Static Headspace Sampling Research Articles

Development of an analytical method to determine methyl alcohol and isopropyl alcohol in food using static headspace gas chromatography.

A method to determine methanol (MeOH) and isopropyl alcohol (IPA) was developed using static headspace sampling (HSS) with gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The optimized HSS-GC and HSS-GC/MS methods were validated according to the parameters. The limit of quantification (LOQ) values for MeOH analyzed by HSS-GC/MS and HSS-GC were 0.50-0.56 and 1.97mg/L, and the corresponding values for IPA were 0.14-0.21 and 1.51mg/L, respectively. Recoveries were determined by spiking sample matrices, such as vinegar and tea. MeOH and IPA showed excellent recoveries of 93.80-107.60% and 93.92-104.32% with corresponding precisions of 0.51-7.38% and 0.90-7.70%, respectively. Compared to solid-phase microextraction-GC/MS and HSS-GC, the HSS-GC/MS method showed outstanding values for limit of detection and LOQ with improved precision and accuracy. This HSS-GC/MS method was successfully used to monitor residual solvents in 100 food and functional food products.

Absolute Quantification of Residual Solvent in Mesoporous Silica Drug Formulations Using Magic-Angle Spinning NMR Spectroscopy.

Porous silica is used as a drug delivery agent to improve the bioavailability of sparsely soluble compounds. In this approach, the active pharmaceutical ingredient (API) is commonly loaded into the porous silica by incipient wetness impregnation using organic solvents. Subsequent solvent elimination is critical as the residual solvent concentration cannot exceed threshold values set by health and safety regulations (e.g., EMA/CHMP/ICH/82260/2006). For dichloromethane and methanol, for example, residual concentrations must be below 600 and 3000 ppm, respectively. Today, EU and USA Pharmacopoeias recommend tedious procedures for residual solvent quantification, requiring extraction of the solvent and subsequent quantification using capillary gas chromatography with static headspace sampling (sHS-GC). This work presents a new method based on the combination of standard addition and absolute quantification using magic-angle spinning nuclear magnetic resonance spectroscopy (MAS qNMR). The methodology was originally developed for absolute quantification of water in zeolites and has now been validated for quantification of residual solvent in drug formations using mesoporous silica loaded with ibuprofen dissolved in DCM and MeOH as test samples. Interestingly, formulations prepared using as-received or predried mesoporous silica contained 5465 versus 484.9 ppm DCM, respectively. This implies that the initial water content of the silica carrier can impact the residual solvent concentration in drug-loaded materials. This observation could provide new options to minimize the occurrence of these undesired solvents in the final formulation.

Optimization of a static headspace GC-MS method and its application in metabolic fingerprinting of the leaf volatiles of 42 citrus cultivars.

Citrus leaves, which are a rich source of plant volatiles, have the beneficial attributes of rapid growth, large biomass, and availability throughout the year. Establishing the leaf volatile profiles of different citrus genotypes would make a valuable contribution to citrus species identification and chemotaxonomic studies. In this study, we developed an efficient and convenient static headspace (HS) sampling technique combined with gas chromatography-mass spectrometry (GC-MS) analysis and optimized the extraction conditions (a 15-min incubation at 100 ˚C without the addition of salt). Using a large set of 42 citrus cultivars, we validated the applicability of the optimized HS-GC-MS system in determining leaf volatile profiles. A total of 83 volatile metabolites, including monoterpene hydrocarbons, alcohols, sesquiterpene hydrocarbons, aldehydes, monoterpenoids, esters, and ketones were identified and quantified. Multivariate statistical analysis and hierarchical clustering revealed that mandarin (Citrus reticulata Blanco) and orange (Citrus sinensis L. Osbeck) groups exhibited notably differential volatile profiles, and that the mandarin group cultivars were characterized by the complex volatile profiles, thereby indicating the complex nature and diversity of these mandarin cultivars. We also identified those volatile compounds deemed to be the most useful in discriminating amongst citrus cultivars. This method developed in this study provides a rapid, simple, and reliable approach for the extraction and identification of citrus leaf volatile organic compound, and based on this methodology, we propose a leaf volatile profile-based classification model for citrus.

Marker Substances in the Aroma of Truffles.

