Glycidyl fatty acid esters in food by LC-MS/MS: method development

An improved method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of glycidyl fatty acid esters in oils was developed. The method incorporates stable isotope dilution analysis (SIDA) for quantifying the five target analytes: glycidyl esters of palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) and linolenic acid (C18:3). For the analysis, 10 mg sample of edible oil or fat is dissolved in acetone, spiked with deuterium labelled analogs of glycidyl esters and purified by a two-step chromatography on C18 and normal silica solid phase extraction (SPE) cartridges using methanol and 5% ethyl acetate in hexane, respectively. If the concentration of analytes is expected to be below 0.5 mg/kg, 0.5 g sample of oil is pre-concentrated first using a silica column. The dried final extract is re-dissolved in 250 μL of a mixture of methanol/isopropanol (1:1, v/v), 15 μL is injected on the analytical C18 LC column and analytes are eluted with 100% methanol. Detection of target glycidyl fatty acid esters is accomplished by LC-MS/MS using positive ion atmospheric pressure chemical ionization operating in Multiple Reaction Monitoring mode monitoring 2 ion transitions for each analyte. The method was tested on replicates of a virgin olive oil which was free of glycidyl esters. The method detection limit was calculated to be in the range of 70-150 μg/kg for each analyte using 10 mg sample and 1-3 μg/kg using 0.5 g sample of oil. Average recoveries of 5 glycidyl esters spiked at 10, 1 and 0.1 mg/kg were in the range 84% to 108%. The major advantage of our method is use of SIDA for all analytes using commercially available internal standards and detection limits that are lower by a factor of 5-10 from published methods when 0.5 g sample of oil is used. Additionally, MS/MS mass chromatograms offer greater specificity than liquid chromatography-mass spectrometry operated in selected ion monitoring mode. The method will be applied to the survey of glycidyl fatty acid esters in food products on the Canadian market.     

Analysis of siloxane pyrolysis products by cryo-GC/FT-IR and GC/MS

On line measurements of infrared and mass spectra of siloxane pyrolysis products separated by gas chromatography are described. The FT-IR absorbance spectra have been recorded from the eluates trapped as small spots on a moving window held at 77 K. Three of the main compounds separated were selected for FT-IR identification performed by comparing the spectra with GC/MS data and by spectral searching using a library of compounds measured under the same conditions.Dedicated to our most honourable teacher Professor Dr. H. Kriegsmann on the occasion of his 70th birthday     

野西瓜种子油中脂肪酸的气相色谱-质谱分析

采用加速溶剂萃取及索氏提取法,用正己烷和乙醚为提取剂从野西瓜种子中提取油脂,经浓H2SO4催化,甲醇甲酯化处理后,以气相色谱-质谱联用技术鉴定出野西瓜种子中的脂肪酸主要组成为:油酸、亚油酸、硬脂酸等,其中不饱和脂肪酸总量占91.4%,主要成分油酸占73.3%。野西瓜种子油具有较高的营养价值,同时也可为生物柴油提供良好的原料。     

Repeatability and pattern recognition of bacterial fatty acid profiles generated by direct mass spectrometric analysis of in situ thermal hydrolysis/methylation of whole cells

Direct CI mass spectrometry profiling of fatty acid methyl esters (FAMEs) from in situ thermal hydrolysis/methylation (THM) of whole bacterial cells with tetramethylammonium hydroxide (TMAH) has been demonstrated as a potential method for real time and fieldable detection/identification of microorganisms. Bacillus anthracis (Ames), Yersinia pestis (Nair. Kenya), Vibrio cholerae (E1 Tor), Brucella melitensis (Abortus wild) and Francisella tularensis (LVS vaccine) were profiled by this method during a 10-month period. Repeatability of the in situ FAME data was calculated using one-way analysis of variance (ANOVA) and a t-test. Artificial neural network (ANN) and multivariate statistics of the FAME profiles were also compared for bacterial identification/classification. Equivalent results were obtained with a multivariate rule building expert system (MuRES) and the ANN. However, the ANN analysis required much less computer time and was deemed the best choice for this application. In situ THM FAME profiles of the bacterial samples provided comparable results with those obtained from the Microbial Identification System (MIDI) (Newark, DE) wet chemistry-gas chromatographic based system.     

Ambient generation of fatty acid methyl ester ions from bacterial whole cells by direct analysis in real time (DART) mass spectrometry

Direct analysis in real time (DART) is implemented on a time-of-flight (TOF) mass spectrometer, and used for the generation of fatty acid methyl esters (FAMEs) ions from whole bacterial cells.     

