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.     

假蒟挥发油化学成分气质联用分析研究

采用常规水蒸气蒸馏法提取出假岛精油,经气相色谱-质谱联机分析,分出60多个峰,鉴定出67种化合物,它们主要是2,4,5-三甲氧基-1-丙烯基苯3．20％）,顺-石竹烯（13．33％）,1,2-二甲氧基-4-（1-丙烯基）苯（12．63％）,细辛（9．94％）,4-甲氧基-6-（2-丙烯基）-1,3-苯并二恶茂（5．71％）,δ-杜松烯（3．03％）etc,占总峰面积的67．84％。     

Analysis of triacetone triperoxide by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry by electron and chemical ionization

The explosive triacetone triperoxide (TATP) has been analyzed by gas chromatography/mass spectrometry (GC/MS) and sub-nanogram detection limits are reported by ammonia positive ion chemical ionization (PICI), electron ionization (EI) and methane negative ion chemical ionization (NICI). Analysis by methane PICI and ammonia NICI gave detection limits in the low nanogram range. Analyses were carried out on (linear) quadrupole and ion trap instruments. Analysis of TATP by PICI using ammonia reagent gas is the preferred analytical method, producing low limits of detection as well as an abundant (greater than 60% of base peak) diagnostic adduct ion at m/z 240 corresponding to [TATP + NH4]+. Isolation of the [TATP + NH4]+ ion with subsequent collision-induced dissociation (CID) produces extremely low abundance product ions at m/z values greater than 60, and the m/z 223 ion corresponding to [TATP + H]+ was not observed. Density functional theory (DFT) calculations at the B88LYP/DVZP level indicate that dissociation of the complex to form NH4+ and TATP occurs at energies lower than peroxide bond dissociation, while protonation of TATP leads to cleavage of the ring structure. These results provide a method for pico-gram detection levels of TATP using commercial instrumentation commonly available in forensic laboratories. As a point of comparison, a detection limit of 15 ng was obtained by flame ionization detection.     

四元共聚物的热裂解色谱-质谱分析

报道了2－丁烯、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸辛酯四元共聚物在不同裂解温度下的热裂解行为。用热裂解色谱－质谱分析方法，研究了裂解温度对裂解产物的影响，并讨论了四元共聚物的热裂解规律。     

Application of comprehensive multidimensional gas chromatography combined with time-of-flight mass spectrometry (GC x GC-TOFMS) for high resolution analysis of hop essential oil

The selection and quality of hops is a major determinant in beer flavour. Brewers acknowledge that distinctive characteristics of different hop varieties can be traced to the composition of their essential oils. The difficulty in characterising complex mixtures such as hop oil using 1-D chromatography is that many compounds co-elute. With the introduction of comprehensive multidimensional capillary gas chromatography (GC x GC), there is a tremendous improvement in the separation power or peak capacity. Recent work using GC x GC with flame ionisation detection has suggested that there may be over 1,000 compounds in hop oil. This work describes the use of GC x GC combined with TOFMS detection (Leco Pegasus 4D instrument) to analyse Target hop oil. The TOFMS spectral acquisition rate of 60 Hz provided sufficient spectra per peak (2-D peak base width of 0.1-0.2 s) for identification (119 components were identified with 45 previously unreported compounds). When analysing results, an advantage of GC x GC coupled to TOFMS is that 2-D chromatograms can be viewed for individual masses that are characteristic of particular functional groups. This allows the analyst to view the various homologous series of compounds although in certain cases coelution may still be present as shown by the esters with mass 75.     