The aim of this study was to identify specific truffle marker substances within the truffle aroma. The aroma profile of different truffle species was analyzed using static headspace sampling with gas chromatography mass spectrometry analysis (SHS/GC-MS). Possible marker substances were identified, taking the additional literature into account. The selected marker substances were tested in an experiment with 19 truffle dogs. The hypothesis “If trained truffle dogs recognize the substances as supposed truffles in the context of an experiment, they can be regarded as specific” was made. As it would be nearly impossible to investigate every other possible emitter of the same compounds to determine their specificity, this hypothesis was a reasonable approximation. We were interested in the question of what it is the dogs actually search for on a chemical level and whether we can link their ability to find truffles to one or more specific marker substances. The results of the dog experiment are not as unambiguous as could have been expected based on the SHS/GC-MS measurements. Presumably, the truffle aroma is mainly characterized and perceived by dogs by dimethyl sulfide and dimethyl disulfide. However, as dogs are living beings and not analytical instruments, it seems unavoidable that one must live with some degree of uncertainty regarding these results.

Development of a fully automated analytical platform based on static headspace-gas chromatography-tandem mass spectrometry for the analysis of five N-nitrosamines in dried aquatic products of animal origin.

The development of rapid and sensitive monitoring methods for trace N-nitrosamines (NAs) in foodstuffs is essential for mitigating the potential health risks to consumers. In the present study, an analytical platform based on one step fully automated static headspace sampling and gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed and validated for the analysis of N-nitrosamines in dried aquatic products of animal origin. The samples and sodium chloride solution mixture were incubated in a heated headspace vial for analyte evaporation, coupled to automatic sampling and online GC-MS/MS analysis. The proposed method requires minimal sample preparation and organic solvent consumption. Five N-nitrosamines including N-nitroso dimethylamine, N-nitroso methyl ethylamine, N-nitroso pyrolidine, N-nitroso piperidine and N-nitroso diphenylamine were selected as model compounds to optimize the significant factors by a using Box-Behnken design. The optimum conditions achieved limits of detections in the range 0.08-0.29 μg kg-1 , with correlation coefficient over 0.998. Relative recoveries in dried aquatic product sample were in the range 76.9-92.4%, with relative SDs of 1.9-7.2%. These results confirm the reliability of the developed method for further application in trace level monitoring of the target analytes in foodstuffs. © 2022 Society of Chemical Industry.

Rapid Discrimination of Aroma Components in Natural and Artificial Agarwood Incense by Static Headspace Sampling – Gas Chromatography – Mass Spectrometry (SHS-GC-MS) with Principal Component Analysis (PCA) and Partial Least Squares – Discrimination Analysis (PLS-DA)

Agarwood is a resinous, fragrant wood produced by tropical tree species of the genus Aquilaria, and is highly valued for its wide range of uses in medicine, incense, and perfume. In this study, the quality of agarwood and patterns of chemical constituents induced in natural and artificial agarwood by physical injury, chemical inducer, and chemical plus fungal infection were compared using static headspace sampling gas chromatography – mass spectrometry (SHS-GC-MS). The optimal agarwood heating temperature was determined to be 180 °C. The fingerprints of 40 batches of agarwood were established. Multivariate statistical analysis was utilized to identify 15 common and ten differentiating components, respectively. Agarwood induced by the physical method was more similar to natural agarwood. Exploration of the pyrolysis products of chromone derivatives and sesquiterpenes was undertaken to discover the causes of differences in chemical compositions between artificial and natural agarwood. Our findings revealed that benzylacetone, baimuxinal, and guaiol were significant for agarwood incense and these compounds may be used as markers for classification.

Traceability of VOCs in tire inner liner by chromatography-mass spectrometry.

