Peptide mass fingerprinting (PMF) of protein digests is a widely-accepted method for protein identification in MS-based proteomic studies. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) is the technique of choice in PMF experiments. The success of protein identification in a PMF experiment is directly related to the amount of amino acid sequence coverage. In an effort to increase the amount of sequence information obtained in a MALDI PMF experiment, performic acid oxidation is performed on tryptic digests of known proteins. Performic acid was chosen as the chemical oxidant due to the ease of use and to the selective oxidation of cysteine, methionine, and tryptophan residues. In experiments performed in our laboratory, performic acid oxidation either increased or did not affect protein sequence coverage in PMF experiments when oxidized tryptic digests were analyzed by MALDI. Negative mode MALDI data were acquired, as well as positive mode MALDI data, due to the enhanced ionization of cysteic acid-containing peptides in negative mode. Furthermore, the confidence in a protein match is increased by observation of mass shifts indicative of cysteine, methionine, and/or tryptophan in oxidized peptide ion signals when comparing MALDI spectra prior to performic acid oxidation and after oxidation due to the low abundance of these residues in the majority of all known and hypothetical proteins.

Petroleum hydrocarbons (PHCs) such as gasoline are ubiquitous organic compounds present at contaminated sites throughout the world. Accidental spills and leakage from underground storage tanks results in the formation of PHC source zones that release hundreds of organic compounds, including the high impact, acutely toxic and highly persistent aromatics (e.g., benzene, toluene, ethylbenzene, xylenes, trimethylbenzenes and naphthalene) into groundwater. Contamination by these compounds continues to persist until the PHC source zone is treated in place or removed. In situ chemical oxidation (ISCO) employing persulfate was identified as a potentially viable technology for the treatment of PHC source zones. The effectiveness and efficiency and, therefore, the overall economic feasibility of a persulfate-based ISCO treatment system depend upon the reactivity of the target organic compounds and the interaction of persulfate with aquifer media. The objective of this research was to investigate the persistence of unactivated and activated persulfate in the presence of aquifer materials, and to examine persulfate oxidation of PHC compounds at both the bench- and pilot-scales. A series of bench-scale studies were performed to estimate persulfate degradation kinetic parameters in the presence of seven well-characterized, uncontaminated aquifer materials and to quantify the changes in specific properties of these materials. Batch experiments were conducted in an experimental system containing 100 g of solids and 100 mL of persulfate solution at 1 or 20 g/L. Column experiments were designed to mimic in situ conditions with respect to oxidant to solids mass ratio and were performed in a stop-flow mode using a 1 g/L persulfate solution. The degradation of persulfate followed a first-order rate law for all aquifer materials investigated. An order of magnitude decrease in reaction rate coefficients was observed for systems that used a persulfate concentration of 20 g/L as compared to those that used 1 g/L due to ionic strength effects. As expected, the column experiments yielded higher reaction rate coefficients than batch experiments for the same persulfate concentration due to the lower oxidant to solids mass ratio. Bench-scale data was used to develop a kinetic model to estimate the kinetic response of persulfate degradation during these tests. The push-pull tests involved the injection of persulfate (1 or 20 g/L) and a conservative tracer into a hydraulically isolated portion of the sandy aquifer at CFB Borden, Canada. The kinetic model developed from the bench-scale data was able to reproduce the observed persulfate temporal profiles from these push-pull tests. This implies that persulfate degradation kinetics is scalable from bench-scale to in situ scale, and bench tests can be employed to anticipate in situ degradation. The estimated reaction rate coefficients indicate that persulfate is a persistent oxidant for the range of aquifer materials explored with half lives ranging from 2 to 600 days, and therefore in situ longevity of persulfate will permit advective and diffusive transport in the subsurface. This is critical for successful delivery of oxidant to dispersed residuals in the subsurface. Activation of persulfate is generally recommended to enhance its oxidation potential and reactivity towards organic compounds. This approach may influence the stability of persulfate-activator system in the presence of aquifer materials. A series of batch tests were performed to investigate persistence of persulfate at two concentrations (1 or 20 g/L) using three contemporary activation strategies (citric acid chelated-ferrous, peroxide and high pH ) in the presence of 4 well-characterized, uncontaminated aquifer materials. Chelation by citric acid was ineffective in controlling the interaction between persulfate and Fe(II) and a rapid loss in persulfate concentration was observed. Higher Fe(II) concentration (600 mg/L) led to greater destabilization of persulfate than lower Fe(II) concentration (150 mg/L) and the persulfate loss was stoichiometrically equivalent to the Fe(II) concentration employed. Subsequent to this rapid loss of persulfate, first-order degradation rate coefficients (kobs) were estimated which were up to 4 times higher than the unactivated case due to the interaction with Fe(III) and CA. Total oxidation strength (TOS) was measured for peroxide activation experiments and was observed to decrease rapidly at early time due peroxide degradation. This was followed by slow degradation kinetics similar to that of unactivated persulfate implying that the initial TOS degradation was peroxide dominated