Determination of the oil absorption value of inorganic powder by tracer-assisted headspace gas chromatography

This paper reports a method for determining the oil absorption value of inorganic powder based on tracer-assisted headspace gas chromatographic (HS-GC) technique. The method was carried out by adding 25 μL droplet of toluene-Dioctyl Phthalate solution onto the surface of 1.0 g inorganic powder, then sealing the headspace vial and shaking it to make the powder spherical. The amount of toluene that not been adsorbed by inorganic powder was quantified using HS-GC with the optimal equilibrium temperature and time conditions of 100 °C and 7 min, respectively. A new mathematical model shows that the oil absorption value can be determined from the signal of toluene. The results show that the employed method has good precision (the relative standard deviation < 3.6 %) and accuracy (R2 = 0.993). This method is simple and accurate, and can be an reliable tool for testing the oil absorption value of inorganic powder sample.

[Determination of Perchloroethylene in blood by headspace gas chromatography-mass spectrometry]

Objective: To establish a method for determination of Perchloroethylene (PCE) in blood by headspace gas chromatography-mass spectrometry (HS/GC-MS) . Methods: From Dctober to December 2021, A total of 3 mL blood samples were taken into a 10 mL headspace bottle, after heated at 60 ℃ for 30 mins, PCE in the top air was separated by VF-WAXms capillary column and detected by GC-MS. The retention time and external standard method were used for qualitative and quantitative analysis of PCE in samples, respectively. Results: There was good linear relationship in the range of 5.09-200.17 μg/L. The linear correlation coefficient was 0.9993.The detection limit was 0.21 μg/L and the lower limit of quantitation was 0.70 μg/L. The recovery rates of samples with different concentrations were 95.3%-103.8%. The intra-batch relative standard deviations (RSD) were 3.2%-4.6%, and inter-batch RSD was 4.0%-6.1%. The samples can be stored at 4 ℃ for three days and at -20 ℃ for seven days. Conclusion: This method is proved to be simple, practical and highly sensitive, which is suitable for the determination of PCE in blood.

Determination of the water vapor transmission rate of cellulose-based papers by multiple headspace extraction analysis

This paper presents a multiple headspace extraction (MHE) analysis technique to determine the water vapor transmission rate of cellulose-based papers. The water vapor passing through the sample in a closed headspace vial is determined by MHE-gas chromatography. The results show that the employed method offers good precision (the relative standard deviation < 3.49 %) and good accuracy. The method is rapid and accurate, and is promising for the determination of the water vapor transmission rate of cellulose-based papers in future studies.

Screening of volatile organic compounds (VOCs) from liquid fungal cultures using ambient mass spectrometry

The potential of fungi for use as biotechnological factories in the production of a range of valuable metabolites, such as enzymes, terpenes, and volatile aroma compounds, is high. Unlike other microorganisms, fungi mostly secrete secondary metabolites into the culture medium, allowing for easy extraction and analysis. To date, the most commonly used technique in the analysis of volatile organic compounds (VOCs) is gas chromatography, which is time and labour consuming. We propose an alternative ambient screening method that provides rapid chemical information for characterising the VOCs of filamentous fungi in liquid culture using a commercially available ambient dielectric barrier discharge ionisation (DBDI) source connected to a quadrupole-Orbitrap mass spectrometer. The effects of method parameters on measured peak intensities of a series of 8 selected aroma standards were optimised with the best conditions being selected for sample analysis. The developed method was then deployed to the screening of VOCs from samples of 13 fungal strains in three different types of complex growth media showing clear differences in VOC profiles across the different media, enabling determination of best culturing conditions for each compound-strain combination. Our findings underline the applicability of ambient DBDI for the direct detection and comparison of aroma compounds produced by filamentous fungi in liquid culture.

Canine olfactory detection of trained explosive and narcotic odors in mixtures using a Mixed Odor Delivery Device

Like using a substandard calibrant to test and calibrate an instrumental detector, when detection canines are regularly exposed to less than optimal training material, their detection proficiency is diminished, risking the lives of their handlers and civilians they are intended to protect. This research examined canine detection proficiency to odor mixtures and the use of mixture training to improve said proficiency. Trained detection canines were tested on their ability to correctly locate their trained target odors, explosives or narcotics, in various mixtures from a series of blanks and distractor odors. After making base measurements, canines were trained on the target odor in mixtures using the Mixed Odor Delivery Device (MODD), which was previously developed to safely contain separated explosive components and deliver the mixed odor to a canine detector for training purposes. Headspace measurements, made using solid phase microextraction with gas chromatography/mass spectrometry (SPME-GC/MS), were also taken of mixture components in and out of the MODD to confirm that odor mixtures were accurately portrayed to the canines during MODD training. Following mixture training, canines were retested on the same mixtures. Results of the headspace analysis showed that the MODD did not alter the delivery of the odorants from the mixture components. As such, canines showed an improved proficiency in detection of target mixtures following mixture training, increasing the detection rate from 63% to 72% for pseudo cocaine mixtures and from 19% to 100% for explosive mixtures.

Simultaneous Determination of Amphiphobicities of Material Surface by A Dual-Indicator Headspace Gas Chromatography

This paper reports on a new method for simultaneously determining the amphiphobicities of material surface by a dual-indicator assisted headspace gas chromatography. After adding 40 μL of both methanol-water and toluene-oil droplets on the sample surface for 20 s, the sample was turned vertically (to remove water and oil) and then placed in a headspace vial. The amount of methanol and toluene in the residual water and oil adhered to material surface was quantified using headspace gas chromatography. The results showed that the method has good measurement precision (RSD < 4.58%). It can be an effective tool for simultaneously determining the amphiphobicities of material surface.

