Headspace Solid-phase Microextraction Method Research Articles

Investigation of aroma components obtained by HS-SPME (Headspace-solid phase microextraction) method of wild strawberry (Fragaria vesca L.) and strawberry (Fragaria x ananassa Duch.) fruits

Wild strawberries (Fragaria vesca) are in the category of non-wood forest products due to their unique fragrance, aroma, and natural ability to grow. In this study, aroma components of wild strawberry (Fragaria vesca) and strawberry (Fragaria x ananassa) fruits were determined by Headspace-Solid Phase Micro-Extraction technique combined with Gas chromatography-mass spectrometry (HS-SPME/GC-MS). In addition, it aimed to compare the results of both fruits with each other by chemical classification of the aroma components determined from wild strawberry and strawberry fruits. As a result of the HS-SPME/GC-MS analysis; 50 and 76 aroma components were determined in wild strawberry and strawberry fruits, respectively. The structure of aroma components was defined as 97.63% of wild strawberries and 98.26% of strawberries. The main components in the aroma compounds are 2-undecanone (10.38%), γ-decalactone (8.81%), and eugenol (7.14%) in wild strawberry fruit; nerolidol (29.44%), γ-decalactone (26.36%) and bisabolol oxide II (4.23%) were found in strawberry fruits. In addition, chemical classes of identified aroma compounds were determined as ester, terpene or terpenoid, fatty acids, aldehyde, and ketone classes in Fragaria vesca and Fragaria x ananassa fruits. When the results are examined, it is seen that strawberry fruits are found to be higher than wild strawberry fruits in terms of percentage of aroma components, number of aroma components, and percentage of dominant components.

Automated Method for the Sensitive Analysis of Volatile Amines in Seawater.

Methylamines are polar, volatile, and organic nitrogen-containing compounds. They are challenging to analyze, limiting our understanding of their occurrence and role within the marine nitrogen cycle. We describe an automated headspace solid-phase microextraction method, coupled with gas chromatography and nitrogen phosphorus detection (HS-SPME-GC-NPD), for analyzing methylamines in seawater. Three SPME conditions were investigated: temperature, equilibration, and extraction. The method was 6-24 times more sensitive to trimethylamine (TMA) than to dimethylamine (DMA) and monomethylamine (MMA). DMA and TMA were detected in small seawater volumes (2.5-10 mL), at volumes 100-400 times that previously reported. Detection limits of 19.1, 6.6, and 4.1 nM (nMol L-1) for MMA, DMA, and TMA, respectively, were measured in 10 mL sample volumes. Sample throughput was 4-6 times greater than previously reported similar methods. According to the Blue Applicability Grade Index (BAGI) metric, the method was considered "practical" and scored 62.5. The method was used to measure methylamines in seawater samples collected from the Southern Ocean. DMA and TMA were detected at concentrations from < LoD-35 nM and < LoD-48 nM, respectively. This study offers a systematic and standardized method for MA analysis in seawater and can significantly advance understanding of their role in marine systems.

A three-dimensional hierarchical porous graphene aerogel as a fiber coating for headspace solid-phase microextraction: Enhancing the enrichment and detection of polychlorinated naphthalenes in fish

In this study, a novel three-dimensional hierarchical porous deep eutectic solvents-modified graphene aerogel (3D DES-GA) was synthesized for use as a solid-phase microextraction (SPME) fiber coating. The SPME fiber was characterized by its fluffy and hierarchical porous structure, uniform thickness, and rapid mass transfer capabilities. This fiber demonstrated a lifetime (≥160 uses) and excellent precision (with relative standard deviations of 2.4–6.6% for single fiber and 6.0–9.8% for fiber-to-fiber repeatability). The SPME fiber also exhibited remarkable extraction performance for polycyclic aromatic hydrocarbons and polychlorinated biphenyls, which are common persistent organic pollutants in environmental samples. When combined with gas chromatography-tandem mass spectrometry, the method allowed for high-efficiency extraction (enrichment factors ranging from 1225 to 4652 folds) and sensitive determination (limit of detection ranging from 0.010 to 0.056 pg g−1) of polychlorinated naphthalenes (PCNs) in complex samples. To validate this method, we applied it to the determination of four PCNs in five types of fish tissues. The results revealed the presence of 1-chloronaphthalene at concentrations of 7.0 ± 2.9–34.8 ± 2.1 pg g−1 and 1,4-dichloronaphthalene at concentrations of 6.0 ± 0.3–10.9 ± 1.4 pg g−1 in three fish species. Compared with reported sample pretreatment methods reported in the literature, this proposed headspace SPME method offers additional advantages, including simplicity of operation and reduced sample and organic solvent consumption.

