Identification of drying oils used in pictorial works of art by liquid chromatography of the 2-nitrophenylhydrazides derivatives of fatty acids

A new HPLC-UV-Vis method for identification of drying oils from binding media or protective film used in pictorial works of art prior to conservation or restoration is proposed. Chromophore derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent selected was 2-nitrophenylhydrazine with 1-ethyl-3-(3-dimethyl animopropyl)carbodiimide hydrochloride/pyridine as catalyst. This reaction was carried out using microwave heating. Mobile phase was methanol/water/n-propanol/acetic acid (80:14:5:1) running in isocratic mode. Absorbance was measured at 400 nm. In these conditions, hydrazides of myristic, palmitic, oleic, and stearic acids were satisfactorily resolved. Method shows good sensitivity, with a detection limit of 15 μmol l⁻¹, and good linearity between 0.03 and 3 mmol l⁻¹. Peak area ratios among fatty acids derivatives allows identification of the drying oils. The stearic/palmitic ratio is the most important, because it allows to differentiate among the different drying oils. The proposed method has been successfully applied to real samples from items of the cultural heritage of Valencia (Spain).     

Trimethylsulfonium hydroxide as derivatization reagent for the chemical investigation of drying oils in works of art by gas chromatography

A procedure for the determination of fatty acids (FA) and glycerol in oils has been developed. The method includes a derivatization step of the FAs into their methyl esters or a transesterification of the triacylglycerols with trimethylsulfonium hydroxide (TMSH), respectively. The analysis is carried out by gas chromatography with parallel flame ionization and mass spectrometric detection. The parameters involved in the transesterification reaction were optimized. Only the stoichiometric ratio of TMSH:total FA amount showed a significant influence on the reaction yield. Relative standard deviations for 10 replicates were below 3% for all FAs studied and their linearity range was 0.5-50 mmol/L, when using heptadecanoic acid as an internal standard. The final procedure was rapid and required little sample handling. It was then tested on fresh oil samples and presented satisfying results, in agreement with previous works.     

Comparative Study of Fatty Acid Components in Oils of Different Olive Varieties Grown in Different Regions of Pakistan by Gas Chromatography‐Mass Spectrometry

Olive oils were extracted from two consecutive crops (2008 and 2009) of three different varieties of olive cultivated at different geographical regions of Pakistan. The profiles of the fatty acid compositions were developed employing GC‐MS techniques and then compared. The purpose of this research paper is to evaluate the olive oil constituents in Olive cultivated in different regions in order to determine the quality of olive oil and to ascertain the suitability of area for best quality products.     

气相色谱–质谱法测定食用植物油中短链脂肪酸的测量不确定度评定

采用气相色谱–质谱法(GC–MS)测定食用植物油中短链脂肪酸含量,对测量结果的不确定度进行评定,探讨提高测量准确度的方法。依据方法建立数学模型,分析得出不确定度主要来源于样品制备过程、计量器具的使用、标准溶液配制、测量设备、人员读数误差、方法回收率,计算各不确定度分量,得到相对标准不确定度和扩展不确定度。结果表明,当食用植物油中短链脂肪酸测定结果为13.1 mg/kg时,其扩展不确定度为1.8 mg/kg(k=2)。测量设备、标准溶液配制过程引入的不确定度较大,应在实验过程中予以控制和关注。     

气流吹扫-注射器微萃取-全二维气相色谱法用于原油组分的表征

建立了气流吹扫-注射器微萃取（GP-MSE）与全二维气相色谱/飞行时间质谱（GC×GC/TOFMS）联用分析原油成分的方法。为了找到适用于原油样品分析的GP-MSE条件,用饱和烃混合标准溶液和15种芳烃的混合标准溶液进行了条件优化,得到的最佳条件如下:取样量5 mg、萃取溶剂正己烷20 μ L、载气流速2 mL/min、加热时间3 min、加热温度300 ℃、冷凝温度-2 ℃。处理后的样品在全二维色谱/飞行时间质谱上进样分析,得到了满意结果。方法的检出限为34~93 μg/L,线性相关系数（R²）>0.99,对50种烃类化合物的回收率在82.0%~107.3%之间,相对标准偏差<10%（n=5）。结果表明GP-MSE-GC×GC/TOFMS法是一种新型绿色、高效、灵敏的分析方法,非常适合原油中挥发性与半挥发性组分的分析。     

