Quantitative moisture measurements in lubricating oils by FTIR spectroscopy combined with solvent extraction approach

Quantitative measurements of moisture in mineral and synthetic polyol ester based lubricating oils using FTIR spectroscopy combined with solvent extraction approach are described. The samples are prepared by mixing dry dimethyl sulfoxide (DMSO) and lubricating oils, and after phase separation, the extracted bottom DMSO layers are analyzed with FTIR. The results from the solvent extraction show that the DMSO is an excellent aprotic solvent for water removal from lubricating oils. The spectroscopic data reveal that near IR region (5400–4800 cm^{− 1}, molecular water) gives the best results for water determination in both mineral and synthetic lubricants, followed by mid-IR region (3800–3200 cm^{− 1}, O―H stretching). However, the water content estimated from the IR region (1800–1550 cm^{− 1}, O―H bending) has the lowest accuracy due to the interference from aminic, phenolic additives and other oxidation products present in the lubricants. The accuracy of the FTIR spectroscopy combined with solvent extraction approach is exemplified by monitoring the water content in mineral oil during oxidation process at 150 °C for 30 days. The quantitative determination of the moisture in the fresh and oxidized oils by the developed approach is shown to be an alternative technique to Karl Fischer titration.     

Electrochemical sensor for predicting transformer overload by phenol measurement

Transformer overload is a significant problem to the power transmission industry, with severe safety and cost implications. Overload may be predicted by measuring phenol levels in the transformer-insulating oil, arising from the thermolytic degradation of phenol-formaldehyde resins. The development of two polyphenol oxidase (PPO) sensors, based on monitoring the enzymatic consumption of oxygen using an oxygen electrode, or reduction of enzymatically generated o-quinone at a screen-printed electrode (SPE), for the measurement of phenol in transformer oil is reported. Ex-service oils were prepared either by extraction into aqueous electrolyte-buffer, or by direct dilution in propan-2-ol, the latter method being more amenable to simple at-line operation. The oxygen electrode, with a sensitivity of 2.87 nA μg⁻¹ ml⁻¹, RSD of 7.0-19.9% and accuracy of ±8.3% versus the industry standard International Electrotechnical Commission (IEC) method, proved superior to the SPE (sensitivity: 3.02 nA μg⁻¹ ml⁻¹; RSD: 8.9-18.3%; accuracy: ±7.9%) and was considerably more accurate at low phenol concentrations. However, the SPE approach is more amenable to field-based usage for reasons of device simplicity. The method has potential as a rapid and simple screening tool for the at-site monitoring of phenol in transformer oils, thereby reducing incidences of transformer failure.     

Thermo- and photooxidation of polyisobutylene. I. Evolutions at temperatures above 50°C

Polyisobutylene films (PIB) were submitted to a thermal oxidation at 100°C and to a photooxidation by exposure to long-wavelength radiations (λ ≥ 300 nm) at 60°C. The modifications of the chemical structure resulting from the oxidation were determined by FT-IR analysis of the polymer films, coupled to chemical treatments that converted specifically the oxidation products. Dissolution of oxidized samples permitted analysis of the polymer by ¹³C- and ¹H-NMR. The structure of the volatile products was determined by mass spectroscopy analysis of the gas phase. Identification of the numerous products formed permitted the proposal of a scheme that accounts for the oxidation of PIB. When the irradiations are carried out at a temperature above 50°C, the depolymerization is favored and the mechanism involves two main routes of oxidation. A direct oxidation starts with the oxidation of radicals obtained by homolysis of the C C bonds on the main chain, and an induced oxidation involves hydrogen abstraction on the methylene and methyl groups by radicals formed by the direct oxidation of the polymer. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1689–1701, 1997     

Quantification of erythromycin in pharmaceutical formulation by transmission Fourier transform infrared spectroscopy

A simple, cost-effective and environmental friendly analytical method was developed for the quantification of erythromycin in tablet formulation using transmission Fourier Transform Infrared (FT-IR) spectroscopy for routine quality control analysis. There is no need of sample preparation except pellet formation for FT-IR analysis. Use of solvent was totally avoided in this method. Calibration was carried out by using simple Beer’s law in the FT-IR region between 1743 and 1697 cm⁻¹. The excellent coefficient of determination (R² = 0.998) was achieved with 0.0247 and 1.14 root mean square error of prediction (RMSEP) and root mean square error of cross validation (RMSECV), respectively. The results of the study revealed that the transmission FT-IR spectroscopy could be effectively used for rapid determination of active ingredients like erythromycin in pharmaceutical formulations to control the quality of finished products.     

