Determination of elements in algae by different atomic spectroscopic methods

The chemistry of substances derived from plants has received a great deal of attention in the last several decades. Today, natural products and their synthetic analogs also play an important role in the pharmaceutical and food industry. Several interesting reviews on algae were published in the last 10 years. Algae, especially the red algae, are very helpful in every day practice in many fields, e.g. algal polysaccharides, agar, carrageenan and some algae extracts are used in agricultural, medicines and in food products, respectively (The Constituents of Red Algae, 1999; Gelling Hydrocolloids in Food Products Applications, 1979, p. 186; Marine Natural Products Chemistry, 1997, p. 337; Algae Polysaccharides, 1983, p. 195). The biological and pharmaceutical properties promote interest among chemists to focus their attention on algae, as yet, a wide open field (Synthesis and Proceedings of the Second EUMAC Workshop, Marine Eutrophication and Bentic Macrophytes, p. 2). The most extensively studied algal phyla are Chlorophyceae (green algae) (J. Phycol. 26 (1990) 670), Rhodophyceae (red algae) (J. Phycol. 25 (1989) 522) and Phaeophyceae (brown algae) (J. Phycol. 31 (1995) 325; J. Phycol. 32 (1996) 614). Concentrations of four elements (Ca, Mg, K, Na) were determined in the above-mentioned algal phyla by different atomic spectroscopic methods (F-AES, ICP-AES) after the digestion of algal samples with cc. HNO₃ in a microwave apparatus. Not only the Ca and Mg contents, but the ratio of the calcium to magnesium was calculated in every case. This ratio was lower (0.5–0.8) in green algae than in the red and brown algae (1.3–14.4). Therefore, the green algae are better magnesium sources than the red and brown. The elemental composition is of great importance in the ion system of human organism. It is usually characterized by the ion quotient ([Ca²⁺]+[Na⁺]:[Mg²⁺]+[K⁺]), which is approximately 1.0 under ideal conditions. However, in the human body this mole ratio generally varies between 2.5 and 4.0. The ion quotient was calculated by averaging between 1 and 2 in different algal phyla. This means that the 2.5–4.0 mole ratio can be decreased by different algal foods in the human organism.     

Binding analysis of farrerol to lysozyme by spectroscopic methods

Binding of farrerol to lysozyme (LYSO) was investigated at 302, 313 and 318 K at pH 7.4 using spectrophotometric techniques such as fluorescence emission, circular dichroism (CD) and UV absorption. The data obtained from fluorescence quenching experiments showed that farrerol was bound to LYSO and the affinity was enhanced by the addition of farrerol. When the concentration ratio of farrerol to LYSO was higher than 5.4, both the binding constant and the binding stoichiometry went up. Based on the thermodynamic parameters evaluated from the van't Hoff equation, the enthalpy change (deltaH degrees ) and entropy change (deltaS degrees ) were derived to be negative values. They indicated that both van der Waals forces and hydrogen bonds are the major interactions between farrerol and LYSO. A value of 2.67 nm for the average distance r between farrerol (acceptor) and tryptophan residues (Trp) of LYSO (donor) was derived from the fluorescence resonance energy transfer. Besides, the change in the conformation of LYSO was observed, being caused by the interaction with farrerol.     

Comparison of two infrared spectroscopic methods for cheese analysis

Two infrared spectroscopic methods, optothermal near infrared (NIR) spectroscopy and Fourier transform mid-infrared-attenuated total reflection (FTIR-ATR) spectroscopy, were applied to 24 cheese samples in order to obtain protein, fat and moisture contents. Reference values of the protein, fat and moisture contents in weight percent were obtained using standard wet chemistry analysis. Prediction correlation coefficients between 0.93 and 0.96 and standard errors of prediction between 2% and 5% were obtained using optothermal spectroscopy while the corresponding values for FTIR-ATR were 0.81–0.92 and 4–9%. Inhomogeneities in the cheeses, primarily due to the fat droplets, are probably the main reason for the differences in the error sizes. The superior results for optothermal spectroscopy are the more attractive because the instrument is easier to use than the FTIR-ATR instrument, it provides results more quickly with simpler statistical analysis and it is more compact and robust.     