and the long-term kinetics were dominated by persulfate degradation. The kobs used to capture TOS degradation for later time were shown to depend upon unactivated persulfate and peroxide degradation rate coefficients, and peroxide concentration. Either a slow peroxide degradation rate and/or higher peroxide concentration allow a longer time for peroxide and persulfate to interact which led to kobs ~1 to 100 times higher than kobs for unactivated persulfate. For alkaline activation, kobs were only 1 to 4 times higher than unactivated persulfate and therefore alkaline conditions demonstrated the least impact on persulfate degradation among the various activation strategies used. For all activation trials, lower stability of persulfate was observed at 1 g/L as compared to 20 g/L due to insufficient persulfate and/or ionic strength effects. A series of batch reactor trials were designed to observe the behavior of the nine high impact gasoline compounds and the bulk PHC fraction measures subjected to various persulfate activation strategies over a 28-day period. This bench-scale treatability used unactivated persulfate (1 or 20 g/L) and activated persulfate (20 g/L). Activation employed chelated-Fe(II), peroxide, high pH or two aquifer materials as activators. No significant oxidation of the monitored compounds was observed for unactivated persulfate at 1 g/L, but 20 g/L persulfate concentration resulted in their near-complete oxidation. Oxidation rates were enhanced by 2 to 18 times by activation with peroxide or chelated-Fe(II). For alkaline activation, pH 11 trials demonstrated ~2 times higher oxidation rates than the unactivated results. For pH 13 activation the oxidation rates of benzene, toluene and ethylbenzene were reduced by 50% while for the remaining monitored compounds they were enhanced by 5 to 100%. Natural activation by both aquifer materials produced oxidation rates similar to the unactivated results, implying that either activation by minerals associated with aquifer material was not significant or that any potential activation was offset by radical scavenging from aquifer material constituents. Acid-catalyzation at pH <3 may enhance oxidation rates in weakly buffered systems. Oxidation of the monitored compounds followed first-order reaction kinetics and rate coefficients were estimated for all the trials. Overall, activated and unactivated persulfate appear to be suitable for in situ treatment of gasoline. Persulfate under unactivated or naturally activated conditions demonstrated significant destruction of gasoline compounds and showed higher persulfate persistence when in contact with aquifer solids as compared to chelated-Fe(II) or peroxide-activated persulfate systems. This observation was used as the basis for selecting unactivated sodium persulfate for a pilot-scale treatment of gasoline-contaminated source zone at CFB Borden, Canada where a ~2000 L solution of persulfate (20 g/L) was injected into a PHC source zone. Concentration of organics and inorganics were frequently monitored over a 4 month period across a 90 point monitoring fence line installed down-gradient. Treatment performance was measured by estimating organic and inorganic mass loading across the monitoring fence. Increased mass loading for sodium was observed over time as the treatment volume moved across the fence-line indicating transport of the inorganic slug created upon oxidant injection. The mass loading also increased for sulfate which is a by-product generated either due to persulfate degradation during oxidation of organic compounds or during its interaction with aquifer materials. Oxidation of organic compounds was evident from the enhanced mass loading of dissolved carbon dioxide. More importantly, a significant (45 to 86%) decrease in mass loading of monitored compounds was observed due to oxidation by injected persulfate. The cumulative mass crossing the monitoring fence-line was 20 to 50% lower than that expected without persulfate treatment. As the inorganic slug was flushed through the source zone and beyond the monitoring fence, the mass loading rate of sodium, sulfate and carbon dioxide decreased and approached background condition. Mass loading of the monitored compounds increased to within 40 to 80% of the pre-treatment conditions, suggesting partial rebound. These investigations assessed the impact of activation on persulfate persistence and treatability of gasoline and served to establish guidelines for anticipating field-scale persulfate behavior under similar conditions. In summary, unactivated persulfate is a stable oxidant in the presence of aquifer materials and its persistence depends upon TOC and Fe(Am) content of the materials, ionic strength, and aquifer to solids mass ratio. Persulfate exhibits significant destruction of gasoline compounds and can be employed for the remediation of gasoline-contaminated sites. Peroxide and chelated-Fe(II) enhance oxidation rates of these compounds, but reduce stability of the persulfate-activator system. Persulfate activation using high pH conditions does not significantly impact persulfate persistence but reduces the overall destruction of gasoline compounds. Therefore, activation imposes a trade-off between enhanced oxidation rates and reduced persulfate persistence. Kinetic model is representative of persulfate degradation at bench- and pilot-scales and can be used for estimation of in situ degradation. The quantification of oxidation rates for gasoline compounds under activated and unactivated persulfate conditions will assist decision-making for identification of appropriate remediation options when targeting contamination by gasoline or by specific high impact gasoline compounds. While persulfate oxidation resulted in partial treatment of a small gasoline source zone, aggressive persulfate load will be required during injection for a complete clean-up. Overall, persulfate-based in situ chemical oxidation was demonstrated to be an effective and a viable technology for the remediation of contaminated soil and groundwater.

