MS Library Research Articles

Non-target screening of organic contaminants in marine salts by gas chromatography coupled to high-resolution time-of-flight mass spectrometry

Gas chromatography coupled to time-of-flight mass spectrometry (GC–TOF MS) has been applied to characterize the organic pollution pattern of marine salt samples collected in saltworks from the Spanish Mediterranean coast. After dissolving the samples in water, a solid-phase extraction was applied reaching with a 250-preconcentration factor. The screening methodology allowed the detection of sample components without any kind of pre-selection of target pollutants. The identity of components detected was established by accurate mass measurements and comparison of experimental full-acquisition spectra with theoretical MS libraries. Several organic pollutants were identified in the samples, like plasticizers – potentially toxic to humans – and fragrances –included within the group of pharmaceuticals and personal care products-, among others. Our results indicate that these contaminants can be found in the marine salt after the crystallization process. GC–TOF MS is a powerful technique for wide-scope screening of (semi)volatile, low-polar organic contaminants, able to investigate the presence of a large number of compounds. Searching of contaminants is not restricted to a target list of compounds. Therefore, unexpected contaminants can be discovered in an efficient way, with better sensitivity and selectivity than other conventional analytical techniques, and making use of the powerful qualitative information provided by full-spectrum acquisition at accurate mass.

Metabolomics Study on Quality Control and Discrimination of Three Curcuma Species based on Gas Chromatograph–Mass Spectrometry

Metabonomic analysis is an important molecular phenotyping method for characterising plant ecotypic variations; hence, it may become a powerful tool for quality control and discrimination of traditional Chinese medicine (TCM). To discriminate and assess the quality of Curcuma phaeocaulis, C. kwangsiensis and C. wenyujin from different ecotypes. The identification of the compositions of essential oils from the three Curcuma species was included in this study. Metabolomics analysis was carried out on all samples by gas chromatography-mass spectrometry (GC-MS) coupled with multivariate statistical analysis. Characterisation of phytochemicals in essential oils was performed by automated matching to the MS library and comparison of their mass spectra (NIST05 database). Principal component analysis (PCA) effectively distinguished the samples from different species and ecotypes. Partial least squares discrimination analysis (PLS-DA) was successfully employed in classifying the GC-MS data of authentic, commercial and introduction cultivation samples. Furthermore, the components contributing significantly to the discrimination, namely curzerenone, germacrone, curdione and epicurzerenone, were screened by PCA and PLS-DA loading plots and further can be used as chemical markers for discrimination and quality control among different groups of samples.

Chemical signature of ecstasy volatiles by comprehensive two-dimensional gas chromatography

A method for ecstasy volatiles 'signature' analysis based on two-dimensional gas chromatography separation and time-of-flight mass spectrometry detection (GC×GC-TOFMS) is presented. Organic impurity volatiles were extracted by head space solid phase microextraction (HS-SPME). The final column phase choice of the four different column combinations tested was a low-polarity 5% phenyl polysilphenylene-siloxane coupled with a polyethylene glycol phase, which best displayed the complex impurity profile. Second dimension ((2)D) retention time reproducibility was found to be about 1% RSD, and area reproducibility of SPME sampling was just over 5% RSD for compounds with S/N ratio of about 100. High similarity of TOFMS spectra of impurities was obtained against commercial MS libraries. 16 components from the two-dimensional profiles were selected for comparison of the 24 ecstasy tablets, most of which proved to be benzodioxole derived compounds. All tablets were correctly classified in eight groups according to their post-tabletting characteristics, when appropriate data pre-treatment was applied. Principal component analysis revealed clustering of samples according to the country of origin. Samples from Macedonia were elevated in N-formyl-MDMA and N-acetyl-MDMA while samples from Australia were elevated in 3,4-methylenedioxypropane and 3,4-methylenedioxyacetophenone. Furthermore, three components were found to be unique for one of the source countries. The additional separation of components on the (2)D column, increased response due to modulation, high acquisition rate with full mass spectra using TOFMS detection, and MS deconvolution extend the possibility of detecting additional markers and route-specific components, especially of low abundant, polar components.