Halogen determination in Arctic aerosols by neutron activation analysis with Compton suppression methods

The study of halogens particularly bromine and chlorine in Arctic aerosolshas received a great deal of attention in the past decade in ozone depletionduring polar sunrise studies. Iodine has also been studied as part of geochemicalcycling. We have shown that all three of the above elements can be determinedsimultaneously with very low detection limits using epithermal NAA in conjunctionwith Compton suppression methods. Besides lowering the background considerably,Compton suppression can eliminate or minimize the overlapping peak of the620 keV photopeak arising form the 1642 keV double escape peak of ³⁸Cl interfering with the 616.9 keV photopeak of ⁷⁹Br(n,) ⁸⁰ Br reaction. Iodine is ideally determined by epithermal NAAbecause of its very good resonance integral cross-section. Although chlorineis usually determined using thermal neutrons via the ³⁷Cl(n,) ³⁸Cl reactions, epithermal NAA is still feasible for the Arcticaerosol, since it has a major sea-salt component.     

Infrared spectroscopic properties of sodium bromide aerosols

The infrared extinction spectra of aqueous NaBr aerosols at ambient temperature have been measured as a function of relative humidity. Submicron-sized aerosol particles atomized from aqueous NaBr solutions at various concentrations are dried and/or mixed with nitrogen at different humidities and spectroscopically monitored as they flow through an infrared absorption cell. Estimated dry particle median diameters range from 0.24 to 0.15 microm, as calculated from Mie extinction theory. Measured deliquescence and efflorescence relative humidities (35-40% and 25-30%, respectively) are in accordance with previously reported ones. Our results show that NaBr particles take up water only moderately over the deliquescence point, with a significant increase at relative humidities above 70%. The effect of particle size onto water uptake properties has been studied, indicating that smaller particles take up lower amounts of water, and only increase their size significantly at relative humidities near saturation. Particle composition and diameter growth factors have been calculated from spectral data and are shown to be consistent with those predicted from thermodynamic data and Kohler theory. Band centers of liquid water in NaBr aerosols relative to pure water are blue-shifted up to 50 cm-1 at low humidities. Particle structure and phase, together with atmospheric implications, are also discussed.     

Chemometric methods in NMR spectroscopic analysis of food products

The main achievements of high-resolution NMR spectroscopy in combination with different chemometric methods in the analysis of food products in the last 40 years are reviewed. The essence of chemometric methods used for the analysis and interpretation of NMR spectra is briefly described. Sample preparation for NMR-spectroscopic analysis is characterized. Methods for the mathematical treatment of NMR spectra (smoothing, Fourier transformation, bucketing, normalization, and selection of spectral ranges) are considered. Currently available methods for the suppression of the signals of macrocomponents, including those for the simultaneous suppression of several signals, are described. The results are illustrated based on examples of analysis of different classes of foodstuffs and beverages with the use of NMR spectroscopy and chemometric methods for classification and discrimination (geographical and botanical origin as well as validating checking the brand authenticity).     

Heterogeneous oxidation reaction of gas‐phase ozone with anthracene in thin films and on aerosols by infrared spectroscopic methods

In this paper, a real‐time laboratory study of the heterogeneous oxidation reaction of gas‐phase ozone with anthracene on surface substrates by using infrared spectroscopy in two distinctly different experimental configurations is reported. One set of kinetic measurements was made by attenuated total internal reflection infrared (ATR‐IR) spectroscopy using approximately 75‐nm films of anthracene adsorbed on ZnSe, for which the reactive uptake coefficient was determined to be (2.0 ± 1.1) × 10^?7. Using an aerosol flow tube coupled to an infrared spectrometer (AFT‐IR), similar measurements were made on (NH₄)₂SO₄ (ammonium sulfate) aerosols coated with a 0.1‐μm film of anthracene. The aerosol kinetic results as a function of the ozone concentration are consistent with a Langmuir–Hinshelwood‐type mechanism, for which the ozone‐partitioning coefficient was K = (1.4 ± 1.7) × 10^?16 cm³ molecule^?1, and the maximum pseudo‐first‐order rate coefficient was k^I_max = (0.035 ± 0.016) s^?1. Infrared spectroscopic and mass spectrometric analysis of the ozonolysis reaction in the bulk phase identified the main ozonolysis products as dihydroxyanthrones, 9,10‐endoperoxide–anthracene, 9,10‐anthraquinone, and anthrone. Larger products were also seen in the mass spectra, most likely the result of secondary product and oligomer formation. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 694–707, 2011     

