Search

Introduction. The aim of this study is to estimate the nutritional value of fish soup from cultured brook trout in terms of a healthy diet for human consumption.

In this study, comparative analyses were carried out with ion chromatography mass-spectrometry (IC-MS/MS) which has no derivatization step, high-performance liquid chromatography (HPLC) technique, as well as two quantitative and two semi-quantitative immunoassays. The results demonstrated that HPLC and quantitative immunoassay methods were well-correlated with IC-MS/MS in determining histamine in various types of fish products. The best correlation was observed with the HistaSure ELISA Fast Track kit (R2 = 0.9903). More than half of the values (68%) obtained by two methods were also statistically similar. The results of semi-quantitative test kits also supported histamine values estimated by quantitative methods, with some exceptions. The best results were found for HistaSure Lateral Flow in supporting the quantitative techniques. Therefore, these methods are found suitable for monitoring histamine in fish products in terms of food safety. Good correlations were also observed HPLC and IC-MS/MS in determining cadaverine, putrescine, and tyramine with the highest value observed for tyramine as R2 = 0.9785. However, no correlation was observed for other biogenic amines, and the majority of the results were significantly different from each other for these amines (p &lt, 0.05). The differences may be caused by the drawbacks reported previously for HPLC. However, further studies are required to confirm the possible effects. This study provides a comparative evaluation of several methods in terms of their suitability in determining biogenic amines in fish products for both monitoring and regulatory purposes.

A library of 24 6-(5-oxo-1-phenylpyrrolidin-3-yl)pyrimidine-5-carboxamides 10{1,2; 1–12} was prepared by a parallel solution-phase approach. The synthesis comprises a five-step transformation of itaconic acid (11) into 1-methyl and 1-phenyl substituted 6-(5-oxo-1-phenylpyrrolidin-3-yl)pyrimidine-5-carboxylic acids 17{1,2} followed by parallel amidation of 17{1,2} with a series of 12 aliphatic amines 18{1–12} to afford the corresponding carboxamides 10 in good overall yields and in 80–100% purity.

By utilizing an underexplored reactivity of N1-substituted pyrazolidine-3-ones, we developed a visible-light-induced aerobic oxidation of N1-substituted pyrazolidine-3-one derivatives yielding the corresponding azomethine imines. The resulting azomethine imines can be further reacted with ynones in situ under copper catalyzed [3 + 2] cycloaddition reaction conditions yielding the corresponding pyrazolo[1,2-a]pyrazoles in good yields. The methodology can be extended to other 1-aryl-substituted pyrazolidinones which undergo endocyclic oxidation deriving the corresponding pyrazolones as single products.

Self-assembly of AgOTf and AgF with the hexatopic ligands hexakis(pyridin-2-yl)benzene (2) and 2,4,6-tris(pyridin-2-yl)-1,3,5-tris(quinolin-2-yl)benzene (3) affords the discrete sandwich-shaped complexes [Ag4F(2)2](OTf)3, [Ag4F(3)2](OTf)3, and [Ag5F(2)2](OTf)4. The solid-state structures of the complexes were characterized by single-crystal X-ray diffraction analysis, which revealed that the fluoride anion is coordinated in the center of the Ag4-square or Ag5-pentagon units which are positioned between two molecules of the hexakis(azaheteroaryl)benzene. The generation of complexes is dictated by a unique cooperation of ligand coordination, argentophilicity, and fluoride anion inclusion. All three complexes adopt highly symmetrical structures in solution, as evidenced by appearance of one set of proton resonances for the two ligands arranged face to face., Multinuclear sandwich-shaped silver(I) complexes are readily assembled by a unique cooperation of nitrogen-coordinating hexaheteroarylbenzene ligands, silver atoms, and fluoride anion.