Many parts of the vehicle cabin generate volatile organic compounds (VOCs), and some are hazardous and/or odorous to humans. In this study, VOCs in the inner liner of automobile spare tire, including raw rubbers and resins, were detected by gas chromatography-mass spectrometry (GC-MS) coupled with an extracting method of static headspace sampling (SHS). The results demonstrated that the sources of VOCs can be traced back to raw rubbers and resins: alkylphenol resins can release a large amount of 2,4,4-trimethyl-1-pentene and 2,2,4,6,6-pentamethyl-3-heptene; chlorobutyl rubber (CIIR) contained 3-methyl-pentane, and methyl-cyclopentane, and these VOCs are odorous. When alkylphenol resin and natural rubber (NR) with low VOCs were used to replace the corresponding resin and NR in the initial formulation, the total volatile organic compounds (TVOCs) in the inner liner could be reduced. We expected that the information gained from this work could provide a basic reference for the manufacture of environmental-friendly tire products.

Profiling soil volatile organic compounds after N fertilization in a soil grown with Rosmarinus officinalis

The biogenic volatile organic compounds (BVOCs) emissions from cultivated plants-soil systems and N fertilization's role on these emissions are mostly unknown. This study aimed to elucidate the BVOCs emissions from a plant-soil system receiving N fertilization using Rosmarinus officinalis as a model case study. We put forward the hypothesis that N fertilization changes the BVOCs emissions patterns irrespectively the presence of Rosmarinus officinalis and that the emissions are related to N availability and bacterial abundance. To test our hypothesis, we established a microcosm (glass static chambers) study in a fully randomized design with four treatments: soil (S), soil and plant (S + P), soil and fertilizer (S + F), soil, plant, and fertilizer (S + P + F); using NH4NO3 as N source. BVOCs were sampled from the microcosms, using the static headspace sampling technique with a solid-phase microextraction (SPME) device and analyzed by gas chromatography–mass spectrometry (HS-SPME-GC–MS). Sampling occurred 1, 2, 3, 4, 7, 10, 15, 17, 22, 25, and 31 days after applying the NH4NO3 and besides BVOCs, we measured soil NH4+ and NO3− concentration as well as 16S rRNA bacterial abundance. Time drives a significant portion of the variation in the chemical diversity and quantity of the different VOCs found throughout the experiment (PERMANOVA; R2 = 0.28, p < 0.001); however, this was dependent on the presence of plant and fertilizer leading to a significant interaction (PERMANOVA; R2 = 0.33, p < 0.001). Individual BVOCs emissions were strongly affected by nitrogen fertilization, plant presence and declined during the time. The most dominant BVOCs detected were benzyl alcohol, acetone, toluene, benzaldehyde, and caprolactam. Interestingly, the BVOCs concentration was negatively associated with soil concentration to NH4+, NO3− and total bacterial abundance.

Simultaneous determination of stable chlorine and bromine isotopic ratios for bromochlorinated trihalomethanes using GC-qMS

Bromochlorinated compounds are organic contaminants originating from different natural and anthropic sources and increasingly found in different environmental compartments. This work presents an online approach for compound specific stable isotope analysis of chlorine and bromine isotope ratios for bromochlorinated trihalomethanes using gas chromatography coupled to quadrupole mass spectrometry (GC-qMS). An evaluation scheme was developed to simultaneously determine stable chlorine and bromine isotope ratios based on the mass spectral data of two target compounds: dibromochloromethane and dichlorobromomethane. The analytical technique was optimized by assessing the impact of different instrumental parameters, including dwell time, split ratios, and ionization energy. Successively, static headspace samples containing the two target compounds at aqueous concentrations ranging from 0.1 mg/L to 5 mg/L were analyzed in order to test the precision and reproducibility of the proposed approach. The results showed a good precision under the optimized instrumental conditions, with relative standard deviations ranging between 0.05% and 0.5% for chlorine and bromine isotope analysis. Finally, the method was tested in a source identification problem in which the simultaneous determination of chlorine and bromine stable isotope ratios allowed the clear distinction of dibromochloromethane from three different manufacturers.

