Laboratory of Analytical Chemistry

Laboratory of, Greece

Laboratory of Analytical Chemistry

Laboratory of, Greece
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Sakkas V.A.,Laboratory of Analytical Chemistry | Kalaboka M.,Laboratory of Analytical Chemistry | Albanis T.,Laboratory of Analytical Chemistry
Science of the Total Environment | Year: 2017

The present study reports the photocatalytic transformation of stevioside, under simulated solar irradiation using TiO2 as a photocatalyst. As a tool of investigating the effect of various aqueous matrices, as well as, the initial stevioside concentration on the variation of the photocatalytic efficiency, a fully nested experimental design was employed. A significant impact on the degradation rate of the sweetener was observed: degradation rate decreases in the order distilled water > river water > lake water, attributed to the increased natural organic matter content of the respective natural water samples. Moreover, the investigation has involved the identification of intermediate compounds, as well as the assessment of mineralization and toxicity evaluation. More than one hundred unknown transformation products, most of them in the form of several isobaric species, were identified. By employing accurate mass determination, we were able to attribute an empirical formula to each species and through MSn analyses we were capable to distinguish several isobaric species. The overall transformation mechanism was assessed and involved the hydroxylation/oxidation of the molecule and the subsequent loss of the glucose units bound to the parent compound. © 2017 Elsevier B.V.

Kalaboka M.,Laboratory of Analytical Chemistry | Sakkas V.A.,Laboratory of Analytical Chemistry | Albanis T.,Laboratory of Analytical Chemistry
Journal of Hazardous Materials | Year: 2016

In the present study, we investigated the possibility to abate Acesulfame K, a persistent emerging contaminant, in aqueous media using zinc oxide based materials. For this purpose, bare and Ce-doped zinc oxide was prepared via an easy and cheap hydrothermal process using different cerium salts as precursors. Their photocatalytic performance was evaluated in different media, namely ultrapure and river water under both UV-vis and visible light. Commercial TiO2 P25 was also employed and used as a reference photocatalyst for comparison purposes. The obtained results pointed out that cerium doped zinc oxide composites exhibit higher performance than TiO2 P25, especially under visible light and in the presence of organic matter, when the activity of the latter is greatly depressed. In particular, ZnO doped with cerium (1%) was the most effective material, and could be a promising alternative to TiO2 P25, especially in the treatment of natural waters. © 2016 Elsevier B.V.

Rozet E.,Laboratory of Analytical Chemistry | Ziemons E.,Laboratory of Analytical Chemistry | Marini R.D.,Laboratory of Analytical Chemistry | Boulanger B.,Arlenda SA | Hubert P.,Laboratory of Analytical Chemistry
Talanta | Year: 2012

Saffaj and Ihssane, recently proposed an uncertainty profile for evaluating the validity of analytical methods using the statistical methodology of γ-confidence β-content tolerance intervals. This profile assesses the validity of the method by comparing the method measurement uncertainty to a predefined acceptance limit stating the maximum uncertainty suitable for the method under study. In this letter we comment on the response (T. Saffaj, B. Ihssane, Talanta 94 (2012) 361-362) these authors have made to our previous letter (E. Rozet, E. Ziemons, R.D. Marini, B. Boulanger, Ph. Hubert, Talanta 88 (2012) 769-771). In particular, we demonstrate that β-expectation tolerance intervals are prediction intervals, we show that β-expectation tolerance intervals are highly useful for assessing analytical methods validation and for estimating measurement uncertainty and finally we show what are the differences and implications for these two topics (validation and uncertainty) when using either the methodology of β-expectation tolerance intervals or the γ-confidence β-content tolerance tolerance interval one. © 2012 Elsevier B.V.

Ortega-Deballon P.,University of Burgundy | Ortega-Deballon P.,University Hospital | Facy O.,University of Burgundy | Facy O.,University Hospital | And 8 more authors.
Annals of Surgical Oncology | Year: 2010

