Study of the GC-MS determination of the palmitic-stearic acid ratio for the characterisation of drying oil in painting: La Encarnación by Alonso Cano as a case study

The correct identification of drying oils plays an essential role in providing an understanding of the conservation and deterioration of artistic materials in works of art. To this end, this work proposes the use of peak area ratios from fatty acids after ensuring that the linear responses of the detector are tested. A GC-MS method, previously reported in the literature, was revisited to its developed and validated in order to identify and quantify of eight fatty acids that are widely used as markers for drying oils in paintings, namely myristic acid (C(14:0)), palmitic acid (C(16:0)), stearic acid (C(18:0)), oleic acid (C(18:1)), linoleic acid (C(18:2)), suberic acid (2C(8)), azelaic acid, (2C(9)) and sebacic acid (2C(10)). The quaternary ammonium reagent m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFAH) was used for derivatization prior to GC-MS analysis of the oils. MS spectra were obtained for each methyl ester derivative of the fatty acids and the characteristic fragments were identified. The method was validated in terms of calibration functions, detection and quantification limits and reproducibility using the signal recorded in SIR mode, since two of the methyl derivatives were not totally separated in the chromatographic run. The proposed method was successfully applied to identify and characterise the most widely used drying oils (linseed oil, poppy seed oil and walnut oil) in the painting La Encarnación. This 17th century easel painting is located in the main chapel of the cathedral in Granada (Spain) and was painted by the well-known artist of the Spanish Golden Age, Alonso Cano (1601-1667).     

Analysis of thermal,oxidative and cold flow properties of methyl and ethyl esters prepared from soybean and mustard oils

Oilseed crop with high oil content and promising ecological adaptability are potential sources for competitive biodiesel production. This study investigates the scope of utilizing biodiesel development through the methyl and ethyl ester from soybean and mustard oil as an alternative fuel. Methyl and ethyl esters of oils having different fatty acids compositions such as soybean (SOME and SOEE) and mustard oil (MUME and MUEE) were prepared by transesterification with methanol and ethanol in the presence of an alkali-KOH catalyst. The gas chromatographic (GC) analysis of oil samples revealed that primary fatty acid composition in soybean oil was linoleic acid (C_18:2, 51.93%), followed by oleic acid (C_18:1, 22.82%), palmitic acid (C_16:0, 11.56%), linolenic acid (C_18:3, 5.95%) and stearic acid (C_18:0, 4.32%). Whereas, the main components in mustard oil were erucic acid (C_22:1, 32.81%), oleic acid (C_18:1, 24.98%), eicosenoic acid (C_20:1, 10.44%), linolenic acid (C_18:3, 8.61%) and palmitic acid (C_16:0, 2.80%). The physicochemical properties (acid value, iodine value, calorific value, flash point, pour point etc.) of methyl and ethyl ester samples were estimated and found to be within the acceptable range of ASTM D6751 standards specifications. The prepared esters and oil samples were examined for cold flow properties by differential scanning calorimetry (DSC). Results revealed better cold flow properties for MUME (−2.55 °C) and MUEE (−3.10 °C) than SOME (3.21 °C) and SOEE (1.83 °C) due to more unsaturated fatty acid content in MU. Thermal and oxidative stability of samples was determined by thermogravimetric analysis (TG) and differential thermal analysis (DTA). The thermal and oxidative stability ranking of the samples was in the order of oil > methyl esters > ethyl esters.

     

Analysis of fatty acids in lung tissues using gas chromatography-mass spectrometry preceded by derivatization-solid-phase microextraction with a novel fiber

