Surface modifications of activated carbon by gamma irradiation

Four commercial activated carbons with different chemical and textural characteristics were modified by gamma irradiation under five different conditions: irradiated in absence of water, in presence of ultrapure water, in ultrapure water at pH = 1.0 and 1000 mg L⁻¹ Cl⁻, in ultrapure water at pH = 7.5 and 1000 mg L⁻¹ Br⁻, and in ultrapure water at pH = 12.5 and 1000 mg L⁻¹ NO₃⁻. Changes in surface chemistry were studied by X-ray photoelectron spectroscopy; pH of point of zero charge, total acidic groups and total basic groups, which were determined by assessment with HCl and NaOH; and textural changes were determined by obtaining the corresponding adsorption isotherms of N₂ and CO₂. Outcomes show that the activated carbon surface chemistry can be modified by gamma irradiation and that the changes depend on the irradiation conditions. Modifications in the sp² hybridization of the surface carbons suggest that the irradiated carbons undergo graphitization. Measurements of structural parameters indicate that the irradiation treatment does not modify the textural properties of the carbons. Finally, studies of pristine and irradiated activated carbons using diffuse reflectance spectroscopy with the Kubelka–Munk function revealed a reduction in band gap energy in the irradiated carbons associated with an increase in sp² hybridization of the carbon atoms.     

Role of activated carbon on micropollutans degradation by ionizing radiation

The objective of this study was to analyze the influence of the presence of activated carbon on the degradation of the triiodinated contrast medium diatrizoate (DTZ) by the simultaneous use of gamma radiation and activated carbon. Four commercial activated carbons (Ceca, Witco, Sorbo, and Merck) with different textural and chemical characteristics were used for this purpose. The percentage DTZ removal obtained was considerably higher with the gamma radiation/activated carbon (GM/AC) system than with radiolysis in the absence of activated carbon, and it depended on the specific activated carbon employed. First, we optimized the amount of activated carbon required to maximize the amount of DTZ removed by the GM/AC system (0.06 g). The degradation constants were higher with the GM/AC system than with radiolysis alone, evidencing a synergic effect that favors pollutant removal. This synergic effect is independent of the textural but not the chemical characteristics of the activated carbon, observing a higher synergic activity for carbons with a higher surface content of oxygen, specifically quinone groups. We also highlight that the synergic effect of the activated carbon requires adsorbent–adsorbate electrostatic interaction and is absent when this interaction is hindered.     

The effects of oxygenation aeration treatment on dissipation behaviors of tricaine mesylate in carp (Cyprinus carpio) muscle and water

Tricaine mesylate (MS-222) is one of the most used anesthetics in fish. It can be absorbed by the human body via food consumption, with related detriments to human health. In this study, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed for the determination of MS-222 in carp muscle and water samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). For cleanup procedure, multiplug filtration cleanup (m-PFC) method with n-Hexane delipidation was adopted. The extraction solvent, cleanup methods and sorbents were optimized. All method validation parameters were in the acceptable range. The dissipation behavior study was followed by the method development. Firstly, the anesthesia dose and time were optimized in application study. Secondly, carps were revived for different period of time with (experimental group) and without (control group) the oxygenation aeration treatment to compare the dissipation rate of MS-222. After being anesthetized for 6 h at 50 mg/L and 12 h of elimination, the concentrations of MS-222 in crap muscle and water of experimental group was lower than those of control group. After 36 h of elimination under oxygenation aeration, over 90% of MS-222 was dissipated in carp muscle. The results showed that the half-life of MS-222 in carp muscle was 6.2 h. The findings suggested that the commonly-used oxygenation aeration treatment in aquaculture production had potential effects in accelerating the dissipation of MS-222 in carp and water. In this study, three days of withdrawal period was recommended in carps after MS-222 administration under oxygenation aeration.     

Multiplex ligation-dependent probe amplification (MLPA) for simultaneous detection of DNA from sunflower,poppy, flaxseed,sesame and soy allergenic ingredients in commercial food products

This work describes a multiplex ligation-dependent probe amplification (MLPA) technique for the simultaneous detection of five food allergens: sunflower, poppy, flaxseed, sesame and soy. Species-specific MLPA half-probes were designed to detect the DNA from the targeted species. Ligated probes were amplified by polymerase chain reaction (PCR) and amplicons were detected using capillary electrophoresis. The specificity of the MLPA system was assessed against DNA from more than 50 plant and animal species. The limit of detection (LOD) of the assay was determined to be 10 mg kg⁻¹in a model cookie experimentally spiked with different concentrations of the target species. The applicability of the MLPA was demonstrated through the analysis of 56 different commercial products (breads, pastries, cereals, chocolates, drinks, etc.), evidencing the presence of one or more undeclared allergenic ingredients in some of the tested samples. Real-time PCR assays were also performed to confirm and complement MLPA results. The MLPA technique has proved as a qualified screening tool for determining the presence of low amounts of sunflower, poppy, flaxseed, sesame and soy in processed foods.     