Investigations on novel electrolytes,solvents and SEI additives for use in lithium-ion batteries: Systematic electrochemical characterization and detailed analysis by spectroscopic methods

Electrolyte solutions have vital function in lithium-ion batteries. Due to their modular composition, there is a broad variety of electrolyte component combinations. In this work, we present electrochemical results on newly investigated electrolyte solution components. The standard electrolyte salt in commercial batteries, LIPF₆, was replaced by new imide and sulfonate anion based salts, with enhanced stability. The use of propylene carbonate was enabled by the application of new SEI forming electrolyte additives. Electrolyte solvents, such as adiponitrile and γ-butyrolactone were investigated in combination with LiBF₄ as electrolyte salt. In order to evaluate these materials, various electrochemical techniques like galvanostatic cycling, conductivity and electrochemical stability window detection, cyclic voltammetry, etc. were applied. Furthermore, the electrode/electrolyte interfaces and interphases were studied via spectroscopic and spectrometric techniques.     

FTIR spectroscopic investigations of supersaturated NaClO4 aerosols

Supersaturated NaClO4 aerosols have been studied using a Fourier transform infrared (FTIR) spectrometer coupled with an aerosol flow tube (AFT). Compared with previous Raman results, the water O-H stretching envelope in the supersaturated solutions of NaClO4 aerosols was more structured in response to changing RH, revealing at the same time the existence of water monomers weakly hydrogen-bonded with ClO4- at extremely high concentrations. Due to enhanced ion interactions in the supersaturated solutions of NaClO4 aerosols, the formation of contact ion pairs (CIPs) could be observed without component decomposition for the nondegenerate nu1 band of ClO4-, and the degenerate nu3 band of ClO4- was successfully related to the formation of CIPs in NaClO4 solutions. Based on these observations, a new mechanism featured by the attack of ClO4- upon hydrated Na+ for CIPs formation in the supersaturated solutions of NaClO4 aerosols was further proposed. The anhydrous NaClO4, characterized by the upper limit deliquescence relative humidity (DRH) of approximately 43% and the disappearance of the nu1 band of ClO4- in the infrared spectra, was observed to form on the silicon windows at low RHs.     

Characterization of clinohumite by selected spectroscopic methods

Clinohumite, a humite group mineral, originated from Pamir Mountains, USSR, is used in the present work. Optical absorption, electron paramagnetic resonance (EPR), near infrared (NIR) and M?ssbauer techniques are used in the characterization of the mineral sample. The optical absorption spectrum indicates that Fe(II) impurity is present in two sites with distorted octahedral structure. NIR results are attributed to water fundamentals. EPR studies on powder sample confirm the presence of Mn(II) in three different sites and also an iron impurity. M?ssbauer studies confirm the presence of iron impurity in two different sites.     

