and DMA, all of which are strongly adsorbed, thus eliminating the need for a multi-step treatment process. ^ Phenylarsonic acid (PA) was subjected to gamma radiolysis under hydroxyl radical generating conditions, which showed rapid degradation of PA. Product analysis and computational calculation both indicate the arsenate group is an ortho, para director. Our results indicate · OH radical mediated processes should be effective for the remediation of phenyl substituted arsonic acids. ^ While hydroxyl radical generating methods, specifically AOTs, appear to be promising methods for the treatment of a variety of arsenic compounds in aqueous media, pilot studies and careful economic analyses will be required to establish the feasibility of AOTs applications in the removal of arsenic. ^

Preservation of nitric oxide availability as nitrite and nitrosothiols

Nitric Oxide (NO) has been known for long to regulate vessel tone. However, the close proximity of the site of NO production to "sinks" of NO such as hemoglobin (Hb) in blood suggest that blood will scavenge most of the NO produced. Therefore, it is unclear how NO is able to play its physiological roles. The current study deals with means by which this could be understood. Towards studying the role of nitrosothiols and nitrite in preserving NO availability, a study of the kinetics of glutathione (GSH) nitrosation by NO donors in aerated buffered solutions was undertaken first. Results suggest an increase in the rate of the corresponding nitrosothiol (GSNO) formation with an increase in GSH with a half-maximum constant EC50 that depends on NO concentration, thus indicating a significant contribution of NO2 mediated nitrosation in the production of GSNO. Next, the ability of nitrite to be reduced to NO in the smooth muscle cells was evaluated. The NO formed was inhibited by sGC inhibitors and accelerated by activators and was independent of O2 concentration. Nitrite transport mechanisms and effects of exogenous nitrate on transport and reduction of nitrite were examined. The results showed that sGC can mediate nitrite reduction to NO and nitrite is transported across the smooth muscle cell membrane via anion channels, both of which can be attenuated by nitrate. Finally, a 2-D axisymmetric diffusion model was constructed to test the accumulation of NO in the smooth muscle layer from reduction of nitrite. It was observed that at the end of the simulation period with physiological concentrations of nitrite in the smooth muscle cells (SMC), a low sustained NO generated from nitrite reduction could maintain significant sGC activity and might affect vessel tone. The major nitrosating mechanism in the circulation at reduced O2 levels was found to be anaerobic and a Cu+ dependent GSNO reduction activity was found to deliver minor amounts of NO from physiological GSNO levels in the tissue.

Preservation of Nitric Oxide Availability as Nitrite and Nitrosothiols

Nitric Oxide (NO) has been known for long to regulate vessel tone. However, the close proximity of the site of NO production to “sinks” of NO such as hemoglobin (Hb) in blood suggest that blood will scavenge most of the NO produced. Therefore, it is unclear how NO is able to play its physiological roles. The current study deals with means by which this could be understood. Towards studying the role of nitrosothiols and nitrite in preserving NO availability, a study of the kinetics of glutathione (GSH) nitrosation by NO donors in aerated buffered solutions was undertaken first. Results suggest an increase in the rate of the corresponding nitrosothiol (GSNO) formation with an increase in GSH with a half-maximum constant EC50 that depends on NO concentration, thus indicating a significant contribution of ∙NO2 mediated nitrosation in the production of GSNO. Next, the ability of nitrite to be reduced to NO in the smooth muscle cells was evaluated. The NO formed was inhibited by sGC inhibitors and accelerated by activators and was independent of O2 concentration. Nitrite transport mechanisms and effects of exogenous nitrate on transport and reduction of nitrite were examined. The results showed that sGC can mediate nitrite reduction to NO and nitrite is transported across the smooth muscle cell membrane via anion channels, both of which can be attenuated by nitrate. Finally, a 2 – D axisymmetric diffusion model was constructed to test the accumulation of NO in the smooth muscle layer from reduction of nitrite. It was observed that at the end of the simulation period with physiological concentrations of nitrite in the smooth muscle cells (SMC), a low sustained NO generated from nitrite reduction could maintain significant sGC activity and might affect vessel tone. The major nitrosating mechanism in the circulation at reduced O2 levels was found to be anaerobic and a Cu+ dependent GSNO reduction activity was found to deliver minor amounts of NO from physiological GSNO levels in the tissue.