Residual solvent analysis with hyper-fast gas chromatography-mass spectrometry and a liquid carbon dioxide cryofocusing in less than 90 s

A new hyper-fast gas chromatography method with less than 90 s runtime including the column cool down was developed for the analysis of four gases and 16 residual solvents, combining a CO₂ cryofocusing with a flow-field thermal gradient gas chromatograph (FF-TG-GC) and ToF-MS. The extremely low analysis time can be achieved by combining the new FF-TG-GC and a very short Rxi-624 Sil MS separation column with a small inner diameter and small film thickness (2.05 m × 0.1 mm × 1.0 µm). The column is inserted into a low thermal mass, resistively heated stainless steel capillary. This enables fast temperature programs with heating rates up to 3000 °C/min and a column cool down within a few seconds. In addition to temporal temperature gradients, the FF-TG-GC can generate a spatial temperature gradient that leads to an improved peak shape. Further, an external liquid CO₂ cryo-trap was designed in order to reduce the injection bandwidths of analytes and to take full advantage of the resolving power of the separation column. No modifications are required to the FF-TG-GC for the use of the cryogenic trap, as the cooled spot is heated by the resistively heated stainless steel capillary during the temperature program. With cryofocusing, analyzed residual solvents are baseline separated. R² values over 0.99 for calibration curves and low relative standard deviations (mainly < 3%) for repeatability tests were obtained.

Volatile organic compounds in a headspace sampling system and asthmatics sputum samples

Background:The headspace of a biological sample contains exogenous VOCs present within the sampling environment which represent the background signal.Study aims:This study aimed to characterise the background signal generated from a headspace sampling system in a clinical site, to evaluate intra- and inter-day variation of background VOC and to understand the impact of a sample itself upon commonly reported background VOC using sputum headspace samples from severe asthmatics.Methods:The headspace, in absence of a biological sample, was collected hourly from 11am to 3pm within a day (time of clinical samples acquisition), and from Monday to Friday in a week, and analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Chemometric analysis identified 1120 features, 37 of which were present in at least the 80% of all the samples. The analyses of intra- and inter-day background variations were performed on thirteen of the most abundant features, ubiquitously present in headspace samples. The concentration ratios relative to background were reported for the selected abundant VOC in 36 asthmatic sputum samples, acquired from 36 stable severe asthma patients recruited at Glenfield Hospital, Leicester, UK.Results:The results identified no significant intra- or inter-day variations in compounds levels and no systematic bias of z-scores, with the exclusion of benzothiazole, whose abundance increased linearly between 11am and 3pm with a maximal intra-day fold change of 2.13. Many of the identified background features are reported in literature as components of headspace of biological samples and are considered potential biomarkers for several diseases. The selected background features were identified in headspace of all severe asthma sputum samples, albeit with varying levels of enrichment relative to background.Conclusion:Our observations support the need to consider the background signal derived from the headspace sampling system when developing and validating headspace biomarker signatures using clinical samples.

Determination of water distribution in sludge by a multiple headspace extraction analytical technique

This paper reported a new method for the determination of the water distribution in sludge. It was based on a multiple headspace extraction (MHE) procedure to step-wise remove the water vapor from a closed vial containing a sludge sample, followed by a gas chromatographic measurement (GC). By plotting the GC signal of water vapor vs. the headspace extraction number, three different trend lines from the profile can be observed. From which two transition points can be determined and thus the stages for the free water, capillary water, and adsorption water release can be divided. Based on the sum of GC peak areas ate each stage, the content of these water types in the sludge can be calculated through a method calibration. The results showed that the MHE-GC method has a better measurement repeatability (RSD < 18.6%) and sensitivity (limit of quantitation = 0.028%) than the thermal drying method (used as a reference method). There was also a good agreement between the MHE-GC and the reference method on the free water and capillary water analysis. Moreover, the results on the adsorption water and bound water testing by the present method is more justifiable than the reference method.

Headspace gas chromatographic method for antimicrobial screening: Minimum inhibitory concentration determination

The headspace gas chromatographic method has been widely used to detect volatile metabolites to reflect the growth state of microorganisms, however, it has never been used for the determination of the minimum inhibitory concentration in antibacterial drugs. This paper reports a new method for evaluating the antimicrobial activity of drugs by measuring the amount of CO₂ produced by bacterial metabolism after treatment with drugs. According to the amount of CO₂ produced by bacterial metabolism, a proper amount of bacterial liquid is selected and added to a drug-containing culture medium as compared with bacteria without drugs in parallel. The amount of CO₂ produced by bacteria is measured by using a headspace gas chromatograph coupled with a thermal conductivity detector to measure the bacteriostasis rate and the minimum bacteriostasis concentration of the tested drug, so as to evaluate its antibacterial activity. The accuracy of this method was verified by comparison with the standard method (the OD method), which indicated that the precision was less than 3 % (expressed by relative standard deviation), the inhibition rate (R² = 0.968) was consistent with the reference method above. This method is simple in operation and can avoid the error caused by the properties of the sample such as volatility, solubility and color in the determination of the minimum inhibitory concentration. It is suitable for the determination of antibacterial activity of drugs, especially natural drugs.

Differences between selected volatile aromatic compound concentrations in sludge samples in various steps of wastewater treatment plant operations