In this article, a laboratory-made sol-gel derived fiber with butyl methacrylate/hydroxy-terminated silicone oil (BMA/OH-TSO) coating was first used for headspace solid-phase microextraction (HS-SPME) of medium and long chain fatty acids after derivatization and applied to the analysis of fatty acids in lung tissues by coupling to gas chromatography-mass spectrometry (GC-MS). The experimental parameters for derivatization, HS-SPME and desorption were optimized. Fatty acids in cancerous lung tissues from five patients with lung cancer were determined under the optimized conditions. Normal lung tissues from the same five patients were used as controls. This fiber showed higher extraction efficiency for fatty acids after derivatization when compared with commercial polydimethylsiloxane (PDMS) and polydimethylsiloxane-divinylbenzene (PDMS/DVB) fibers due to the three-dimensional network in the coating. The method presented in this paper showed satisfactory precision, accuracy, linearity and limits of detection (LODs). The relative standard deviation values were below 13.3% (n = 5) and the recoveries obtained ranged from 76.35% to 107.0%. The results obtained using the SPME method were also compared with those got by using liquid-liquid extraction (LLE) technique. It was found that the sensitivity could be enhanced by the SPME method. The analysis of the cancerous lung tissues and normal controls from five patients with lung cancer indicated that the main components of lung tissue were palmitic acid (C_16:0), stearic acid (C_18:0) and lignoceric acid (C_24:0). A comparison between the levels of the fatty acids in cancerous lung tissues and normal controls from the same a patient with lung cancer shows that most of the saturated fatty acids showed higher levels in cancerous lung tissues, while unsaturated fatty acids showed higher levels in normal controls on the whole.     

Single Cell Oil Production from Hydrolysates of Inulin by a Newly Isolated Yeast <Emphasis Type="Italic">Papiliotrema laurentii</Emphasis> AM113 for Biodiesel Making

Microbial oils are among the most attractive alternative feedstocks for biodiesel production. In this study, a newly isolated yeast strain, AM113 of Papiliotrema laurentii, was identified as a potential lipid producer, which could accumulate a large amount of intracellular lipids from hydrolysates of inulin. P. laurentii AM113 was able to produce 54.6% (w/w) of intracellular oil in its cells and 18.2 g/l of dry cell mass in a fed-batch fermentation. The yields of lipid and biomass were 0.14 and 0.25 g per gram of consumed sugar, respectively. The lipid productivity was 0.092 g of oil per hour. Compositions of the fatty acids produced were C_14:0 (0.9%), C_16:0 (10.8%), C_16:1 (9.7%), C_18:0 (6.5%), C_18:1 (60.3%), and C_18:2 (11.8%). Biodiesel obtained from the extracted lipids could be burnt well. This study not only provides a promising candidate for single cell oil production, but will also probably facilitate more efficient biodiesel production.     

An Efficient Method for Determination of the Degree of Substitution of Cellulose Esters of Long Chain Aliphatic Acids

The determination of the degree of substitution (DS) of fatty acid cellulose esters, representing a broad range of substituents (C₆, C₁₂, C₁₈ and C₂₂), was performed by alkaline hydrolysis of the ester groups and the quantification of fatty acids by gas chromatography-mass spectrometry (GC-MS) as their trimethylsilyl derivatives. The method was optimized and compared with established techniques for the DS determination (elemental analysis and alkaline hydrolysis/titrimetry). The results demonstrated that alkaline hydrolysis/GC-MS is a rapid, reliable and powerful method for analysis of fatty acid cellulose esters, particularly when different acyl substituents are present.     

Nonglyceride complex of the seed oil ofOnopordum acanthium

Extraction of the comminuted seeds has yielded an oil from which have been isolated: C₃₃-C₂₅, C₁₈ and C₁₇ paraffinic hydrocarbons, C_18:1, C_18:2, C_18:3, C_17:1, C_17:2 and C_17:3 olefinic hydrocarbons, ethyl esters of C_32:0, C_31:0, C_30:0, C_29:0, and C_28:0 fatty acids, sterols with molecular weights of 414, 412, and 400, and the alcohols α-amyrin and lupeol with their natural acetates. Extraction of the uncomminuted seeds has shown that the paraffinic hydrocarbons, ethyl esters, and alcohol acetates pass into the oil from the husks of the seeds. This is the first time that the C_31:0 and C_29:0 fatty acids have been detected as natural compounds, and it is the first time that the ethyl esters of C₃₄, C₃₃, C₃₂, C₃₁, and C₃₀ fatty acids have been isolated from seed oils of higher plants.     