Optimization and comparison of headspace hot injection and trapping, headspace solid-phase microextraction, and static headspace sampling techniques with gas chromatography–mass spectrometry for the analysis of volatile compounds in kimchi

The identification of volatile compounds (VCs) related to flavors is important for confirming food quality, and instrumental techniques are required to effectively and accurately identify and determine the VCs responsible for such flavors. The VCs related to kimchi flavor were analyzed by headspace hot injection and trapping (HS-HIT), which is a type of multiple headspace sample enrichment sampling technique. For the HS-HIT sampling technique, the cool injection system temperature was optimized to −40 °C and the multiple sampling frequency was optimized to nine injections. Moreover, HS-HIT was compared with static headspace (SHS) and headspace solid-phase microextraction (HS-SPME) sampling techniques for the VC analysis of kimchi. The overall peak intensities in the total ion chromatograms (TICs) with SHS and HS-SPME were lower than with HS-HIT. Although the HS-HIT sampling technique was complementary to the HS-SPME sampling technique for VC analysis, it allowed more sulfur compounds characteristic of kimchi to be identified than the SHS and HS-SPME sampling techniques. Therefore, we recommend the use of the HS-HIT sampling technique with GC-MS for identifying the VCs associated with kimchi flavor. This study confirmed the usefulness of the HS-HIT sampling technique for the analysis of VCs.

The application research of solid‐phase extraction and headspace gas chromatography in the detection of methanol in transformer oil

Methanol in transformer oil has been recently proposed as new marker of the aging of solid insulation in power transformers. Because the concentration of methanol in transformer oil is usually less than 500 µg/l and even less than 50 µg/l that cannot be detected by common methods. This paper combined static headspace sampling and solid‐phase extraction (SPE) as pretreatment, used SPE to adsorb and concentrate sample, headspace sampling to desorb and inject methanol in to the gas chromatography. The experiments show that it will achieve the optimal performance when headspace conditions were the equilibrium temperature of 90°C and the equilibrium time of 25 min. The linear relation between the concentration of methanol and the peak area was satisfying in the concentration range from 10 to 600 µg/l with goodness of fit of 0.997. In addition, this method can be applied in practical work. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Polyamidoamine dendrimer–digoxin impregnated PVC film in the fingerprint detection of herbs’ essential oil coupled to gas chromatography–mass spectrometry

Third-generation polyamidoamine (G3 PAMAM) dendrimer–digoxin (PAMAM-Dig) is prepared, and conjugation is confirmed by 1H-NMR, Fourier transform infrared spectroscopy (FT-IR), and thermal analysis. Then, PAMAM-Dig impregnated polyvinyl chloride (PAMAM-Dig/PVC) film has been prepared by mixing PAMAM-Dig, PVC powder, and 2-nitrophenyl octyl ether (O-NPOE) as the plasticizer in tetrahydrofuran. Differential scanning calorimetry (DSC) evaluation shows the as-prepared film is thermally stable below 200 °C. The film is mounted above the powder as well as the essential oil of Thymus vulgaris. The Taguchi orthogonal array is used to optimize the experimental conditions for adsorption of volatile constituents. At optimized conditions, the obtained fingerprint was the same or better than static headspace sampling of the essential oil. The chromatogram pattern had also obtained by floating the fiber in the essential oil, and more components have observed. Film-to-film variations were less than 10%. All obtained patterns are compared with those of different solvent extracts of Thymus vulgaris. It is concluded that PAMAM-Dig/PVC film could apply for fingerprint analysis of herbs’ volatile and semi-volatile constituents with no need for prior extraction.

Adsorbent-SERS Technique for Determination of Plant VOCs from Live Cotton Plants and Dried Teas.

We developed a novel substrate for the collection of volatile organic compounds (VOCs) emitted from either living or dried plant material to be analyzed by surface-enhanced Raman spectroscopy (SERS). We demonstrated that this substrate can be utilized to differentiate emissions from blends of three teas, and to differentiate emissions from healthy cotton plants versus caterpillar-infested cotton plants. The substrate we developed can adsorb VOCs in static headspace sampling environments, and VOCs naturally evaporated from three standards were successfully identified by our SERS substrate, showing its ability to differentiate three VOCs and to detect quantitative differences according to collection times. In addition, volatile profiles from plant materials that were either qualitatively different among three teas or quantitatively different in abundance between healthy and infested cotton plants were confirmed by collections on Super-Q resin for dynamic headspace and solid-phase microextraction for static headspace sampling, respectively, followed by gas chromatography to mass spectrometry. Our results indicate that both qualitative and quantitative differences can also be detected by our SERS substrate although we find that the detection of quantitative differences could be improved.

Characterization of the Major Odorants in Cempedak-Differences to Jackfruit.