Sewage sludge, one of the main wastes generated during wastewater treatment, constitutes an important source of emissions of volatile chemical compounds such as volatile aromatic compounds These substances may undergo various changes as a result of operations and unit processes, which affects their concentrations in sewage sludge. An important factor determining the potential hazardousness of volatile organic compounds is the quality of wastewater delivered to wastewater treatment plants and the technical and equipment solutions applied to wastewater. In this study, a rapid and sensitive headspace gas chromatography method, coupled with tandem mass spectrometry using the standard addition method, was developed for the determination of selected volatile aromatic compounds in sewage sludge samples collected at different stages from three wastewater treatment plants located in Poland. This study attempted to assess the relationship between differences in the emissions of representative VACs and the given stage of the technological process within three analysed wastewater treatment plants. Toluene was detected with the highest frequency in analysed samples, at concentrations varying from 0.234 ± 0.035 ng/g of sludge to 28.3*10²±3.2*10² ng/g of sludge. The highest concentration levels were determined for p-cresol, with concentrations ranging from 44.0*10¹±5.6*10¹ ng/g of sludge (sludge from aerobic chamber, wastewater treatment plant no.2) to 47.7*10²±6.9*10² ng/g of sludge (sludge from aerobic chamber, wastewater treatment plant no.1), while the lowest concentration levels were observed for chlorobenzene, with concentrations ranging from 0.1300 ± 0.0030 ng/g of sludge (sludge from anaerobic chamber, wastewater treatment plant no.2), to 0.2606 ± 0.0046 ng/g of sludge (primary sludge, wastewater treatment plant no.1). The repeatability of the method was better than 10%, with accuracy levels in the ranges 89%-108%.Wastewater treatment technologies and residual sludge management in the selected wastewater treatment plantsinfluenced volatile aromatic compounds emission. Furthermore, the diversity of the wastewater quality, depending on the catchment area, is also an important factor determining the differentiation in volatile aromatic compounds emission. The microbial composition of raw wastewater highly influenced not only the treatment effectiveness of wastewater treatment plants but also the production of intermediate products, such as volatile aromatic compounds, which may contribute to odour emissions.

In-situ headspace analysis of metabolic carbon dioxide of aerobic bacteria for assessing antimicrobial activity of natural products

Headspace analysis of the volatile metabolites has been used as a good strategy for monitoring the microbial growth in several applications, but never been established for the evaluation of the activity of microbial inhibitor in the field of drug screening from natural products. We report on a new method for the determination of antimicrobial activity of drug compounds or crude extracts from natural products by measuring the amount of metabolic carbon dioxide produced in the drug-bacteria incubation system. 2 mL of medium containing bacteria and drug of interest was incubated at 37 °C for 24 h. The amount of metabolic carbon dioxide partitioned in the headspace was measured to evaluate the drug antimicrobial activity using headspace gas chromatography (HS-GC) coupled with thermal conductive detector (TCD). The principle and the standard procedure of the present method have been developed and verified. As a result, the precision of the present method was less than 4% (expressed as relative standard deviation), and an excellent agreement was found on both inhibition rate (R² = 0.935) and the half inhibition concentration (R² = 0.994) between the present method and a reference method (optical density method). By comparison, the present method is simpler and safer regarding the microorganism contamination due to the in-situ incubation and detection in the closed system, and suitable for the routine analysis of antimicrobial activity of natural products with high flexibility in both bacterial strains and sample properties.

Emission of volatile organic compounds from yellow onion (Allium cepa L.) bulbs during storage

Fresh onions (Allium cepa L.) emit volatile organic compounds (VOCs) naturally in very low concentrations. The aim of the present study was to determine the emission rate of low-boiling VOCs from healthy and naturally infected onion bulbs at 4, 15, and 25 °C and to evaluate the applicability of the VOC method to monitor quality changes during 12 weeks of storage of two cultivars ('Hystand' and 'Hoza') of yellow onions. VOCs were extracted from the headspace of bulbs by solid phase micro-extraction (SPME) up to 5 times during storage and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of twenty-nine compounds were measured and twenty-seven of these were identified while thirteen were reported for the first time from yellow onion bulbs. Acetone (0.10-18.0 nmol kg^-1 day^-1), dimethyl disulfide (0.12-18.9 nmol kg^-1 day^-1) and hexanal (0.05-4.40 nmol kg^-1 day^-1) were among the most abundant volatiles emitted from healthy bulbs. The concentration of these compounds as well as the total volatiles decreased with time in storage. However, microbial infection resulted in higher emission of propene, carbon disulfide, isoprene, pentane, 2-methylfuran, 3-methylfuran, 1-propenethiol, hexane, and methyl propyl sulfide, indicating that VOC emission may be used as an indicator to monitor natural senescence and decay of stored onion bulbs.

Characterization of Male-Produced Aggregation Pheromone of the Bean Flower Thrips Megalurothrips sjostedti (Thysanoptera: Thripidae)

Aggregation of the bean flower thrips, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), has been observed on cowpea, Vigna unguiculata (L.) Walp. To understand the mechanism underpinning this behavior, we studied the responses of M. sjostedti to headspace volatiles from conspecifics in a four-arm olfactometer. Both male and female M. sjostedti were attracted to male, but not to female odor. Gas chromatography/mass spectrometry (GC/MS) analyses revealed the presence of two distinct compounds in male M. sjostedti headspace, namely (R)-lavandulyl 3-methylbutanoate (major compound) and (R)-lavandulol (minor compound); by contrast, both compounds were only present in trace amounts in female headspace collections. A behavioral assay using synthetic compounds showed that male M. sjostedti was attracted to both (R)-lavandulyl 3-methylbutanoate and (R)-lavandulol, while females responded only to (R)-lavandulyl 3-methylbutanoate. This is the first report of a male-produced aggregation pheromone in the genus Megalurothrips. The bean flower thrips is the primary pest of cowpea, which is widely grown in sub-Saharan Africa. The attraction of male and female M. sjostedti to these compounds offers an opportunity to develop ecologically sustainable management methods for M. sjostedti in Africa.

Volatolomics: A broad area of experimentation

Chemical analysis (detection and monitoring) of compounds associated with the metabolic activities of an organism is at the cutting edge of science. Volatile metabolomics (volatolomics) are applied in a broad range of applications including: biomedical research (e.g. disease diagnostic tools, personalized healthcare and nutrition, etc.), toxicological analysis (e.g. exposure tool to environmental pollutants, toxic and hazardous chemical environments, industrial accidents, etc.), molecular communications, forensics, safety and security (e.g. search and rescue operations). In the present review paper, an overview of recent advances and applications of volatolomics will be given. The main focus will be on volatile organic compounds (VOCs) originating from biological secretions of various organisms (e.g. microorganisms, insects, plants, humans) and resulting fusion of chemical information. Bench-top and portable or field-deployable technologies-systems will also be presented and discussed.