Survival of Freeze-dried Leuconostoc mesenteroides and Lactobacillus plantarum Related to Their Cellular Fatty Acids Composition during Storage

Lactic acid bacteria strains Lactobacillus plantarum CWBI-B534 and Leuconostoc ssp. mesenteroïdes (L. mesenteroïdes) Kenya MRog2 were produced in bioreactor, concentrated, with or without cryoprotectants. In general, viable population did not change significantly after freeze-drying (p?>?0.05). In most cases, viable population for cells added with cryoprotectants was significantly lower than those without (p?16:0), palmitoleic (C_16:1), stearic (C_18:0), oleic (C_18:1), linoleic (C_18:2), and linolenic (C_18:3) acids were identified. Four of them, C_16:0, C_16:1, C_18:0, and C_18:1, make up more than 94% or 93% of the fatty acids in L. mesenteroides and L. plantarum, respectively, with another one, namely, C18:3, making a smaller (on average 5–6%, respectively) contribution. The C_18:2 contributed very small percentages (on average?≤?1%) to the total in each strain. C_16:0 had the highest proportion at most points relative to other fatty acids. Moisture content and water activity (a _w) increased significantly during the storage period. It was observed that C_16:1/C_16:0, C_18:0/C_16:0 and C_18:1/C_16:0 ratios for freeze-dried L. mesenteroides or L. plantarum, with or without cryoprotectants, did not change significantly during the storage period. According to the packaging mode and storage temperatures, C_18:2/C_16:0 and C_18:3/C_16:0 ratios for freeze-dried L. mesenteroides and L. plantarum with or without cryoprotectants decreased as the storage time increased. However, a higher C_18:2/C_16:0 or C_18:3/C_16:0 ratio for L. mesenteroides and L. plantarum was noted in the freeze-dried powder held at 4 °C or under vacuum and in dark than at 20 °C or in the presence of oxygen and light.     

Nonglyceride complex of the seed oil ofOnopordum acanthium

Extraction of the comminuted seeds has yielded an oil from which have been isolated: C₃₃-C₂₅, C₁₈ and C₁₇ paraffinic hydrocarbons, C_18:1, C_18:2, C_18:3, C_17:1, C_17:2 and C_17:3 olefinic hydrocarbons, ethyl esters of C_32:0, C_31:0, C_30:0, C_29:0, and C_28:0 fatty acids, sterols with molecular weights of 414, 412, and 400, and the alcohols -amyrin and lupeol with their natural acetates. Extraction of the uncomminuted seeds has shown that the paraffinic hydrocarbons, ethyl esters, and alcohol acetates pass into the oil from the husks of the seeds. This is the first time that the C_31:0 and C_29:0 fatty acids have been detected as natural compounds, and it is the first time that the ethyl esters of C₃₄, C₃₃, C₃₂, C₃₁, and C₃₀ fatty acids have been isolated from seed oils of higher plants.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 612–615, September–October, 1979.     

Quantitative Determination of Isostearic Acid Isomers in Skin Creams by GC-MS-SIM

“Isostearic acid” is frequently listed as an ingredient of skin creams and other cosmetics. In the four skin creams analyzed, “isostearic acid” was esterified with isopropanol, as well as sorbitan or polyglycerols. “Isopropyl isostearate” was isolated by HCl treatment and saponification whereas emulsifiers (sorbitan or polyglycerol isostearates) were enriched by means of a C₁₈-cartridge. Fatty acids in the resulting lipid fraction were transferred into methyl esters. 25:0 and 19:0 methyl esters were used as internal standards. GC-EI-MS was used to determine that “isostearic acid” was a mixture of many methyl-branched isomers of stearic acid (18:0) in all four skin creams. Thus, it may be better termed “isostearic acids”. The branched-chain nature of isostearates was verified by formation and analysis of picolinyl esters of skin cream fatty acids by GC-EI-MS. Twenty-five 18:0 isomers were detected and the main products had one methyl branch on carbons C₁₀–C₁₄. Two late eluting isostearic acid isomers were identified as 16-methyl heptadecanoic acid (i18:0) and 15-methyl heptadecanoic acid (a18:0). GC-EI-MS in the selected ion monitoring (SIM) mode with m/z 87 as quantification ion was used for the determination of i18:0 methyl ester. The quantities of i18:0 in the samples amounted to 10–20 mg g^?1 skin cream. The contribution of i18:0 to the sum of all 18:0 isomers in the four skin cream samples was 8.5 ± 1.1%. Instead of determining all individual isostearates in a product, we suggest the quantitative determination of i18:0 followed by multiplication with factor 11.75 (~reciprocal value of 8.5%, see above) as a simple method for the quantification of isostearates in cosmetics.     