气相色谱-质谱法分析橡苔浸膏中的挥发性化学成分

 用挥发油提取器提取橡苔浸膏中的挥发油,利用气相色谱-质谱法(GC-MS)分析了其中的化学成分,采用GC峰面积归一化法定量,鉴定出24种化合物,共占挥发油总量的83%以上     

Supersonic gas chromatography/mass spectrometry

A new gas chromatography/mass spectrometry (GC/MS) system was designed and evaluated which we have named 'Supersonic GC/MS'. It is based on a modification of a commercially available GC/MS system to include a supersonic molecular beam (SMB) MS interface. In this system the standard electron ionization (EI) ion source was replaced with a fly-through EI ion source mounted in the path of the SMB. A hyperthermal surface ionization (HSI) ion source combined with a 90 degrees ion mirror (for the EI-produced ions) was also added, and placed inside the quadrupole mass analyzer in place of its original EI ion source. The 'Supersonic GC/MS' system requires 18 cm added bench space plus the addition of an air-cooled 60 L/s diffusion pump and a 537 L/min rotary pump. The system is user friendly since all the gas flow rates, heated zones, sampling and data analysis are performed the same way as the original system and are computer-controlled via the original software. Similar EI sensitivity was obtained as with the original system for hexachlorobenzene and octafluoronaphthalene, while improved EI detection limits were demonstrated for methyl stearate and eicosane due to the significant enhancement of their molecular ion abundances. A GC/MS detection limit of 500 ag for pyrene was demonstrated using HSI. Good supersonic expansion cooling was achieved with large alkanes, despite the use of a rotary pump at the nozzle chamber instead of a diffusion pump. High temperature GC/MS analysis was demonstrated for large polycyclic aromatic hydrocarbons (PAHs) including ovalene and decacyclene (ten rings). Library searches with EI mass spectra are demonstrated, and it is explained why the enhancement of the molecular ion actually improves the library search in most cases. The analysis of large phthalate esters is also described, and the improvement obtained is shown to originate from their enhanced molecular and high mass fragment ions.     

Early gas chromatography/mass spectrometry

Spectroscopy Laboratory, The Dow Chemical Company, Midland, Michigan, USA In December 1955 or thereabouts, the authors coupled a homemade gas chromatograph to a research time-of-flight mass spectrometer constructed by W. C. Wiley, I. H. McLaren, and D. B. Harrington. This unique gas chromatography/mass spectrometry (GC/MS) instrument generated mass spectra at a lo-kHz rate for display on an oscilloscope; eluted gas chromate graphic components, such as methanol, acetone, benzene, toluene, and carbon tetrachloride, could be visually identified immediately from the oscilloscope display. Many years of further research and development in many laboratories worldwide were necessary, however, to make continuous on-line GC/MS the uniquely valuable analytical tool that it is today.     

Determination of pesticide residues in olives and olive oil by matrix solid-phase dispersion followed by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry

A novel analytical approach has been developed and evaluated for the quantitative analysis of a selected group of widely used pesticides (dimethoate, simazine, atrazine, diuron, terbuthylazine, methyl-parathion, methyl-pirimiphos, endosulfan I, endosulfan II, endosulfan sulphate, cypermethrin and deltamethrin), which can be found at trace levels in olive oil and olives. The proposed methodology is based on matrix solid-phase dispersion (MSPD), (with a preliminary liquid-liquid extraction in olive oil samples) using aminopropyl as sorbent material with a clean-up performed in the elution step with Florisil, followed by mass spectrometric identification and quantitation of the selected pesticides using both gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode and liquid chromatography tandem mass spectrometry (LC-MS-MS) in positive ionization mode. The recoveries obtained (with mean values between 85 and 115% (obtained at different fortification levels) with RSD values below 10% in most cases, confirm the usefulness of the proposed methodology for the analyses of these kind of complex samples with a high fat content. Moreover, the obtained detection limits, which were below 5 microg kg(-1) by LC-MS analyses and ranged from 10 to 60 microg kg(-1) by GC-MS meet the requirements established by the olive oil pesticide regulatory programs. The method was satisfactorily applied to different olives and olive oil samples.     