미더덕의 향기 성분

미더덕 육과 체액을 이용한 천연 조미료의 제조를 위하여 본래의 향과 가열에 따른 변화를 비교해보기 위하여 SDE법과 SPME법으로 미더덕 향기성분을 분석하였다. SDE 추출법으로 얻어진 미더덕 육에 함유된 주요 성분으로서는 hexanal <TEX>$371.3\;{\mu}g/g$</TEX>, 1-tridecanol <TEX>$80.1\;{\mu}g/g$</TEX>, (Z)-4,5-dimethyhex02-en-4-ol <TEX>$72.1\;{\mu}g/g$</TEX> 등이 있었고, 그 외 다량의 alcohol, aldehydes 및 acids가 얻어졌다. SDE 추출법으로 얻어진 alcohol은 농도도 높았지만 미더덕 육향기성분의 주체가 되는 것으로 나타났다. SPME 추출법으로 얻어진 미더덕 육에는 9종의 alcohols, 1종의 acid, 1종의 aldehyde, 1종의 hydrocarbon, 1종의 ester, 1종의 amine 및 2종의 ketones이 포함되어 있었다. 이들 중 함량이 가장 높았으며 그 중 1-nonanol, 1-decanol 및 1-tridecanol이 주성분이었다. SPME법으로 얻어진 향기성분 중 1-nonanol <TEX>$31.6\;{\mu}g/g$</TEX>, (E)-2-butanoic acid dibutylester <TEX>$20.3\;{\mu}g/g$</TEX> 및 heptadecanoic acid <TEX>$26.7\;{\mu}g/g$</TEX>으로 전체 향기성분 추출물의 62.1%를 차지하였다. 따라서 SPME법으로 얻어진 향기성분이 SDE법보다 추출효율은 낮았지만 원래 향에 가까운 것으로 나타났다. The flavor extracts of Mideoduck muscle and its juices were concentrated by simultaneous distillation and extraction (SDE) and solid-phase microextraction (SPME) methods. Each component present in the extracts was identified with GC and GC-MS by the n-paraffin hydrocarbon retention index and standard MS library data system. By SDE, <TEX>$371.3\;{\mu}g/g$</TEX> of hexanal, <TEX>$80.1\;{\mu}g/g$</TEX> of 1-tridecanol, <TEX>$72.1\;{\mu}g/g$</TEX> of (Z)-4,5-dimethylhex-2-en-4-ol with other alcohols, aldehydes and acids were present in the flavor extracts, with the alcohols having the highest composition and being the most important factor in Mideoduck muscle flavor. By SPME, 9 alcohols, 1 acid, 1 aldehyde, 1 hydrocarbon, 1 ester, 1 amine and 2 ketones were detected in the extracts, with alcohol such as 1-nonanol, 1-decanol and 1-tridecanol as the major components. In SPME, the muscle sample, consisting of <TEX>$31.6\;{\mu}g/g$</TEX> of 1-nonanol, <TEX>$20.3\;{\mu}g/g$</TEX> of (E)-2-butenedioic acid dibutylester, and <TEX>$26.7\;{\mu}g/g$</TEX> of heptadecanoic acid made up the 62.1% of total flavor extracts of Mideoduck muscle. The results of the SPME methods were similar to the composition of the raw material flavor of the sample even at a low concentration.

Comprehensive two-dimensional gas chromatography, retention indices and time-of-flight mass spectra of flavonoids and chalcones

The applicability of comprehensive two-dimensional gas chromatography (GC × GC) for flavonoids analysis was investigated by separation and identification of flavonoids in standards, and a complex matrix natural sample. The modulation temperature was optimized to achieve the best separation and signal enhancement. The separation pattern of trimethylsilyl (TMS) derivatives of flavonoids was compared on two complementary column sets. Whilst the BPX5/BPX50 (NP/P) column set offers better overall separation, BPX50/BPX5 (P/NP) provides better peak shape and sensitivity. Comparison of the identification power of GC × GC-TOFMS against both the NIST05 MS library and a laboratory (created in-house) TOFMS library was carried out on a flavonoid mixture. The basic retention index information on high-performance capillary columns with a non-polar stationary phase was established and database of mass spectra of trimethylsilyl derivatives of flavonoids was compiled. TOFMS coupled to GC × GC enabled satisfactory identification of flavonoids in complex matrix samples at their LOD over a range of 0.5–10 μg/mL. Detection of all compounds was based on full-scan mass spectra and for each compound a characteristic ion was chosen for further quantification. This study shows that GC × GC-TOFMS yields high specificity for flavonoids derived from real natural samples, dark chocolate, propolis, and chrysanthemum.