Catalytic conversions in green aqueous media: Part 4. Selective hydrogenation of polyunsaturated methyl esters of vegetable oils for upgrading biodiesel

This study deals with the influence of operating parameters on the selective hydrogenation of crude polyunsaturated methyl esters of linseed, sunflower and soybean oils in order to achieve high selectivities up to 79.8 mol% of monounsaturated (C18:1) fatty acid methyl esters (FAME) which is 1st generation biodiesel of increased oxidative stability, energy and environmental performance at a low pour point employing water-soluble Rh/TPPTS catalytic complexes [TPPTS = P(C₆H₄-m-SO₃Na)₃] in green aqueous/organic two-phase systems. This study also discloses the great potential of biphasic selective catalytic hydrogenation to produce 2nd generation biodiesel from polyunsaturated FAME of alternative, non-food oil feedstocks which are originally not suitable for biodiesel production or give poor quality biodiesel but combine the advantage that they would not affect food production. Because the mixture of methyl esters of linseed oil mainly consists of C18:3 FAME it constitutes a good model to investigate the effects of parameters on the whole spectrum of the stepwise hydrogenation: C18:3 (linolenates) → C18:2 (linoleates) → C18:1 (oleates)  C18:0 (stearate) and to obtain first information on the selective hydrogenation of alternative, non-food oils with a high C18:3 FAME content to make them suitable for 2nd generation biodiesel formulations.     

Optimization of Fatty Acid Determination in Selected Fish and Microalgal Oils

The use of ten fatty acid methyl ester reference standards coupled with a detailed quantification method was shown to significantly optimize the fatty acid determination of selected fish and microalgal oils when compared to methods that use only one reference standard (C19:0 or C23:0) as a relative response factor. When using the mixture of ten reference standards after transesterifying oils with NaOH/BF₃, determination of total fatty acids, eicosapentaenoic acid and docosahexaenoic acid improved by an average of 7.3, 11.5 and 8.4%, respectively. Furthermore, improvements of 13.9, 18.9 and 6.8% of total fatty acids, EPA and DHA, respectively, were obtained when using the mixture of reference standards for fatty acid determination after directly extracting and transesterifying oil contained in microalgal cells with a mixture of methanol, HCl and chloroform. Fatty acid methyl ester standards dissolved in isooctane showed <5% variability throughout 130 days of stability testing when stored at ?20 °C. The optimized method can be used for improving the quantification of fatty acids in both oils (fish and microalgal oils) and dry microalgal cells.     

Pyrolysis of residual palm oil in spent bleaching clay by modified tubular furnace and analysis of the products by GC–MS

In this study, spent bleaching clay containing 26.6 wt.% of residual palm oil was pyrolyzed using a tubular furnace. Carboxylic acids ranging from C₉-C₁₈ and alkanes ranging from C₁₆-C₄₄ were the major classes of compounds found in the pyrolytic products analyzed using GC-MS. Significant amounts of monoaromatic compounds, alkenes, alcohols, ketones, aldehydes, esters, nitrogenated compounds, and polycyclic aromatic hydrocarbons (PAHs) were found in the bio-oil produced in this study. The bio-oil resulting from the pyrolysis process gave n-hexadecanoic acid as the major compound. Decomposition temperature of the adsorbed oil determined using TGA was found to be in the range of 573-683 K. Topographical and elemental analyses of the clay was done using SEM-EDX. The functional groups were determined using FTIR.     