Volatile Compounds Content and Sensory Profile of Katuk (Sauropus androgynus) Leaves After Household Scale Heating

Katuk (Sauropus androgynus) is an indigenous Indonesian plant, and the leaves are often consumed as fresh or processed vegetables. Despite its potential, there are no reports on the volatile compounds content and sensory profile of Katuk leaves after being processed using household scale heating. Therefore, this study aimed to determine the volatile compounds content and sensory profiles of Katuk leaves after household scale heating (steaming and boiling). The extraction of constituents was carried out using the headspace-solid phase microextraction method, followed by identification with gas chromatography-mass spectroscopy. The sensory profile analysis was performed using the free choice profiling method with untrained panelists. The analysis results showed the presence of 16 volatile compounds derived from 7 groups, including aldehydes (5 compounds), alcohol (3 compounds), other components (3 compounds), ketones (2 compounds), as well as benzene, terpenoids, and esters (1 compound). The dominant compounds found in fresh Katuk leaves were alcohol [(Z)-3-hexene-1-ol]. Meanwhile, aldehydes (benzaldehyde, nonanal, benzeneacetaldehyde, and (E)-2-pentenal) and alcohol (1-Heptanol and Nerolidol) were dominant in the steamed samples, with benzene (naphthalene) being predominantly found in the boiled samples. The sensory profile analysis results showed that fresh Katuk leaves had a grassy and earthy aroma with a grassy flavor, while the boiled samples had a smooth and juicy texture. The dominant attributes found in steamed Katuk leaves included moist, tender, and tasteless. Based on these findings, household scale heating could modify the composition of volatile compounds, thereby affecting the sensory profile. The results obtained were expected to serve as a foundation for the processing of Katuk leaves at both industry and household levels.

Classification of produced water samples using class-oriented chemometrics and comprehensive two-dimensional gas chromatography coupled to mass spectrometry

Produced water (PW) is a type of wastewater that arises during oil and gas production. Due to its potential environmental impact, PW is one of the most closely monitored forms of wastewater in the petroleum industry. The total oil and grease (TOG) content in the water is a crucial parameter for assessing the environmental impact of PW. Traditional methods for analyzing TOG in PW can be time-consuming and may not be compatible with green chemistry principles. In this study, an alternative method for classifying PW samples is proposed using a one-class classifier (OCC) model, which has proven useful for classification problems. To achieve this goal, headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography (GC×GC) were employed to obtain TOG profiles from PW. A series of simulated PW samples containing TOG were generated using a mixture design comprising four petrochemicals at concentrations ranging from 10 mg L-1 to 50 mg L-1. The polydimethylsiloxane (PDMS) fiber showed the most representative extraction of analytes. The optimization of the HS-SPME method was performed using a Doehlert design with two variables, and the final conditions were set at 80 °C and 70 min for extraction temperature and time, respectively. A pixel-based data approach was used to implement data-driven soft independent modeling by class analogy (DD-SIMCA). Although DD-SIMCA is a developing area in GC×GC studies, the proposed model produced outstanding results with a sensitivity of 94.3 %, specificity of 95.0 %, and accuracy of 94.5 %, considering the complex and broad compositional range of the modeled mixtures. These findings demonstrated the effectiveness of the OCC model approach in classifying PW samples according to environmental regulations.

