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131.
Hexavalent chromium Cr(VI) is a notorious ground water contaminant toxic to humans and animals. Assessment of an exposure risk for aquatic receptors necessitates frequent Cr(VI) concentration data from a range of surface and groundwater locations at Cr(VI) contamination sites. In this work, we demonstrate that enhanced ultraviolet-visible (UV-vis) spectroscopy using a liquid waveguide capillary cell (LWCC) offers an easy-to-use and economical methodology for the determination of chromate anion CrO(4)(2-) in Hanford natural waters without chemical pretreatment and generation of hazardous waste. Direct determination of CrO(4)(2-) in actual surface and ground water samples with the complexities of competing ions, dissolved organics, and other potential interfering agents was achieved by measuring the chromate optical absorbance at 372 nm. For a 100 cm path length LWCC, the detection limit for chromate was found to be as low as 0.073 ppb. A quantitative relationship between the intensity of the absorbance signal and water pH allowed for the straightforward calculation of total Cr(VI) content in natural water. The described method is applicable for in-field monitoring of Cr(VI) in environmental water samples at trace levels. 相似文献
132.
A Simple and Fast HPLC Method to Determine Lycopene in Foods 总被引:1,自引:0,他引:1
Tatiana Cucu Kevin Huvaere Marie-Anne Van Den Bergh Christine Vinkx Joris Van Loco 《Food Analytical Methods》2012,5(5):1221-1228
Carotenoids, among which lycopene—the principal pigment found in tomatoes—are lipophilic compounds which play a very important role in human health and nutrition. They are also recognised as strong antioxidants due to their ability to trap singlet oxygen and eliminate the peroxyl radical. The availability of reliable information on lycopene content of foods is essential both for the evaluation of diet and for epidemiological research relating the intake of lycopene. This paper describes a simple and fast HPLC/UV method for lycopene determination in a wide range of food products. All-E-lycopene together with its Z isomers were eluted isocratically using a carotenoid C30 reversed-phase column. The in-house validated HPLC method had a limit of quantification of 60 ng lycopene/g product and high precision and accuracy. The analytical method was successfully applied to several food products such as raw vegetables and fruits and also processed foods. Tomato and tomato-containing products contained the highest amounts of lycopene. While raw foods and minimally processed foods contained above 94% of all-E-lycopene, processed foods (such as soups, pasta sauces, pizza and cheese) contained from 76% to 87% of all-E-lycopene. 相似文献
133.
134.
Leda Cristina Muzzi Cunha Maria Lúcia Guerra Monteiro Bruno Reis Carneiro da Costa-Lima Juliana Maria Guedes-Oliveira Bruna Leal Rodrigues Alice Raquel Fortunato Jéssica Diogo Baltar Renata Valeriano Tonon Tatiana Koutchma Carlos Adam Conte-Junior 《Journal of Food Processing and Preservation》2021,45(3):e15272
135.
136.
Tatiana B Tribess Carmen C Tadini 《Journal of the science of food and agriculture》2006,86(9):1328-1335
Pasteurisation of orange juice (OJ) is necessary to prevent spoilage due to microorganisms and enzymes, mainly pectin methylesterase (PME). PME has a higher thermal resistance than the bacteria and yeasts existing in OJ and therefore its inactivation is used as a parameter to define the time/temperature combination of the thermal process. The enzyme has isoforms with different activities and thermal resistances. A three‐parameter model can be used to describe the kinetics of PME inactivation, where the more and less thermally resistant fractions are represented. In this study the thermal inactivation kinetics was evaluated at six pH values (3.6, 3.7, 3.8, 3.9, 4.0 and 4.1), three minimal temperatures (82.5, 85.0 and 87.5 °C) and at least six holding times for each condition. It was found that the thermolabile PME fraction (a) was influenced by pH and processing temperature. A slower reaction rate constant (k1) was found for juices with pH values of 3.8 and 3.9 at the studied temperatures. The highest inactivation levels were obtained in juices with pH values of 3.6 and 3.7. Copyright © 2006 Society of Chemical Industry 相似文献
137.