GC determination of N-nitrosamines by supersonic molecular beam MS equipped with triple quadrupole analyzer, GC/SMB/QQQ/MS

The determination of 14 N-nitrosamines by a supersonic molecular beam electron ionization mass spectrometer equipped with triple quadruple analyzer, GC/SMB/EI/QQQ/MS is presented. The supersonic molecular beam electron ionization ion source allows the elucidation of the molecular ion of 13 out of the 14 examined nitrosamines (except for diphenylnitrosamine which was degraded before the analysis). It was possible to use the molecular ions of all the nitrosamines as the parent ions for multiple reactions monitoring mode, which in turn allows significant increase of specificity and lowering of the method limit of detection of the higher molecular weight nitrosamines. The instrumental LOD for different N-nitrosamines was 1–5 pg injection⁻¹. The proposed method was exemplified by analysis of N-nitrosamines and N-nitrosatables in rubber teats according to the British Standard BS EN 12868:1999.     

A UPLC/MS/MS method for comprehensive profiling and quantification of fatty acid esters of hydroxy fatty acids in white adipose tissue

Analytical and Bioanalytical Chemistry - Fatty acid esters of hydroxy fatty acids (FAHFAs) are recently discovered lipids with antidiabetic and anti-inflammatory effects. We have developed an...     

Modified MALDI MS fatty acid profiling for bacterial identification

Bacterial fatty acid profiling is a well‐established technique for bacterial identification. Ten bacteria were analyzed using both positive‐ and negative‐ion modes with a modified matrix‐assisted laser desorption ionization mass spectrometry (MALDI MS) approach using CaO as a matrix replacement (metal oxide laser ionization MS (MOLI MS)). The results show that reproducible lipid cleavage similar to thermal in situ tetramethyl ammonium hydroxide saponification/derivatization had occurred. Principal component analysis showed that replicates from each organism grouped in a unique space. Cross validation (CV) of spectra from both ionization modes resulted in greater than 94% validation of the data. When CV results were compared for the two ionization modes, negative‐ion data produced a superior outcome. MOLI MS provides clinicians a rapid, reproducible and cost‐effective bacterial diagnostic tool. Copyright © 2013 John Wiley & Sons, Ltd.     

调味品中氯丙醇的GC/ECD和GC/MS/MS衍生化检测方法研究及应用

报道了调味品中氯丙醇的衍生化气相色谱(GC／ECD)和衍生化气相色谱双串联质谱法(GC／MS／MS)测定。GC／ECD测定酱油中3—氯—1，2—丙二醇(3—MCPD)的检出限达到0．01mg／kg，回收率为91％～104％，变异系数为2．27％～7．96％；GC／MS／MS同时测定酱油中1，3—二氯—2—丙醇、2，3—二氯—1—丙醇和3—氯—1，2—丙二醇，1，3—二氯—2—丙醇、2，3—二氯—1—丙醇的检出限为0．02mg／kg，3—氯—1，2—丙二醇的检出限为0．01mg／kg，回收率在92％～106％，变异系数为3．51％～13．33％。     

Statistical evaluation of an analytical GC/MS method for the determination of long chain fatty acids

In-depth evaluation of an analytical method to detect and quantify long chain fatty acids (C₈-C₁₆) at trace level concentrations (25-1000 μg/l) is presented. The method requires derivatization of the acids with methanolic boron trifluoride, separation, and detection by gas chromatography-mass spectrometry. The calibration experiments passed all the tested performance criteria such as linearity, homoscedasticity, and ruggedness. The detection limits and related quantities were computed by applying the method detection limit, and the calibration line approximation. The values obtained by applying the latter approach were more reliable and consistent with the actual statistical theory of detection decisions and yielded the following concentrations: C₈, 87.6 μg/l; C₁₀, 45.2 μg/l; C₁₁, 39.9 μg/l; C₁₂, 37.7 μg/l; C₁₄, 41.4 μg/l and C₁₆, 40.6 μg/l. Two different gas-liquid chromatographic columns were tested and similar results achieved, which shows the ruggedness of the method.     

型煤中硫的还原热解MS和GC/MS分析

以煤和生物质为主要原料的商用型煤为研究对象,采用还原热解（AP-TPR）在线质谱（MS）联用,以及离线色谱/质谱（GC/MS）分析法,定性和定量研究了家用型煤释放的含硫化合物。不同组成的型煤表现出各自不同的硫释放特性。对于生物型煤来说,仅检测到少量二烷基硫醚和脂肪硫醇的存在。褐煤型煤检测到种类最多的有机硫化物。在高阶煤制成的型煤中没有检测到氧化态的硫化物,其典型特征是存在一些噻吩类硫化物。     

Preparation of fatty acid methyl esters by direct transesterification of lipids with aluminium chloride-methanol

A new and simple procedure has been developed that allows the direct transesterification of lipids, using aluminium chloride as a catalyst and methanol as the esterifying alcohol. The concentration of the salt and reaction conditions have been investigated for the different lipid classes. Comparative studies, performed with boron trifluoride-methanol, indicate that the same values are obtained when using either reagent. In addition, the method has been adapted for transesterification in the presence of silica gel and other adsorbents, thus allowing the preparation of fatty acid methyl or ethyl esters directly from samples previously fractionated by thin-layer chromatography. This new reagent is very stable and easy to handle, the fatty acids being generated in the same tube without further purification steps.     