Screening the volatiles of cempedak [Artocarpus integer (Thunb.) Merr.] pulp for odor-active compounds by aroma extract dilution analysis and gas chromatography (GC)-olfactometry of static headspace samples revealed a total of 55 odorants, among which 47 were identified. Using stable isotopically substituted odorants as internal standards, these compounds were quantitated by GC-mass spectrometry, and odor activity values (OAVs) were calculated as ratios of the natural concentrations in cempedak pulp to the orthonasal odor detection thresholds. An aroma reconstitution model based on the 41 compounds with OAVs >1 in their natural concentrations successfully mimicked the characteristic aroma of cempedak pulp including the pronounced sulfury, oniony note which is intense in cempedak pulp but absent in jackfruit pulp. Further sensory tests finally showed that 2-(methylsulfanyl)propane, 2-(methylsulfanyl)butane, and 2-(methylsulfanyl)pentane are the key compounds responsible for this unique aroma note in cempedak pulp and vitally contribute to the aroma difference between cempedak pulp and jackfruit pulp.

Tandem Mass Spectrometric Quantification of 93 Terpenoids in Cannabis Using Static Headspace Injections.

The therapeutic effect of Cannabis largely depends on the content of its pharmacologically active secondary metabolites, mainly phytocannabinoids, flavonoids, and terpenoids. Recent studies suggest there are therapeutic effects of specific terpenoids as well as synergistic effects with other active compounds in the plant. Although Cannabis contains an overwhelming milieu of terpenoids, only a limited number are currently reported and used for metabolic analysis of Cannabis chemovars. In this study, we report the development and validation of a method for simultaneous quantification of 93 terpenoids in Cannabis air-dried inflorescences and extracts. This method employs the full evaporation technique via a static headspace sampler, followed by gas chromatography-mass spectrometry (SHS-GC/MS/MS). In the validation process, spiked terpenoids were quantified with acceptable repeatability, reproducibility, sensitivity, and accuracy. Three medical Cannabis chemovars were used to study the effect of sample preparation and extraction methods on terpenoid profiles. This method was further applied for studying the terpenoid profiles of 16 different chemovars acquired at different dates. Our results demonstrate that sample preparation methods may significantly impact the chemical fingerprint compared to the nontreated Cannabis. This emphasizes the importance of performing SHS extraction in order to study the natural terpenoid contents of chemovars. We also concluded that most inflorescences expressed relatively unique terpenoid profiles for the most pronounced terpenoids, even when sampled at different dates, although absolute concentrations may vary due to aging. The suggested method offers an ideal tool for terpenoid profiling of Cannabis and sets the scene for more comprehensive works in the future.

Characterization of the Major Odor-Active Compounds in Jackfruit Pulp.

An aroma extract dilution analysis applied to the volatiles isolated from jackfruit ( Artocarpus heterophyllus Lam.) pulp by solvent extraction and solvent-assisted flavor evaporation resulted in the detection of 48 odorants with flavor dilution (FD) factors between 1 and ≥8192. Application of gas chromatography-olfactometry to static headspace samples revealed additional five highly volatile odorants. The structures of 44 out of the 53 detected odorants could be assigned. These 44 compounds were quantitated using stable isotopically substituted odorants as internal standards, and their odor activity values (OAVs) were calculated as the ratio of the natural concentrations in jackfruit pulp and the odor threshold values in water. High OAVs were in particular obtained for ethyl 3-methylbutanoate (74000), ethyl butanoate (1800), 3-methylbutanal (1500), and 2-methylpropanal (1400). An aroma model solution based on the natural concentrations of the 35 compounds for which OAVs > 1 had been calculated fully mimicked the characteristic jackfruit pulp aroma.

Fast identification of Bacteria for Quality Control of Drinking Water through A Static Headspace Sampler Coupled to a Sensory Perception System.