The contamination of aquifer systems by petroleum hydrocarbons is a global problem. Underground storage tanks used for storing these hydrocarbons often leak, resulting in subsurface contamination. The hazards associated with petroleum hydrocarbon contamination are mainly attributable to the BTEX compounds, namely benzene, toluene, ethylbenzene and xylenes together with trimethylbenzenes (TMBs) and naphthalene due to their potential to impact human health and the ease with which they can enter the groundwater system. In situ chemical oxidation (ISCO) is the delivery of strong chemical oxidants to the subsurface for the purpose of treating organic contaminants. ISCO can be an effective way to remediate organic contaminants from the soil and groundwater. Sodium persulphate is one of the newer oxidants to gain widespread use in treating petroleum hydrocarbon contamination, though without being fully understood. This investigation tested the ability of unactivated sodium persulphate in treating dissolved phase and residual BTEX contamination through bench-scale laboratory tests and a pilot-scale field study. A degradation potential batch reactor test was carried out to assess the efficacy of unactivated sodium persulphate in oxidizing petroleum hydrocarbons present in contaminated groundwater as well as its effect on aquifer material from a field site. This test was carried out at a sodium persulphate concentration of 20 g/L. Results from this test did not follow the expected first-order degradation, and so subsequent experiments were carried out using a sodium persulphate concentration of 100 g/L. A test to determine the degree of interaction between the oxidant and aquifer material was also conducted. It was found that the degree of natural oxidant interaction for the field site in question was very low. 1000 kg of sodium persulphate was dissolved in nearly 10,000 L of water and injected into the subsurface. Electrical conductivity (EC), pH, sodium, persulphate, sulphate and BTEX were all monitored during the subsequent 152-day post-injection monitoring period. An empirical relationship was determined between EC and the concentration of sodium in groundwater. This enabled the use of EC as a real-time tracer to track the progress of the injectate. Field results supported predictions based on a simulation model that density-driven flow would play an important role in the delivery of the injectate. A portion of the injectate was believed to have been missed by the monitoring network. Areas that did show elevated tracer results in some cases showed a decrease in BTEX concentrations. Results were categorized in four ways. The first category had wells that showed strong evidence of injectate presence but little to no change in BTEX levels. The second category was comprised of wells that showed a reduction in BTEX levels along with the presence of injectate. BTEX levels in some wells rebounded towards the end of the study period. The third category consisted of wells that showed the presence of dilute injectate but did not show any reduction in BTEX concentrations. The fourth and final category was of wells that showed no evidence of having been affected by the injectate in any way. BTEX levels were the same as background. The oxidation of BTEX by unactivated sodium persulphate was found to be successful, though the vagaries of oxidant delivery and field sampling made difficult the accurate determination of the degree of success.

