GC Methods for the Determination of Methanol and Ethanol in Insulating Mineral Oils as Markers of Cellulose Degradation in Power Transformers

Methanol and ethanol in transformer oils have been recently proposed as new markers of thermal and mechanical degradation of cellulose (the solid insulation in power transformers). In this work, we optimized and compared the performance of two headspace gas chromatographic methods based on flame ionization (HS–GC–FID) and mass spectrometry detection (HS–GC–MS) to determine methanol and ethanol in insulating mineral oil. For methanol and ethanol, the detection limits were 12 and 27 μg kg^?1 (HS–GC–FID) and 1.3 and 3.1 μg kg^?1 (HS–GC–MS). Repeatability was evaluated in transformer oils for both the methods at different concentration levels of analytes and RSD values were found to lie between 1.8 and 16 %. The accuracy of the methods was assessed under a proficiency test (Cigré JWG A2/D1.46). The methods were compared by a F-test and a one-sided paired t test performed on 21 transformer oils in service. Correlations of methanol and ethanol content in sampled oils against their actual time of service are provided. For each sample, the content of traditional markers (furan-2-carbaldehyde and CO₂) was also measured, finding a correlation between light alcohols and CO₂ content. This indicates that methanol and ethanol determination may be helpful in providing further information on the thermal degradation conditions of transformers’ solid insulation. The method developed is currently routinely applied by the laboratories of Sea Marconi Technologies for the assessment of transformers’ conditions.     

Expedient Total Synthesis of Triciribine and Its Prodrugs

Triciribine (TCN, 1) and its monophosphate (TCNP, 2) are tricyclic nucleotide derivatives that have potential antineoplastic activity. Triciribine inhibits the phosphorylation, activation, and signaling of Akt-1, -2, and -3, which may result in the inhibition of Akt-expressing tumor cell proliferation. Both TCN and TCNP have very low bioavailability, and the development of both drugs as intravenous (IV) treatments was halted because of the toxicity induced by the high doses needed for their use as general cytotoxic agents. This publication describes an expedient and straightforward total synthesis of amino acid prodrugs (3, 4) of TCN and TCNP. In our study, both the prodrugs significant improved the plasma exposure of the parent drugs and the prodrugs.     

Characterisation of lavender essential oils by using gas chromatography-mass spectrometry with correlation of linear retention indices and comparison with comprehensive two-dimensional gas chromatography

Nine samples of lavender essential oil were analysed by GC–MS using low-polarity and polar capillary columns. Linear retention indices (LRI) were calculated for each component detected. Characterisation of the individual components making up the oils was performed with the use of an mass spectrometry (MS) library developed in-house. The MS library was designed to incorporate the chromatographic data in the form of linear retention indices. The MS search routine used linear retention indices as a post-search filter and identification of the “unknowns” was made more reliable as this approach provided two independent parameters on which the identification was based. Around 70% of the total number of components in each sample were reliably characterised. A total of 85 components were identified. Semi-quantitative analysis of the same nine samples was performed by gas chromatography (GC) with flame ionisation detection (FID). The identified components accounted for more than 95% of each oil. By comparing the GC–MS results with the results from the GC×GC–FID analysis of a lavender essential oil, many more components could be found within the two-dimensional separation space.     

Pyrolysis of vegetable oil soaps—Palm, olive, rapeseed and castor oils

Saponified, palm, olive, rapeseed and castor oils were pyrolysed (at 750 °C for 20 s) by pyrolysis gas chromatography with mass selective and flame ionisation detection (Py-GC/MSD and FID) to clarify their thermochemical behaviours. The liquefiable compounds recovered from palm, olive and rapeseed oils mainly contained linear alkenes (up to C₁₉) and alkanes (up to C₁₇), both similar to those found in gasoline (C₄-C₁₀) and diesel fuel (C₁₁-C₂₂) boiling range fractions of petroleum, whereas in the case of castor oil a significant amount of undesired oxygen-containing products (e.g., ketones and phenols) were formed. The obtained data on reaction mechanisms can also be utilised in applications where various biofuels are produced, for example, from the extractive-derived by-product (tall oil) of kraft pulping.     