A new method for determination of underivatized biogenic amines in cheese based on ion exchange chromatography coupled with tandem mass spectrometric detection was proposed. The method was applied to the analysis of 10 biogenic amines (trimethylamine, putrescine, cadaverine, histamine, 2-phenylethylamine, spermine, spermidine, tryptamine, agmatine, and tyramine) in different types of cheese. The amines were extracted only with water without any additional derivatization step or sample cleanup. This is a great advantage in terms of simplicity of sample pretreatment procedure compared with other currently existing methods in the literature. Biogenic amines were separated using cation exchange column, under gradient elution conditions by mixing formic acid (1.00 M) and deionized water. Detection was achieved using tandem MS/MS, with the instrument set into multiple reaction monitoring mode to ensure high specificity. The detection and quantification limits were in the ranges of 12–46 μg/L and 40–153 μg/L, respectively. The exceptions were spermidine and spermine, with detection limits of 0.8 and 5.4 mg/L, respectively. The linearity for most of the biogenic amines was from 10 μg/L up to 10 mg/L. The best recoveries were observed for trimethylamine, tyramine, and cadaverine, and were 89, 94, and 102%, respectively. The results showed that this method can be used for routine determination of biogenic amines in different types of cheeses as well other food matrices. It must be stressed that the proposed method is capable of determining 10 biogenic amines, including tyramine, which is reported to cause food intoxication commonly associated with cheeses.

The authors gratefully acknowledge the support of Slovenian Research Agency (P1-0034 and P1-0153). The support of the British Council (Partnership in Science Award RNP 7/2008), Slovenian Technology Agency TIA (VALOR08-02) and SPIRIT Slovenija (P-MR-09/104) is also gratefully acknowledged.

Separation of 57 species from solutions of commercial melamines and analysis by high resolution mass spectrometry using electrospray ionisation and atmospheric pressure chemical ionisation is reported. Structures for melamine-based crosslinked polymers were also confirmed with two orthogonal techniques for characterisation of polymers: Fourier Transform Infrared Spectrometry (FTIR) and Nuclear Magnetic Resonance spectroscopy (NMR), respectively. Accurate mass measurements of melamine–formaldehyde resin structures were achieved in the ppm range, using an internal calibration standard reserpine. Results were within 5 ppm of calculated formulae. Relative isotopic abundances of [M+H] + ions were evaluated for different fractions. Results were independent of the mobile phase used. NMR studies also confirmed structures of fractions and their thermal stability up to 70 °C. Differences in NMR spectra were explained by change of conformation and it was confirmed that this is a reversible process by reheating samples. Stability at 70 °C was confirmed by MS, since when the temperature of the ion transfer capillary in MS was set above this temperature decomposition occurred.

Iron gall ink was the most widely used writing ink for paper from the Middle Ages to the twentieth century. Unfortunately, the ink ingredients contain corrosive transition metal ions and acids that cause severe damage to the paper carrier. New or improved paper conservation methods for iron gall ink stabilization are constantly sought. The aim of the study was evaluation of a recently proposed stabilization treatment, adapted to lower relative humidity, applied to various model and historical paper samples containing iron gall ink. The effect of stabilization treatment on paper samples during artificial thermal aging was followed by the determination of the molecular weight distribution by size exclusion chromatography and colorimetry. Migration of iron and copper compounds from the ink lines was monitored by laser ablation inductively coupled plasma mass spectrometry. The results demonstrate that effective stabilization of iron gall ink-containing paper can be successfully achieved by interleaving with papers impregnated with the antioxidant tetrabutylammonium bromide and alkaline buffer under experimental conditions. Negative side effects of the stabilization treatment, such as migration of iron or copper ions from the ink lines and changes of color after the treatment and after accelerated thermal degradation, were limited, proving that the proposed stabilization treatment can be considered for future use by conservators.

Vinylogous peptides 3 with a vinyl fragment inserted into the peptide C–N bond were prepared from ynones 6 and enaminones 7 that are easily available from Boc-protected α-amino acids 4. Coupling at the C terminus was achieved by 1,4-addition of amino esters 5 to the C≡C bond in 6 or by substitution of the NMe2 group in 7 to give N-terminal vinylogues 3a–p. Coupling at the N terminus of 3 and 7, in contrast, required temporary protection of the acidolytically labile enamino moiety. Thus, cyclization of 6 or 7 with hydroxylamine, removal of the Boc group with HBr–AcOH, acylation of free amine 10 with BocGlyOH (4a), and hydrogenolytic deprotection of the enamino moiety in the presence of GlyOMe (5a) led to tripeptides 3q–s with vinylogous amide as the central building block.