Analysis of long-chain fatty acids in grey wastewater with in-vial derivatisation

The presence and levels of long-chain fatty acids (C₆–C₂₀) in grey wastewater from bathrooms have been investigated. The acids were purified and concentrated by solid-phase extraction on strong anion exchange discs, in-vial derivatised to their corresponding methyl ester and subsequently analysed by GC-MS. The method was able to quantify the acids at concentration <1?µg/L with a recovery of 31–97%. The levels of fatty acids were found in the range of <0.5 to 27?100?µg/L and the highest levels were found for the saturated lauric (C₁₂), palmitic (C₁₆) and stearic (C₁₈) acids. The treatment efficiency of a local treatment plant was evaluated by comparing concentrations of fatty acids at the inlet and the outlet. It was found that the treatability decreases with increasing chain length for the saturated acids (19–100% degradation) whereas the corresponding mono unsaturated acids were more easily degraded.     

<em>In Vitro</em> Anti-diabetic Activities and Chemical Analysis of Polypeptide-k and Oil Isolated from Seeds of <em>Momordica charantia</em> (Bitter Gourd)

The amino acid and fatty acid composition of polypeptide k and oil isolated from the seeds of Momordica charantia was analysed. The analysis revealed polypeptide k contained 9 out of 11 essential amino acids, among a total of 18 types of amino acids. Glutamic acid, aspartic acid, arginine and glycine were the most abundant (17.08%, 9.71%, 9.50% and 8.90% of total amino acids, respectively). Fatty acid analysis showed unusually high amounts of C18-0 (stearic acid, 62.31% of total fatty acid). C18-1 (oleic acid) and C18-2 (linoleic acid) were the other major fatty acid detected (12.53% and 10.40%, respectively). The oil was devoid of the short fatty acids (C4-0 to C8-0). Polypeptide k and oil were also subjected to in vitro α-glucosidase and α-amylase inhibition assays. Both polypeptide k and seed oil showed potent inhibition of α-glucosidase enzyme (79.18% and 53.55% inhibition, respectively). α-Amylase was inhibited by 35.58% and 38.02%, respectively. Collectively, the in vitro assay strongly suggests that both polypeptide k and seed oil from Momordica charantia are potent potential hypoglycemic agents.     

Determination of astaxanthin and astaxanthin esters in the microalgae <Emphasis Type="Italic">Haematococcus pluvialis</Emphasis> by LC-(APCI)MS and characterization of predominant carotenoid isomers by NMR spectroscopy

The oily product ZANTHIN® consists of natural astaxanthin, which is manufactured from the microalgae Haematococcus pluvialis by supercritical CO₂ extraction. An HPLC method was developed to separate all of the components of the complex astaxanthin extract using a C₃₀ column. The separation resulted in different isomers of astaxanthin accompanied by two other carotenoids. The main component consisted of astaxanthin singly esterified with several different fatty acids. C18:3, C18:2, C18:1 and C16:0 were identified as the most commonly occurring fatty acids. Doubly esterified astaxanthin was also found, although in lower concentrations compared to singly esterified astaxanthin. After performing a detailed fatty acid analysis by GC-MS, the peaks from the extract were assigned via HPLC-MS. A trans to cis transmutation of the all-trans compound was performed by thermal treatment in order to obtain an enrichment of cis isomers as the basis for unambiguous identification via NMR experiments. The all-trans as well as the 9- and 13-cis isomers of astaxanthin were characterized in detail by UV/Vis, ¹H, and ¹H,¹H COSY NMR spectroscopy.     

HPLC of fatty acid esters of mono- and polyhydric alcohols. Part 1: Analytical separation

This paper shows how simply and yet very rapidly fatty acid esters of monohydric alcohols, but particularly partial and full fatty acid esters of fully hydric alcohols can be separated and determined by means of high-pressure liquid chromatography on LiChrosorb RP-8 with methanol/water. We have separated quantitatively the methylesters of the fatty acids C_8:0 to C_22:0 and C_24:0, the i-propyl-, i-butyl-, n-hexyl- and i-octyl-esters of the even-numbered fatty acids C_8:0 to C_18:0, mono- and difatty acid esters of the 1,3-bis-(2-hydroxyethyl)-5,5-dimethyl-hydantoin, mono-, di- and triesters of the trimethylolpropane as well as the tetraesters of the penta-erythrite.     