Analysis of cholesterol oxidation products by Fast gas chromatography/mass spectrometry

The aim of the present study was to set‐up a Fast gas chromatography/mass spectrometry method for the analysis of cholesterol oxidation products (COPs). A silylated mixture of seven oxysterol standards was injected into a Fast GC/MS system. A capillary GC column (10 m×0.1 mm internal diameter×0.1 μm film thickness) coated with 95% dimethyl‐ and 5% diphenyl‐polysiloxane, was used. The method gave a fast (total analysis time=3.5 min) and satisfactory resolution (R>1.2) of the COPs standards, with a good repeatability and sensitivity, similar to those of conventional GC/MS; recoveries were tested on mice liver. Fast GC/MS method suitability for COPs analysis in food was also tested on an oxidized sardine fillet, which had been previously saponified and purified by NH₂ solid‐phase extraction (SPE); a good repeatability and sensitivity was also obtained. The analytical performance of the Fast GC/MS method for the determination of COPs, together with the consequent significant reduction of the analysis time and consumables, demonstrates that Fast GC/MS represents a valid alternative to conventional GC/MS and evinces the great potential of such an analytical technique, which could be applied for both food and biological samples.     

Analysis of dinitrofluoranthenes by high resolution capillary gas chromatography/mass spectrometry

This paper reports the retention indices of eighteen of the possible twenty-five dinitrofluoranthene isomers.     

Study on the photostability of guaiazulene by high-performance liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry

The photostability of guaiazulene (1,4-dimethyl-7-isopropylazulene; GA), a natural azulenic compound used in cosmetic and health-care products, as well as in pharmaceutical preparations, was investigated in solution (methanol, ethanol, acetonitrile), by different techniques: gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry and UV detection (LC/APCI-MS and HPLC/UV). A solar simulator (xenon-arc lamp) was used as UV-A radiation source. The study involved: monitoring compound decomposition, identifying products of photodegradation (PPs), assessing the role of oxygen and evaluating the kinetics of the process. Minor PPs are volatile compounds and were characterized by GC/MS, while oligomeric polyoxygenated compounds, tentatively characterized on the basis of MS and MS/MS spectra, were found to be the main photoproducts. The photodegradation was found to be enhanced by the presence of oxygen; nevertheless, determination of the singlet oxygen quantum yield for GA gave a lower value than that for the reference standard Rose Bengal. The obtained results and the developed stability-indicating methods (GC/MS and LC/MS) are of interest for stability studies and/or quality control purposes of GA as raw material or cosmetic products.     

Gas chromatography and gas chromatography/mass spectrometry for the characterization of complex mixtures of large oligosaccharides

High temperature gas chromatography and gas chromatography/mass spectrometry are used in the characterization of complex natural mixtures of permethylated oligosaccharides released from proteins or lipids. The high resolution allows separation of isomeric compounds and the mass range extends to oligosac-charides around molecular mass 2000 daltons or 10 sugar residues for isomalto-oligosaccharides. The mass spectra of permethylated oligosaccharide alditols from mucin glycopeptides are very informative and the approach allows a simple and rapid characterization of these complex components.     

Identification of potential antioxidant compounds in the essential oil of thyme by gas chromatography with mass spectrometry and multivariate calibration techniques

Thyme species are used in traditional medicine throughout the world and are known for their antiseptic, antispasmodic, and antitussive properties. Also, antioxidant activity is one of the interesting properties of thyme essential oil. In this research, we aim to identify peaks potentially responsible for the antioxidant activity of thyme oil from chromatographic fingerprints. Therefore, the chemical compositions of hydrodistilled essential oil of thyme species from different regions were analyzed by gas chromatography with mass spectrometry and antioxidant activities of essential oils were measured by a 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging test. Several linear multivariate calibration techniques with different preprocessing methods were applied to the chromatograms of thyme essential oils to indicate the peaks responsible for the antioxidant activity. These techniques were applied on data both before and after alignment of chromatograms with correlation optimized warping. In this study, orthogonal projection to latent structures model was found to be a good technique to indicate the potential antioxidant active compounds in the thyme oil due to its simplicity and repeatability.     