A simple and practical four-step protocol for the parallel synthesis of 7-heteroaryl-pyrazolo[1,5- $$a$$ ]pyrimidine-3-carboxamides was developed. The synthesis starts with transformation of commercially available 2-acetylpyridine and acetylpyrazine with $$N,$$ $$N$$ -dimethylformamide dimethylacetal into the corresponding $$(E)$$ -3-(dimethylamino)-1-(heteroaryl)prop-2-en-1-ones followed by cyclisation with methyl 5-amino-1 $$H$$ -pyrazole-4-carboxylate to give methyl 7-heteroarylpyrazolo[1,5- $$a$$ ]pyrimidine-3-carboxylates. Hydrolysis of the ester group and subsequent amidation of the so formed carboxylic acids with 12 primary and secondary aliphatic amines furnished a library of 24 title compounds in good overall yields and purity.

Seventy-eight salted fish products originating from Turkey and European countries were analyzed for their content of biogenic amines (BA), water activity (aw), salt and moisture, and their microbiological counts. About 10% of the samples exceeded regulated histamine levels established by the FDA and/or EU authorities. The highest histamine value was found for brined anchovy as 422 ppm. Among the other BAs, the highest level was obtained for tyramine as 524 ppm. The low aw (

Structural changes of carboxymethyl cellulose (CMC) during biodeterioration with Bacillus subtilis subsp . subtilis NCIB 3610 were studied with small-angle X-ray scattering (SAXS), size exclusion chromatography, and viscosity measurements. Cleavage of CMC polymers changed flow characteristics from those of non-Newtonian pseudoplastic fluid to those of Newtonian fluid. The viscosity decreased from 10 to 1.4 mPas and the concentration of reducing sugar increased by 18-fold. Upon biodeterioration the average radius of gyration decreased from 147 to 123 A; cleaved polymer chains remained in close contact in unstirred medium as reflected by a relatively large apparent radius of gyration. However, such degraded CMC aggregates were easily dispersed with shear stress. The results suggest that biodeterioration mainly affects CMC structural features that are larger than 5 nm. Furthermore, the results also suggest that CMC metabolism and biodeterioration may be decoupled; B. subtilis subsp . subtilis NCIB 3610 produces cellulases that effectively cleave CMC but cannot efficiently utilize hydrolyzed products. There were no structural or rheological changes observed in the absence of B. subtilis subsp . subtilis NCIB 3610 growth.

Iron gall inks were the most often used inks from the Middle Ages until the 20th century; examples include the drawings by Leonardo and scores by Bach. These masterpieces are threatened by the corrosive properties of the ink. In order to increase the longevity of the materials, stabilisation treatments have been developed during the last two decades. Their effectiveness has often been determined by comparing rates of degradation during accelerated tests. However, such evaluation using historical materials is limited by the amount of material required by various analytical methodologies. The paper describes the use of size exclusion chromatography (SEC) of cellulose containing iron gall ink, derivatised using phenyl isocyanate. A linear correlation is observed between the weight average degree of polymerisation obtained with SEC and the one obtained using viscometry, with a slope of 1.4. The method was used to evaluate the extent of stabilisation of historic documents containing iron gall inks during accelerated degradation. Despite considerable uncertainty, also caused by the heterogeneity of historic materials, it is demonstrated that efficient stabilisation by factors of 10 and 20 times is achievable using a calcium phytate treatment.