Multivariate Association of Graph-Theoretic Variables and Physicochemical Properties

Abstract

We used canonical correlation analysis to examine the multivariate association between two distinct data sets commonly measured or calculated for approximately 600 chemicals: (1) measured or calculated values of select physieochemical properties (i.e., K _ow, boiling point, heat of vaporization, molecular weight, water solubility, molecular volume, hydrogen bonding potential, and vapor pressure) and (2) calculated algorithmically-derived variables (i.e., topological and neighborhood indices derived from graph theory). Canonical correlation analysis identified eight highly significant associations between linear combinations of graph-theoretic variables and linear combinations of physicochemical properties. The set of graph theoretic variables was significantly related to all physieochemical properties, explaining 55% to 99% of the variation in these properties.     

TLC–direct bioautography as a method for evaluation of antibacterial properties of Thymus vulgaris L. and Salvia officinalis L. essential oils of different origin

ABSTRACT

The dot-blot bioautography was used to evaluate the antibacterial properties of Thymus vulgaris L. and Salvia officinalis L. essential oils (EOs) produced by three different manufacturers. The whole samples were applied at three concentrations on thin-layer chromatography (TLC) plates which were then subjected to bioautography against Bacillus subtilis. The samples of the highest activity were found. Then, they were separated using TLC and once again subjected to bioautography against B. subtilis. As was proved, only the essential oils of T. vulgaris L. possessed strong antibacterial properties for which mostly thymol and carvacrol were responsible. Their contents were calculated using TLC–UV densitometry. The highest contents were found in the essential oils of the highest antibacterial activity revealed in the dot-blot test. It means that a dot-blot test can be used for simple and fast evaluation of antibacterial properties of essential oils.     

Chemical Composition and Synergistic Potential of Mentha pulegium L. and Artemisia herba alba Asso. Essential Oils and Antibiotic against Multi-Drug Resistant Bacteria

The essential oils were obtained by hydrodistillation from aerial parts of Mentha pulegium L. (M. pulegium L.) and Artemisia herba alba (A. herba alba) Asso. and analyzed by gas chromatography–flame ionization detector chromatograpy (GC–FID) and gaz chromatography–mass spectrometry (GC–MS). The antibacterial activities of the oils were determined by the disk diffusion method and a microdilution broth assay against six bacteria stains. The combinations of these essential oils with antibiotics were evaluated against two multi-drug-resistant bacteria strains: imipenem-resistant Acinetobacter baumannii (IRAB S3310) and methicillin-resistant Staphylococcus aureus (MRSA S19). The chemical analysis of M. pulegium essential oil revealed the presence of pulegone (74.8%) and neoisomenthol (10.0%). A. herba alba essential oil was characterized by camphor (32.0%), α-thujone (13.7%), 1,8-cineole (9.8%), β-thujone (5.0%), bornéol (3.8%), camphene (3.6%), and p-cymene (2.1%). All strains tested except Pseudomonas aeruginosa were susceptible to these oils. The combinations of essential oils with antibiotics exerted synergism, antagonism, or indifferent effects. The best effect was observed with A. herba alba essential oil in association with cefoxitin (CX) against MRSA S19. However, for IRAB S3310, the strongest synergistic effect was observed with M. pulegium in association with amikacin (AK). This study demonstrated that M. pulegium and A. herba alba essential oils have antibacterial activities which could be potentiated by antibiotics especially in the case of IRAB S3310.     

Polarographic determination of cyanide as contaminant in pralidoxime mesylate formulations

A method for the polarographic determination of cyanide as contaminant in pralidoxime mesylate (PM) formulations was developed. The volatile cyanide formed in the formulations was stabilized as tetracyanonickelate (TCN) anion complex after reaction with ammoniacal Ni(II) solution. The stable TCN anion complex (K(stb)=10(31)) was determined by anodic stripping voltammetry at the hanging mercury drop electrode (HMDE). The polarographic signal was proportional to the cyanide concentration and the high concentration of PM did not interfere. The linear range of calibration was from 1.2 to 16 mug cyanide with r=0.998. The RSD was 1.3% (n=5) for 2.4 mug cyanide and a detection limit of 0.8 mug cyanide was calculated. The proposed method is adequate as a quality control of PM formulations.     