Surface oxidation of rubber crumb with ozone

Rubber crumb derived from the grinding of used truck tread and tyres is used as a low cost filler in rubber compounds based on diene rubber. In order to expand its application to other fields, the surface modification of the rubber crumb could be an interesting and feasible solution. In fact, the surface modification of rubber crumb may be used as a tool to expand its use in applications to compounds with polar rubber matrices or where hydrophilic surface of the rubber crumb could be desirable, for example in water-based dispersion or as filler for asphalt. In the present work, ozone has been used as the active agent to cause surface oxidation and functionalisation of rubber crumb in a fluidized bed reaction. The rubber crumb reacts swiftly with ozone producing CO₂ in the initial stages of reaction and then leading to the desired surface oxidized product. The rate constant of the reaction between ozone and rubber crumb has been determined by FT-IR spectroscopy, monitoring the consumption of ozone in the gas phase in the presence of the crumb. A rate constant value of 5.03 × 10⁻³ s⁻¹  g⁻¹ of rubber crumb was determined. The degree of the surface oxidation of the rubber crumb can be determined by FT-IR spectroscopy using as reference the intensity of the ketone band at about 1710 cm⁻¹. Additionally the nominal ratio between the amount of ozone (in mg) reacted with rubber crumb (in g) can be used as a parameter for the degree of the surface oxidation. The surface oxidized rubber crumb shows surface acidity and hydrophilicity. Thermogravimetric analysis, differential thermal analysis and pyrolysis-GC clearly demonstrate that the ozonization of the rubber crumb is directed exclusively to the surface of the crumb and does not affect the bulk properties at all.     

Photo- and thermoinitiated oxidation of high-impact polystyrene. I. Characterization by FT-IR spectroscopy

The photo- and thermooxidative degradation of different grades of high-impact polystyrene (HIPS) has been studied by FT-IR spectroscopy. The oxidized films were treated with NH₃ and SF₄ for the rapid identification and resolution of the various carbonyl species, alcohols, and hydroperoxides. All the sample gave similar oxidation products, but in varying quantities. The heterogenity in the film was also determined by micro-FT-IR spectroscopy. The thermal degradation processes at different temperature were compared. © 1994 John Wiley & Sons, Inc.     

Stability of polyynes in air and their degradation by ozonolysis

Polyyne solutions in n-hexane or other aliphatic hydrocarbons having C₆H₂, C₈H₂ and C₁₀H₂ as main components were found to be unstable at relatively high concentration (≈10⁻² M) and to separate in few hours a brown precipitate. This phenomenon does not occur in more dilute solutions. The precipitate recovered from the mentioned solutions was analysed by FT-IR spectroscopy and thermogravimetry and found to be constituted by polyyne chains crosslinked and oxidized by oxygen resembling in some way the product obtained by photolysing acetylene in water solution and in presence of air. Polyynes react very quickly with ozone producing as main product polymeric ozonides which are insoluble in hydrocarbons and which have been studied with FT-IR spectroscopy. The oxidized nature of the chains highly crosslinked by ozonides, peroxide and oxygen bridges has been confirmed. The oxidized polyyne fraction remaining in solution after ozonolysis was studied by electronic absorption spectroscopy and by liquid chromatography. Extensive chain breaking was found as expected although some degree of unsaturation was preserved even in the final oxidized products.     

Grafting of model primary amine compounds to cellulose nanowhiskers through periodate oxidation

This study demonstrates regioselective oxidation of cellulose nanowhiskers using 2.80–10.02 mmols of sodium periodate per 5 g of whiskers followed by grafting with methyl and butyl amines through a Schiff base reaction to obtain their amine derivatives in 80–90 % yield. We found a corresponding increase in carbonyl content (0.06–0.14 mmols/g) of the dialdehyde cellulose nanowhiskers with the increase in oxidant as measured by titrimetric analysis and this was further evidenced by FT-IR spectroscopy. Grafting of amine compounds to the oxidized cellulose nanowhiskers resulted in their amine derivatives, which are found to be partially soluble in DMSO. Therefore, the reduction reaction between amines and carbonyl groups was confirmed through ¹³C NMR spectra, which was also supported by copper titration, XPS, and FT-IR spectroscopy. Morphological integrity and crystallinity of the nanowhiskers was maintained after the chemical modification as studied by AFM and solid-state ¹³C NMR, respectively.     