A simple five-step diversity-oriented synthesis of 1-substituted 4-aryl-6-oxo-1,6-dihydropyridine-3-carboxamides was developed. Treatment of dimethyl 2-((dimethylamino)methylidene)-3-oxopentanedioate with twenty primary amines gave 1-substituted methyl 4-hydroxy-6-oxo-1,6-dihydropyridine-3-carboxylates. Transformation into the corresponding 4-tosyloxy and 4-chloro derivatives, followed by Suzuki-Miyaura arylations gave a series of eleven N-substituted methyl 4-aryl-6-oxo-1,6-dihydropyridine-3-carboxylates. Combinatorial screening was employed to establish suitable reaction conditions for Suzuki-Miyaura arylation of N-alkylpyridones. Hydrolysis of the esters followed by parallel solution-phase amidation of the corresponding carboxylic acids with primary and secondary amines furnished a library of seventeen final products.

In this study, 65 traditional fish samples, 35 of which originated from 11 European countries and 30 from Turkey were analysed for biogenic amines, water activity (a w), pH, %salt, %water phase salt, moisture contents and microbial counts in terms of food safety. In total, eleven samples contained histamine values between 70 and 1,544 mg/kg, which are over FDA permitted level of 50 mg/kg, four of which also exceeded EU and Turkish permitted limit of either 100 or 200 mg/kg. The highest histamine value was attributed to fish paste at 1,544 mg/kg and among other biogenic amines, the highest value was observed for cadaverine at 1,862 mg/kg represented by smoked bonito. Putrescine levels in most of the fermented samples were found to be high between 141 and 836 mg/kg. Some of the other highest levels of biogenic amines were phenylethylamine, tyramine and tryptamine at 219, 783 and 517 mg/kg, respectively. This study shows that although most products of traditional fish-processing types from these countries are safe for biogenic amine development, some are still lacking effective preventive actions. This situation suggests the awareness on seafood safety for such processing types.

Mulberry (Morus spp. L., Moraceae) fruits, leaves, bark and branch have been used in traditional medicine as diuretic, hypoglycemic and hypotensive. The mechanism of their effects is correlated with the content of active components. Objective of this work was to evaluate and compare antioxidant properties of different extracts of two Morus species growing in Serbia: Morus alba L. (white mulberry) and Morus nigra L. (black mulberry). Potential antioxidant activity, content of antioxidant compounds (phenolics and flavonoids) and radical scavenging capacity, tested by DPPH method, were evaluated. The phenolic and flavonoid composition of different Morus extracts was determined by the HPLC method. The extracts prepared from fruits, leaves and roots of M. alba and M. nigra exhibited different characteristics. The highest extraction yield was achieved by M. alba leaves extraction (23.40%). M. nigra roots extract shown the highest total phenolics (186.30 mg CAE/g), while highest total flavonoids content (67.37 mg RE/g) was determined for M. nigra leaves extracts. In addition, black mulberry leaves extracts with the highest antioxidant activity had the highest phenolic acids contents. The dominant phenolic components in the samples were rutin and chlorogenic acid. All investigated mulberry dry extracts shown high content of phenolic compounds and significant antioxidant activity. This work contributes to knowledge of the antioxidant properties of Morus species. The obtained results may be useful in the evaluation of new dietary supplements and food products.

Oxidative processes lead to enhanced degradation of cellulose in alkaline environment, especially in the presence of transition metals, such as iron and copper. Considerable parts of collections of manuscripts, drawings, maps and archival materials throughout the world are seriously damaged as the result of the use of iron gall inks and copper based pigments. The research on cellulose degradation and stabilization in the presence of transition metals is therefore crucial for the development of paper stabilization methods. The aim of this study was to evaluate the possibility of slowing down oxidative degradation of papers containing transition metals by their contact with paper folders containing antioxidant. The paper discusses the degradation rate constants of paper samples with elevated amounts of copper and iron ions and their mixtures during accelerated thermal ageing in contact with papers containing none or various amounts of quaternary ammonium salt. Their efficiency in respect to concentration of the antioxidants is presented. The research demonstrates that effective stabilization of paper samples with higher amounts of iron and copper ions in mildly alkaline environment by interleaving with papers, impregnated with antioxidant tetrabutylammonium bromide can be achieved under given conditions. Simple conservation procedure was proposed and evaluated for iron gall ink containing paper samples.

