Monitoring the Degradation of Tetracycline by Ozone in Aqueous Medium Via Atmospheric Pressure Ionization Mass Spectrometry

The degradation of tetracycline (1) by ozone in aqueous solution was investigated. High performance liquid chromatography (HPLC), UV-visible spectroscopy (UV-Vis), and total organic carbon (TOC) analyses revealed that although tetracycline was quickly consumed under this oxidative condition, it did not mineralize at all. Continuous monitoring by electrospray ionization mass spectrometry in the positive ion mode, ESI(+)-MS, revealed that tetracycline (1), detected in its protonated form ([1 + H]+) of m/z 445, reacted to yield almost exclusively two unprecedented oxidation products (2 and 3) via a net insertion of one and two oxygen atoms, respectively. Compound 2, suggested to be formed via an initial 1,3-dipolar cycloaddition of ozone at the C11a-C12 double-bond of 1, and Compound 3, proposed to be produced via a subsequent ozone attack at the C2-C3 double-bond of 2, were detected in their protonated forms in the ESI(+)-MS, i.e., [2 + H]+ of m/z 461 and [3 + H]+ of m/z 477, and were further characterized by ESI(+)-MSn. LC-APCI(+)-MS (liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry in the positive ion mode) experiments corroborated the results

Determination of metals in medicinal plants highly consumed in Brazil

In this work, samples of the medicinal plants: Boldo (Peumus boldus), Castanha da Índia (Aesculus hippocastanum), Chá Verde (Camelia sinensis), Erva Cidreira (Melissa officinalis), Espinheira Santa (Maytenus ilicifolia), Guaraná (Paullinia cupana), Maracujá (Passiflora sp.), Mulungu (Erythrina velutina), Sene (Cassia angustifolia) and Valeriana (Valeriana officinalis) were evaluated BY using the Neutron Activation Analysis technique (NAA- k0) in order to determine the levels of metals and other chemical contaminants. The results showed the presence of non essential elements to the human body. The diversity of chemical impurities found even at low concentration levels, considering the potential for chronic toxicity of these elements, reinforces the need to improve the implementation of good practices by growers and traders, and the hypothesis of lack of quality control in plant products.Neste trabalho, amostras de Boldo (Peumus boldus), Castanha da Índia (Aesculus hippocastanum), Chá Verde (Camelia sinensis), Erva Cidreira (Melissa officinalis), Espinheira Santa (Maytenus ilicifolia), Guaraná (Paullinia cupana), Maracujá (Passiflora sp.), Mulungu (Erythrina velutina), Sene (Cassia angustifolia) e Valeriana (Valeriana officinalis) foram investigadas utilizando a técnica Análise por Ativação Neutrônica (AAN-k0), a fim de se determinar os teores de metais e outros elementos químicos contaminantes. Os resultados revelaram a presença de elementos não essenciais ao organismo humano. A diversidade de impurezas químicas encontradas, mesmo em níveis de baixa concentração, considerando o potencial de toxicidade crônica desses elementos, reforça a necessidade de melhorias na aplicação de boas práticas pelos produtores e comerciantes e a hipótese de falta de controle de qualidade nos produtos vegetais

Tailoring activated carbon by surface chemical modification with O, S, and N containing molecules

In this work the surface of activated carbon was chemically modified in order to introduce O, S and N containing groups. The activated carbon surface was selectively oxidized with concentrated HNO3 under controlled conditions. Characterization by thermogravimetric analyses, infrared spectroscopy and NaOH titration suggested the formation of mainly -COOH and small amounts of -OH groups, with concentration of approximately 4.10(21) groups/g of carbon. These -COOH functionalized carbons showed high adsorption capacity for metal cations in aqueous solution in the following order: Pb+2>Cu+2>Ni+2 >Cd+2~Co+2>Ca+2 , suggesting a cation exchange mechanism via a surface complex [COO-M+2]. These -COOHsurf groups can be reacted with SOCl2 to produce a surface acylchloride group, -COCl. This surface -COCl group proved to be a very reactive and versatile intermediate for the grafting of different S and N containing molecules onto the carbon surface, such as 1,2-ethaneditiol (EDT-, HSCH2CH2SH) 1,7-dimercapto-4-thioheptane (DMTH-HSCH2CH2CH2SCH2CH 2CH2SH) or 1,2-ethylenediamine (EDA- NH2CH2CH2NH2 ) and triethyltetraamine, TEA (H2NCH2CH2NHCH2CH 2NHCH2CH2 NH2). The characterization of these materials was carried out by TG, IR and TPDMS (Temperature Programmed Decomposition Mass Spectrometry) experiments suggesting the formation of thioesther and amide surface groups, i.e. -COSR and -CONHR, with yields of approximately 50 and 75% for the reaction with DME and EDA, respectively. Preliminary adsorption experiments showed that these materials can efficiently remove metals such as Pb+2, Cu+2 and Ni+2 from aqueous medium