Evaluation of Container Closure System Integrity for Storage of Frozen Drug Products: Impact of Capping Force and Transportation

Frozen-state storage and cold-chain transport are key operations in the development and commercialization of biopharmaceuticals. Today, several marketed drug products are stored (and/or shipped) under frozen conditions to ensure sufficient stability, particularly for live viral vaccines. When these products are stored in glass vials with stoppers, the elastomer of the stopper needs to be flexible enough to seal the vial at the target's lowest temperature to ensure container closure integrity and thus both sterility and safety of the drug product. The container closure integrity assessment in the frozen state (e.g., -20°C, -80°C) should include container closure integrity (CCI) of the container closure system (CCS) itself, impact of processing (e.g., capping process on CCI), and impact of shipment and movement on CCI in the frozen state. The objective of this work was to evaluate the impact of processing and shipment on CCI of a CCS in the frozen state. The impact on other quality attributes was not investigated. In this light, the ThermCCI method was applied to evaluate the impact of shipping stress and variable capping force on CCI of frozen vials and to evaluate the temperature limits of rubber stoppers. In conclusion, retaining CCI during cold storage is mostly a function of vial-stopper combination, and temperatures below -40°C may pose a risk to the CCI of a frozen drug product. Variable capping force may have an influence on the CCI of a frozen drug product if not appropriately assessed. Regarding the impact of shipment on the CCI of glass vials, no indication was given at room temperature, -20°C, or -75°C when compared with static storage at such temperatures.LAY ABSTRACT: Today, several marketed products are stored (and/or shipped) under frozen conditions to ensure sufficient stability. When these products are stored in glass vials with stoppers, the elastomer of the stopper needs to be flexible enough to seal the vial and ensure container closure integrity and thus both sterility and safety of the drug product. The impact of processing and shipment on the container closure integrity (CCI) of a container closure system (vial, stopper, and flip-off cap) in the frozen state is assessed. A helium-leakage test at low temperature (ThermCCI) was used to evaluate the impact of shipping stress and variable capping force on CCI of frozen vials as well as the temperature limits of rubber stoppers. In conclusion, it was found that retaining CCI during cold storage is mostly a function of vial-stopper combination and that temperatures below -40°C may pose a risk to the CCI of a frozen drug product. Variable capping force may have an influence on the CCI of a frozen drug product if not appropriately assessed. Additionally, it was observed that the shipment of the frozen glass vials did not affect the CCI.

Variability of single bean coffee volatile compounds of Arabica and robusta roasted coffees analysed by SPME-GC-MS

We report on the analysis of volatile compounds by SPME-GC-MS for individual roasted coffee beans. The aim was to understand the relative abundance and variability of volatile compounds between individual roasted coffee beans at constant roasting conditions. Twenty-five batches of Arabica and robusta species were sampled from 13 countries, and 10 single coffee beans randomly selected from each batch were individually roasted in a fluidised-bed roaster at 210 °C for 3 min. High variability (CV = 14.0–53.3%) of 50 volatile compounds in roasted coffee was obtained within batches (10 beans per batch). Phenols and heterocyclic nitrogen compounds generally had higher intra-batch variation, while ketones were the most uniform compounds (CV < 20%). The variation between batches was much higher, with the CV ranging from 15.6 to 179.3%. The highest variation was observed for 2,3-butanediol, 3-ethylpyridine and hexanal. It was also possible to build classification models based on geographical origin, obtaining 99.5% and 90.8% accuracy using LDA or MLR classifiers respectively, and classification between Arabica and robusta beans. These results give further insight into natural variation of coffee aroma and could be used to obtain higher quality and more consistent final products. Our results suggest that coffee volatile concentration is also influenced by other factors than simply the roasting degree, especially green coffee composition, which is in turn influenced by the coffee species, geographical origin, ripening stage and pre- and post-harvest processing.

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Volatile compounds associated with individual roasted coffee beans were analysed by SPME-GC-MS.

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High inter- and intra-batch variability was observed, especially for 3-ethylpyridine.

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Multivariate statistics allowed prediction of coffee origin (species and location).

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Variability of volatiles is wide, with different chemical classes showing diverse behaviour.

Phylogenetic trends in the evolution of inflorescence odours in Amorphophallus

The chemical composition of inflorescence odours of 80 species of Amorphophallus (Araceae) were determined by headspace-thermal desorption GC-MS. When compared to published molecular phylogenies of the genus, the data reveal evidence both of phylogenetic constraint and plasticity of odours. Dimethyl oligosulphides were found as common constituents of Amorphophallus odours and were the most abundant components in almost half of the species studied. Odours composed mainly of dimethyl oligosulphides, and perceived as being 'gaseous', were only found among Asian species, and some of these species clustered in certain clades in molecular phylogenies; e.g. in two clades in Amorphophallus subgenus Metandrium. However, some species with gaseous odours were found to be closely related to species producing odours more reminiscent of rotting meat in which various minor components accompany the dominant dimethyl oligosulphides. These two broad types of odours have co-evolved with other inflorescence characteristics such as colour, with species with rotting meat odours having darker inflorescences. Species producing pleasant odours characterised by benzenoid compounds constitute two broad groups that are not related in published phylogenies. Species having fruity odours containing 1-phenylethanol derivatives mainly occur in a clade in subgenus Metandrium while those with anise odours composed almost solely of the 2-phenylethanol derivative 4-methoxyphenethyl alcohol are restricted to a clade in subgenus Scutandrium. Phylogenetic mapping of odours also indicates that the evolution of some odour types is likely to have been influenced by ecological factors. For example, species producing fishy odours dominated by trimethylamine and occurring in N and NE Borneo are not all closely related. Conversely, two sister species, A. mossambicensis and A. abyssinicus, which are morphologically very similar and have overlapping geographical distribution, produce odours which are very different chemically. The pressure of pollinator resource has therefore been a factor influencing the evolution of odours in Amorphophallus, driving both the divergence of odour types in some taxa and the convergence of odour types in others.