The Pholasin chemiluminometric method for determination of polyphenols in wine was evaluated by comparison with liquid chromatography with mass-spectrometric detection. The results were also compared with the conventional Singleton-Rossi spectrophotometric method for determination of total polyphenols. A total of 141 wine samples were examined using all three methods and the results indicated a good agreement between the chemiluminometric and the Singleton-Rossi methods; however, the chromatographic data correlated reasonably well with the chemiluminometric data only for gallic acid, but less well or not at all with other determined phenolic antioxidants: trans-resveratrol, (+)-catechin, (−)-epicatechin, quercetin, vanillic-, caffeic-, caftaric-, p-coumaric-, 3,4-dihydroxybenzoic-, ellagic-, sinapic-, ferullic-, and ellagic acid.

Furocoumarins are a group of naturally occurring oxygen heterocyclic compounds synthesized by different plants (mainly Citrus species). They have several physiological effects, e.g. photoreactivity and inhibition of intestinal and liver drug metabolism, which imply the need to control their concentration in products intended for human use. We tested different sample preparation approaches and LC with different detection modes: UV, APCI–MS/MS and ESI–MS/MS for the determination of bergapten (BGPT) and bergamottin (BGMT) in different samples of beverages and cosmetics. Direct injection of sample solutions was applicable only for essential oils, while liquid–liquid extraction proved to be time-consuming and unsuitable for our samples. Solid-phase extraction with a preconcentration factor of 20 yielded repeatable recoveries for aqueous solutions (97.4% for BGPT, 64.6% for BGMT) and the concentration range was > 0.1 mg/l for UV detection and 2–1000 µg/l for MS/MS detection. Results of sample analysis indicated some problems connected both to detection and the extraction. The standard addition method for quantification yielded the most reliable results. Copyright © 2008 John Wiley & Sons, Ltd.

In chemiluminometry, we measure the very faint light as a consequence of chemical reactions. During oxidation of cellulose, several reaction pathways lead to light production and in the present work we investigated chemiluminescence as a consequence of peroxide formation.With C-13-1 labelled glucose we studied oxidation of the end groups by following the emission of (CO2)-C-13 using gas chromatography-mass spectrometry. A mechanism of peroxyacyl radical formation is suggested. Its proposed decomposition is a first-order reaction, which is reflected in chemiluminometric experiments. From these, we calculated the activation energy of the process, which depends on the temperature and is approximately 75 kJ mol(-1) at T > 100 degrees C and similar to 55 kJ mol(-1) at T < 100 degrees C.Evidence is also presented on self-absorption of chemiluminescence in cellulose, suggesting that the phenomenon may account for up to 50% intensity loss. (c) 2007 Elsevier Ltd. All rights reserved.

When applying biosynthetic engineering approaches at the early stages of drug discovery, e.g. aiming to develop novel tetracycline analogues, target compounds are generally produced by engineered microorganisms in low yields. Rapid and reliable identification of metabolites with desired structural modification directly from bacterial cultures is therefore of great importance.Structural elucidation of atypical tetracyclines was carried out by fragmentation applying electrospray ionisation tandem mass spectrometry (ESI-MS/MS) (triple quadrupole - linear ion trap; Applied Biosystems 4000 QTRAP) and a high-resolution mass spectrometer (Agilent Technologies 6224 TOF). Fragmentation patterns were obtained either with direct injection or by applying separation of target compounds with high-performance liquid chromatography (HPLC) prior to mass spectrometry. In-source and CID fragmentation were compared. Theoretical calculations of target structures using the Gaussian programme suite were carried out with the aim of strengthening experimental structural elucidation.Recombinant strains of Amycolatopsis sulphurea producing atypical tetracyclines chelocardin, modified chelocardin analogues (9-demethylchelocardin and 2-carboxyamido-2-deacetyl-chelocardin (CDCHD), and anhydrotetracycline (ATC) were analysed by collision-induced dissociation (CID) fragmentation with higher collision energies to yield structurally important fragments which were identified. We have demonstrated that ATC is more prone to fragmentation compared to its epimer, which was further supported by comparison of both structures calculated with ab initio calculations.We have demonstrated that fragmentation patterns of atypical tetracyclines in CID-MS spectra enable rapid structural elucidation of target metabolites produced by cultures of genetically engineered bacteria. This method is of significant importance for early stages of drug development considering that isolation of target metabolites produced at low concentration is challenging. Copyright © 2015 John WileySons, Ltd.