Multi-walled carbon nanotubes-based magnetic solid-phase extraction for the determination of zearalenone and its derivatives in maize by ultra-high performance liquid chromatography-tandem mass spectrometry

A simple and rapid magnetic solid-phase extraction (M-SPE) procedure using multi-walled carbon nanotube-magnetic nanoparticles (MWCNT-MNPs) as sorbents was established for purification of zearalenone (ZEA), α-zearalenol (α-ZOL), β-zearalenol (β-ZOL), zearalanone (ZAN), α-zearalanol (α-ZAL) and β-zearalanol (β-ZAL) in maize. The main parameters affecting the clean-up efficiency were thoroughly investigated, and high purification efficiencies for all analytes were obtained. The resulting MWCNT-MNP-ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was validated for maize samples. The matrix effects were greatly minimized using the M-SPE approach, with signal suppression/enhancement values decreased from 69.9–127.6% to 92.1–103.8%. Consequently, complex matrix-matched calibration curves were not necessary and the calibrations constructed in acetonitrile could be applied for accurate quantification of the targeted mycotoxins in real samples. The average recoveries ranged from 75.8 to 104.1% and the inter- and intra-day precision values expressed as RSDs, were all lower than 14%. Limits of detection and quantification were in the range of 0.03–0.04 and 0.07–0.10 μg/kg, respectively. The analytical performance of the developed method was also successfully evaluated with maize samples, and this method was proved to be a powerful tool for monitoring ZEA and its derivatives in maize.     

Gas-cooled reactor thermal hydraulic analyses with MELCOR

Pursuant to the Energy Policy Act of 2005, the High Temperature Gas-Cooled Reactor (HTGR) has been selected as the reference design for the Next Generation Nuclear Plant (NGNP). Stemming from a U.S. Nuclear Regulatory Commission (NRC) HTGR research initiative, a need was identified for validation of systems-level computer code modeling capabilities in anticipation of the eventual need to perform licensing analyses. Because the NRC has used MELCOR for light water reactors (LWR) in the past and because MELCOR was recently updated to include gas-cooled reactor (GCR) physics models, MELCOR is among the system codes of interest to the NRC. This paper describes MELCOR modeling of the General Atomics' Modular High Temperature Gas-Cooled Reactor (MHTGR). The MHGTR is a suitable design for demonstration of MELCOR GCR modeling competency for two reasons: 1) the MHTGR is a predecessor to the more advanced General Atomics’ Gas-Turbine Modular High Temperature Reactor (GTMHR), and 2) experimental data useful for benchmark calculations may soon become available. Using the most complete literature references available for the MHTGR design, researchers at Texas A&M University (TAMU) constructed a MELCOR input deck for the MHTGR to partially validate MELCOR GCR modeling capabilities. Normal and off-normal system operating conditions were modeled with appropriate boundary and initial conditions. MELCOR predictions of system response were obtained for steady-state, pressurized conduction cool-down (PCC), and depressurized conduction cool-down (DCC) scenarios. Code results were checked against nominal MHTGR design parameters, physical intuition, and anticipated GCR thermal hydraulic response. No inherent deficiencies in MELCOR modeling capability were observed, suggesting that the newly-implemented GCR models are adequate for systems-level analysis. If and when experimental benchmark data becomes available, further validation activities may proceed given the modeling efforts discussed herein.     

A study of the negotiated-settlement practice in regulation: Some evidence from Florida

Negotiated settlements have become a frequently used alternative to contested proceedings when setting prices charged by public utilities under the US rate-of-return regulatory model. The behavior of the representatives of consumer advocates and the firms during settlement negotiations determine customer prices. This paper examines this behavior by using data from the Florida Public Service Commission to estimate the payoff functions of both parties. The estimation suggests that the advocate and the firm weight the present rate change more than the consumer's future average price and the firm's future operating revenue in their settlement decisions. It also indicates that the time saved by settlements is not a primary reason for their popularity.     

Labelling accuracy in Tasmanian seafood: An investigation using DNA barcoding

Mislabelling of seafood products has been documented in numerous countries for over three-quarters of a century. With a trend towards increased consumption of seafood, the informed consumer demands accurately labelled products that provide full disclosure of composition. DNA barcoding can be used to accurately identify a seafood product to species based on its genetic signature, and so provides a means to test the authenticity and accuracy of seafood labelling. This can be especially useful for products such as fillets which have few or no unambiguous identifying characters, and can easily be mislabelled. We investigated labelling accuracy in seafood retailers in Tasmania, Australia. Thirty-eight seafood products were obtained from seafood retailers, sequenced for the barcoding gene region cytochrome oxidase subunit 1(CO1), and subsequently identified to species level by querying GenBank and Barcode of Life Data Systems (BOLD) DNA sequence records. Results were compared with standard fish names (SFN) prescribed under the Australian Fish Names Standard (AFNS) and FishBase. Of the 38 samples, none were deemed to have been mislabelled under Australian regulation, although in some cases naming discrepancies and ambiguity may cause confusion for some consumers. Our work, while reflecting high standards in Tasmanian seafood, highlights the need for mandatory standard labelling across all seafood products so as to eliminate any possible misrepresentation.