不同方法制备的介孔Ni/MgO催化剂上水蒸气重整苯酚制氢

利用浸渍法和水热共沉淀法两种方法,制备了介孔Ni/MgO催化剂,用于水蒸气重整生物质油模型物苯酚制取氢气;利用XRD、N2吸附/脱附、H2-TPR、TEM以及TG等手段对催化剂进行了表征。结果表明,以介孔MgO为载体,采用浸渍法制备的介孔NiO/MgO固溶体,具有较高的比表面积(60.6m2/g)以及较大的孔径(10.1nm)。与水热共沉淀法制备的催化剂相比,浸渍法制备的NiO/MgO前驱体经还原后的所得到介孔Ni/MgO催化剂Ni颗粒较小(5.0-6.0nm),分布均匀,具有较高的分散度(19.44%)。较大的比表面积能有效地促进活性金属颗粒的分散,而介孔有利于反应物和产物在催化剂孔道中的扩散。因此,该Ni/MgO催化剂在水蒸气重整苯酚制氢反应中具有较高的催化活性、稳定性和优异的抗积炭能力。     

Probing chiral interfaces by infrared spectroscopic methods

Biological homochirality on earth and its tremendous consequences for pharmaceutical science and technology has led to an ever increasing interest in the selective production, the resolution and the detection of enantiomers of a chiral compound. Chiral surfaces and interfaces that can distinguish between enantiomers play a key role in this respect as enantioselective catalysts as well as for separation purposes. Despite the impressive progress in these areas in the last decade, molecular-level understanding of the interactions that are at the origin of enantiodiscrimination are lagging behind due to the lack of powerful experimental techniques to spot these interactions selectively with high sensitivity. In this article, techniques based on infrared spectroscopy are highlighted that are able to selectively target the chiral properties of interfaces. In particular, these methods are the combination of Attenuated Total Reflection InfraRed (ATR-IR) with Modulation Excitation Spectroscopy (MES) to probe enantiodiscriminating interactions at chiral solid-liquid interfaces and Vibrational Circular Dichroism (VCD), which is used to probe the structure of chirally-modified metal nanoparticles. The former technique aims at suppressing signals arising from non-selective interactions, which may completely hide the signals of interest due to enantiodiscriminating interactions. Recently, this method was successfully applied to investigate enantiodiscrimination at self-assembled monolayers of chiral thiols on gold surfaces. The nanometer size analogues of the latter--gold nanoparticles protected by a monolayer of a chiral thiol--are amenable to VCD spectroscopy. It is shown that this technique yields detailed structural information on the adsorption mode and the conformation of the adsorbed thiol. This may also turn out to be useful to clarify how chirality can be bestowed onto the metal core itself and the nature of the chirality of the latter, which is manifested in the metal-based circular dichroism activity of these nanoparticles.     

Optical spectroscopic methods for intraoperative diagnosis

Molecular analytical methods are increasingly needed for a quick and reliable analysis of tissue in an operating room to provide more information during operations. In this Trends article, we highlight the current state and the developments of optical spectroscopic methods as intra operative tools. The clinical problem and challenges are illustrated on the example of brain tumor surgery. While fluorescence microscopy is already used, vibrational spectroscopy techniques will complement the standard method for brain tissue diagnostics. New portable instruments are currently available and can be stationed in the operating room for quick evaluation of tissue. The promise and limitations of fluorescence and vibrational spectroscopy as intraoperative tools are surveyed in this report.     

Uncommon methods for spectroscopic analyses of polymers

The commonly used spectroscopic analyses of polymers include infrared (IR), nuclear magnetic resonance (NMR), mass(MS), x-ray(XR), and the rapidly growing near infrared(NIR). The uncommon methods that are not frequently used include nuclear quadrupole resonance(NQR), electron spin resonance, and combination techniques such as gas chromatography-infrared, thermal-infrared, gas chromatography-mass spectroscopy, and even thermal-gas chromatography-infrared or mass spectroscopy. The use of two of these methods (thermal-infrared(TGA-IR) and NQR is described. Appropriate examples are shown to point out how useful they can be.     

Ion-induced spectroscopic methods for the analysis of surfaces,interfaces and thin films

A shift is taking place in modern surface and thin-film spectroscopic techniques from the field of surface science in a pure academic sense to problem-oriented applications related to material science and technology. This has been rendered possible and promoted among other things by a number of significant methodological and instrumental developments in ion-induced spectroscopic methods.     