Background. Hyperthermic intraperitoneal chemotherapy (HIPEC) achieves good results in selected patients with peritoneal carcinomatosis. There are two main procedures to deliver this therapy: the open abdomen and the closed abdomen techniques. A true comparison of the two techniques has never been performed. The aim of this study was to compare blood and abdominal tissue concentrations of oxaliplatin after open and closed techniques to deliver HIPEC. Methods. Nine pigs underwent HIPEC at 42-43°C for 30 min with oxaliplatin (400 mg/m2) according to two techniques: closed (three animals) or open (six animals). The open technique used either an external heater with a pump (three animals) or an intra-abdominal heating cable (three animals) to achieve hyperthermia. Temperature homogeneity, systemic absorption, and abdominal tissue mapping of the penetration of oxaliplatin with each technique were studied. Two additional pigs underwent hyperthermia with dyes instead of oxaliplatin to depict the distribution of the liquid within the abdomen with both techniques. Results. Hyperthermia was satisfactory with both techniques. The closed technique achieved higher temperatures within the diaphragmatic area, while the open technique obtained higher temperatures in the mid and lower abdomen (P<0.001 for both comparisons). The systemic absorption of oxaliplatin was higher with the open technique (P<0.04 for all comparisons), as was the accumulation within the abdominal cavity. The operating time for the two techniques was not greatly different. Conclusions. Intraperitoneal hyperthermia can be achieved with both techniques. The open technique had far higher systemic absorption and abdominal tissue penetration of oxaliplatin than the closed technique. © Society of Surgical Oncology 2010.

Irakli M.N.,Cereal Institute | Samanidou V.F.,Laboratory of Analytical Chemistry | Katsantonis D.N.,Cereal Institute | Biliaderis C.G.,Laboratory of Food Chemistry and Biochemistry | Papadoyannis I.N.,Laboratory of Analytical Chemistry
Cereal Research Communications | Year: 2016

Pigmented rice (Oryza sativa L.) genotypes become increasingly important in the agroindustry due to their bioavailable compounds that have the ability to inhibit the formation and/or to reduce the effective concentration of reactive cell-damaging free radicals. This study aimed at determining the concentrations of free, and bound phytochemicals and their antioxidant potential (DPPH and ABTS assays) as well as the vitamin E and carotenoids contents of non-pigmented and pigmented rice genotypes. The results confirmed that the content of total phenolics and flavonoids contents, as well as the antioxidant capacity (DPPH and ABTS assays) of pigmented rice was several-fold greater than non-pigmented ones (4, 4, 3 and 5 times, respectively). Compounds in the free fraction of pigmented rice had higher antioxidant capacity relative to those in the bound form, whereas the non-pigmented rice cultivars exhibited the opposite trend. Ferulic acid was the main phenolic acid of all rice genotypes, whereas black rice contained protocatechuic and vanillic acids in higher contents than red rice and non-pigmented rice genotypes. For vitamin E (tocopherols and tocotrienols) and carotenoids (lutein, zeaxanthin and β-carotene) contents, no obvious concentration differences were observed between non-pigmented and pigmented rice, with the black rice exhibiting the highest carotenoid content. Overall, pigmented rice genotypes contain a remarkable amount of bioactive compounds with high antioxidant capacity; therefore, they have great potential as a source of bioactives for developing functional food products with improved health benefits. © 2016 Akadémiai Kiadó, Budapest.

Barbosa A.F.,Federal University of Alfenas | Santos P.G.,Federal University of Alfenas | Lucho A.M.S.,Laboratory of Analytical Chemistry | Schneedorf J.M.,Federal University of Alfenas
Journal of Electroanalytical Chemistry | Year: 2011

Kefiran, an exopolysaccharide isolated from kefir d'acqua grains, has anti-inflammatory and antimicrobial activities, however, a mechanism of action directly associated with biomembranes is not yet understood. The influence of kefiran on a l-α-Phosphatidylcholine/cholesterol supported bilayer lipid membrane using a Pt electrode was studied by voltammetry and electrochemical impedance spectroscopy. The interaction of the oligosaccharide with s-BLMs promoted the access of Fe(CN)63-/4- probe ions to the electrode surface. Kefiran was found to induce molecular pores at the s-BLM surface within 5 min at 11.4 μmol/L. The suggested mechanism seems to involve hydrogen bonding between the carbohydrate and the phosphate head group of the phospholipid with a carpet-like model of interaction. The overall results can be contributed to direct molecular interactions between the prebiotic oligosaccharides and the cell surfaces, which can be related to the biological activity of kefiran in several experimental models. © 2011 Elsevier B.V. All rights reserved.