Analysis of the Aroma Volatile Profile of Muscadine Grape Germplasm by Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry

Muscadine grapes (Vitis rotundifolia) are native to the southeastern U.S., where they are valued for their unique flavor and fruity aroma. Despite having a diverse aroma profile, muscadine germplasm is virtually unexplored in terms of its aroma volatile content and composition, which is crucial in determining the value of its products. The aim of this research was to characterize 24 muscadine genotypes with distinct uses and origin for their aroma-related volatile profiles using the headspace solid-phase microextraction method coupled with gas-chromatography mass spectrometry. In total, 63 volatile compounds were detected, and genotypes significantly differed for 43 of the volatile compounds. We also profiled the aroma volatile content and composition of the commercially cultivated muscadine cultivar Carlos at various stages of berry ripeness. Characteristic differences were observed in the composition of the volatile compounds as ripening progressed. This is the first study to have evaluated the aroma volatile composition of a wide variety of muscadine germplasms, including juice and fresh fruit cultivars, as well as the related species Vitis popenoei and its complex hybrids between V. rotundifolia and Vitis vinifera. The results obtained from this study will help identify muscadine genotypes and better design crosses to produce fresh fruit and wine selections with the desired aroma profiles. This knowledge will lead to the development of new muscadine cultivars and significantly contribute to the expansion of muscadine use in the future.

Development and validation of a multiple headspace solid-phase microextraction method for accurate and precise analysis of the aroma of Tawny and White Port wines.

An accurate and precise Multiple Headspace Solid-Phase Microextraction (MHS-SPME) method was developed and validated for quantifying the volatile composition of White and Tawny Port wines. SPME extraction conditions were optimised using a four-factor three-level Box-Behnken design with three blocks and two replications. Optimal extraction conditions were similar for both Port wines. The method showed good linearity (0.001-50mg/L), precision (<5%), and detection limits (<1μg/L), well below the olfactory detection threshold. Recoveries higher than 95% were obtained. Twenty-three aroma compounds were quantified in Tawny and, for the first time, in White Port wines, including five acids, fourteen esters, the most abundant class, and four norisoprenoids, whose levels apparently increased with age. White Port wines had a lower abundance of aroma compounds. Results show that this MHS-SPME method is suitable for analysing volatile composition of White and Tawny Port wines, with reduced costs, manipulation time and eliminating matrix effects.

Exploring Volatile Organic Compounds in Rhizomes and Leaves of Kaempferia parviflora Wall. Ex Baker Using HS-SPME and GC-TOF/MS Combined with Multivariate Analysis.

Volatile organic compounds (VOCs) play an important role in the biological activities of the medicinal Zingiberaceae species. In commercial preparations of VOCs from Kaempferia parviflora rhizomes, its leaves are wasted as by-products. The foliage could be an alternative source to rhizome, but its VOCs composition has not been explored previously. In this study, the VOCs in the leaves and rhizomes of K. parviflora plants grown in a growth room and in the field were analyzed using the headspace solid-phase microextraction (HS-SPME) method coupled with gas chromatography and time-of-flight mass spectrometry (GC-TOF-MS). The results showed a total of 75 and 78 VOCs identified from the leaves and rhizomes, respectively, of plants grown in the growth room. In the field samples, 96 VOCs were detected from the leaves and 98 from the rhizomes. These numbers are higher compared to the previous reports, which can be attributed to the analytical techniques used. It was also observed that monoterpenes were dominant in leaves, whereas sesquiterpenes were more abundant in rhizomes. Principal component analysis (PCA) revealed significantly higher abundance and diversity of VOCs in plants grown in the field than in the growth room. A high level of similarity of identified VOCs between the two tissues was also observed, as they shared 68 and 94 VOCs in the growth room and field samples, respectively. The difference lies in the relative abundance of VOCs, as most of them are abundant in rhizomes. Overall, the current study showed that the leaves of K. parviflora, grown in any growth conditions, can be further utilized as an alternative source of VOCs for rhizomes.