Determination of protein-bound methionine oxidation in the hippocampus of adult and old rats by LC-ESI-ITMS method after microwave-assisted proteolysis

Protein-bound methionine (Met) oxidation has been associated with normal aging and a variety of age-related diseases, including Alzheimer’s disease and Parkinson’s disease. Monitoring the changes of protein-bound methionine content in the brain in response to normal aging and oxidative stress is of great interest and could be used as an indicator of oxidative stress of rats in pathological conditions. We have developed a rapid analytical method for the determination of oxidized products of protein-bound methionine in rat brain. The assay involved rapid acid proteolysis with microwave irradiation and solid-phase extraction of the free amino acids followed by LC-ESI-ITMS analysis. Detection was achieved in positive ionization with an ion trap mass spectrometer operating in multiple-reaction monitoring mode. The calibration curves of the analytes were linear (r ² > 0.99) in the range between 0.098 and 1.560 μg/mL. Intra- and inter-day relative standard deviation percentages were <9% and <8%, respectively. The assay performance was sufficient to support a rapid analytical tool for monitoring brain protein-bound methionine oxidation levels. The content of protein-bound Met and methionine sulfoxide (MetO) in the hippocampus of adult and old rats with or without H₂O₂ treatment was determined by employing the new method. The content of protein-bound MetO was significantly increased in old rats after exposure to H₂O₂. This result indicates increased sensitivity to Met oxidation in the hippocampus of old rats.     

先锋褐煤及其热溶残煤的过氧化氢氧解

利用1-甲基萘（1-MN）对先锋褐煤进行热溶,并在温和条件下分别对原煤及其热溶残煤进行过氧化氢氧化。结合元素分析和FT-IR对各级产物进行结构表征,用GC/MS对氧化反应水溶性产物的甲酯化衍生物进行分析。结果表明,先锋褐煤在1-MN中的热溶率较低,320 ℃下热溶残煤（TR）的收率为81.01%,该煤主要以共价键交联的大分子结构为主,非共价键缔合的小分子含量较低,并以脂肪结构为主,含一定量的羰基以及少量的羟基和芳香结构。原煤和热溶残煤氧化水溶性产物中α,ω-二羧基烷酸含量较高,同时还发现,相当含量的芳香酸及三元羧酸存在,其中,α,ω-二羧基烷酸主要以丙二酸和丁二酸为主;原煤中可溶小分子易被氧化并生成较复杂的产物。与原煤相比,热溶残煤结构更为规整,氧化主要以共价键交联的大分子结构的氧化解聚为主,氧解率较低,水溶性氧解产物也较简单,种类较少,据此推测先锋褐煤的桥键主要以为-CH₂-和-CH₂-CH₂-为主。     

Determination of phosphate compounds in meat products by 31-Phosphorus Nuclear Magnetic Resonance spectroscopy with methylenediphosphonic acid after alkaline extraction

Modification of the extraction procedure and application of the ³¹P NMR method for the determination of polyphosphates in meat products were studied. In the elaborated procedure threefold water extraction at alkaline pH (borate buffer and 0.1 M EDTA) was applied. Furthermore, the new external standard for ³¹P NMR determination of phosphates was proposed. Obtained recoveries were between 95 and 99% and variation coefficients (CV) was ≤5%, indicating an increase in accuracy and the precision of the proposed procedure in relation to the spectrophotometric method. The described procedure of sample preparation with ³¹P NMR method was applied for the determination of polyphosphate additives in meat products. The satisfactory precision (CV = 0.39-3.40%) shows the benefit of the NMR method in the routine analysis of the phosphate ions in meat products.     

1H and 13C NMR spectroscopic study of oxidation of D,L‐cystine and 3,3′‐dithiobis(propionic acid) with hydrogen peroxide in aqueous solution

The oxidation of symmetrical disulfides [D ,L ‐cystine ( 1 ) and 3,3′‐dithiobis(propionic acid) ( 2 )] with hydrogen peroxide in D₂O–NaOH solution (pH 10–11) was studied by NMR spectroscopy. Assignments of the proton and carbon NMR signals of starting materials ( 1 and 2 ) and products of oxidation are based on conventional 1D NMR methods (DEPT, selective spin decoupling). Formation of C—S bond cleavage products or, in case of 2 , partially oxidized intermediates was not detected. The accelerating effect of Cu²⁺ cations, but not Fe³⁺ cations, on the oxidation rate of 1 in basic medium was demonstrated. Copyright © 2002 John Wiley & Sons, Ltd.     

