An automated gas chromatographic-mass spectrometric method for the quantitative analysis of the odor-active molecules present in the vapors emanated from wine

Multimethod Approach to Investigate the Factors Influencing High-Temperature Fuming of Bitumen

Bitumen is heated at high temperatures during asphalt paving applications. In these circumstances, there is the possibility for fuming. These fumes can vary in intensity and, if significant, may attract complaints. The bitumen's chemical composition depends on the crude oil from which it originates. A tool to screen bitumen and evaluate its potential to release fumes would be highly beneficial. In this study, three methods have been employed to investigate a series of bitumen samples that were known to produce complaints by (a) quantifying benzene, toluene, ethylbenzene, and m, o, p-xylene (BTEX), (b) measuring the partition coefficients of these analytes, and (c) measuring the volatile mass of bitumen exposed to isothermal heating. It was found that the concentration of BTEX varied significantly between bitumen samples. The partition coefficients of these analytes are substantially the same between samples. Finally, the volatile mass of each sample varies significantly between samples, independent of bitumen grade or country of origin. These volatile masses correlate strongly with fuming complaints from bitumen and can be used as predictors of bitumen fuming risk.

Spoilage markers for freshwater fish: A comprehensive workflow for non-targeted analysis of VOCs using DHS-GC-HRMS

Changes of volatile organic compounds (VOCs) patterns during 6 days of storage at +4 °C were investigated in different freshwater fish species, namely carp and trout, using dynamic headspace gas chromatography time-of-flight mass spectrometry (DHS-GC-TOFMS). DHS parameters were systematically optimized to establish optimum extraction and pre-concentration of VOCs. Moreover, different sample preparation methods were tested: mincing with a manual meat grinder, as well as mincing plus homogenization with a handheld homogenizer both without and with water addition. The addition of water during sample preparation led to pronounced changes of the volatile profiles, depending on the molecular structure and lipophilicity of the analytes, resulting in losses of up to 98 % of more lipophilic compounds (logP > 3). The optimized method was applied to trout and carp. Trout samples of different storage days were compared using univariate (Mann-Whitney U test, fold change calculation) and multivariate (OPLS-DA) statistics. 37 potential spoilage markers were selected; for 11 compounds identity could be confirmed via measurement of authentic standards and 10 compounds were identified by library spectrum match. 22 compounds were also found to be statistically significant spoilage markers in carp. Merging results of the different statistical approaches, the list of 37 compounds could be narrowed down to the 14 most suitable for trout spoilage assessment. This study comprises a systematic evaluation of the capabilities of DHS-GC coupled to high-resolution (HR) MS for studying spoilage in different freshwater fish species, including a comprehensive data evaluation workflow.

Studying dynamic aroma release by headspace-solid phase microextraction-gas chromatography-ion mobility spectrometry (HS-SPME-GC-IMS): method optimization, validation, and application

To understand aroma perception from complex food matrices' determination of dynamic aroma release during simulated oral processing is necessary. In this study optimization, validation and application of a novel method coupling headspace-solid phase microextraction (HS-SPME) with gas chromatography-ion mobility spectrometry (GC-IMS) is presented. Thirteen character impact compounds imparting different chemical properties are studied to understand capabilities and limitations of the method. It was shown for the first time that the temperature of the IMS sample inlet can be increased up to 200 °C without instrumental constraints. Linear calibration was possible for eleven of the thirteen compounds with one decade dynamic range. The limit of detection and quantitation were 2.1-63.0 ppb and 7.2-210.1 ppb, respectively. Diacetyl could be detected in negative polarity mode of IMS, however with lower precision compared to the compounds detected in positive mode. Limitations of the method were short HS-SPME extraction time, which in the case of caproic acid was not sufficient for reliable quantification. Additionally, δ-decalactone could not be detected due to maximum GC temperature of 200 °C. Application of the method to determine dynamic aroma release from a dairy matrix was successfully shown for nine compounds. Analysis of complex food matrix was performed with similar precision compared to analysis in aqueous solution, thus proving high robustness of the method towards matrix effects.