The use of thermal and spectroscopic methods to study chemically modified materials

The application of thermal and spectroscopic techniques in the characterisation of chemically modified materials is illustrated with several examples: ethylene vinyl acetate (EVA) copolymers which had been hydrolysed under alkaline conditions, amosite asbestos fibres which had been reacted with alkyldimethylchlorosilanes, and a polymeric composite material which had been affected by moisture.The authors acknowledge the following for assistance in the project: Rhona MacBeth, Conservator, Courtauld Institute of Art and presently at the Boston Museum of Fine Arts, for the TMA measurements, conditioning of composite samples, and useful discussions. PL-Thermal Sciences (John Gearing for the DETA measurements on EVA). PL-Thermal Sciences (Epsom Laboratories) for the use of Dynamic Mechanical Thermal Analysis equipment.     

Evaluation of chromatographic and spectroscopic methods for the analysis of petroleum-derived compounds in the environment

Summary Analytical protocols have been adapted for the study of hydrocarbons at the trace level in the environment. Various samples, including sediments and biota, were collected from the Kuwaiti environment, treated according to the protocol and analyzed by chromatographic and spectroscopic methods. The methods used were synchronous scanning fluorescence spectroscopy (SSFS); high-performance liquid chromatography (HPLC) on C18 reversed-phase and NH2 normal-phase columns with UV and fluorescence detectors; gas chromatography on fused-silica capillary columns (GC) with flame ionization detector (FID), mass spectrometer (MS) and flame photometric detector (FPD); and high-resolution molecular spectrofluorimetry in Shpol'skii matrix at 10 K (HRSS). The different methods were found to give complementary information. SSFS was useful for fast evaluation and preliminary assessment of oil pollution during extended programs; it permitted sample selection for deeper analyses but, when applied to biota, needed special care in the clean-up procedure. GC/FID, was used to analyze saturated and ethylenic compounds and was useful for obtaining information on the origin of hydrocarbons but inconvenient for analyzing the aromatic fraction. GC/FPD was difficult to use with sediment samples and yielded little information on biota samples, although it did permit confirmation of high oil contamination in some examples. HPLC on a normal-phase column with UV and fluorescence detectors was useful for the fractionation of samples and for the separation of different families of aromatic compounds according to aromatic carbon number. GC/MS was used to quantify polycyclic aromatic hydrocarbons (PAHs) of less than four cycles but was not sensitive enough for PAHs of higher molecular weight. HRSS, however, was useful for the quantification of heavy PAHs and was also faster, could be automated, and gave accurate results. However, in an oil-pollution study, it must be backed up by the other techniques. In fact, no single analytical technique was found to be sufficient, and only judicious combinations of the tested techniques yielded adequate information on the origin of hydrocarbons in the environment.     

Silica gel modified with lumogallion for aluminum determination by spectroscopic methods

Simple, easy to use and selective method of Al(III) sorption-spectroscopic (SS) determination was proposed. For this purpose, silica modified with tridecyloctadecylammonium chloride(SGII) using adsorption technique and glass slide modified with thin silica-poly(dimethyldiallyl-ammonium chloride) (SGI) composite film obtained by sol-gel technique were worked out. It was shown that lumogallion (LG) easily absorbs on SGI and SGII. Obtained sorbents SGIII and SGIV, respectively, were used for aluminum(III) determination by diffuse reflectance and spectrophotometric methods. The ranges of determination were (mg L⁻¹): (0.08-0.54), s_r ≤ 0.13, n = 4 for SGIII and (0.05-2.0), s_r ≤ 0.11, n = 4 for SGIV. The detection limits (blank + 3σ) for aluminum were 70 and 30 μg L⁻¹ using SGIII and SGIV, respectively, where σ is the standard deviation of blank estimation. The accuracy of the developed spectrophotometric method was examined by the determination of standard addition of aluminum in alcohol-free beverages. The relative error did not exceed 9%. SGIII can be regenerated by 0.05 M EDTANa₂H₂ solution and reused. SGIV was shown to be perspective for determination of aluminum in solution in the range of 0.01-0.13 mg L⁻¹ by solid phase luminescent technique.