Solvent-saturated solid matrix technique for increasing the efficiency of headspace extraction of volatiles

Due to the slow mass transfer rate of substance in solid media, very limited amount of volatiles can be released from the solid matrix to the headspace in the static headspace analysis. Thus, low sensitivity is often the main problem of static headspace analysis of the volatiles contained in a solid sample. Here, we reported on a solvent-saturated solid matrix (SSSM) technique which successfully enhanced the headspace extraction efficiency, and improved the sensitivity of the headspace analysis of the volatiles in solid sample. By adding a small amount of high-boiling-point solvent (e.g. glycerin) onto the solid sample to form a surface-covered solvent layer, the headspace extraction efficiency can be significantly increased by up to 2.5 times higher than that of the conventional one. Based on the experimental investigation of the performance of different amounts of solvent used for the headspace extraction of volatiles in air-dried lotus flower samples, the possible mechanism for the SSSM assisted headspace extraction has been proposed and validated, which showed that a saturation point of solvent existed for a given amount of solid sample, and the maximum extraction efficiency could be obtained at this saturation point. Moreover, positive results were also achieved when applying this new technique in the headspace extraction of the volatiles to the other two solid samples, which means this newly developed technique may open up a new avenue, and also serve as a general strategy for improving the sensitivity of headspace analysis of the volatiles entrapped in solid matrices.

Method Development for Container Closure Integrity Evaluation via Headspace Gas Ingress by Using Frequency Modulation Spectroscopy

USP <1207.1> Section 3.5 states that "A deterministic leak test method having the ability to detect leaks at the product's maximum allowable leakage limit is preferred when establishing the inherent integrity of a container-closure system." Ideally, container closure integrity of parenteral packaging would be evaluated by measuring a physical property that is sensitive to the presence of any package defect that breaches package integrity by increasing its leakage above its maximum allowable leakage limit. The primary goals of the work presented herein were to demonstrate the viability of the nondestructive, deterministic method known as laser-based gas headspace analysis for evaluating container closure integrity and to provide a physical model for predicting leak rates for a variety of container volumes, headspace conditions, and defect sizes. The results demonstrate that laser-based headspace analysis provides sensitive, accurate, and reproducible measurements of the gas ingress into glass vial-stopper package assemblies that are under either diffusive or effusive leak conditions. Two different types of positive controls were examined. First, laser-drilled micro-holes in thin metal disks that were crimped on top of 15R glass vials served as positive controls with a well-characterized defect geometry. For these, a strong correlation was observed between the measured ingress parameter and the size of the defect for both diffusive and effusive conditions. Second, laser-drilled holes in the wall of glass vials served as controls that more closely simulate real-world defects. Due to their complex defect geometries, their diffusive and effusive ingress parameters did not necessarily correlate; this is an important observation that has significant implications for standardizing the characterization of container defects. Regardless, laser-based headspace analysis could readily differentiate positive and negative controls for all leak conditions, and the results provide a guide for method development of container closure integrity tests.LAY ABSTRACT: The new USP 39 <1207>, "Package Integrity Evaluation-Sterile Products", states in section 3.4.1: "tracer gas tests performed using … laser-based gas headspace analysis [have] been shown to be sensitive enough to quantitatively analyze leakage through the smallest leak paths found to pose the smallest chance of liquid leakage or microbial ingress in rigid packaging." In addition, USP <1207> also states that "for such methods, the limit of detection can be mathematically predicted on the basis of gas flow kinetics." Using the above statements as a foundation, this paper presents a theoretical basis for predicting the gas ingress through well-defined defects in product vials sealed under a variety of headspace conditions. These calculated predictions were experimentally validated by comparing them to measurements of changes in the headspace oxygen content or total pressure for several different positive controls using laser-based headspace analysis. The results demonstrated that laser-based headspace analysis can, by readily differentiating between negative controls and positive controls with a range of defect sizes on the micron scale, be used to assess container closure integrity. The work also demontrated that caution must be used when attempting to correlate a leak rate to an idealized defect-size parameter.

A pressure-affected headspace-gas chromatography method for determining calcium carbonate content in paper sample

The present work reports on the development of a pressure-affected based headspace (HS) analytical technique for the determination of calcium carbonate content in paper samples. By the acidification, the carbonate in the sample was converted to CO₂ and released into the headspace of a closed vial and then measured by gas chromatography (GC). When the amount of carbonate in the sample is significant, the pressure created by the CO₂ affects the accuracy of the method. However, the pressure also causes a change in the O₂ signal in the HS-GC measurement, which is a change that can be used as an indirect measure of the carbonate in the sample. The results show that the present method has a good precision (the relative standard deviation<2.32%), and good accuracy (the relative differences compared to a reference method was<5.76%). Coupled with the fact that the method is simple, rapid, and accurate, it is suitable for a variety of applications that call for the analysis of high carbonate content in paper samples.

Headspace Fourier transform infrared spectroscopy for the differentiation of Pandanus species

Headspace Fourier Transform Infrared Spectroscopy (HS-FTIR) in tandem with chemometrics was applied to differentiate several species of the genus Pandanus. The headspace was generated from each Pandanus sample after incubation in a tightly sealed sample chamber. The resulting FTIR spectra of the headspace samples were found to be almost similar, but the application of principal component analysis (PCA) effectively differentiated the species. The unique spectral features for some samples were highlighted in the second-derivative FTIR spectra. A higher variance was exhibited in the PCA bi-plot of the 2nd derivative spectral data. The principal components differentiated not only the species, but also the cultivars or varieties, which formed distinct but proximate clusters. The manner of clustering obtained in this study resembled the behavior reported in a Random Amplified Polymorphic DNA analysis conducted on the Pandanus samples. The results demonstrate the potential of headspace FTIR spectroscopy as a simple, rapid, non-destructive, and relatively inexpensive method to discriminate between plant species and varieties.

