Comparison of data processing strategies using commercial vs. open-source software in GC-Orbitrap-HRMS untargeted metabolomics analysis for food authentication: thyme geographical differentiation and marker identification as a case study.

Untargeted analysis of gas chromatography-high-resolution mass spectrometry (GC-HRMS) data is a key and time-consuming challenge for identifying metabolite markers in food authentication applications. Few studies have been performed to evaluate the capability of untargeted data processing tools for feature extraction, metabolite annotation, and marker selection from untargeted GC-HRMS data since most of them are focused on liquid chromatography (LC) analysis. In this framework, this study provides a comprehensive evaluation of data analysis tools for GC-Orbitrap-HRMS plant metabolomics data, including the open-source MS-DIAL software and commercial Compound Discoverer™ software (designed for Orbitrap data processing), applied for the geographical discrimination and search for thyme markers (Spanish vs. Polish differentiation) as the case study. Both approaches showed that the feature detection process is highly affected by unknown metabolites (Levels 4-5 of identification confidence), background signals, and duplicate features that must be carefully assessed before further multivariate data analysis for reliable putative identification of markers. As a result, Compound Discoverer™ and MS-DIAL putatively annotated 52 and 115 compounds at Level 2, respectively. Further multivariate data analysis allowed the identification of differential compounds, showing that the putative identification of markers, especially in challenging untargeted analysis, heavily depends on the data processing parameters, including available databases used during compound annotation. Overall, this method comparison pointed out both approaches as good options for untargeted analysis of GC-Orbitrap-HRMS data, and it is presented as a useful guide for users to implement these data processing approaches in food authenticity applications depending on their availability.

Degradation of limonene and trans-cinnamaldehyde in soil, and detection of their metabolites by UHPLC and GC-HRMS.

Two commercial biopesticides were studied to determine their persistence in two soil types, such as sandy clay loam and clay loam soils. For this purpose, an orange oil-based biopesticide was used, being limonene its main ingredient. The other biopesticide was based on cinnamon extract and trans-cinnamaldehyde as its main component. Degradation of these compounds was monitored, and transformation products or metabolites were detected. Limonene and its metabolites were analyzed by gas chromatography (GC) and trans-cinnamaldehyde by ultra-high-performance liquid chromatography (UHPLC). Both techniques were coupled to a high-resolution mass (HRMS) analyzer, such as quadrupole (Q)-Orbitrap. Limonene and trans-cinnamaldehyde were rapidly degraded as result of first-order kinetics. Possible metabolites such as thymol, cymene, isoterpinolene and cymenene for limonene, and hydroxycinnamic acid for trans-cinnamaldehyde were tentatively identified. Moreover, four other metabolites of trans-cinnamaldehyde, some of them not previously described, were also detected.

Tracing the dissipation of difenoconazole, its metabolites and co-formulants in tomato: A comprehensive analysis by chromatography coupled to high resolution mass spectrometry in laboratory and greenhouse trials.

The study evaluated Ceremonia 25 EC®, a plant protection product (PPP) containing difenoconazole, in tomato crops, to identify potential risks associated with PPPs, and in addition to this compound, known metabolites from difenoconazole degradation and co-formulants present in the PPP were monitored. An ultra high performance liquid chromatography coupled to quadrupole-Orbitrap mass analyser (UHPLC-Q-Orbitrap-MS) method was validated with a working range of 2 µg/kg (limit of quantification, LOQ) to 200 µg/kg. Difenoconazole degradation followed a biphasic double first-order in parallel (DFOP) kinetic model in laboratory and greenhouse trials, with high accuracy (R2 > 0.9965). CGA-205374, difenoconazole-alcohol, and hydroxy-difenoconazole metabolites were tentatively identified and semi-quantified in laboratory trials by UHPLC-Q-Orbitrap-MS from day 2 to day 30. No metabolites were found in greenhouse trials. Additionally, 13 volatile co-formulants were tentatively identified by gas chromatography (GC) coupled to Q-Orbitrap-MS, detectable up to the 7th day after PPP application. This study provides a comprehensive understanding of difenoconazole dissipation in tomatoes, identification of metabolites, and detection of co-formulants associated with the applied PPP.

Degradation study of the trans-cinnamaldehyde and limonene biopesticides and their metabolites in cucumber by GC and UHPLC-HRMS: Laboratory and greenhouse studies.

Degradation of trans-cinnamaldehyde and limonene in cucumber was evaluated under laboratory and greenhouse conditions. Two commercial biopesticides, one based on cinnamon extract and other from orange oil, were utilized. Compound degradation was monitored using gas chromatography (GC) and ultra-high-performance liquid chromatography (UHPLC) coupled to a quadrupole-high-resolution mass analyzer (Q-Orbitrap). In both studies, trans-cinnamaldehyde followed a second-order degradation kinetics, whereas limonene followed a first-order kinetics. The half-life values (DT50 or t1/2) for trans-cinnamaldehyde ranged from 2.02 to 2.49 h, while for limonene this value ranged from 0.49 to 6.17 h. Non-targeted analysis (suspect and unknown modes) allowed for the detection of trans-cinnamaldehyde and limonene metabolites. Benzyl alcohol, cinnamyl alcohol, cinnamic acid, p-tolylacetic acid and 4-hydoxycinnamic acid were tentatively identified as trans-cinnamaldehyde metabolites. While three limonene metabolites, carvone, limonene-1,2-epoxide, and perillyl alcohol, were tentatively identified. Greenhouse studies have not revealed any metabolites of these compounds because the parent compounds degrade more quickly.

Development of novel methods based on GC-HRMS and LC-HRMS for the determination of non-phthalate plasticizers in soil.