Comparison of Amomum tsaoko crevost et Lemaire from four regions via headspace solid-phase microextraction: Variable optimization and volatile characterization

A novel headspace solid-phase microextraction method combined with gas chromatography–mass spectrometry was developed to extract volatiles from fresh Amomum tsaoko (FAT) from four districts. The single-factor experiment found an optimum extraction fiber (2 cm) coating with 50/30-μm divinylbenzene-carbon-polydimethylsiloxane, and the response surface design experiment determined that optimal extraction was achieved with equilibration and extraction times of 31 and 32 min at 42°C, respectively. Fifty compounds were identified in FATs from four regions, of which the main volatiles, including ( E )-2-octenal, ( E )-2-decenal, 2-isopropylbenzaldehyde, neral, geranial, and eucalyptol, accounted for a large proportion. Additionally, of the 50 compounds, 32 volatiles determined by orthogonal partial least squares-discriminant analysis contributed to the differentiation of FATs from the four distinct regions. Hierarchical clustering analysis revealed that four FATs were divided into three groups based on the volatiles identified. The four FATs had similar odor profiles, but the odor intensity of the Kongdang sample was weaker than that of the other samples. Therefore, this study not only developed a feasible method to extract volatiles from FAT but also established a theoretical basis for differentiating FATs from different regions. • Important variables of HS-SPME were optimized, and maximum extraction efficiency was achieved. • Fifty volatiles were identified in fresh Amomum tsaoko (FATs) from four regions. • OPLS-DA and HCA were used to differentiate FATs for the first time. • Odor profiles of four FATs were clarified.

Determinación de timol y carvacrol en una matriz orgánica de alimento para cerdo utilizando Headspace SPME-GC-MS

In recent years, oregano essential oil has been used as an animal food additive due to its antifungal and antibacterial properties as well as s synthetic antibiotic substitute. It is desirable to develop fast and effective thymol and carvacrol quantification method in a swine feed organic matrix. In this work, a performance comparison between the Soxhlet solvent extraction technique using petroleum ether and ethyl acetate and the head space-solid phase microextraction (HS-SPME) technique is made. A 24 design of experiments is performed for defining HS-SPME parameters: equilibrium temperature of 40 ºC, extraction temperature of 40 ºC, ionic strength of 0.57 M, and extraction time of 40 min. The HS-SPME method is more efficient for extracting thymol and carvacrol extraction from an organic matrix. Limits of detection and quantification values using Soxhlet extraction with ethyl acetate were 3.7 and 12.5 μL-1 for thymol and 1.4 and 4.7 μg L-1 for carvacrol, respectively; while LOD and LOQ for HS-SPME were 0.9 and 3.1 μg L-1 for thymol and 0.6 and 1.9 μg L-1 for carvacrol, respectively. The head space-solid phase microextraction method has the potential for quality control in the industry for active compounds present in oregano’s essential oil as an additive into an organic matrix.

Improved sample storage, preparation and extraction of blueberry aroma volatile organic compounds for gas chromatography

Aroma profiles of blueberries contain a heterogeneous mixture of volatile organic compounds (VOCs), and headspace sampling is the most efficient approach to VOC extraction from berries. Typically, headspace solid-phase microextraction (HS-SPME) has been applied to blueberry VOCs. Though HS-SPME has been the most common choice for headspace sampling, the fiber chemistry introduces selectivity to the extraction: preferential sorption may skew aroma profiles. Dynamic headspace (DHS) is an attractive substitute for HS-SPME, given its improved sensitivity and lessened bias imparted due to extraction phase selectivity. DHS extractions tend to yield a larger number of compounds and require even less sample than HS-SPME. These two extraction techniques were applied to homogenized blueberries and extracts were subjected to analysis by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Major chemical classes were identified with filtering scripts for GC×GC-TOFMS data. The HS-SPME and DHS methods were assessed for reproducibility and chemical diversity (i.e., recovered chemical classes).

Evaluation of three extraction methods for the isolation of PAHs from recycled paperboard materials intended for food contact applications