Identification, Synthesis, and Field Tests of the Sex Pheromone of Margarodes prieskaensis (Jakubski)

Here, we report the identification and synthesis of the sex pheromone of female Margarodes prieskaensis (Jakubski), and the attractiveness of the synthetic pheromone to males in field trapping tests. Volatile organic compounds were collected from virgin females using a sample enrichment probe (SEP). Analyses by gas chromatography coupled to mass spectrometry revealed the presence of only two constituents. By scaling up the SEP, sufficient of the major constituent was collected for ¹H and ¹³C nuclear magnetic resonance (NMR) analyses and ancillary NMR techniques. The sex attractant was identified as (2R,4R,6R,8R)-2,4,6,8-tetramethylundecan-1-ol. The enantiomerically pure compound was synthesized from octadecyl (2R,4R,6R,8R)-2,4,6,8-tetramethylundecanoate, a minor component of the uropygial (preen) gland secretion of the domestic goose, Anser domesticus. Field trapping experiments, carried out in vineyards in the Northern Cape Province of South Africa, showed that the synthetic compound was as attractive to winged males of M. prieskaensis as virgin females. The second compound detected was identified as the corresponding acetate, but addition of this did not affect the attractiveness of the major component. We believe this to be the first identification of a sex attractant of the Margarodidae.

Accurate determination of fiber water-retaining capability at process conditions by headspace gas chromatography

This work reports on a method for the accurate determination of fiber water-retaining capability at process conditions by headspace gas chromatography (HS-GC) method. The method was based the HS-GC measurement of water vapor on a set closed vials containing in a given amount pulp with different amounts of water addition, from under-saturation to over-saturation. By plotting the equilibrated water vapor signal vs. the amount of water added in pulp, two different trend lines can be observed, in which the transition of the lines corresponds to fiber water-retaining capability. The results showed that the HS-GC method has good measurement precision (much better than the reference method) and good accuracy. The present method can be also used for determining pulp fiber water-retaining capability at the process temperatures in both laboratory research and mill applications.

Composition of the C6+ Fraction of Natural Gas by Multiple Porous Layer Open Tubular Capillaries Maintained at Low Temperatures

As the sources of natural gas become more diverse, the trace constituents of the C₆+ fraction are of increasing interest. Analysis of fuel gas (including natural gas) for compounds with more than 6 carbon atoms (the C₆+ fraction) has historically been complex and expensive. Hence, this is a procedure that is used most often in troubleshooting rather than for day-to-day operations. The C₆+ fraction affects gas quality issues and safety considerations such as anomalies associated with odorization. Recent advances in dynamic headspace vapor collection can be applied to this analysis and provide a faster, less complex alternative for compositional determination of the C₆+ fraction of natural gas. Porous layer open tubular capillaries maintained at low temperatures (PLOT-cryo) form the basis of a dynamic headspace sampling method that was developed at NIST initially for explosives in 2009. This method has been recently advanced by the combining of multiple PLOT capillary traps into one "bundle," or wafer, resulting in a device that allows the rapid trapping of relatively large amounts of analyte. In this study, natural gas analytes were collected by flowing natural gas from the laboratory (gas out of the wall) or a prepared surrogate gas flowing through a chilled wafer. The analytes were then removed from the PLOT-cryo wafer by thermal desorption and subsequent flushing of the wafer with helium. Gas chromatography (GC) with mass spectrometry (MS) was then used to identify the analytes.

Evaluation of Container Closure System Integrity for Frozen Storage Drug Products

Sometimes, drug product for parenteral administration is stored in a frozen state (e.g., -20 °C or -80 °C), particularly during early stages of development of some biotech molecules in order to provide sufficient stability. Shipment of frozen product could potentially be performed in the frozen state, yet possibly at different temperatures, for example, using dry ice (-80 °C). Container closure systems of drug products usually consist of a glass vial, rubber stopper, and an aluminum crimped cap. In the frozen state, the glass transition temperature (Tg) of commonly used rubber stoppers is between -55 and -65 °C. Below their Tg, rubber stoppers are known to lose their elastic properties and become brittle, and thus potentially fail to maintain container closure integrity in the frozen state. Leaks during frozen temperature storage and transportation are likely to be transient, yet, can possibly risk container closure integrity and lead to microbial contamination. After thawing, the rubber stopper is supposed to re-seal the container closure system. Given the transient nature of the possible impact on container closure integrity in the frozen state, typical container closure integrity testing methods (used at room temperature conditions) are unable to evaluate and thus confirm container closure integrity in the frozen state. Here we present the development of a novel method (thermal physical container closure integrity) for direct assessment of container closure integrity by a physical method (physical container closure integrity) at frozen conditions, using a modified He leakage test. In this study, different container closure systems were evaluated with regard to physical container closure integrity in the frozen state to assess the suitability of vial/stopper combinations and were compared to a gas headspace method. In summary, the thermal physical container closure integrity He leakage method was more sensitive in detecting physical container closure integrity impact than gas headspace and aided identification of an unsuitable container closure system.

LAY ABSTRACT

Sometimes, drug product for parenteral administration is stored in a frozen state (e.g., -20 °C or -80 °C), particularly during early stages of development of some biotech molecules in order to provide sufficient stability. Container closure systems for drug products usually consist of a glass vial, rubber stopper, and an aluminum crimped cap. In the frozen state, the glass transition temperature (Tg) of commonly used rubber stoppers is between -55 and -65 °C. Leaks during frozen temperature storage and transportation are likely to be transient, yet they can possibly risk container closure integrity and lead to microbial contamination and sterility breach. After thawing, the rubber stopper is expected to re-seal the container closure system. Given the transient nature of the possible impact on container closure integrity in the frozen state, typical container closure integrity testing methods (used at room temperature conditions) are unable to evaluate and thus confirm container closure integrity in the frozen state. Here we present the development of a novel method (thermal container closure integrity) for direct measurement of container closure integrity by a physical method (physical container closure integrity) at frozen conditions, using a modified He leakage test. In this study, we found that the thermal container closure integrity He leakage method was more sensitive in detecting physical container closure integrity impact than gas headspace and aided identification of an unsuitable container closure system.