Biamperometric and Differential Pulse Polarographic Methods for the Assay of Nomifensine Maleate

Abstract

Biamperometric titration and differential pulse polarography (DPP) are described for the analysis of nomifensine maleate powder and commercial capsules (Merital^R -50 mg). The biamperometric method involved the titration in cold dil. HCl medium against 0.01 M - NaN0₂ and electrometric detection of end point. The mean percent recoveries obtained were 100.0 ± 0.87 and 99.2 ± 0.95 for the authentic powder and capsules, respectively. The DPP method was performed by measuring the peak current, i_P, obtained from the recorded differential polarogram under constant 50mV modulation amplitude. The peak current was measured at the peak potential of ? 1.02 V on the dropping mercury electrode (DME) versus Ag/AgCl/KCl (sat.) reference electrode at pH 5.0 (acetate buffer). A linear relationship between peak current and concentration was demonstrated in the range 3 to 30μg ml^?1. The mean percent recovery for the capsules was 103.1 ± 1.26.     

Characterization of the leaf essential oils of an endemic species Cinnamomum perrottetii from Western Ghats,India

Essential oils from the leaf of Cinnamomum perrottetii Meissn. collected from three distinct populations in the southern Western Ghats, India were analysed by GC–FID and GC–MS. A total of 56 volatile constituents representing 92.2–96.3% of the oils were identified. Variations in the chemical constituents of the oils were found. Only three major components namely, α-pinene (5.1–6.6%), tau-cadinol (8.7–20.5%) and α-cadinol (7.3–13%) out of 10 were found in all three samples. To the best of our knowledge, this is the first report on the chemical compositions of leaf essential oil of C. perrottetii.     

Analysis of Polychlorinated Biphenyl Residues in Waste Oils by High-Performance Liquid Chromatography

Abstract

The qualitative analysis of polychlorinated biphenyl residues (PCBs) in waste mineral oils can be rapidly and accurately carried out by high-performance reverse phase liquid chromatography (HPLC) using a 25 cm HC-ODS Sil-X (Perkin-Elmer) column and a gradient elution system consisting of water-acetonitrile where the latter increases with linear program from 50 to 77% over 9 minutes.     

13C nuclear magnetic resonance spectroscopy to determine olive oil grades

¹³C nuclear magnetic resonance spectroscopy was used in a first attempt to differentiate olive oil samples by grades. High resolution ¹³C NMR Distortionless Enhancement by Polarization Transfer (DEPT) spectra of 137 olive oil samples from the four grades, extra virgin olive oils, olive oils, olive pomace oils and lampante olive oils, were measured. The data relative to the resonance intensities (variables) of the unsaturated carbons of oleate (C-9 and C-10) and linoleate (L-9, L-10 and L-12) chains attached at the 1,3- and 2-positions of triacylglycerols were analyzed by linear discriminant analysis. The 1,3- and 2- carbons of the glycerol moiety of triacylglycerols along with the C-2, C-16 and C-18 resonance intensities of saturated, oleate and linoleate chains were also analyzed by linear discriminant analysis. The three discriminanting functions, which were calculated by using a stepwise variable selection algorithm, classified in the true group by cross-validation procedure, respectively, 76.9, 70.0, 94.4 and 100% of the extra virgin, olive oil, olive pomace oil and lampante olive oil grades.     

Essential Oils from Residual Foliage of Forest Tree and Shrub Species: Yield and Antioxidant Capacity

Increasing applications and markets for essential oils could bring new opportunities for cost-effective and sustainable management of unused forestry biomass; however, better knowledge of the production and application of such essential oils is necessary. The objective of this work is to contribute to greater knowledge of the essential oil production on a pilot scale from foliage biomass of wild shrubs and tree residues produced in some forestry enhancement operations and to study their antioxidant capacity (ORAC—oxygen radical absorbance capacity). Fresh biomass (twigs) of seven species (E. globulus, E. nitens, P. pinaster, P. sylvestris, R. officinalis, C. ladanifer, and J. communis) was manually collected in Spain in two different periods and was ground at 30 mm and distilled in a 30 L stainless steel still with saturated steam. The essential oil components were identified by GC–MS and quantified by GC–FID, and their antioxidant activity was determined with the ORAC method. Promising results on essential oil yield were obtained with E. globulus, E. nitens, R. officinalis, and J. communis. All essential oils studied exhibited antioxidant capacity by the ORAC assay, particularly that from C. ladanifer. Moreover, oxygenated sesquiterpenes contents, one of the minor components of oils, were significantly correlated with ORAC values.     