Christodoulou E.A.,Laboratory of Analytical Chemistry
Current Organic Chemistry | Year: 2010

In recent years there has been considerable interest in the synthesis and separation of enantiomers of organic compounds especially because of their importance in the biochemistry and pharmaceutical industry. Major differences in biological activity have been observed in chiral molecules. These differences in stereochemistry can influence the pharmacological, metabolic or toxicological activity of the finished drug formulations. In other words isomer specific pharmaceuticals often exhibit increased potency, higher bioavailability and reduced side effects when compared to racemic pharmaceutical compounds. The development of new practical methods for the preparation of enantiomerically pure substances is thus vital and nowadays, pharmaceutical industry demands detailed investigations of chiral molecules, in compliance with the regulatory requirements. In this review some of the most important methods developed for the enantiomeric resolution by high pressure liquid chromatography, from the last decade, are described. The mechanisms of the different separation principles are briefly discussed. Also the major chiral stationary phases, commercially available, are presented, including a guide provided to help the readers selecting the appropriate chiral stationary phase. Finally the most common chiral selectors used as additives in mobile phases are described, including their advantages and their limitations. © 2010 Bentham Science Publishers Ltd.

Miljanic S.,Laboratory of Analytical Chemistry | Dijanosic A.,Laboratory of Analytical Chemistry | Meic Z.,Laboratory of Analytical Chemistry
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2010

Surface-enhanced Raman scattering (SERS) of the cationic and the neutral form of rhodamine 19 octadecylamide (R19OA) has been studied in the silver citrate colloid using NIR excitation at 1064 nm. Cationic molecules readily adsorb onto negatively charged silver nanoparticles through a positively charged xanthene part of the molecules resulting in surface enhancement of Raman scattering. Due to a lack of the positive charge in molecular structure, SERS spectrum of neutral molecules is not observed. Nevertheless, a broad band appearing at 1240 cm-1 in the spectrum of the cationic form indicates conversion of the cationic into the neutral species occurring close to the silver surface. The observed band most likely arises from a vibration of the ring formed in the molecular structure after conversion, but before complete desorption of the neutral molecules from the metal surface. Upon addition of HCl and NaOH in the silver sol, equilibrium is shifted toward the cationic and the neutral form of R19OA, respectively, followed by corresponding changes in the Raman spectrum. In addition, FT-SERS spectra of two rhodamine dyes, rhodamine 19 (R19) and rhodamine 6G (R6G), that are structurally related to R19OA, have been studied under the same experimental conditions for comparison. © 2009 Elsevier B.V. All rights reserved.

Hubert C.,Laboratory of Analytical Chemistry | Ziemons E.,Laboratory of Analytical Chemistry | Rozet E.,Laboratory of Analytical Chemistry | Breuer A.,Laboratory of Analytical Chemistry | And 5 more authors.
Talanta | Year: 2010

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great biocompatibility. In this framework, a high-speed and costless analytical method for the determination of stannic ions, Sn(IV), in the presence of stannous ions, Sn(II), has been developed. The separation of these two ions was carried out using differential pulse polarography (DPP). For this purpose, the tin species contents in the catalyst is quantitatively extracted under inert condition to avoid any changes in the ratio Sn(IV)/Sn(II). Polarography showed well-shaped oxidation and reduction peaks respectively at -650 and -860 mV for stannous ions. The peak of the stannic ion was well separated and appeared at -1210 mV. Many parameters such as extraction process, extraction time, pH, chelating agents and polarographic conditions were optimized. We have also demonstrated that no oxidation of the stannous ions occurred during the sample preparation. The dosing range considered in this study extends between 10 and 40 μg/mL, corresponding to 6.8% and 27.2% of the degradation product (Sn(IV)) in the catalyst, regarding to the sampling. Finally this method was successfully validated using the total error concept. © 2009 Elsevier B.V. All rights reserved.

Kalomiraki M.,Laboratory of Analytical Chemistry | Thermos K.,University of Crete | Chaniotakis N.A.,Laboratory of Analytical Chemistry
International Journal of Nanomedicine | Year: 2016

Dendrimers are large polymeric structures with nanosize dimensions (1-10 nm) and unique physicochemical properties. The major advantage of dendrimers compared with linear polymers is their spherical-shaped structure. During synthesis, the size and shape of the dendrimer can be customized and controlled, so the finished macromolecule will have a specific “architecture” and terminal groups. These characteristics will determine its suitability for drug delivery, diagnostic imaging, and as a genetic material carrier. This review will focus initially on the unique properties of dendrimers and their use in biomedical applications, as antibacterial, antitumor, and diagnostic agents. Subsequently, emphasis will be given to their use in drug delivery for ocular diseases. ©2016 Kalomiraki et al.

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