Larry Keener Sophia M Nicholson‐Keener Tatiana Koutchma 《Journal of the science of food and agriculture》2014,94(10):1947-1953
Trade in food and food ingredients among the nations of the world is rapidly expanding and, with this expansion, new supply chain partners, from globally disparate geographic regions, are being enrolled. Food and food ingredients are progressively sourced more from lesser developed nations. Food safety incidents in the USA and Canada show a high unfavorable correlation between illness outbreaks and imported foods. In the USA, for example, foodborne disease outbreaks caused by imported food appeared to rise in 2009 and 2010, and nearly half of the outbreaks, associated with imported food, implicated foods imported from areas which previously had not been associated with outbreaks. Projecting supply chains into new geographical regions raises serious questions about the capacity of the new supply chain partners to provide the requisite regulatory framework and sufficiently robust public health measures for ensuring the safety of the foods and foodstuffs offered for international trade. The laws, regulation and legislation among the many nations participating in the global food trade are, at best, inconsistent. These inconsistencies frequently give rise to trade disputes and cause large quantities of food to be at risk of destruction on the often dubious pretext that they are not safe. Food safety is often viewed through a political or normative lens. Often as not, this lens has been wrought absent scientific precision. Harmonization of food safety legislation around sound scientific principles, as advocated by the US Food Safety Modernization Act (FSMA), would ultimately promote trade and likely provide for incremental improvement in public health. Among the priority roles of most national governments are the advancement of commerce and trade, preservation of public health and ensuring domestic tranquility. Achieving these priorities is fundamental to creating and preserving the wealth of nations. Countries such as the Netherlands, Canada, Germany, Japan and the USA, for example, have very stable governments, are leaders in trade and commerce and enjoy high standards of public health. It is not by accident or coincidence that these nations are also among the world's wealthiest. Attainment of national priorities, especially those related to promoting trade in foodstuffs and also in preserving public health (food safety), would benefit greatly from international efforts in harmonizing food safety regulations and legislation. © 2013 Society of Chemical Industry 相似文献
138.
Ekaterina S. Lokteva Aleksey E. LazhkoElena V. Golubina Vadim V. TimofeevAlexander V. Naumkin Tatiana V. YagodovskayaSergey N. Gaidamaka Valery V. Lunin 《The Journal of Supercritical Fluids》2011,58(2):263-271
Carbonaceous deposits formation was established as the primary reason of Pd/TiO2 catalyst deactivation during reductive processing of CCl4 to form hydrodechlorination and oligomerization products. Three methods of carbonaceous deposits elimination were tested: (1) extraction by supercritical CO2, (2) oxidation by ozone in supercritical CO2, and (3) low-temperature glow-discharge oxygen plasma treatment. Synchronic thermal analysis confirms effective carbonaceous deposits removal during regeneration by ozone or low temperature glow-discharge oxygen plasma; by XPS deep oxidation of surface Pd after oxidative treatment (by ozone or oxygen plasma) was found. Thus H2 reduction was proposed as the second step making possible full regeneration of initial catalytic activity of Pd/TiO2. 相似文献
139.
Jan Suchanicz Irena Jankowska-Sumara Tatiana V. Kruzina 《Journal of Electroceramics》2011,27(2):45-50
Lead-free Na0.5Bi0.5TiO3 -BaTiO3 ceramics have been prepared in the whole range of concentrations and studied at room-temperature by means of X-ray, Raman
scattering and infrared techniques. X-ray measurements revealed rhombohedral, rhombohedral-tetragonal boundaries and tetragonal
modifacations depending on the contents of BaTiO3. The distinct changes of the Raman and infrared spectra with increasing of BaTiO3 content, which were correlated with X-ray results, were observed. The broad phonon spectra indicated the disorder in the
A site of Na0.5Bi0.5TiO3 -BaTiO3 system. 相似文献
140.
M. E. Henry Bergmann Tatiana Iourtchouk Johanna Rollin 《Journal of Applied Electrochemistry》2011,41(9):1109-1123
Bromide electrolysis was carried out on laboratory-scale cells in the range of 1–1,005 mg [Br−] dm−3 using boron-doped diamond (BDD) anodes. These studies were part of fundamental research activities on drinking water electrolysis
for disinfection. Synthetic water systems were mostly used in the experiments, which varied the temperature between 5 and
30 °C, the current density between 50 and 700 A m−2, and the rotation rate of the rotating anode between 100 and 500 rpm (laminar regime). Hypobromite and bromate were found
as by-products, as expected. Bromite was not detected. Higher bromate levels were formed at higher current density, but no
clear relationship was observed between bromate concentration and the rotation rate or temperatures between 5 and 30 °C. Bromate
yields higher than 90% were found at higher charge passed. Perbromate was found as a new potential synthesis or disinfection
by-product (DBP), but no perbromate was detected at the lowest bromide concentrations and under drinking water conditions.
The perbromate yield was about 1%, and somewhat lower when bromate was used as a starting material instead of bromide. At
a temperature of 5 °C more perbromate was detected compared with experiments at 20°. Approximately 20 times more perchlorate
was formed compared with perbromate formation in the presence of chloride ions of equimolar concentration. State of mechanistic
considerations is presented and a mechanism for perbromate formation is proposed. The reaction from bromate to perbromate
was found to be limited that is in contrast to the earlier studied chlorate-to-perchlorate conversion. In the measured concentration
range, reduction processes at the mixed oxide cathode showed a much higher impact on the resulting concentration for perbromate
than for bromate. 相似文献