Search results for "complex mixtures"
showing 10 items of 825 documents
Screening and authentication of tea varieties based on microextraction-assisted voltammetry of microparticles
2015
Abstract A simple electrochemical methodology for screening and authentication of green, black and red tea varieties is proposed. It is based on the record of the voltammetric response of microparticulate films of antioxidant compounds resulting from an ethanolic micro-extraction of commercial tea herbal preparations in contact with aqueous buffers. The obtained voltammetric responses led us to differentiate between diverse tea varieties upon application of bivariant and multivariant chemometric techniques, including discrimination of mixtures of teas with sensitivity estimated of 5.0 μA mg −1 with a detection limit of 0.01 mg of tea sample. Under the proposed conditions 100% discrimination…
Atomic fluorescence determination of inorganic arsenic in soils after microwave-assisted distillation
2000
Abstract An inexpensive microwave-assisted distillation procedure has been developed for quantitative determination of inorganic arsenic in soils by atomic fluorescence spectrometry (AFS). After reduction of As(V) to its trivalent state with potassium iodide, inorganic arsenic was distilled as AsCl 3 that was finally determined by atomic fluorescence after hydride generation with NaBH 4 in HCl medium. The different parameters that control the distillation: concentration and volume of HCl, time of distillation, sample weight, and oven load, were studied. The methodology developed has a detection limit of 0.015 μg l −1 , which corresponds to a concentration of 0.006 μg of As per gram of soil,…
Development of a new peat-based oil sorbent using peat pyrolysis
2013
The growing use and transport of crude oil and oil products has led to increasing numbers of oil spillages of various scales. Oil sorbents have been extensively used for remediation of the consequences of such accidents. The aim of this study is to investigate the possible use of peat and its thermal treatment products for oil sorption. Peat as an oil sorbent has poor buoyancy characteristics, relatively low oil sorption capacity and low hydrophobicity. However, thermal treatment (low-temperature pyrolysis and synthesis of peat-based activated coal) helps to significantly improve its sorptive characteristics. Peat is a potential material for oil sorption because it has such advantages as lo…
Different Sorption Behaviors for Wine Polyphenols in Contact with Oak Wood
2007
The evolution of polyphenols of enological interest- monomeric anthocyanins, (+)-catechin, (-)-epicatechin, gallic acid, and trans-resveratrol-in the presence of oak wood was investigated in aging-model conditions. Disappearance kinetics showed that, except for gallic acid, all of the wine polyphenols tend to disappear from the model wine in presence of oak wood, to reach an equilibrium after 20 days of contact. At equilibrium, the higher disappearance rates were obtained for monomeric anthocyanins and trans-resveratrol with values of 20 and 50%, respectively. For monomeric anthocyanins, the rate of disappearance seemed to be independent of their nature. In order to evaluate the contributio…
Glycoconjugate vaccines and immune interactions, and implications for vaccination schedules.
2011
Conjugate vaccines using diphtheria toxoid variant (CRM(197)), diphtheria toxoid and tetanus toxoid (TT) as carrier protein may induce immune interactions (interference or impairment as measured by lower antibody levels, or enhancement [higher antibody levels]) when coadministered with other vaccines. Immune enhancement occurs when two TT conjugates are coadministered. CRM(197) conjugate vaccines induce immune bystander interference when given with diphtheria-tetanus-acellular pertussis vaccines, which reduces responses to coadministered Haemophilus influenzae type b vaccine conjugated to TT. These bystander effects are greater as the amount of CRM(197) administered increases. When large am…
Synthesis of Liquid-Crystalline Colloids in Nonpolar Media and their Manipulation in Electric Fields
2009
The first synthesis of anisotropic liquid-crystalline colloids in silicone oil by a direct (radical) polymerization of a monomer in THF/silicone oil mixtures with the help of siloxane containing stabilizers is described. The size of the colloids is in the lower μm range and can be adjusted by varying the mixture. The resulting colloids show a bipolar director configuration if they are small (<1.5 μm) and a radial configuration if they are larger. The colloids are sterically stabilized, and, due to the nonpolarity of the solvent, the disturbing effects of migrating ions are excluded and experiments in the electric field can be conducted. Both line formation in DC fields and a periodic switch…
Pectin as Drug-Release Vehicle
2020
Pectin as a natural biopolymer is extensively used for pharmaceutical and biomedical applications, essentially due to its gelling properties that could be influenced by pectin sources and extraction methods. This chapter focuses on an overview of pectin drug delivery systems classified by their administration routes. Oral drug delivery systems have been mainly developed, as pectin could be used in tablets as binder or matrix excipients and in microparticles/beads obtained by ionotropic gelation. The main objective is to target the colon, as pectin is resistant in acidic pH and sensitive to pectinolytic enzymes in the colon. To obtain suitable properties, pectin could be used in its native s…
Herbal hepatotoxicity: a hidden epidemic
2011
Complementary and alternative therapies, including herbal products, have become increasingly popular in the general population and among patients and physicians. Regulations and pharmacovigilance regarding herbal drugs are still incomplete and need to be improved. In fact, herbals are commonly marketed on the Internet, and in many countries they are sold as food supplements, which are beyond the control of drug regulatory agencies. In Europe and the U.S., reports of hepatotoxicity from these products, including those advertised for liver diseases, are accumulating. Many herbal drugs are also commonly used in children, and in women during pregnancy and lactation, because they are believed to…
Growth of nucleation mode particles in the summertime Arctic: a case study
2016
Abstract. The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m−3, we observe growth of small particles, < 20 nm in diameter, into sizes ab…
Soil microbial biomass and bacterial diversity in southern European regions vulnerable to desertification
2022
Abstract Soil functionality is strongly dependent on the soil microbiota, which in turn is affected by soil quality and climate. Among global change factors, desertification is the most threatening ecosystem change affecting southern Europe, but the effects on the soil microbiota are largely unknown. In this study, we investigated soil microbial biomass and bacterial diversity in regions of southern European countries (Spain, Portugal and Italy), most under desertification risk, and related to key soil chemical-physical indicators and land use. Soil microbial biomass was positively related, to soil organic carbon (SOC) but bacterial diversity was negatively correlated with it. pH was the mo…