Gas Chromatography Olfactometry (GC-O) for the (Semi)Quantitative Screening of Wine Aroma

This review discusses the different approaches developed by researchers in the last 40 years for the qualitative and semi-quantitative screening of odorants, with special emphasis in wine aroma profiling. In the first part, the aims and possibilities of Gas chromatography-olfactometry (GC-O) as odour-screening and aroma profiling technique are discussed. The critical difference between approaches is whether the ranking of odorants is carried out on an extract containing all the odorants present in the product, or on an extract representative of the odorants contained in the vapour phases that cause the odour and flavour. While the second alternative is more direct and can be more efficient, it requires a good understanding of the factors affecting orthonasal olfaction, handling volatiles (purging, trapping, eluting, and separating) and about the sensory assessment of GC effluents. The review also includes an updated list compiling all the odorants detected in wine by GC-O, including retention indexes and odour descriptions with a general guideline for the identification of odorants.

GC-MS analysis of e-cigarette refill solutions: A comparison of flavoring composition between flavor categories

OBJECTIVES

Electronic cigarette refill solutions (e-liquids) are available in various flavor descriptions that can be categorized as fruit, tobacco, and more. Flavors increase sensory appeal, thereby stimulating e-cigarette use, and flavoring ingredients can contribute to e-cigarette toxicity. We aim to inform toxicologists, sensory scientists, and regulators by determining flavoring compounds in e-liquids with various flavors, and compare results between flavor categories.

METHODS

Gas chromatography - mass spectrometry (GC-MS) was used to identify 79 flavorings in 320 e-liquids, classified in 15 flavor categories. Ten flavorings highly prevalent in e-liquids according to information from manufacturers were quantified. Flavoring prevalence was defined as the number of e-liquids with the flavoring as percentage of the total number of e-liquids. The method was validated in terms of specificity, linearity, repeatability, recovery, and sensitivity.

RESULTS

The mean number of flavorings per e-liquid was 6 ± 4. Flavoring prevalence was highest for vanillin (creamy/vanilla flavor), ethyl butyrate (ethereal/fruity), and cis-3-hexenol (fresh/green). Based on similarities in flavoring prevalence, four clusters of categories were distinguished: (1) fruit, candy, alcohol, beverages; (2) dessert, coffee/tea, nuts, sweets; (3) menthol/mint; and (4) spices, tobacco, and unflavored. Categories from cluster 4 generally had less flavorings per e-liquid than fruit, candy, alcohol, beverages (cluster 1) and dessert (cluster 2) (p < 0.05). Flavoring concentrations varied between e-liquids within the categories.

CONCLUSIONS

We evaluated flavoring compositions of 320 e-liquids using a simple GC-MS method. Flavoring prevalence was similar within four clusters of typically fresh/sweet, warm/sweet, fresh/cooling, and non-sweet flavor categories. To compare flavoring concentrations between individual flavor categories, additional research is needed.

Static Headspace Analysis Using Low-Pressure Gas Chromatography and Mass Spectrometry, Application to Determining Multiple Partition Coefficients: A Practical Tool for Understanding Red Wine Fruity Volatile Perception and the Sensory Impact of Higher Alcohols

To evaluate the partition coefficients of volatiles between the liquid and gas phases, an analytical method was developed and optimized using static headspace analysis and low-pressure injection gas chromatography coupled to mass spectrometry (SHS-LP-GC/MS). Two different types of analytical columns were coupled for low-pressure chromatography injection: a narrow restriction microbore column on the inlet side and a mega-bore column on the mass spectrometer side. Coupling these two columns and static headspace analysis to gas chromatography and mass spectrometry resulted in a simple, fast, sensitive, and accurate approach. Several points have been optimized: time to reach the thermodynamic equilibrium in the gas phase, syringe filling rate, gas injection rate, and volume ratio between the gas and liquid phases. This new method was used to determine partition coefficients between the liquid and gas phases and study multicomponent mixtures for which particular perceptive interactions had previously been highlighted. The partition coefficients of 9 esters and 5 higher alcohols were determined in dilute alcohol solution (12% v/v) and dearomatized red wine. These partition coefficients revealed modifications in ester headspace release in the presence of higher alcohols for the first time in this type of matrix. The correlation of these results with sensory data highlighted the role of physicochemical, presensory effects on sensory modifications for the first time, suggesting that this type of interaction may partly modulate qualitative and quantitative fruity perception.