Comparative Response Characterization of a Universal Acoustic Flame Detector for Chromatography

The relative response towards a wide variety of hydrocarbons was measured simultaneously in both the acoustic flame detector (AFD) and the flame ionization detector (FID). The compounds examined included alkanes, aromatics, unsaturates, aldehydes, ketones, alcohols, carboxylic acids, and a number of hetero-atomic organic analytes. A very close linear correlation was found between AFD and FID response for these analytes with regression providing an r ² coefficient of 0.9103. The observed universal AFD response towards hydrocarbons was attributed to a reduction in flame burning velocity through the capture of key propagating species such as hydrogen radicals. While a few minor exceptions to this correlation were observed, the most notable differences occurred for organometallic compounds, which responded 2–3 orders of magnitude more strongly in the AFD than anticipated by their FID response alone. It was found that the metals present in such analytes are directly responsible for generating the greatly increased AFD response observed, which is attributed to their known radical scavenger properties. Results indicate that overall the AFD provides a uniform response towards most hydrocarbons that is qualitatively very similar to that of an FID. For those analytes containing metals or other moieties that may be capable of significantly altering flame burning velocity, an enhanced AFD response is to be anticipated.     

Development and evaluation of gas and liquid chromatographic methods for the analysis of fatty amines

In contrast to the plethora of publications on the separation of fatty acids, analogous studies involving fatty amines are scarce. A recently introduced ionic‐liquid‐based capillary column for GC was used to separate trifluoroacetylated fatty amines focusing on the analysis of a commercial sample. Using the ionic liquid column (isothermal mode at 200°C) it was possible to separate linear primary fatty amines from C₁₂ to C₂₂ chain length in less 25 min with MS identification. The log of the amine retention factors are linearly related to the alkyl chain length with a methylene selectivity of 0.117 kcal/mol for the saturated amines and 0.128 kcal/mol for the mono‐unsaturated amines. The sp² selectivity for unsaturated fatty amines also could be calculated as 0.107 kcal/mol for the ionic liquid column. The commercial sample was quantified by GC with flame ionization detection (FID). An LC method also was developed with a reversed phase gradient separation using acetonitrile/formate buffer mobile phases and ESI‐MS detection. Native amines could be detected and identified by their single ion monitoring chromatograms even when partial coelution was observed. The analysis of the commercial sample returned results coherent with those obtained by GC–FID and with the manufacturer's data.     

Curcuma ecalcarata – new natural source of pinocembrin and piperitenone

Phytochemical analysis of the rhizome extract of Curcuma ecalcarata, a hitherto uninvestigated south Western Ghats endemic species, resulted in the isolation and identification of the diaryl heptanoid trans, trans-1,7-diphenyl-5-hydroxy-4,6-heptadiene-3-one (1), steroid β-sitosterol (2), flavanone pinocembrin (4) and monoterpenoids piperitenone (3) and 8-hydroxy piperitone (5). HPTLC estimation of pinocembrin in the rhizome revealed the plant as a rich source of pinocembrin (0.37% dry wt.). The rhizome essential oil was isolated by hydrodistillation and analysed by GC–FID, GC–MS and ¹³C NMR. Among the 30 constituents identified in the oil, monoterpenoids predominated (94.2%) followed by sesquiterpenoids (5.8%). The major compound consisting of 65.2% of the oil was isolated and identified as piperitenone (3). The study highlights the plant as a rich source of the flavanone pinocembrin and the volatile aroma compound piperitenone.     