Use of poorly absorbing materials and low-contrast photometric reactions in thermal lens spectrometry

The capability of thermal lens spectroscopy as a highly sensitive method applicable to indicator reactions, the products of which appear poorly absorbing and/or insufficiently contrasting and, which there-fore cannot be utilized in traditional spectrophotometric analysis, are considered in a study of a number of model systems (phenanthrene, unsubstituted dibenzo-p-dioxin, polysaccharides, lyposaccharides, and other materials). It is shown that, in thermal lens spectrometry, the sensitivity of determination in such reactions can be increased by significantly increasing the sensitivity of thermo-optical measurements due to the formation of colloidal reaction products and the exploitation of the kinetic behavior of such reactions. Along with the increase in the sensitivity of absorbance measurements due to the thermo-optical effect itself, these factors also favor a gain in sensitivity in comparison to the spectrophotometry by 1–2 orders of magnitude.     

Visible light-induced photocatalysis through surface plasmon excitation of platinum-metallized titania for photocatalytic bleaching of rhodamine B

Abstract  

Nanocomposites consisting of titania nanoparticles and metallic platinum were prepared via a soft chemical reduction method. The detailed structural, compositional, and optical characterization and physicochemical properties of the obtained products were analyzed by X-ray diffraction, nitrogen adsorption, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and FT-IR spectroscopy techniques. Employing photodegradation of rhodamine B as the model reaction, we found that the as-prepared Pt/TiO₂ nanocomposite showed an excellent photocatalytic oxidation activity under visible light irradiation. On the basis of these results, the intrinsic mechanism of visible light-induced photocatalytic oxidation of organic compounds on the platinized titania is proposed and discussed. The superior visible light-driven photocatalytic efficiency of the Pt/TiO₂ nanocomposite photocatalyst can be ascribed to the high efficiency of charge-pair separation due to the presence of deposited Pt serving as electron sinks to retard the rapid e⁻–h⁺ couple recombination; the good photoabsorption capacity in the visible light region; and the higher concentration of surface hydroxyl groups, which are able to effectively scavenge photogenerated valence band holes. Accumulation of the holes at the catalyst surface increases the probability of the formation of OH· as a reactive species that readily oxidizes the organic dye molecule.     

Development of an improved analytical method for the determination of carcinogenic polycyclic aromatic hydrocarbons in transformer oil

Polynuclear aromatic hydrocarbons (PAHs) are natural constituents of transformer oils and are essential in prolonging transformer in-service lifetime. Issues concerning PAH carcinogenicity demand methods that provide qualitative and quantitative information on the PAH composition of new and in-service oils to allow informed operational decisions to be made. However, current analytical methods focus on PAH fingerprinting, as opposed to quantitative analysis and are also cumbersome, relying on the use of large (>100 ml) volumes of organic solvents, some of which are hazardous. This paper reports a method for the improved quantification of carcinogenic PAHs in transformer oils that is both simple and repeatable. The method uses commercially available solid-phase extraction columns and millilitre volumes of relatively non-hazardous solvents. Extraction efficiencies of > or =74% were obtained for the Environmental Protection Agency priority PAHs. The method has potential for automation and high-throughput analysis and thus is of interest to industries that use transformer oils.     

Structural Characterization of Oxidized Glycerophosphatidylserine: Evidence of Polar Head Oxidation