Elucidation of fatty acid profiles in vegetable oils exploiting group-type patterning and enhanced sensitivity of comprehensive two-dimensional gas chromatography

The present research is focused on the use of comprehensive 2-D GC (GCxGC) for the thorough elucidation of fatty acid (FA) profiles contained in vegetable oils; the samples analysed consisted of extra-virgin olive oil and refined hazelnut oil. The enhanced sensitivity and the formation of group-type patterns provided by GCxGC enabled the identification and quantification of both well-known and rather unexpected FAs contained in the lipid matrices. Peak assignment was, in most cases, supported by using pure standard compounds. Of particular interest was the identification of a series of odd-numbered FAs in both samples. The results attained to demonstrate the usefulness of GCxGC also for the analysis of supposedly low-complex samples.     

Kinetic study of the drying step of supported catalysts by reversed-flow gas chromatography

Summary Application of reversed-flow gas chromatography to study the drying step in the preparation of supported catalysts is proposed. It is demonstrated that this technique can be applied to investigate the kinetic law followed, as well as to obtain kinetic parameters of drying (rate constants, activation energies and frequency factors). Amaterial illustrating this application is -Al₂O₃ impregnated with usual organic solvents (n-C₅H₁₂,n-C₆H₁₄,n-C₇H₁₆, CH₃COCH₃ and CH₃CH₂OH). It was found that in all cases above a simple first-order law based onone kind of active site is followed. Moreover, it was observed that the activation energyE _a of the drying process increases almost linearly with the relative molecular mass of the solvent, whereas for the same solventE _a increases with the amount used. The operation of a kinetic compensation effect suggests similar activated complexes of the various solvents used.     

Analysis of plant oils by subcritical fluid chromatography using pattern fitting

A new method for analyzing plant oils was developed, which allows determination of fatty acid (FA) and triglyceride (TG) compositions of oils directly from their chromatograms without complete separation and peak identification. TGs of oils were separated by subcritical fluid chromatography using an octadecyl-silica column, carbon dioxide mobile phase and flame ionization detector. Observed chromatograms were compared with simulated ones, which were generated using FA compositions and predicted retentions of TGs on the assumption that FAs are combined with glycerol at random. FA compositions were determined by minimizing the differences between observed and simulated chromatograms through trial and error. Compared with GC analysis, relative errors of calculated FA compositions were less than 10% for main components (mol fraction>0.2). However, cocoa butter presented large errors even for main components because of the selective bonding of FAs to glycerol. Application of this method to the analysis of blended oils was also demonstrated, where FA compositions and mixing ratio were determined.     

Optimization and validation of organochlorine compounds in adipose tissue by SPE‐gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C₁₈‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP₁₈ SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C₁₈‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Tracking juniper berry content in oils and distillates by spectral deconvolution of gas chromatography/mass spectrometry data

The complex nature of botanicals and essential oils makes it difficult to identify all of the constituents by gas chromatography/mass spectrometry (GC/MS) alone. In this paper, automated sequential, multidimensional gas chromatography/mass spectrometry (GC-GC/MS) was used to obtain a matrix-specific, retention time/mass spectrometry library of 190 juniper berry oil compounds. GC/MS analysis on stationary phases with different polarities confirmed the identities of each compound when spectral deconvolution software was used to analyze the oil. Also analyzed were distillates of juniper berry and its oil as well as gin from four different manufacturers. Findings showed the chemical content of juniper berry can be traced from starting material to final product and can be used to authenticate and differentiate brands.     