Thermally produced ω-(o-alkylphenyl)alkanoic acids provide evidence for the processing of marine products in archaeological pottery vessels

ω-(o-Alkylphenyl)alkanoic acids with 16, 18 and 20 carbon atoms were identified in archaeological pottery vessels from coastal sites in Southern Brazil. Such compounds are presumed to form during heating of triunsaturated fatty acids (C_16:3, C_18:3 and C_20:3), which are commonly found in the tissues of marine animals. The detection of these unusual cyclic compounds together with the isoprenoid fatty acids, 4,8,12-trimethyltetradecanoic acid and phytanic acid and substantial quantities of archaeological bones of fish and mollusca, provides evidence for the processing of marine animal products in archaeological pottery.     

Characterization of ganoderma spore lipid by stable carbon isotope analysis: implications for authentication

The ratios of stable carbon isotopes (¹³C/¹²C) of ganoderma fruiting body, ganoderma spore, ganoderma spore lipid (GSL) and individual fatty acids in GSL were determined by gas chromatography–stable isotope ratio mass spectrometry and elemental analysis–stable isotope ratio mass spectrometry. These values fall into a range from −26.9 to −23.3‰, suggesting that the cut log as the Ganoderma-cultivated substrate in Fujian, China, may belong to C3 plants. Eighteen fatty acids were identified and their abundances measured by gas chromatography–mass spectrometry in the six GSL samples with C_16:0, C_18:0, C_18:1 and C_18:2 as major constituents, and C_16:1 is evidently enriched compared with the other edible vegetable oils. On the basis of the compositions of fatty acids and stable carbon isotopes in GSL, we have developed a novel method to detect the adulteration of GSL products with cheaper edible vegetable oils. An example of ideal blending between GSL and C4 or C3 vegetable oil is further provided to expound the discrimination procedures and corresponding sensitive indicators. Simultaneously, the carbon isotope fractionation in the biosynthesis of individual fatty acids was observed, revealing that the formation of C_18:0 from C_16:0 in ganodema spores had no conspicuous ¹³C enrichment of +0.4‰ for Ganoderma sinensis spore and +0.1‰ for G. lucidum spore; the desaturation of C_18:0 to C_18:1 resulted in a distinct ¹³C depletion of −1.4‰ for G. sinensis spore and −0.9‰ for G. lucidum spore; and the next desaturation from C_18:1 to C_18:2 displayed no evident ¹³C fractionation of −0.1‰ for G. sinensis spore and −0.2‰ for G. lucidum spore. Figure Ganoderma lucidum has been widely used in traditional Chinese medicines. Ganoderma spore lipid (GSL) extracted from the spores of G. lucidum has been approved as a health food supplement. However, because of rarity, GSL has become a target for adulteration with cheaper vegetable oils.     

Experimental determination of the (vapor + liquid) equilibrium data of binary mixtures of fatty acids by differential scanning calorimetry

(Vapor + liquid) equilibrium (VLE) data for three binary mixtures of saturated fatty acids were obtained by differential scanning calorimetry (DSC). However, changes in the calorimeter pressure cell and the use of hermetic pans with holes (? = 250 mm) in the lids were necessary to make it possible to apply this analytical technique, obtaining accurate results with smaller samples and shorter operational times.The systems evaluated in this study were: myristic acid (C_14:0) + palmitic acid (C_16:0), myristic acid (C_14:0) + stearic acid (C_18:0), and palmitic acid (C_16:0) + stearic acid (C_18:0), all measured at 50 mm Hg and with mole fractions between 0.0 and 1.0 in relation to the most volatile component of each diagram. The fugacity coefficients for the components in the vapor phase were calculated using the Hayden and O’Connell method [J.G. Hayden, J.P. O’Connell, Ind. Eng. Chem. Process Design Develop. 14 (3) (1975) 209–216] and the activity coefficients for the liquid phase were correlated with the traditional g^E models (NRTL [H. Renon, J.M. Prausnitz, Aiche J. 14 (1968) 135–144], UNIQUAC [D.S. Abrams, J.M. Prausnitz, Aiche J. 21 (1975) 116–128], and Wilson [J.M. Prausnitz, N.L. Linchtenthaler, E.G. Azevedo, Molecular Thermodynamics of Fluid-phase Equilibria, River-Prentice Hall, Upper Saddle, 1999]). The sets of parameters were then compared in order to determine which adjustments best represented the VLE.