Reagent injections designed to provide in stiu mass destruction of soil and groundwater contaminants are commonly prone to failure due to inadequate distribution of the injected reagent. Reagent injections, in particular in situ chemical oxidation (ISCO) injections, require contact between the treatment reagent and targeted contaminant to allow for mass destruction in source zones and plumes. Subsurface heterogeneities that exist at all spatial scales prevent remediation specialists from accurate prediction of reagent distribution in the subsurface, even when significant site characterization and hydraulic testing has previously taken place. A prototype probe system was developed to provide real-time monitoring of the distribution of injected reagents. This thesis focused on laboratory testing of the system to verify that the design was capable of indicating the presence of an injected reagent in the field. Temperature and two-wire dipole resistance sensors were developed with low-cost materials to provide feedback on the electrical conductivity (EC) signatures produced by typical reagents mixed as salt solutions. Sensors were attached to sections of PVC conduit and wired to a data acquisition system to control measurements and store data. The temperature sensor was found to accurately respond to temperature changes in comparison to a commercial datalogger. Measured temperature differences between the constructed sensor and commercial datalogger were relatively constant, indicating that the constructed sensor could be calibrated to measurements from a commercial logger. Static cell experiments were conducted in beakers with varying concentration sodium chloride (NaCl), potassium permanganate (KMnO4) and sodium persulfate (Na2S2O8) solutions to determine dipole resistance sensor response to variations in EC. Different fixed resistors were wired with the dipole sensor circuit to determine the impact on sensor readings. Results indicated a nonlinear correlation between two-wire dipole resistance sensor response and increasing EC. Each constructed dipole sensor behaved uniquely. Raw sensor response was calibrated to EC by accounting for the influence of the fixed resistor. Data was fit to a second-order polynomial with form y = aEC2 + bEC + c, with r2 ranging from 0.92-1.00 for experiments with 4-6 measurement points. Calibrations were accurate within the range of EC for each static cell experiment; trends extrapolated beyond the measurement range were subject to significant error. The choice of fixed resistor did not appear to alter the accuracy of probe calibrations. Flow cell experiments were designed to analyze dipole resistance sensor response to continuous changes in EC. EC breakthrough curves (BTCs) were produced by injecting NaCl tracer solutions into the flow cell. Initial flow cell experiments conducted in an open water system showed agreement between dipole sensor measurement and handheld EC measurements on the rising limb of BTCs and divergence between the two datasets on the falling limb of BTCs. To resolve these issues, a more sophisticated tank with a porous medium was built and tested to compare sensor response from s prototype probe and a commercial EC datalogger. EC BTCs were measured under two scenarios: (1) conditions with deionized water (DI) circulating through the tank as the background solution, and (2) conditions with a simulated groundwater solution with elevated EC circulating through the tank as the background solution. BTCs produced agreement between EC recorded by the commercial logger and dipole resistance measurements for both the rising and falling limbs of BTCs. Results indicated the dipole resistance sensor was not capable of resolving fine changes in EC that occurred during breakthrough. A calibration of all in situ measurements from the experiments with porous medium confirmed the simulated groundwater experiments were subject to significantly less variability than the deionized water experiments. The calibration applied to the simulated groundwater measurements produced BTCs that matched very closely with those recorded by the commercial logger. Two field trials were also conducted during ISCO injections at contaminated sites where probes were installed in existing monitoring wells. The field trials did not successfully correlate dipole resistance sensor measurements with oxidant concentration. Observations from the second trial indicated the dipole sensor measurements correlated with EC of water samples. This work has provided a theoretical representation of two-wire dipole resistance sensor response to EC and has verified expected results through laboratory experiments. It has analyzed the influence of temperature and choice of fixed resistors on two-wire dipole resistance sensor readings, has extensively tested sensor response to EC during static cell and BTC experiments, and has displayed the prototype probe is capable of indicating the presence of injected reagents that have an EC signature. Further research avenues include pilot-scale testing in the field and developing a design for use with a direct-push rig.