Analytical platform for metabolome analysis of microbial cells using methyl chloroformate derivatization followed by gas chromatography–mass spectrometry

This protocol describes an analytical platform for the analysis of intra- and extracellular metabolites of microbial cells (yeast, filamentous fungi and bacteria) using gas chromatography-mass spectrometry (GC-MS). The protocol is subdivided into sampling, sample preparation, chemical derivatization of metabolites, GC-MS analysis and data processing and analysis. This protocol uses two robust quenching methods for microbial cultures, the first of which, cold glycerol-saline quenching, causes reduced leakage of intracellular metabolites, thus allowing a more reliable separation of intra- and extracellular metabolites with simultaneous stopping of cell metabolism. The second, fast filtration, is specifically designed for quenching filamentous micro-organisms. These sampling techniques are combined with an easy sample-preparation procedure and a fast chemical derivatization reaction using methyl chloroformate. This reaction takes place at room temperature, in aqueous medium, and is less prone to matrix effect compared with other derivatizations. This protocol takes an average of 10 d to complete and enables the simultaneous analysis of hundreds of metabolites from the central carbon metabolism (amino and nonamino organic acids, phosphorylated organic acids and fatty acid intermediates) using an in-house MS library and a data analysis pipeline consisting of two free software programs (Automated Mass Deconvolution and Identification System (AMDIS) and R).

Characterization of bacterial lipid profiles by using rapid sample preparation and fast comprehensive two‐dimensional gas chromatography in combination with mass spectrometry

The bacteria fatty acid profile has been extensively studied for taxonomic classification purposes, since bacteria, in general, contain particular and rare fatty acids, compared with animal and plant tissues. As for any real-world sample type, the development of rapid and reliable methods for (i) sample identification (in this case, bacterium type), and (ii) constituent identification (in this instance, the fatty acid profile) is desirable. In this research, a half-an-hour procedure, to analyze bacteria, was developed: a 2-min one-step sample preparation step was followed by a relatively fast comprehensive 2D GC-MS separation (25 min). Furthermore, dedicated MS libraries were constructed for the identification of bacteria and fatty acids. Finally, data processing, only qualitative at this stage, was carried out with the support of a novel comprehensive 2D GC software.

Analysis of volatile oils of &lt;I&gt;Ligusticum chuanxiong Hort&lt;/I&gt;. from different geographical origins by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

The volatile oils of 23 Ligusticum chuanxiong Hort. samples from 4 different regions were analyzed by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/TOF MS). The group-type separation of 4 terpenoids and phthalides was well accomplished based on a DB-Petro x DB-17 column system. With the MS library search, 215 compounds were tentatively identified based on the NIST database and the 43 compounds of them were confirmed by using the retention index or comparing with the standard compounds in a typical sample from Xindu City. Twenty three samples were apparently classified into 4 groups by partial least square-discriminant analysis. A brief list of 20 differential compounds is presented, including cnidilide, 3-n-butylphthalide and butylidene phthalide. DPPH (1,1-diphenyl-2-picrylhydrazyl), stable free radical scavenging assay was adopted to differentiate the antioxidative potency of these samples, which was expressed as EC50. Based on the orthogonal partial least square model the biochemical discrimination of samples was achieved with ligustilide, senkyunolide A and neocnidilide as important differential compounds according to geographical origins. All the results indicated that phthalides exert a great influence on the chemical and biochemical classifications of Rhizoma Chuanxiong, and the samples from Pengzhou City have the highest contents of phthalides.

Application of preparative capillary gas chromatography (pcGC), automated structure generation and mutagenicity prediction to improve effect-directed analysis of genotoxicants in a contaminated groundwater

The importance of groundwater for human life cannot be overemphasised. Besides fulfilling essential ecological functions, it is a major source of drinking water. However, in the industrial area of Bitterfeld, it is contaminated with a multitude of harmful chemicals, including genotoxicants. Therefore, recently developed methodologies including preparative capillary gas chromatography (pcGC), MOLGEN-MS structure generation and mutagenicity prediction were applied within effect-directed analysis (EDA) to reduce sample complexity and to identify candidate mutagens in the samples. A major focus was put on the added value of these tools compared to conventional EDA combining reversed-phase liquid chromatography (RP-LC) followed by GC/MS analysis and MS library search. We combined genotoxicity testing with umuC and RP-LC with pcGC fractionation to isolate genotoxic compounds from a contaminated groundwater sample. Spectral library information from the NIST05 database was combined with a computer-based structure generation tool called MOLGEN-MS for structure elucidation of unknowns. Finally, we applied a computer model for mutagenicity prediction (ChemProp) to identify candidate mutagens and genotoxicants. A total of 62 components were tentatively identified in genotoxic fractions. Ten of these components were predicted to be potentially mutagenic, whilst 2,4,6-trichlorophenol, 2,4-dichloro-6-methylphenol and 4-chlorobenzoic acid were confirmed as genotoxicants. The results suggest pcGC as a high-resolution fractionation tool and MOLGEN-MS to improve structure elucidation, whilst mutagenicity prediction failed in our study to predict identified genotoxicants. Genotoxicity, mutagenicity and carcinogenicity caused by chemicals are complex processes, and prediction from chemical structure still appears to be quite difficult. Progress in this field would significantly support EDA and risk assessment of environmental mixtures.