Elimination of Listeria inoculated in ready-to-eat carrots by combination of antimicrobial coating and γ-irradiation

A combined treatment of an edible coating composed of trans-cinnamaldehyde (TCN; 0.5% p/p) with γ-irradiation was investigated against Listeria inoculated in peeled mini-carrots. First, the D₁₀ value (γ-irradiation dose required to eliminate 90% of the bacterial population) of TCN was evaluated under air. This treatment resulted in a 3.66-fold increase in relative bacterial radiosensitivity (RBR) as compared to the control without antimicrobial coating. Secondly, the shelf life of mini-carrots during 21 day of storage at 4 °C was studied. Antimicrobial coating containing TCN was assayed in combination with two irradiation doses (0.25 and 0.5 kGy). Results suggested that the inactive coating did not have any antimicrobial effect against Listeria while the coating containing TCN resulted in a 1.29 log reduction in carrots packed under air after 21 days of storage. Hence, these observations indicated that the combination of irradiation with antimicrobial coating played an important role in enhancing the radiosensitization of Listeria to γ-irradiation.     

Determination of trans fat in edible oils: current official methods and overview of recent developments

The adverse effects of dietary trans fat on biomarkers of chronic disease are well documented. Regulatory authorities in many countries have enacted legislation aimed at reducing trans fat content of their food supplies, either by requiring trans fat labeling on pre-packaged foods or by limiting the amount of trans fat in oils used for food production. Increased use by the food industry of oils with a low trans fat content necessitates reevaluation of official methods used by the food industry and regulatory agencies for the determination of total trans fat. Attenuated total reflection–Fourier-transform infrared (ATR–FTIR) spectroscopy and gas chromatography with flame ionization detection (GC–FID) are two techniques used in official methods approved by method-endorsing organizations, for example AOAC International and the American Oil Chemists’ Society. Here, we review current official ATR–FTIR and GC–FID methods for determination of trans fat, with a focus on factors affecting quantification of low levels of trans fat. We include new data on method performance that have only recently become available, and provide an overview of notable recent developments in lipid analysis (e.g. IR spectroscopy procedures, ionic-liquid GC columns, and multidimensional chromatographic techniques) that have the potential to substantially improve the accuracy, sensitivity, and/or speed of trans fat determination.     

Study on essential oils from the leaves of two Vietnamese plants: Jasminum subtriplinerve C.L. Blume and Vitex quinata (Lour) F.N. Williams

The essential oil constituents of the leaves of Jasminum subtriplinerve (Oleaceae) and Vitex quinata (Verbanaceae) cultivated in Vietnam were analysed by gas chromatography – flame ionisation detector (GC–FID) and gas chromatography – mass spectrometry (GC–MS) techniques. The main constituents identified in J. subtriplinerve were mainly oxygenated monoterpenes represented by linalool (44.2%), α-terpineol (15.5%), geraniol (19.4%) and cis-linalool oxide (8.8%). The quantitative significant components of V. quinata were terpene hydrocarbons comprising of β-pinene (30.1%), β-caryophyllene (26.9%) and β-elemene (7.4%). The chemical compositions of the essential oils are being reported for the first time.     

Phosphorus‐Doped Carbon Nitride Tubes with a Layered Micro‐nanostructure for Enhanced Visible‐Light Photocatalytic Hydrogen Evolution

Phosphorus‐doped hexagonal tubular carbon nitride (P‐TCN) with the layered stacking structure was obtained from a hexagonal rod‐like single crystal supramolecular precursor (monoclinic, C2/m). The production process of P‐TCN involves two steps: 1) the precursor was prepared by self‐assembly of melamine with cyanuric acid from in situ hydrolysis of melamine under phosphorous acid‐assisted hydrothermal conditions; 2) the pyrolysis was initiated at the center of precursor under heating, thus giving the hexagonal P‐TCN. The tubular structure favors the enhancement of light scattering and active sites. Meanwhile, the introduction of phosphorus leads to a narrow band gap and increased electric conductivity. Thus, the P‐TCN exhibited a high hydrogen evolution rate of 67 μmol h^?1 (0.1 g catalyst, λ >420 nm) in the presence of sacrificial agents, and an apparent quantum efficiency of 5.68 % at 420 nm, which is better than most of bulk g‐C₃N₄ reported.