Orientador: Elisa Helena Giglio Ponsano / Banca: Marcia Marinho / Banca: Aparecida de Fátima Michelin / Resumo: O interesse da população pelo consumo de alimentos saudáveis, práticos e com maior durabilidade é cada vez mais frequente. Para atender a essa demanda, as indústrias de alimentos têm buscado trabalhar com ingredientes naturais, visando minimizar o uso de aditivos sintéticos. O estudo objetivou investigar se a inclusão de diferentes especiarias em hambúrguer bovino afeta o crescimento bacteriano, a oxidação lipídica e as características sensoriais dos produtos. Foram elaboradas 4 formulações de hambúrguer: controle (sem aditivos), açafrão (1%), gengibre (1%) e urucum (1%). Os produtos foram analisados quanto à contagem bacteriana total (CBT) nos dias 0, 7 e 15 (armazenamento a 4 °C) e 0, 15 e 60 (armazenamento a -30 °C) e quanto à rancidez, nos dias 0, 30 e 60 (armazenamento a -30 °C). A aceitação dos atributos sensoriais e a intenção de compra foram avaliadas com o uso de escalas hedônicas. Todos os hambúrgueres formulados com especiarias e mantidos a 4 °C apresentaram menor CBT que a formulação controle, enquanto que, para os armazenados a -30 °C, o mesmo ocorreu apenas com os que continham gengibre. Menores valores de oxidação lipídica foram encontrados nas formulações contendo as especiarias, com 0, 30 e 60 dias de armazenamento a -30 °C. As formulações controle e gengibre lideraram a aceitação dos provadores nos atributos aparência e cor, enquanto que, para os demais atributos, não houve diferença entre as formulações com especiarias. Na intenção de compra, tanto os hambú... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The population's interest in consuming healthier, more practical and durable foods is increasingly frequent. In order to meet this demand, the food industry has sought to work with natural ingredients in order to minimize the use of synthetic additives. The study aimed to investigate if the inclusion of different spices in bovine burger affects bacterial growth, lipid oxidation and sensorial characteristics of the products. Four hamburger formulations were prepared: control (without additives), saffron (1%), ginger (1%) and annatto (1%). The products were analyzed for total bacterial count (TBC) on days 0, 7 and 15 (storage at 4 °C) and 0, 15 and 60 (storage at -30 °C) and, for rancidity, on days 0, 30 and 60 (storage at -30 °C). The acceptance of the sensory attributes and the purchase intent were evaluated using hedonic scales. All burgers formulated with spices and kept at 4 °C had lower TBC than the control formulation, whereas for those stored at -30 °C, the same occurred only with the ginger-made ones. Lower lipid oxidation was found for the formulations containing the spices, with 0, 30 and 60 days of storage at -30 °C. Control and ginger formulations led the acceptance of the tasters for the attributes appearance and color, while for the other attributes no differences among the formulations with spices were detected. In the purchase intention trial, both the ginger-made and the control group burgers aroused greater interest from the tasters. It was concluded that the... (Complete abstract click electronic access below) / Mestre

Recentemente, o uso de persulfato em processo de oxidação química in situ em áreas contaminadas por compostos orgânicos ganhou notoriedade. Contudo, a matriz sólida do solo pode interagir com o persulfato, favorecendo a formação de radicais livres, evitando o acesso do oxidante até o contaminante devido a oxidação de compostos reduzidos presentes no solo ou ainda pela alteração das propriedades hidráulicas do solo. Essa pesquisa teve como objetivos avaliar se as interações entre a solução de persulfato com três solos brasileiros poderiam eventualmente interferir sua capacidade de oxidação bem como se a interação entre eles poderia alterar as propriedades hidráulicas do solo. Para isso, foram realizados ensaios de oxidação do Latossolo Vermelho (LV), Latossolo Vermelho Amarelo (LVA) e Neossolo Quartzarênico (NQ) com solução de persulfato (1g/L e 14g/L) por meio de ensaios de batelada, bem como a oxidação do LV por solução de persulfato (9g/L e 14g/L) em colunas indeformadas. Os resultados mostraram que o decaimento do persulfato seguiu modelo de primeira ordem e o consumo do oxidante não foi finito. A maior constante da taxa de reação (kobs) foi observada para o reator com LV. Essa maior interação foi decorrente da diferença na composição mineralógica e área específica. A caulinita, a gibbsita e os óxidos de ferro apresentaram maior interação com o persulfato. A redução do pH da solução dos reatores causou a lixiviação do alumínio e do ferro devido a dissolução dos minerais. O ferro mobilizado pode ter participado como catalisador da reação, favorecendo