The present work is part of a comprehensive study aiming to identify and quantify an array of harmful contaminants at very low concentrations in recycled paperboard materials intended for food contact applications. In this initial study, three commonly used extraction techniques were optimized and tested for their efficacy and accuracy in isolating 13 polycyclic aromatic hydrocarbons (PAHs) from three commercially available food packaging materials made from recycled paperboard. The techniques were Soxtec extraction (SE), ultrasound-assisted extraction (UAE), and headspace solid-phase microextraction (HS-SPME), followed by gas chromatography-mass spectrometry (GC/MS) analysis. The recoveries of all three methods were rather satisfactory; 10 out of 13 substances were recovered at rates between 70 and 124% using the SE method, 8 out of 13 substances were recovered at rates between 50 and 134% using the UAE method, and finally, 8 out of 13 substances were recovered at rates between 70 and 105% using the HS-SPME method. Regarding accuracy, the HS-SPME method gave the best results at 125 μg kg−1, as 7 out of 13 concentration values were within acceptable limits, while only five and four concentration values were within limits for the UAE and SE methods, respectively. Furthermore, the results of both the calculated RSD and HorRat values indicated that HS-SPME is more accurate for extracting PAHs than the other two methods.

Characterization of the Key Aroma Compounds of Shandong Matcha Using HS-SPME-GC/MS and SAFE-GC/MS.

Shandong matcha has the quality characteristics of bright green color, seaweed-like aroma and strong, fresh and brisk taste. In order to identify the characteristic aroma components and clarify the contribution of the grinding process to the aroma of Shandong matcha. Three grades of Shandong matcha and corresponding tencha material were firstly tested with sensory evaluation, and the volatile components were extracted with headspace solid-phase microextraction (HS-SPME) and solvent-assisted flavor evaporation (SAFE) and analyzed using GC–MS. The sensory evaluation results showed that high-grade matcha (M-GS) had prominent seaweed-like, fresh and roasted notes, whereas medium and low-grade matcha (M-G1, M-G2) were gradually coupled with grassy, fatty and high-fired aromas. GC–MS results showed that in the HS-SPME method, heterocyclic compounds (45.84–65.35%) were the highest in Shandong matcha, followed by terpenoids (7.44–16.92%) and esters (6.91–15.27%), while in the safe method, esters were the highest (12.96–24.99%), followed by terpenoids (10.76–25.09%) and heterocyclic compounds (12.12–17.07%). As a whole, the composition of volatile components between M-G1 and M-G2 is relatively close, and there are more differences in volatile components between them and M-GS. The volatile components unique to M-GS were screened using the odor activity value (OAV) evaluation method, with components such as 3-methyl-2-butene-1-thiol, 3-ethyl-Phenol, 2-thiophenemethanethiol, 2,4-undecadienal, (E,E)-2,6-nonadienal, (E,Z)- being evaluated. There were other differentially volatile components, that is, volatile components that coexist in the three grades of matcha, but with different concentrations and proportions. M-G1 and M-G2 contained more volatile substances with high-fired aroma, such as 2-ethyl-3-methyl-pyrazine, coumarin and 5,6,7,8-tetrahydroquinoxaline. The grinding process not only changes the appearance of tencha, but also increases the content of volatile components of matcha as a whole, enhancing the aroma and flavor characteristics of matcha. In this study, the contents of 24 volatile components in matcha were mainly increased, such as benzene, (2,2-dimethoxyethyl)-, cis-7-decen-1-al, safranal and fenchyl acetate. The dual factors of material tencha and matcha grinding technology are indispensable in forming the differences in aroma and flavor of Shandong matcha at different levels.

Volatile components analysis of Camellia oleifera shells and related products based on HS-SPME-GC-MS

The headspace-solid phase microextraction method with the off-flavor database was used to establish odor components in Camellia oleifera shells (COS) and the corresponding particleboard (PB). The concentration of the odor components remarkably varied in fresh COS compared with dry shell and particleboard, owing to the reaction of volatile aroma compounds during drying and hot pressing. Relative odor activity value (ROAV) analysis was used to compare the key and characteristic aroma components of different products. There were four key aroma compounds found in fresh COS, which were m-cresol, p-cresol, borneol, and 2,3-xylenol; 16 found in dry COS, including 2-nonenal, n-decanal, geraniol, borneol, etc.; and 13 found in COS PB, including n-decanal, 2-nonenal, vanillin, isoeugenol, etc. Among them, m-cresol, p-cresol, 2-nonenal, n-decanal and 2,3-xylenol may be the main difference in fresh COS with dry COS and COS PB. The spatial distribution region of principal component analysis reflects the variances among samples. During the drying of the COS, the gradual peroxidation or reduction of fatty acids through lipoxygenases affect the content of the aroma substances, which leads to the difference of the compounds among samples. This study helps to realize the utilization of Camellia oleifera shells as a new interior decoration and building material by providing basic information on aroma substances.