Whatman cellulose impregnated with calcium and magnesium carbonates was oxidized and chemiluminescence accompanying this oxidation has been measured. It was shown that magnesium ions in deacidified cellulose pulp promote the light emission significantly. On the other hand, acid papers give the more pronounced light signals at temperatures close to ambient. The relation between chemiluminescence runs and paper degradation has been implicated, with an attempt to extrapolate half-lives of paper samples to conditions close to ambient.

Laser cleaning is an attractive and advanced technique of cleaning cultural heritage materials. However, in the case of paper-based substrates, it may lead to surface discoloration and long-term destabilisation of the cellulosic component. The origin of discoloration during pulsed laser removal (Nd:YAG laser, 532 and 1064 nm) of carbonaceous soiling was studied using UV resonance Raman spectroscopy and X-ray photoelectron spectroscopy. It was concluded that macromolecular conjugated systems are the most probable cause of discoloration, formed as a consequence of thermolytic reactions. With chemiluminometry, we analysed the processes following irradiation. Using photo-ageing and thermally accelerated ageing, it was indicated that, even at fluences lower than the ablation threshold of cellulose, long-term destabilisation of the material should be taken into account. By using much lower laser shot repetition rates than usual, i.e. 1 s-1, we can allow the substrate to cool between consecutive laser shots, thus minimising the adverse effects of laser treatment. Acoustic monitoring was shown to be an affordable possibility for on-line process control. The amplitude of shock waves was shown not to be wavelength dependent (532 or 1064 nm); however, the parameter can be used to monitor the progress of cleaning.

Irradiation by light is considered to be one of the primary sources of damage exerted upon cellulosic substrates at ambient conditions. Yet, contrary to studies on thermal ageing of cellulose, only limited attention is devoted to light induced degradation of paper.This research demonstrates that extensive oxidative degradation of cellulose, accompanied by formation of hydroxyl radicals, occurs during exposure to light with λ G 340 nm. As demonstrated by size exclusion chromatography, degradation is not random. No high-molecular weight fraction appears in the irradiated sample, meaning that cross-linking is not a dominant process. This justifies the use of viscometry for light-irradiated cellulosic materials. Studies show that the rate of degradation, carbonyl formation and brightness decrease may be reduced by addition of magnesium carbonate. C 2005 Elsevier Ltd. All rights reserved.

The kinetic data obtained from chemiluminescence (CL) accompanying oxidation of cellulose containing pulps were compared with those from polymerization degree determinations and mechanism of CL accompanying the oxidation of cellulose was discussed. At the same time, the CL method has been used to explore the effect of oxygen and water in a reactor allowing the humidity control. The specially designed chemiluminometer Lumipol 3 has been used for this purpose coupled with humidity control chamber. An addition of water flow to oxidized pulp sheet leads to an immediate increase of CL and to its relaxation decay. The similar phenomenon has been observed when water flow was stopped, the decay of the signal following the initial increase, however, occurred with slower kinetics. The signal increase due to wetting and drying was strongly pronounced by the presence of Mg(HCO3)(2) and by the origin of the pulp sheet, and in the case of wetting, also by the total amount of water being in contact with the surface of pulp sheet. (C) 2004 Elsevier Ltd. All rights reserved.

Sample properties, such as crystallinity, morphology and size, potentially influencing chemiluminescence emission during atmospheric oxidation of cellulose, were studied. In order to obtain samples with 30.7, 26.4, 14.6, and 0.0% crystallinity, microcrystalline cellulose was milled to different extents. It was shown that crystallinity has no major influence on chemiluminescence emissions either as a result of thermal or photo-oxidation. Pulp beating to different degrees was used to obtain pulp fibres of different morphology and thus different surfaces exposed to atmospheric oxygen. It was determined that the more refined the fibres, the larger is the content of peroxides present in the material. As a consequence, higher chemiluminescence emissions were observed. With the aim of sample miniaturisation samples of 0.11, 0.21, 0.47 and 0.70 mm were compared with the usual sample size of 9 mm diameter. The minimum sample diameter giving a satisfactory signal was 0.47 mm.