气相色谱-质谱法测定卷烟烟气总粒相物中的乳酸

以三甲基氢氧化硫为甲酯化试剂,正戊醇为内标,采用CP-FFAP毛细管柱(25 m×0.15 mm i.d.×0.25μm d.f)和选择离子模式,建立了卷烟烟气总粒相物中乳酸的气相色谱-质谱分析方法。该方法的线性范围为0.285~0.0570mg/mL乳酸(r=0.9997),平均回收率为97.99%,RSD为1.58%。并用该法测定了部分卷烟烟气总粒相物中的乳酸。     

Sub PPB level determination of eperison in human plasma by GC/MS

Summary Very low concentrations (down to 0.2 ng/mL) of an antispasmodic drug (Eperison) can be extracted from human plasma and analyzed by GC/MS. For sample preparation and preconcentration, solid phase extraction (SPE) has been employed. A double focussing mass spectrometer was interfaced with a capillary GC column for the GC/MS analysis. The gas chromatograph was equipped with an on-column injector to avoid thermal decomposition.     

Integrated multidimensional and comprehensive 2D GC analysis of fatty acid methyl esters

Fatty acid methyl ester (FAME) profiling in complex fish oil and milk fat samples was studied using integrated comprehensive 2D GC (GC × GC) and multidimensional GC (MDGC). Using GC × GC, FAME compounds – cis‐ and trans‐isomers, and essential fatty acid isomers – ranging from C18 to C22 in fish oil and C18 in milk fat were clearly displayed in contour plot format according to structural properties and patterns, further identified based on authentic standards. Incompletely resolved regions were subjected to MDGC, with Cn (n = 18, 20) zones transferred to a ²D column. Elution behavior of C18 FAME on various ²D column phases (ionic liquids IL111, IL100, IL76, and modified PEG) was evaluated. Individual isolated Cn zones demonstrated about four‐fold increased peak capacities. The IL100 provided superior separation, good peak shape, and utilization of elution space. For milk fat‐derived FAME, the ²D chromatogram revealed at least three peaks corresponding to C18:1, more than six peaks for cis/trans‐C18:2 isomers, and two peaks for C18:3. More than 17 peaks were obtained for the C20 region of fish oil‐derived FAMEs using MDGC, compared with ten peaks using GC × GC. The MDGC strategy is useful for improved FAME isomer separation and confirmation.     

Characterization of chloroprene and maleic anhydride copolymer by 13C-NMR spectroscopy and pyrolysis GC/MS

The radical copolymerizations of chloroprene (CP) and maleic anhydride (MAH) were carried out with AIBN in 1,4-dioxane at 60°C. The monomer reactivity ratios were estimated as r₁ (CP) = 0.38 and r₂ (MAH) = 0.07. Microstructures in the copolymer of chloroprene (CP) and maleic anhydride (MAH) were investigated by 75.4 MHz ¹³C-and 300 MHz ¹H-NMR spectroscopies. Resonances were assigned to the monomer sequence dyads CC, CM, and MC (C = chloroprene, M = maleic anhydride). Well resolved fine structure in the ¹³C-NMR spectra showed that 1,2- and 3,4-structural chloroprene units were negligible in the copolymer. The pyrolysis characterization of the copolymer was also investigated by the pyrolysis gas chromatography mass spectrometry (GC/MS). The fragments of CP and MAH monomers and CP-MAH hybrid dimer, CO, and CO₂ were identified after pyrolysis of the copolymer. © 1994 John Wiley & Sons, Inc.     

Separation and determination of polyethylene glycol fatty acid esters in cosmetics by a reversed-phase HPLC/ELSD

A comprehensive analytical method was established for the separation of polyethylene glycol (PEG) stearates according to the distribution of ethylene oxide (EO) and subsequent determination of the surfactants in cosmetic samples by using a high-performance liquid chromatography–evaporative light scattering detection. Separation of the PEG stearates comprising approximately up to 82 EO adducts was performed on a reversed-phase YMC-Pack C₈ column using water–acetonitrile gradient elution. The PEG oligomers were separated in order of the increasing number of EO adducts. Quantitation of the PEG fatty acid esters, which was separated as single peak per each component, was performed by chromatography on a reversed-phase Wakosil 10 C₁₈ column using water–methanol gradient elution. The standard curve to quantify the PEG stearates was constructed by the log–log plot, which showed good linearity with the correlation coefficients (R²) 0.998 and more. Working range, repeatability, limit of detection and recovery were acceptable for analysis of the surfactants in cosmetic products. The analytical methods were applied to characterize the PEG stearates according to the EO distributions, then to quantify the surfactants in cosmetic products.