Analysis of small carbohydrates in several bioactive botanicals by gas chromatography with mass spectrometry and liquid chromatography with tandem mass spectrometry

Bioactive botanicals contain natural compounds with specific biological activity, such as antibacterial, antioxidant, immune stimulating, and taste improving. A full characterization of the chemical composition of these botanicals is frequently necessary. A study of small carbohydrates from the plant materials of 18 bioactive botanicals is further described. The study presents the identification of the carbohydrate using a gas chromatographic‐mass spectrometric analysis that allows detection of molecules as large as maltotetraose, after changing them into trimethylsilyl derivatives. A number of carbohydrates in the plant (fructose, glucose, mannose, sucrose, maltose, xylose, sorbitol, and myo‐, chiro‐, and scyllo‐inositols) were quantitated using a novel liquid chromatography with tandem mass spectrometric technique. Both techniques involved new method developments. The gas chromatography with mass spectrometric analysis involved derivatization and separation on a Rxi^®‐5Sil MS column with H₂ as a carrier gas. The liquid chromatographic separation was obtained using a hydrophilic interaction type column, YMC‐PAC Polyamine II. The tandem mass spectrometer used an electrospray ionization source in multiple reaction monitoring positive ion mode with the detection of the adducts of the carbohydrates with Cs⁺ ions. The validated quantitative procedure showed excellent precision and accuracy allowing the analysis in a wide range of concentrations of the analytes.     

Identification of sources of oil spills in soils and sediments by gas chromatography/mass spectrometry

Gas chromatography/mass spectrometry has been applied to the study of the residual oil contamination of the sediments in the area of an emergency mazut spill in an industrial enterprise. The contamination level appeared to be very high in nearly all samples collected within a rather wide area; however, the oil in the studied samples have undergone significant weathering; therefore, we have concluded that they had got into the sediments long before the spill under consideration or had been accumulating in them systematically for many years. The methodology of the identification of oil in soils taking into account their transfer and weathering is considered; it employs characteristics of the hydrocarbon type composition along with the individual marker compounds.     

Differentiation of essential oils in Atractylodes lancea and Atractylodes koreana by gas chromatography with mass spectrometry

Atractylodes rhizome is a valuable traditional Chinese medicinal herb that comprises complex several species whose essential oils are the primary pharmacologically active component. Essential oils of Atractylodes lancea and Atractylodes koreana were extracted by hydrodistillation, and the yield was determined. The average yield of essential oil obtained from A. lancea (2.91%) was higher than that from A. koreana (2.42%). The volatile components of the essential oils were then identified by a gas chromatography with mass spectrometry method that demonstrated good precision. The method showed clear differences in the numbers and contents of volatile components between the two species. 41 and 45 volatile components were identified in A. lancea and A. koreana, respectively. Atractylon (48.68%) was the primary volatile component in A. lancea, while eudesma‐4(14)‐en‐11‐ol (11.81%) was major in A. koreana. However, the most significant difference between A. lancea and A. koreana was the major component of atractylon and atractydin. Principal component analysis was utilized to reveal the correlation between volatile components and species, and the analysis was used to successfully discriminate between A. lancea and A. koreana samples. These results suggest that different species of Atractylodes rhizome may yield essential oils that differ significantly in content and composition.     

Determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans by gas chromatography/tandem mass spectrometry and gas chromatography/triple mass spectrometry in a quadrupole ion trap

The determination of tetra- to octachlorodibenzo-p-dioxins and tetra- to octachlorodibenzofurans (PCCD/Fs) by high-resolution gas chromatography/tandem mass spectrometry (HRGC/MS/MS) and high-resolution gas chromatography/triple mass spectrometry (HRGC/MS(3)) in a quadrupole ion trap, equipped with an external ion source, is presented. MS/MS involves a typical four-step process, namely ionization, parent ion isolation, collision-induced dissociation (CID) and mass analysis of the daughter ions. For the MS(3) experiment, the MS/MS scan function is used with the addition of selected daughter ion isolation, their CID and the mass analysis of second-generation product ions called 'grand-daughter ions.' For both methods, the energies necessary for the CID of the 17 PCDD/Fs were determined and optimized using multiple scan functions with different CID amplitudes. The CID efficiency, defined as the signal ratio of fragment ions detected from the major dissociation channels to molecular ions isolated, was 1.15-2.40 V for parent ion dissociation (MS/MS) and 1.05-1.50 V for daughter ion dissociation (MS(3)) and for all the chloro congeners. The same sensitivity (1 pg microl(-1)) can be reached with both the MS/MS and MS(3) methods and linear responses were obtained between 1 and 100 pg microl(-1) injected.