New HS-SPME-GC-BID method for the determination of volatile constituents in distilled beverages

To maintain quality control in the production of distilled beverages, it is necessary to perform several types of chromatographic analysis, where gas chromatography (GC) coupled with mass spectrometry (GC/MS) and flame ionization detector (GC-FID) have been used as traditional analysis techniques for volatile organic compounds. More recently the dielectric barrier discharge ionization detector (BID) has been coupled to GC (GC-BID) which is more sensitive than the FID and the thermal conductivity detector (TCD) for analyzing various volatile compounds. This study aims to develop a new method for determining higher alcohols, n-butanol, and ethyl acetate in cachaça and whisky samples using headspace solid-phase microextraction (HS-SPME) followed by GC-BID. The HS-SPME method was optimization with multivariate analysis. The analytical results were provided by the weighted linear Square (WLS) method for linearity correction, internal standard addition (ISA) as a calibration method for matrix effect correction, reproducibility, recovery and accuracy. The best conditions for extraction of the compounds by HS-SPME were obtained for 50 °C, 20 min and without addition of NaCl. The WLS regression allowed to obtaining satisfactory correlation coefficients (0.9632 to 0.9992). The matrix effect (ME) was verified for n-propanol, isobutanol and isoamyl in both matrices. The recovery values of the cachaça matrix ranged from 81.24 to 106.94 %, except for isoamyl alcohol, and ranged from 82.06 to 106.25 % for the whisky matrix, except for n-butane. The precision ranged from 0.66 to 7.38 % and 0.62 to 6.77 % for the cachaça and whisky samples, respectively. Limit of detection (LOD) values ranged from 0.26 to 0.51 mg L-1, while limit of quantification (LOQ) values ranged from 0.78 to 1.55 mg L-1. The validation process and statistical methods were successfully applied to quality assurance of the analysis of cachaça and whiskey samples, where n-propanol, ethyl acetate, isobutanol and isoamyl were detected for all samples within the maximum content for higher alcohols and ethyl acetate, except n-butanol. The method can be satisfactorily applied to quantify higher alcohols and esters in samples of alcoholic beverages.

Looking beyond the Active Substance: Comprehensive Dissipation Study of Myclobutanil-Based Plant Protection Products in Tomatoes and Grapes Using Chromatographic Techniques Coupled to High-Resolution Mass Spectrometry.

A comprehensive evaluation of the dissipation of a myclobutanil plant protection product was performed in tomato and grape samples. Different temperature conditions (3 and 22 °C) were evaluated. A biphasic kinetic model provided a suitable adjustment (R2 > 0.95), with persistence (residual level, RL50) lower than 24 days in all cases. Solid-liquid extraction and ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-Q-Orbitrap-HRMS) were used for metabolites' elucidation, identifying six myclobutanil metabolites, four out of them described for the first time and one of them confirmed using 1H, 13C, (1H-1H)-COSY, (1H-13C)-HMQC, and (1H-13C)-HMBC nuclear magnetic resonance (NMR). Their degradation curves were also evaluated, increasing their concentrations when the myclobutanil concentration decreases. Additionally, coformulants present in the commercial formulation were monitored employing headspace solid-phase microextraction method (HS-SPME)-gas chromatography coupled to HRMS (GC-Q-Orbitrap-HRMS). Seven coformulants were quantified in tomato samples. Their dissipation curves were studied, and it was observed that they were almost degraded 12 days after application.