Letter to the Editor: ESI-MS–MS library of 1,253 compounds for application in forensic and clinical toxicology

We read with great interest the article entitled “ESI-MS–MS library of 1,253 compounds for application in forensic and clinical toxicology” by Dresen et al. [1], presenting an electrospray ionization tandem mass spectrometry library for 1,253 compounds relevant in clinical and forensic toxicology, developed using a hybrid tandem mass spectrometer with a linear ion trap. Using information-dependent acquisition (IDA) algorithms, the authors previously developed a “multi-target screening” method with 301 drugs in which multiple reaction monitoring (MRM) was used for the survey scan and the enhanced product ion (EPI) scan as dependent scan mode [2]. A library was then generated with the EPI spectra obtained at collision energies of 20, 35, and 50 eV in the positive mode. The more recent paper presents a “new” library built using the automatic collision energy spread feature, which sums the three independent spectra generated [1]. As we mentioned three years ago, the enhanced mass scan mode can also be used for the survey scan [3]. In particular, a library of EPI spectra for more than 1,000 compounds, acquired at collision energies of 15, 40, and 65 eV and summed using the collision energy spread feature has already been built. Moreover, because of their specificity and reproducibility, these EPI spectra have also recently been proven to be helpful for elucidation of metabolites [4, 5] or for identification of peaks interfering with one (or more) MRM transitions [6]. Dresen and coworkers did not cite our first paper (published in Clinical Chemistry) in their work [3]. They—and, we are afraid, the reviewers of this paper—may not have identified this previous work as relevant to their study, despite the obvious similarities in the use of these composite EPI spectra [3]. However, we must admit that, owing to the use of the total scan mode as survey scan, our method is much less selective than the target screening method reported here by Dresen et al., i.e. much more suited to clinical or forensic toxicology—where the question asked by clinicians or the judiciary is whether an individual had been intoxicated at all, and not whether they had taken a molecule in a necessarily limited pre-defined list, particularly regarding metabolites.

Characterization of the yerba mate (Ilex paraguariensis) volatile fraction using solid‐phase microextraction‐comprehensive 2‐D GC‐MS

The present research is focused on the use of a solid-phase microextraction-comprehensive 2-D GC methodology, in the analysis of the volatile fraction of yerba mate. Yerba mate is used for the generation of a tea-like beverage, widely consumed in South America. A rapid-scanning quadrupole mass spectrometer (qMS), employed as a detection system and operated at a 25 Hz scanning frequency, supplied high-quality mass spectra. The effectiveness of the 3-D comprehensive 2-D GC-qMS experiment was compared to that of GC-qMS analysis on the same sample. Peak identification, in both applications, was achieved through MS library matching, with the support of linear retention index data. Apart from a great increase in the number of analytes separated (approx. by a factor of 5) and identified (approx. by a factor of 3.5), the comprehensive 2-D GC-qMS approach enabled the determination of a high number of hazardous contaminants (aliphatic hydrocarbons, polycyclic aromatic hydrocarbons, and plasticizers), barely visible in the GC-qMS analysis.

The development and inter-laboratory verification of LC–MS libraries for organic chemicals of environmental concern

The development, verification, and comparison study between LC–MS libraries for two manufacturers’ instruments and a verified protocol are discussed. Compounds in the libraries are among those considered by the U.S. EPA Office of Water as threats to drinking water including pesticides, drugs of abuse, and pharmaceuticals. The LC–MS library protocol was verified through an inter-laboratory study that involved Federal, State, and private laboratories. The results demonstrated that the libraries are transferable between the same manufacturer's product line, and have applicability between manufacturers. Although ion abundance ratios within mass spectra were shown to be different between the manufacturers’ instruments, the NIST search engine match probability was at 96% or greater for 64 out of 67 compounds evaluated.