Determination of the solubility of low volatility liquid organic compounds in water using volatile-tracer assisted headspace gas chromatography

This study reports a new headspace gas chromatographic method (HS-GC) for the determination of water solubility of low volatility liquid organic compounds (LVLOs). The HS-GC analysis was performed on a set of aqueous solutions containing a range of concentrations of toluene-spiked (as a tracer) LVLOs, from under-saturation to over-saturation. A plot of the toluene tracer GC signal vs. the concentration of the LVLO results in two lines of different slopes that intersect at the concentration corresponding to the compound's solubility in water. The results showed that the HS-GC method has good precision (RSD <6.3%) and good accuracy, in which the relative deference between the data measured by the HS-GC method and the reference method were within 6.0%. The HS-GC method is simple and particularly suitable for measuring the solubility of LVLOs at elevated temperatures. This approach should be of special interest to those concerned about the impact of the presence of low-volatility organic liquids in waters of environmental and biological systems.

The Application of Noninvasive Headspace Analysis to Media Fill Inspection

The results of a proof-of-principle study demonstrating a new analytical technique for detecting microbial growth directly in pharmaceutical containers are described. This analytical technique, laser-based headspace analysis, uses tunable diode laser absorption spectroscopy to nondestructively determine gas concentrations in the headspace of a media-filled pharmaceutical container. For detecting microbial growth, the levels of headspace oxygen and carbon dioxide are measured. Once aerobic microorganisms begin to divide after the lag phase and enter the exponential growth phase, there will be significant consumption of oxygen and concomitant production of carbon dioxide in the sealed container. Laser-based headspace analysis can accurately measure these changes in the headspace gas composition. The carbon dioxide and oxygen measurement data for the representative microorganisms Staphylococcus aureus, Bacillus subtilis, Candida albicans, and Aspergillus brasiliensis were modeled using the Baranyi-Roberts equation. The mathematical modeling allowed quantitative comparisons to be made between the data from the different microorganisms as well as to the known growth curves based on microbial count. Because laser-based headspace analysis is noninvasive and can be automated to analyze the headspace of pharmaceutical containers at inspection speeds of several hundred containers per minute on-line, some potential new applications are enabled. These include replacing the current manual human visual inspection with an automated analytical inspection machine to determine microbial contamination of media fill and pharmaceutical drug product vials.

LAY ABSTRACT

A novel analytical technique has been demonstrated for detecting microbial growth in media-filled pharmaceutical containers. This analytical technique, laser-based headspace analysis, uses tunable diode laser absorption spectroscopy to determine gas concentrations in the headspace of a pharmaceutical container. For detecting microbial growth, the levels of headspace oxygen and carbon dioxide are measured. The study shows that once aerobic microorganisms begin to grow after the lag phase and enter the exponential growth phase there will be a significant consumption of oxygen in the sealed container as well as a corresponding production of carbon dioxide. Headspace analysis can accurately measure and monitor these changes in the headspace gas composition and could therefore be used to detect contaminated pharmaceutical containers. Because the technique can be automated to analyze hundreds of containers a minute on-line, there are opportunities for implementing a headspace inspection machine to perform automated inspection of media fills used to validate aseptic filling operations.

Field portable low temperature porous layer open tubular cryoadsorption headspace sampling and analysis part II: Applications

This paper details the sampling methods used with the field portable porous layer open tubular cryoadsorption (PLOT-cryo) approach, described in Part I of this two-part series, applied to several analytes of interest. We conducted tests with coumarin and 2,4,6-trinitrotoluene (two solutes that were used in initial development of PLOT-cryo technology), naphthalene, aviation turbine kerosene, and diesel fuel, on a variety of matrices and test beds. We demonstrated that these analytes can be easily detected and reliably identified using the portable unit for analyte collection. By leveraging efficiency-boosting temperature control and the high flow rate multiple capillary wafer, very short collection times (as low as 3s) yielded accurate detection. For diesel fuel spiked on glass beads, we determined a method detection limit below 1 ppm. We observed greater variability among separate samples analyzed with the portable unit than previously documented in work using the laboratory-based PLOT-cryo technology. We identify three likely sources that may help explain the additional variation: the use of a compressed air source to generate suction, matrix geometry, and variability in the local vapor concentration around the sampling probe as solute depletion occurs both locally around the probe and in the test bed as a whole. This field-portable adaptation of the PLOT-cryo approach has numerous and diverse potential applications.

Field portable low temperature porous layer open tubular cryoadsorption headspace sampling and analysis part I: Instrumentation

Building on the successful application in the laboratory of PLOT-cryoadsorption as a means of collecting vapor (or headspace) samples for chromatographic analysis, in this paper a field portable apparatus is introduced. This device fits inside of a briefcase (aluminum tool carrier), and can be easily transported by vehicle or by air. The portable apparatus functions entirely on compressed air, making it suitable for use in locations lacking electrical power, and for use in flammable and explosive environments. The apparatus consists of four aspects: a field capable PLOT-capillary platform, the supporting equipment platform, the service interface between the PLOT-capillary and the supporting equipment, and the necessary peripherals. Vapor sampling can be done with either a hand piece (containing the PLOT capillary) or with a custom fabricated standoff module. Both the hand piece and the standoff module can be heated and cooled to facilitate vapor collection and subsequent vapor sample removal. The service interface between the support platform and the sampling units makes use of a unique counter current approach that minimizes loss of cooling and heating due to heat transfer with the surroundings (recuperative thermostatting). Several types of PLOT-capillary elements and sampling probes are described in this report. Applications to a variety of samples relevant to forensic and environmental analysis are discussed in a companion paper.