Non-oxidized phosphatidylserine (PS) is known to play a key role in apoptosis but there is considerable research evidence suggesting that oxidized PS also plays a role in this event, leading to the increasing interest in studying PS oxidative modifications. In this work, different PS (1-palmitoyl-2-linoleoyl-sn-glycero-3-phospho-L-serine (PLPS), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS) were oxidized in vitro by hydroxyl radical, generated under Fenton reaction conditions, and the reactions were monitored by ESI-MS in negative mode. Oxidation products were then fractionated by thin layer chromatography (TLC) and characterized by tandem mass spectrometry (MS/MS). This approach allowed the identification of hydroxyl, peroxy, and keto derivatives due to oxidation of unsaturated fatty acyl chains. Oxidation products due to oxidation of serine polar head were also identified. These products, with lower molecular weight than the non-modified PS, were identified as [M – 29 – H]^– (terminal acetic acid), [M – 30 – H]^– (terminal acetamide), [M – 13 – H]^– (terminal hydroperoxyacetaldehyde), and [M – 13 – H]^– (terminal hydroxyacetaldehyde plus hydroxy fatty acyl chain). Phosphatidic acid was also formed in these conditions. These findings confirm the oxidation of the serine polar head induced by the hydroxyl radical. The identification of these modifications may be a valuable tool to evaluate phosphatidylserine alteration under physiopathologic conditions and also to help understand the biological role of phosphatidylserine oxidation in the apoptotic process and other biological functions.     

Infrared study of aging of edible oils by oxidative spectroscopic index and MCR-ALS chemometric method

One of the most suitable analytical techniques used for edible oil quality control is Fourier transform mid infrared spectroscopy (FT-MIR). FT-MIR spectroscopy was used to continuously characterize the aging of various edible oils thanks to a specific aging cell. There were differences in the spectra of fresh and aged oils from different vegetable sources, which provide the basis of a method to classify them according to the oxidative spectroscopic index value. The use of chemometric treatment such as multivariate curve resolution-alternative least square (MCR-ALS) made it possible to extract the spectra of main formed and degraded species. The concentration profiles gave interesting information about the ability of the various oils to support the oxidative treatment and showed that all oils present the same aging process. Both methods led to concordant results in terms of induction times determined by the oxidative spectroscopic index and the appearance of oxidation products revealed by MCR-ALS.     

Application of Fourier-transform infrared (FT-IR) transmission spectroscopy for the estimation of roxithromycin in pharmaceutical formulations

A quick and reliable analytical method for the quantitative assessment of roxithromycin in pharmaceutical formulations was developed using Fourier-transform infrared (FT-IR) transmission spectroscopy for routine quality control. The sample preparation was avoided except grinding for pellet formation and eliminated the use of toxic solvents. For the determination of roxithromycin, conventional KBr was used in the form of pellets for acquisition of the FT-IR spectra of standards and samples. The calibration model was developed based on simple Beer's law using the FT-IR carbonyl region (CO) from 1765 to 1705 cm⁻¹. The excellent coefficient of determination (R²) was achieved (0.9992) with 0.01 mg standard error of calibration. This work clearly revealed the capability of the transmission FT-IR spectroscopy and extended its application for determining the exact quantity of roxithromycin to control the processing formulation and quality of finished product with the analysis time of less than 3 min using the neat solid samples.     

Study of valence state of iodine in simulated fuel solution of medical isotope production reactor

The effects of temperature, heating-time, concentration of HNO₃ and γ-ray irradiation on the valence states of iodine in a simulated fuel solution of a medical isotope production reactor (MIPR) were investigated. About 83% of I⁻ was oxidized to IO₃ ⁻ and 10% of I⁻ was oxidized to I₂ in uranyl nitrate solution after heating at 70 °C for 6 hours. Heating and existence of oxidant, U and ionizing radiation accelerate the oxidation process of iodine, and results in most of the iodine being produced in high oxidation states such as in IO₃ ⁻ and IO₄ ⁻. The results indicate that the production of ¹³¹I by MIPR can be carried out by extraction of iodine in high oxidation states from the fuel solution.     

Solid phase oxidation of arsenite and the effect of gamma radiation

The oxidation of solid arsenite by bromate, chlorate and perchlorate ions has been studied at different temperatures and at a constant composition of 12. Arsenite is completely oxidized to arsenate. The fraction oxidized // — time /t/ data are reproducible. The rate of oxidation increases with an increase in temperature. Gamma radiation has no significant effect on the temperature independence of the oxidation process of this particular composition, although delayed oxidation appears with irradiated systems. The kinetics of oxidation process follows the conventional first order. The activation energies for the oxidation of As/III/ to As/V/ are 30.5, 44.0 and 67.9 kJ mol^–1, respectively, for bromate, chlorate and perchlorate systems, and for irradiated 29.8 and 67.3 kJ mol^–1, respectively, for bromate and perchlorate systems.