Degradation of pullulan samples of narrow molecular weight distribution was studied in O2 and N2 atmosphere at 180 °C and in air at 80 °C, 65% RH. At higher temperatures, size exclusion chromatographic analyses provided evidence for non-random degradation and formation of cross-links, a phenomenon depending on the concentration of carbonyl groups. Initial degradation rates in oxidative and inert environments were comparable, while at longer reaction times extensive cross-linking was typical of degradation in oxygen. At 80 °C, in a moderately alkaline environment, the degradation remains random, as demonstrated by the mono-modal distributions of molecular weights. Furthermore, there was no evidence of cross-linking. Correlations between the concentration of aldehyde end-groups in the pullulan samples, rates of degradation and the content of peroxides after a pre-oxidation treatment, as determined by the use of chemiluminometry, were demonstrated. This leads to the conclusion that aldehyde groups, via the peroxide intermediates, have the decisive influence on the rates of oxidative degradation of polysaccharides.

A new chromatographic method for determination of hydroperoxides in cellulose is described, whereby the sample is dispersed in phosphate buffer solution (pH 7) of FeCl(3), EDTA and the hydroxyl radical scavenger, N,N'-(5-nitro,1,3-phenylene)bisglutaramide. The reaction time, concentration of reagents and chromatographic conditions for subsequent separation and quantification of hydroxylated products are optimised. The limit of detection is 0.14 micro mol L(-1) H(2)O(2) which corresponds to 2.1 micro mol hydroperoxides per kg of cellulose (mass of sample: 0.4 g). It was shown that in the concentration range of H(2)O(2) up to 15 micro mol L(-1) the method gives linear response and that adsorption of reaction products on fibres is negligible. For cellulose samples, this corresponds to a linear range of 2.1-225 micro mol of hydroperoxides per kg. Due to possible side reactions of hydroxyl radicals in the suspension of analyte, it is recommended that the standard addition technique is used. In purified cotton cellulose, the steady state concentration of hydroperoxides at room conditions was found to be 15.1+/-1.5 micro mol kg(-1).

International audience; In this study, stability of statin drugs in different conditions, such as various pH, diverse solvents ratio, presence of UV, and sunlight have been investigated. Results suggest strong dependence of statins upon pH, potential environmental persistence towards sun light, and UV light degradation via singlet excited state obtained by excitation into the pi-pi* band. In acidic conditions interconversion between lactone and hydroxy acid forms in aqueous solutions at room temperature is retarded, while for the same sun-exposed samples are accelerated. Longer exposures lead to the degradation processes. Statin interconversion in water is much lower than in acetonitrile.

Corrosion of copper in ammonia solutions is significantly affected by a large number of parameters such as the concentration of ammonia, pH, temperature, concentration of Cu 2+ , the presence/absence of dissolved oxygen, the chemical nature, and the concentration of the anion but also by selected corrosion products, in particular, Cu + , various adsorbed intermediates, and finally passive films. In the present work we try to elucidate the corrosion of copper in a wide potential window [from ―1.4 to 0 vs mercury/mercurous sulfate electrode (MSE)] and in a broad range of concentrations of various species (0.2-3.5 mol/L NH 3 , 0-0.1 mol/L Cu 2+ , pH 10-12.5). Then, we focus on the first peak occurring within ―1.0 to ―0.6 V vs MSE with the aim to explain the underlying mechanism. We show that the reaction order of the dissolution reaction with respect to ammonia is 2. We further show that using conventional electrochemical methods in combination with an optical method (scanning electron microscopy), a two-step (electrochemical-chemical) reaction yielding Cu 2 O is identified as the most likely passivation mechanism, consistent with previous assumptions by other authors. Finally, we confirm this mechanism by performing impedance analysis at various experimental conditions.