Analytical Characterization of Fatty Acids Composition of Datura alba Seed Oil by Gas Chromatography Mass Spectrometry

Methyl ester derivatives of fatty acids were analyzed for the determination of the constituents of Datura alba seed oil. Gas chromatography coupled to mass spectrometer was used for these analyses. Results delivered that there were saturated as well as unsaturated fatty acids in Datura alba seed oil. Total of 15 different fatty acid components were identified and quantified. Methyl linoleate was found in highest concentration (16.22%) among the identified analytes of interest. In addition methyl esters of Palmitic acid (6.59%), Oleic acid (5.41%) and Stearic acid (1.35%) were found. Concentrations of rest of the detected fatty acids were less than 1%. From the literature it appears that no such work has been performed for the determination of fatty acids in Datura alba seed oil.     

杂色鲍脂肪酸及烯醚键基团的气相色谱/质谱分析

研究了简便快速分析杂色鲍中脂肪酸及烯醚键基团的方法.杂色鲍经F0lch法提取总脂,以10%浓硫酸.甲醇溶液为衍生试剂,于60℃水浴衍生15 min,采用气相色谱/质谱联用技术进行分析,共鉴定出31个化合物,包括25种脂肪酸和6种脂肪醛二甲基缩醛.杂色鲍脂肪酸以C16:0、C20:4(n-6)、C20:5(n-3)、C1...     

Characterisation of beeswax in works of art by gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry procedures

Pyrolysis (Py) with in situ derivatisation with hexamethyldisilazane-gas chroma-break tography-mass spectrometry (GC-MS) and a gas chromatography-mass spectrometry procedure based on microwave-assisted saponification were used to identify the organic components in small sized beeswax samples. With the latter procedure quantitative recoveries can be made and hydrocarbons, alcohols and omega-1-diols in the neutral fraction, and fatty acids and omega-1-hydroxy acids in the acidic fraction can be efficiently separated and detected. Both procedures were used to characterise a wax anatomic sculpture "The Plague" (1691-1694) by Gaetano Zumbo, resulting in the identification of beeswax and a Pinaceae resin. The GC-MS analysis brought to light some essential differences in beeswax composition between the raw material and the old modelled wax thus giving some clear indications about the recipe used by the sculptor.     

血液中吗啡类毒品硅烷化气相色谱-质谱分析

建立和确证了血液中吗啡类毒品(吗啡、 6-单乙酰吗啡、可待因)的液相萃取-硅烷化-GC/MS-SIM检测的方法.以乙基吗啡为内标,以V(CHCl3)∶V(异丙醇)∶V(正庚烷)＝50∶17∶33混合溶剂为萃取溶剂,以MSTFA 为硅烷化试剂,采用GC/MS-SIM检测方式,吗啡、6-单乙酰吗啡、可待因的线性相关系数均大于0.99,最低血液检测浓度可达到5 ng/mL;定量范围10～1000 ng/mL;日内重复性小于15%.该方法可用于海洛因吸食者血液中的毒品及其代谢物的检验.     

Analysis of essential oils by direct sampling from plant secretory structures and capillary gas chromatography

It is of fundamental importance to know the true composition of the essential oil produced by the secretory structures of a plant, both from a biogenetic and a chemotaxonomic point of view. This paper considers a method which combines direct sampling with on-column CGC and studies the oils directly from the secretory structures: some examples are given (Humulus lupulus L., Tagetes erecta L., and Tagetes patula L.). For each plant, the composition of the distilled oil is compared to that obtained by direct sampling, and a photograph of the secretory structures taken by electroscanning microscopy is given.     

Polycyclic aromatic hydrocarbons (PAHs) in edible oils by gas chromatography coupled with mass spectroscopy

The occurrence of polycyclic aromatic hydrocarbons (PAHs) in nine edible oils of three categories of oil samples, such as soy bean oil, mustard oil and coconut oil, has been studied to determine the contamination degree of this type of oil samples. Eight major carcinogenic polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, anthracene, phenanthrene, fluorene, pyrene, crysene, benzo(a)pyrene and benzo(a)anthracene, were identified and quantified in the extract of edible oils collected from Bangladeshi Markets by gas chromatography and mass spectroscopy. All of the carcinogenic PAHs are not present in the edible oils. A few of the carcinogenic PAHs are present in the oils but it is within the permissible limit. The results for the recoveries of naphthalene, fluorene, phenanthrene, anthracene, pyrene, crysene, benzo(a)anthracene and benzo(a)pyrene were in the range of 56–84%. The limit of detection (LOD) of the GC–MS method, established at signals three times that of the noise for naphthalene, fluorene, phenanthrene, anthracene, pyrene, crysene, benzo(a)anthracene and benzo(a)pyrene, was 2.0–2.5 ng, respectively.     