The aim of this study was to develop and implement a methodology composed by a Static Head-Space-Sampler (SHS) coupled to a Sensory Perception System (SPS) for the extraction of Volatile Organic Compounds (VOC’s) emitted by bacterial species in the water. The SPS was performed by means of a chamber of 16 Metal-Oxide-Semiconductor (MOS) gas sensors and a software with pattern recognition methods for the detection and identification of bacteria. At first, the tests were conducted from the sterile and polluted water with the Escherichia coli bacteria and modifying the incubation temperatures (50 °C, 70 °C and 90 °C), with the objective to obtain an optimal temperature for the distinguishing of species. Furthermore, the capacity of the methodology to distinguish the important compounds was assessed, in this case, E. coli and other bacteria like Pseudomonas aeruginosa and Klebsiella oxytoca, which formed similar analytes. The validation of the proposed methodology was done by acquiring water samples from different unitary operations of an aqueduct of the municipality of Toledo (North of Santander, Colombia), which were analyzed by the membrane filter technique in the laboratories of the University of Pamplona, along with the SHS-SPS system. The results showed that it was possible to distinguish polluted water samples in a fast way through the sensory measurement equipment using pattern recognition techniques such as Principal Component Analysis (PCA), Discriminant Function Analysis (DFA) and a probabilistic neural network (PNN), where a 95% of differentiation was obtained through PCA and 100% of the classification with DFA. The PNN network achieved the 86.6% of success rate with the cross-validation technique “leave one out”.

Implementing Dynamic Headspace With SPME Sampling of Virgin Olive Oil Volatiles: Optimization, Quality Analytical Study, and Performance Testing.

Competition and interaction phenomena among volatiles during their adsorption process by solid phase microextraction (SPME) fibers in static headspace sampling procedure (SHS) cast doubt on its ability to quantify virgin olive oil volatiles. SPME fibers being excellent traps, their use was analyzed with a new device allowing the concentration of volatiles in a dynamic headspace sampling procedure (DHS). A central composite experimental design optimized the main variables of the device (4 g sample weight, 40 °C temperature, 150 mL/min flow rate, 50 min adsorption time), while values of the analytical quality control parameters of the method (repeatability, limits of detection and quantification, working range, sensitivity, and resolution) were compared with those ones from static headspace. DHS shows better precision results for aldehydes and alcohols than SHS and allowed analyzing higher concentrations with no problem of saturation. In 19 of 28 compounds analyzed in 50 samples the chromatographic areas were higher when running DHS. The concentration values of volatile compounds in these samples after applying SHS and DHS are discussed together with the ability of the new method for distinguishing virgin olive oil by their categories (extra virgin, virgin, and lampante) by the volatiles quantified in commercial oils.

Identification and quantitation of furan in irradiated fruit and vegetable juice

This paper describes the use of gas chromatography/mass spectroscopy (GC/MS) using static headspace sampling for the determination of furan in irradiated fruit and vegetable juice. The data presented demonstrate that furan is generated in juice as a result of treatment with ionizing radiation, but at low part-per-billion concentrations. The amount of furan increases with increasing dose in a non-linear second order relationship. Furthermore, it was found that furan interacts with the ionizing radiation in such a way that the amount of furan can be reduced in the absence of precursor compounds commonly found in juice products. Several possible precursors have been identified, including glucose, fructose, and ascorbic acid. We conclude that the formation of furan is complex and proceeds through a multi step process.

Biological and chemical strategies for exploring inter- and intra-kingdom communication mediated via bacterial volatile signals.

Airborne chemical signals emitted by bacteria influence the behavior of other bacteria and plants. We present an overview of in vitro methods for evaluating bacterial and plant responses to bacterial volatile compounds (BVCs). Three types of equipment have been used to physically separate the bacterial test strains from either other bacterial strains or plants (in our laboratory we use either Arabidopsis or tobacco plant seedlings): a Petri dish containing two compartments (BI Petri dish); two Petri dishes connected with tubing; and a microtiter-based assay. The optimized procedure for the BI Petri dish system is described in this protocol and can be widely used for elucidation of potential function in interactions between diverse microbes and those plant and chemical volatiles emitted by bacteria that are most likely to mediate bacterial or plant responses to BVCs. We also describe a procedure for metabolome-based BVC profiling via dynamic (i.e., continuous airflow) or static headspace sampling using solid-phase microextraction (SPME). Using both these procedures, bacteria-bacteria communications and bacteria-plant interactions mediated by BVCs can be rapidly investigated (within 1-4 weeks).