Headspace solid-phase microextraction method for extracting volatile constituents from the different parts of Saudi Anethum graveolens L. and their antimicrobial activity

Anethum graveolens L. is a famous aromatic herb that is widely used as a spice and has been applied in folk medicine to cure many diseases. The current work was carried out to compare the chemical composition and antimicrobial potency of essential oils obtained from the different parts of Saudi Arabia. graveolens. The oil constituents were extracted by headspace solid-phase microextraction and were quantified and qualitatively identified using GC/MS. As a result, essential oil isolated from A. graveolens seeds exhibited the highest antimicrobial activity compared to oils isolated from other parts, followed by flowers, leaves and stems. All tested A. graveolens essential oil samples exhibited stronger antifungal activities against Aspergillus parasiticus when compared to itraconazole. To the best of our knowledge, the current work is the first report comparing different parts of Saudi A. graveolens plant with respect to their essential oil chemical composition and antimicrobial potentials. The essential oil of A. graveolens seeds have the highest contents of carvone and limonene and show superior antimicrobial activities compared to other parts of the plant.

Optimization and Validation of a Headspace Solid-Phase Microextraction with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometric Detection for Quantification of Trace Aroma Compounds in Chinese Liquor (Baijiu).

The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79–117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R2 > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME–GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices.

Single Wavelengths of LED Light Supplement Promote the Biosynthesis of Major Cyclic Monoterpenes in Japanese Mint.

Environmental light conditions influence the biosynthesis of monoterpenes in the mint plant. Cyclic terpenes, such as menthol, menthone, pulegone, and menthofuran, are major odor components synthesized in mint leaves. However, it is unclear how light for cultivation affects the contents of these compounds. Artificial lighting using light-emitting diodes (LEDs) for plant cultivation has the advantage of preferential wavelength control. Here, we monitored monoterpene contents in hydroponically cultivated Japanese mint leaves under blue, red, or far-red wavelengths of LED light supplements. Volatile cyclic monoterpenes, pulegone, menthone, menthol, and menthofuran were quantified using the head-space solid phase microextraction method. As a result, all light wavelengths promoted the biosynthesis of the compounds. Remarkably, two weeks of blue-light supplement increased all compounds: pulegone (362% increase compared to the control), menthofuran (285%), menthone (223%), and menthol (389%). Red light slightly promoted pulegone (256%), menthofuran (178%), and menthol (197%). Interestingly, the accumulation of menthone (229%) or menthofuran (339%) was observed with far-red light treatment. The quantification of glandular trichomes density revealed that no increase under light supplement was confirmed. Blue light treatment even suppressed the glandular trichome formation. No promotion of photosynthesis was observed by pulse-amplitude-modulation (PAM) fluorometry. The present result indicates that light supplements directly promoted the biosynthetic pathways of cyclic monoterpenes.

Citrus Varieties with Different Tolerance Grades to Tristeza Virus Show Dissimilar Volatile Terpene Profiles

Plants produce considerable amounts of volatile organic compounds (VOCs) with several biological functions, including protection against biotic agents such as viruses and their vectors. In citrus species, these metabolites can be related with their different susceptibility/tolerance toward the Tristeza virus (CTV), one of the main biotic constraints for the citrus industry. The objective of this study was to compare the VOCs pattern from the leaves of a CTV-susceptible citrus variety such as Citrus aurantium and from three CTV-tolerant varieties: Citrus volkameriana, Carrizo citrange, and Forner-Alcaide no. 5. The VOCs emitted were analyzed via the headspace SPME method, while plant metabolites sequestered in the leaves were analyzed by heptane extraction followed by GC-MS. The results indicated that the majority of the VOCs emitted and sequestered in the leaves of the varieties tolerant and susceptible to CTV are constituted mainly by volatile terpenes (VTs) that exhibit strong qualitative/quantitative differences among the profiles of the four citrus species. In detail, the VOC emission indicated different patterns between C. aurantium and C. volkameriana and from both of them in comparison with Forner-Alcaide no. 5 and Carrizo citrange that exhibited more similarities, with the last two characterized by a higher presence of sesquiterpenes. The data obtained from the analysis of the VOCs sequestered in leaf tissues of the CTV-tolerant varieties indicated a higher presence of monoterpenes such as limonene, α-pinene, and p-cymene, known to be the main components of several plant extracts showing deterrent properties toward viruses and insect vectors. As VOC evaluation is a fast and noninvasive measure of phenotypic dynamics, allowing the association of plant phenotypes in accordance to plant disease resistance and/or stress tolerance, the possible implications of such differences in terms of tolerance grade to CTV and/or its related vectors are discussed.