a formação de radicais livres, mas foi o principal responsável pelo consumo do oxidante. Parte do ferro oxidado pode ter sido precipitado como óxido cristalino favorecendo a obstrução dos poros. Devido à maior relação entre massa de persulfato e massa de solo, a constante kobs obtida no ensaio com coluna foi 23 vezes maior do que a obtida no ensaio de batelada, mesmo utilizando concentração 1,5 vezes menor no ensaio com coluna. Houve redução na condutividade hidráulica do solo e o fluxo da água mostrou-se heterogêneo após a oxidação devido a mudanças na estrutura dos minerais. Para a remediação de áreas com predomínio de solos tropicais, especialmente do LV, pode ocorrer a formação de radicais livres, mas pode haver um consumo acentuado e não finito do oxidante. Verifica-se que o pH da solução não deve ser inferior a 5 afim de evitar a mobilização de metais para a água subterrânea e eventual obstrução dos poros por meio da desagregação dos grãos de argila. / Recently the persulfate application for in situ chemical oxidation at areas contaminated by organic compounds gained notoriety. However, the persulfate can interact with the solid matrix of the soil favoring the formation of free radicals, avoiding the oxidant access to the contaminant due to the oxidation of reduced compounds present in the soil or by changing the hydraulic properties of the soil. This research aimed to evaluate if the interactions between the persulfate solutions and three Brazilian tropical soils could eventually interfere on the persulfate oxidation capacity and if the interaction between them could modify the hydraulic properties of the soil. For such, oxidation tests were performed with soils: Latossolo Vermelho (LV), Latossolo Vermelho Amarelo (LVA) and Neossolo Quartzarênico (NQ) with persulfate solution (1 and 14 g/L) through batch tests and LV oxidation by persulfate solution (9 and 14 g/L) on undisturbed columns. The results showed that persulfate decay followed a first order model and oxidant consumption was not finite. The higher reaction rate coefficient (kobs) was observed in the reactor with LV. This higher interaction was due to the difference in the mineralogical composition and surface area. Kaolinite, gibbisita and iron oxides showed greater interaction with persulfate. The pH reduction on the reactor solution caused the aluminum and iron leaching due to dissolution of minerals. The mobilized iron may have participated as a reaction catalyst favoring the formation of free radicals although it was the major responsible for the oxidant consumption. Part of oxidized iron may have been precipitated as crystalline oxide favoring the clogged pores. As a consequence of the higher mass proportion between persulfate and soil, the kobs constant obtained in the column test was 23 times higher than the one observed on the batch test, even utilizing a concentration 1.5 times lower than bath test. There was a reduction in the soil hydraulic conductivity and the water flow proved to be heterogeneous after oxidation due to changes in minerals structure. For remediation purposes in areas with predominance of tropical soils, especially LV, the formation of free radicals may occur but an accented and not finite oxidant consumption may happen. It is verified that the pH solution should not be inferior than 5 to prevent the mobilization of metals to the groundwater and a possible pores clogging by the breakdown of the clay grains.

A utilização de ozônio como agente oxidante tem apresentado resultados positivos para a degradação de contaminantes orgânicos em subsuperfície. O ozônio apresenta alta reatividade, tanto com os compostos orgânicos de interesse quanto com os compostos inorgânicos presentes no meio, principalmente com os íons metálicos constituintes da matriz sólida, mobilizando os para a água subterrânea. Este estudo detectou e quantificou os íons metálicos de interesse presentes na matriz solida, sendo estes: Fe, Al, Mn, Cr, Pb, Ni e Zn. Também foram determinados os íons que foram mobilizados da matriz sólida, a partir da injeção do ozônio em solo proveniente de uma área contaminada por compostos orgânicos. / The use of ozone as an oxidizing agent has shown positive results for the degradation of organic contaminants in the subsurface. Ozone is highly reactive with both the organic compounds of interest as with inorganic compounds present in the environment, especially with the metal ions of the solid matrix constituents, mobilizing them into groundwater. This study detected and quantified the metal ions of interest present in the solid matrix, namely: Fe, Al, Mn, Cr, Pb, Ni and Zn. lons that have been mobilized from the solid matrix due to the ozone injection in soil from a contaminated area for organic compounds were also determined.

M. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Macadamia activated carbon (MAC) was impregnated with different concentrations of nitric acid and heated under reflux to improve the structural characteristics of the adsorbent for both considerable reduction and enhanced removal of Cr(VI). The chemical oxidation of ACs increased the surface oxygenated functional groups. Adsorption of Cr(VI) was carried out by varying parameters such as contact time, pH, concentration, and adsorbent dosage. The optimum operating conditions for the adsorption of Cr(VI) were pH 1, contact time 240 min, adsorbent dosage 10.67 g/L and Cr(VI) concentration 100 mg/L. The results showed that the Macadamia–based AC could be used efficiently for the treatment of chromium-containing solutions as a low-cost alternative compared to commercial AC and other adsorbent reported. The results showed that treated MAC performed better than untreated MAC, signifying the effect of secondary treatment on the enhanced removal of pollutants. Comparable to the application of ACs is the development of imprinting technologies for selective metal ion remediation in environmental samples. The combination of ion imprinting effects and functionalized carbon adsorbents produce materials which effectively remove and selectively recognize the target analyte. Macadamia activated carbon (MAC) was chemically pre-treated with nitric acid to generate carboxyl groups on the surface. The carboxylated MAC was then reacted with triethylenetetramine, N,N’-diisopropylcarbodiimide and CrCl3.6H2O to produce MACN20-imprinted sorbents (MACN20-IIP). MACN20-non imprinted (MACN20-NIP) counterparts were prepared, but Cr3+ was excluded in the synthesis. Alteration of surface structural characteristics and characterization of prepared adsorbents as confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, Brunauer–Emmett–Teller and scanning electron microscopy. MACN20-IIP and MACN20-NIP adsorbents were evaluated for their Cr3+ uptake from aqueous solution in batch format. Maximum conditions were achieved at pH 5, 50 mg/L Cr(III) initial concentration and 33.33 g/L of adsorbent dosage. Presence of co-ions slightly diminished the removal of Cr(III) by MAC-IIP adsorbents. Application of the MACN20-IIP and MACN20-NIP on spiked acid mine drainage artificial sample led to collapse in the removal efficiency of MACN20-NIP while MACN20-IIP still showed good removal efficiencies. These results demonstrated that surface imprinting led to better adsorption rates and capacity. The data was better described by the Freundlich multilayer adsorption and pseudo-second order kinetic rate model. The combination of both the carbon sorbent and the surface-mediated IIPs effectively improved total chromium remediation in aqueous systems.

In this work a method for determination of canagliflozin and its degradation products by HPLC with UV and MS detector was developed. The developed method was used to study the forced degradation of canagliflozin and to investigate the major degradation products resulting from exposure of canagliflozin to oxidative stress. Canagliflozin is a phenolic glycoside derivative and a glucose-sodium transporter 2 inhibitor that stimulates urinary glucose excretion by suppressing glucose reabsorption from the proximal tubule in the kidneys. Canagliflozin is used to control blood glucose levels in patients with type 2 diabetes. In an optimized method, an Agilent Poroshell 120 SB-Aq (2.1 × 100 mm, 2.7 µm) column was used and a mixture of buffer (10mM HCOOH adjusted with ammonium hydroxide to pH 3.5) and acetonitrile as a mobile phase. The method validation included testing of accuracy, repeatability, the limit of detection and quantification, linearity and linear dynamic range, the robustness of the method, and testing of sample stability. The limit of detection of the method was 8.9·10-5 mg ml-1 (2.0·10-7 mol l-1 ) and the limit of quantification was 3.0·10-4 mg ml-1 (6.8·10-7 mol l-1 ). At a concentration of 0.3 mg ml-1 , the repeatability (n = 7) was 0.17 % and 0.75 % for the retention time and the peak...

Mozzarella cheese was made from milk fortified with iron so that the cheese contained 25 and 50 ppm iron. Iron was added to the milk in three ways: (1) complexed to casein (ferric-casein), (2) complexed to whey protein (ferric-whey protein), and (3) ferric chloride (FeCl3·6H20) added directly to milk. Cheese quality was determined by chemical, physical, and sensory characteristics and compared with a control cheese. Chemical oxidation, during 28 days storage, was determined by absorbance of malondialdehyde at 535 nm using the thiobarbituric acid assay (TBA). Physical properties were assessed by the Arnott test for melt, helical viscometer for stretch, and b* value for cook color. Sensory properties were tested by panelists trained to detect metallic and oxidized off-flavors and by large, untrained consumer panels. There were no significant differences in iron-fortified cheeses based on the method of adding iron to milk. There were no significant differences in TBA-measured oxidation caused by adding iron, method of adding iron, or by storage ( α=.05). Stretch was increased by addition of iron. Melt and cook color were not affected by iron fortification. The trained sensory panel scored metallic and oxidized off-flavors slightly higher in the iron-fortified cheeses than in the controls, although at a level that was slightly perceptible. When cooked on a pizza, the iron-fortified cheese was rated comparable to the control cheese by consumer panels. Based on the popularity of pizza and on these observations, it was concluded that iron-fortified Mozzarella cheese can be used as an appropriate food vehicle to supplement the diets of populations that are at risk for iron deficiency anemia (e.g., children and pregnant women).