Scent emission profiles from Darwin's orchid--Angraecum sesquipedale: Investigation of the aldoxime metabolism using clustering analysis

The display of scent is crucial for plants in attracting pollinating insects to flowers and ensuring successful pollination and reproduction. The large number of aldoxime volatile species present in the scent of the Madagascan orchid Angraecum sesquipedale has been suggested to play a primary role in attracting the sphingid moth Xanthopan morgani praedicta. By solid phase micro-extraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), we monitored the scent release from different flowers of a single orchid, day and night throughout the entire flowering period. In separate experiments, the diurnal release was monitored in 3h intervals and the tissue specific release from the different floral parts was tracked. Numerous novel compounds related to the aldoxime metabolism not previously detected in A. sesquipedale were identified and positioned into a proposed pathway for aldoxime metabolism. From the results, we hypothesize that (E/Z)-phenylacetaldoxime and its derivatives could be important attractants for the pollinating moth X. morgani praedicta. By applying an untargeted Partitioning Around Medoids (PAM) cluster analysis to the metabolite profiles in the scent, the proposed pathways for the formation of aldoximes were substantiated. With this study, we demonstrate the powerful utility of a bioinformatics tool to aid in the elucidation of the routes of formation for volatiles and provide a benchmark and guidelines for future detailed observations of hawkmoth pollination of Angraecum species, and in particular A. sesquipedale, in the wild.

A simple method for the accurate determination of the Henry's law constant for highly sorptive, semivolatile organic compounds

A novel technique is developed to determine the Henry's law constants (HLCs) of seven volatile fatty acids (VFAs) with significantly high solubility using a combined application of thermal desorber/gas chromatography/mass spectrometry (TD/GC/MS). In light of the strong sorptive properties of these semi-volatile organic compounds (SVOCs), their HLCs were determined by properly evaluating the fraction lost on the surface of the materials used to induce equilibrium (vial, gas-tight syringe, and sorption tube). To this end, a total of nine repeated experiments were conducted in a closed (static) system at three different gas/liquid volume ratios. The best estimates for HLCs (M/atm) were thus 7,200 (propionic acid), 4,700 (i-butyric acid), 4,400 (n-butyric acid), 2,700 (i-valeric acid), 2,400 (n-valeric acid), 1,000 (hexanoic acid), and 1,500 (heptanoic acid). The differences in the HLC values between this study and previous studies, if assessed in terms of the percent difference, ranged from 9.2% (n-valeric acid) to 55.7% (i-valeric acid). We overcame the main cause of errors encountered in previous studies by performing the proper correction of the sorptive losses of the SVOCs that inevitably took place, particularly on the walls of the equilibration systems (mainly the headspace vial and/or the glass tight syringe).

Effect of extraction and concentration processes on properties of longan syrup

Longan (Dimocarpus longan Lour.) syrup is a novel liquid sweetener produced from longan, one of the traditional and economic fruits in the Northern of Thailand. In this research, the effect of extraction and concentration processes on properties of longan syrup was investigated. There were two extraction methods (juice extractor and hydraulic press) and three concentration methods (direct heating, steam heating and vacuum evaporation). Results overall showed that the extraction method had no significant (p ≥ 0.05) effect on longan syrup properties, while concentration resulted in the quality changes of longan syrup. Concentration using direct heating of longan juice caused reduction of sucrose content, and longan syrup dark in color. The headspace volatile compounds of longan syrup were sampled using direct headspace technique and further characterized using gas chromatography-mass spectrometry. The identified volatile compounds could be divided into two groups of aroma characteristics which were (1) floral aroma: 3-methybutyl acetate, (β)-ocimene and 2-phenylethyl alcohol and (2) caramel aroma: butyraldehyde, furfural and benzaldehyde. 2-Phenylethyl alcohol, contributing to floral odor, was retained using vacuum evaporation as a concentration method. Result revealed that the optimal concentration process for longan syrup production was vacuum evaporation, providing the highest floral volatile and lowest caramel volatile. Sensory tests confirmed that longan flavor of the syrup produced from the vacuum evaporation process had significantly higher hedonic scores than other processes.

Instrumental and sensory characterisation of Solaris white wines in Denmark

This study aimed to investigate the volatile and non-volatile compositions as well as sensory properties of the most common monovarietal white wine (var. Solaris) in Denmark. Using dynamic headspace sampling (DHS) coupled to gas chromatography-mass spectrometry (GC-MS), 79 volatile compounds were identified. Among the major non-volatile components glycerol, sulphite, sugars and organic acids were analysed. A primary sensory difference was observed among wine samples, half of which were characterised by floral and fruity flavours (peach/apricot, Muscat, melon, banana and strawberry) while the remainder were described by less pleasant flavours, such as chemical, wood and rooibos/smoke. Partial least squares regression (PLS) showed that acetates and ethyl esters of straight-chain fatty acids were associated with floral and fruity odours while ethyl esters of branched-chain fatty acids were less associated with them. The study also suggested that differences in vintage were less characteristic than differences caused due to sulphite management by producers.

Analytical strategies based on multiple headspace extraction for the quantitative analysis of aroma components in mushrooms

Headspace (HS) and headspace solid phase microextraction (HS-SPME) analysis by gas chromatography-mass spectrometry (GC/MS) have been found to be suitable methods for the analysis of volatile organic compounds. The objectives of this paper are to study the possibilities of multiple headspace extraction (MHE) for the quantitative determination of volatile compounds in mushroom samples and to compare the results obtained using three different sample treatment techniques. For this purpose, HS with two different injection techniques (pressure-loop system and gas-tight syringe autosampling system) and HS-SPME have been studied. Three processes were optimized for the analysis of 20 volatile compounds by experimental design technique based on Central Composite Design (CCD) and Full Factorial Design depending on the used methodology. Once the designs were finished, a trade off among optimum conditions for each compound analyzed was reached. At optimum conditions, appropriate extraction time and sample amount for the three techniques used were established. Finally, the methods were validated in terms of linearity, detection and quantitation limits and repeatability. The most suitable method was then applied to the quantitative analysis of seven mushroom samples. A detailed comparison of the analytical performance characteristics of HS and HS-SPME as sample treatment techniques for final GC/MS determination is given. In addition, MHE has been proved to be an adequate technique to avoid matrix effects in complex samples quantitation. Its applicability to the determination of volatile mushroom components, along with its limitations, is discussed in this work.