A New Cytotoxic Friedelane Acid – Pluricostatic Acid – and Other Compounds from the Leaves of Marila pluricostata

Bioassay-guided fractionation of the dichloromethane extract of the leaves of Marila pluricostata led to the isolation of 2α,3β-dihydroxy-D:A-friedoolean-28-oic acid (pluricostatic acid), a new friedelane triterpenoid, (1), ten known triterpenoids and three sterols. Their chemical structures were elucidated through spectroscopic analysis. The less polar fractions, on GC/MS analysis and comparison with a MS library, resulted in the identification of twenty four sesquiterpenoids. The new triterpenoid acid 1 showed cytotoxicity against the MCF-7, H-460, and SF-268 human cancer cell lines with GI50 values from 1.2 to 3.3 μg/mL.

Application of comprehensive two-dimensional gas chromatography to sterols analysis

The applicability of comprehensive two-dimensional gas chromatography (GC×GC) for sterol analysis was investigated by separation and identification of endogenous sterols in standards, and spiked in human urine. The modulation temperature was optimized to achieve the best separation and signal enhancement. The separation pattern of trimethylsilyl (TMS) derivatives of sterols was compared on two complementary column sets. Whilst the BPX5/BPX50 column set offers better overall separation, BPX50/BPX5 provides better peak shape and sensitivity. Comparison of the identification power of GC×GC–TOFMS against both the NIST05 MS library and a laboratory created (in-house) TOFMS library was carried out on a free sterols extract of urine, derivatised and spiked at the World Anti-Doping Agency (WADA) limit of 2 ng mL −1. The average match quality for 19 analysed sterols on the BPX50/BPX5 column set was 950/1000 when searched against the in-house library; only four were identified against the NIST05 library, at a match threshold of 800. The match quality of GC×GC–TOFMS spectra was superior to that for analysis using 1D GC–TOFMS for sterols spiked in urine at 10 ng mL −1. An r 2 > 0.997 was obtained for the concentration range between 0.25 ng mL −1 and 10 ng mL −1 for three selected sterols. The lowest limit of detection (LOD) was obtained for estrone (0.1 ng mL −1) and the highest LOD was for 5α-androstan-3α,11β-diol-17-one, epitestosterone and cholesteryl butyrate (1 ng mL −1), using a match threshold of at least 800 and signal-to-noise ratio of at least 10. TOFMS coupled to GC×GC enabled satisfactory identification of sterols in urine at their LOD. A minimum acceptable match (MAM) criterion for urinary sterols using 2D retention times and TOF mass spectra is introduced. This study shows that GC×GC–TOFMS yields high specificity for steroids derived from urine, with detection limits appropriate for use in doping control.

Determination of Ion Structures in Structurally Related Compounds Using Precursor Ion Fingerprinting

Structurally-related alkaloids were analyzed by electrospray ionization/multiple stage mass spectrometry (ESI/MS(n)) at varying collision energies to demonstrate a conceptual algorithm, precursor ion fingerprinting (PIF). PIF is a new approach for interpreting and library-searching ESI mass spectra predicated on the precursor ions of structurally-related compounds and their matching product ion spectra. Multiple-stage mass spectra were compiled and constructed into "spectral trees" that illustrated the compounds' product ion spectra in their respective mass spectral stages. The precursor ions of these alkaloids were characterized and their spectral trees incorporated into an MS(n) library. These data will be used to construct a universal, searchable, and transferable library of MS(n) spectra. In addition, PIF will generate a proposed structural arrangement utilizing previously characterized ion structures, which will assist in the identification of unknown compounds.

Determination of volatile compounds in Brazilian distilled cachaça by using comprehensive two-dimensional gas chromatography and effects of production pathways

Comprehensive two-dimensional gas chromatography (GC × GC) was applied to the study of cachaça production. Effects of bidistillation, and the use of charcoal filtration in the production of artisan cachaça, as well as the effects of multi-distillation on volatile products in commercial cachaça were investigated. Volatile compounds were collected and concentrated onto a polyacrylate solid-phase microextraction fibre, and analyzed using GC × GC on a non-polar (BPX5)–polar (BP20) column set. More than 100 compounds, comprising various homologous series were tentatively identified using MS library matching and comparison with retention indices. Phthalate organic contamination following the use of ion exchange resin for removal of copper ion was evident. Charcoal successfully removes this contamination product. Prediction of compounds within particular homologous series aids component identification.