Characterization of substituted polyacetylene microstructure by pyrolysis gas chromatography

A series of substituted acetylenes has been polymerized with WOC14/Ph4Sn metathesis catalyst and [Rh(cod)OMe]2 insertion catalyst, and the thermal degradation of the polyacetylenes prepared has been studied using pyrolysis capillary gas chromatography (Py-GC) with flame ionization and mass spectrometric detection to obtain information on the effect of the catalyst on the head-tail (H-T) isomerism of polyacetylenes (poly(phenylacetylene), poly[(4-methylphenyl)acetylene], poly(benzylacetylene), poly((2-fluorophenyl)acetylene], poly[(3-fluorophenyl)acetylene], and poly[(4-fluoro-phenyl)acetylenel). Cyclotrimers have been found to be the main pyrolysis products in all cases. Direct Py-MS connection was used to determine the temperature profiles of the released pyrolysis products. 1,3,5-Trisubstituted benzenes were found to be the predominant pyrolysis products of the polymers prepared with the insertion catalyst, which proves the presence of long head-to-tail sequences of monomeric units in these polyacetylenes. On the other hand, both 1,2,4- and 1,3,5-trisubstituted benzenes are present in significant amounts in the pyrolysis products of polymers prepared with the metathesis catalyst, which proves the presence of a significant content of the head-to-head (HH) and tail-to-tail (TT) linkages in these isomers of polyacetylenes. Contents of the regular (HT) and inverse (HH-TT) monomer linkages (RML and IML, respectively) in polymer chains were determined from the relative amounts of di-, tri-, and tetrasubstituted benzenes found in the Py-GC products.     

Chemical characterization of gorse pyrolytic oils by capillary gas chromatography

Thermochemical conversion of biomass produces solid charcoal, gaseous fuels, and condensable oils. Because these oils vary widely in composition depending on the cellulosic feedstock and the operating conditions used, analysis of the oils is necessary in order to determine the best ways of utilizing or disposing of them. The major components of the organic oil from pyrolysis of gorse have been characterized by capillary gas chromatography – mass spectrometry. A qualitative study of the aqueous oil from the same source has also been attempted.     

Identification of drying oils in mixtures of natural binding media used for artistic and historic works by capillary electrophoresis

To characterise the technologies and to find the appropriate treatments, the identification of the binding media of artistic and historic objects is of high importance for the restorer and conservator. Often applied together with other binders, in the present paper, the applicability of a CZE method was ascertained for the identification of the constituents of drying oils in mixtures with animal glues and/or plant gums. The drying oils are identified after alkaline hydrolysis due to their content of long‐chain saturated and unsaturated fatty acids (palmitic, stearic, oleic, linoleic, linolenic) and shorter‐chain dicarboxylic acids (pimelic, suberic, azelaic, sebacic). The dicarboxylic acids occur as products of the unsaturated acids by oxidative degradation during the drying process. The possible interferences in CE caused by the other binders are amino acids and/or monosaccharides. Such interferences could be expected as indirect UV detection has to be used, which is highly unspecific. It was found that none of the constituents of the animal glues or plant gums migrate in the time window of the analytes, thus not obstructing the identification of the analytes in any of the oil mixtures with one binder, or with a combination of both. No interference is observed even in excess of the glues. The method was applied for the identification of a drying oil in a paint layer from a ceremonial mask originating from Papua New Guinea. There is evidence that the oil is most probably from candlenut tree (Aleurites moluccana).