Determination of radix ginseng volatile oils at different ages by comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectrometry

Comprehensive 2-D GC (GC x GC) coupled with TOF MS or flame ionization detector (FID) was employed to characterize and quantify the chemical composition of volatile oil in the radixes of Panax ginseng C. A. Mey. (ginseng) at different ages. Thirty-six terpenoids were tentatively identified based on the MS library search and retention index in a ginseng sample at the age of 3 years. An obvious group-type separation was obtained in the GC x GC-TOF MS chromatogram. The data collected by GC x GC-FID were processed using a principal component analysis (PCA) method to classify the samples at different ages. The compounds responsible for the significant differentiation among samples were defined. It was found that the relative abundances of alpha-cadinol, alpha-bisabolol, thujopsene, and n-hexadecanoic acid significantly rise with the increase in age.

Direct Conversion of Sunflower Shells to Alkanes and Aromatic Compounds

Deoxy-liquefaction runs were performed at final temperatures of 350, 400, 450, and 500 °C, with only 10 wt % distilled water as medium. The influence of the final temperature on the properties of biopetroleum obtained from sunflower shell samples (with kernels 5 wt %) via deoxy-liquefaction was examined in relation to the yield and distribution of products (i.e., gas, solid, liquid), especially the compositions of oil products. Furthermore, the liquid oil with a maximum yield and H/C molar ratio of 1.99 and higher heating value (HHV) of 46.9 MJ/kg was obtained at 450 °C. The biopetroleum analyzed by gas chromatography−mass spectrometry (GC−MS) with the National Institute of Standards and Technology (NIST) 98 MS library was mainly composed of benzene derivatives, phenolic derivatives, and alkanes (C7−C19). What is special is that the content of (Z,Z)-9,12-octadecadienoic acid (RT = 21.26 min), which came from the few sunflower kernels decreased from 21.32% at 350 °C to zero at 500 °C. This suggested that deoxy-liquefaction in a closed system could realize not only the deoxygenation of biomass but the deoxygenation of linoleic acid by controlling the final temperature. Moreover, the biopetroleum obtained can be upgraded to transport fuel or separated for chemical products.

Classical electron ionization mass spectra in gas chromatography/mass spectrometry with supersonic molecular beams

A major benefit of gas chromatography/mass spectrometry (GC/MS) with a supersonic molecular beam (SMB) interface and its fly-through ion source is the ability to obtain electron ionization of vibrationally cold molecules (cold EI), which show enhanced molecular ions. However, GC/MS with an SMB also has the flexibility to perform 'classical EI' mode of operation which provides mass spectra to mimic those in commercial 70 eV electron ionization MS libraries. Classical EI in SMB is obtained through simple reduction of the helium make-up gas flow rate, which reduces the SMB cooling efficiency; hence the vibrational temperatures of the molecules are similar to those in traditional EI ion sources. In classical EI-SMB mode, the relative abundance of the molecular ion can be tuned and, as a result, excellent identification probabilities and very good matching factors to the NIST MS library are obtained. Classical EI-SMB with the fly-through dual cage ion source has analyte sensitivity similar to that of the standard EI ion source of a basic GC/MS system. The fly-through EI ion source in combination with the SMB interface can serve for cold EI, classical EI-SMB, and cluster chemical ionization (CCI) modes of operation, all easily exchangeable through a simple and quick change (not involving hardware). Furthermore, the fly-through ion source eliminates sample scattering from the walls of the ion source, and thus it offers full sample inertness, tailing-free operation, and no ion-molecule reaction interferences. It is also robust and enables increased column flow rate capability without affecting the sensitivity.

Micro-bore Column Fast Gas Chromatography-Mass Spectrometry in Essential Oil Analysis

The present research is focused on the use of micro-bore column fast gas chromatography in combination with rapid-scanning quadrupole mass spectrometry for mediumly-complex essential oil analysis. A basil essential oil sample was initially subjected to conventional GC-MS (analysis time: 25 min) under optimum analytical conditions. Peak identification was carried by using a dual-filtered MS library search procedure: the first filter deleted “hits” with a less than 90% spectral similarity, while the second filter eliminated matches with a linear retention index (LRI) outside a pre-defined LRI window. The same essential oil sample was analyzed under optimized fast GC-MS conditions by using a micro-bore column, with the same aforementioned MS library search process (analysis time: 5.3 min). Resolution was altogether similar in both applications, with the same number of compounds reliably-identified, namely fifty-nine. The experiment demonstrated the usefulness of the rapid GC approach in this type of experiment.