Non-phthalate plasticizers (NPPs) are a suitable alternative to phthalates, which are harmful compounds for human, animal health, and the environment. In this study, 28 commercial non-phthalate plasticizers (NPPs) from different families, including adipates, citrates, phosphates, sebacates, trimellitates, benzoates and cyclohexanoates, were determined. Two novel methods for determining these alternative compounds in soil were developed using gas chromatography coupled to high-resolution mass spectrometry (GC-HRMS-Q-Orbitrap) and liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS-Q-Orbitrap). Solid-liquid extraction (SLE) with ethyl acetate or acetonitrile, along with water as extraction solvents, were employed. In most cases, the GC method exhibited recoveries ranging from 84.9 % to 110.8 % at 20, 40 and 200 µg/kg, while the LC method achieved recoveries between 73.1 % and 115.4 % at 10, 20, 40 and 200 µg/kg. Most of the relative standard deviation (RSD) values were below 20 % for both methods. The validated methods were then applied to analyse soil samples collected from four different areas in Almeria. The results indicated that the compounds detected most frequently at high concentrations were 1-hydroxycyclohexyl phenyl ketone (HCPK) using GC, in the range 29.1-67.4 µg/kg and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) using LC, in the range 39.9-51.5 µg/kg. Additionally, suspect and unknown analysis were carried out, and other plasticizers as phthalates, were also detected, in addition to other substances present in the analysed samples. All the soils exhibited the presence of a few plasticizers, either phthalic and/or non-phthalic.

Unveiling Coformulants in Plant Protection Products by LC-HRMS Using a Polyhydroxy Methacrylate Stationary Phase.

A polyhydroxy methacrylate-based stationary reversed phase was used for the determination of coformulants in 20 plant protection products (PPPs). These samples were analyzed by liquid chromatography coupled to Q-Orbitrap high-resolution mass spectrometry (LC-Q-Orbitrap-HRMS) in full-scan MS and data-dependent acquisition (ddMS2) modes. A total of 92 coformulants were tentatively identified in these formulations by nontargeted and unknown analyses. Twelve out of them were quantified by analytical standards. The most concentrated coformulant was the anionic surfactant dodecylbenzenesulfonic acid, whose highest content was obtained in the Score 25 sample (6.87%, w/v). Furthermore, triethylene glycol monomethyl ether, 4-s-butyl-2,6-di-tert-butylphenol, 1-ethyl-2-pyrrolidone, sorbitan monostearate, 2,6-dimethylaniline, palmitamide, and N-lauryldiethanolamine were quantified for the first time in these products. Hence, the polyhydroxy methacrylate-based stationary phase increased the identification of new coformulants in PPPs, being complementary to conventional C18. This strategy could be applied in future studies to estimate potential coformulant residues from PPPs applied to crops.

Monitoring of Volatile Additives from Plant Protection Products in Tomatoes Using HS-SPME-GC-HRMS: Targeted and Suspect Approaches.

Additives present in plant protection products (PPPs) are normally not monitored after sample treatments. In this study, the fate of additives detected by targeted and nontargeted analysis in tomato samples treated with two PPPs was carried out. The study was carried out in a greenhouse for 12 days, in which two applications with each PPP were made. Compounds were extracted by applying a headspace solid phase microextraction (HS-SPME) and analyzed by gas chromatography coupled to high resolution mass spectrometry (GC-HRMS), performing targeted and suspect approaches. Three targeted and 15 nontargeted compounds were identified at concentration levels of up to 150 µg/kg. Compounds detected encompassed benzene, toluene, indene, and naphthalene derivatives, as well as conservatives and flavouring compounds. Most of them degraded in less than 7 days after the second application, following first-order kinetic. This study aims to reduce knowledge gaps regarding additives and their fate under real climatic conditions of greenhouses cultivations.

Critical evaluation of MS acquisition conditions and identification process in LC-Q-Orbitrap-MS for non-targeted analysis: pesticide residues as case of study.

In routine measurements, the length of analysis time and the number of samples analysed during a given time unit are crucial. Additionally, the analytical method used has to provide reliable results and be able to identify and quantify any compound present in the matrix. High-resolution equipment, including Orbitrap analysers, is commonly used for non-targeted determinations. However, researchers still rely on trial and error to achieve the best acquisition conditions on the mass spectrometer, which is a tedious and time-consuming process that can lead to errors. Moreover, tentative compound identification, particularly when using a non-targeted approach, heavily depends on commercial databases. All of these issues can ultimately result in incomplete identification of compounds in the study matrix. In this framework, the study presented here has a dual objective: to use the experimental design tool to optimise critical parameters in mass spectrometry using LC-Q-Orbitrap-MS equipment when working in a non-targeted approach and to compare the mzCloud™ and ChemSpider™ commercial databases included in Compound Discoverer software with TraceFinder home-made databases generated to evaluate the ability to identify compounds. The study's noteworthy findings reveal that employing an experimental design has facilitated rapid optimisation of the mass spectrometer's multiplexing and loop parameters. Furthermore, the study highlights that the lack of harmonisation in commercial databases poses a disadvantage in the identification of compounds, leading to superior results when using home-made databases. In the latter databases, around 80% of the compounds were identified, which is approximately twice the number identified in commercial databases (around 40% in the best case with ChemSpider™).

Uncovering the Dissipation of Chlorantraniliprole in Tomatoes: Identifying Transformation Products (TPs) and Coformulants in Greenhouse and Laboratory Studies by UHPLC-Q-Orbitrap-MS and GC-Q-Orbitrap-MS.

The present study addressed the dissipation of the insecticide chlorantraniliprole in tomatoes treated with Altacor 35 WG under laboratory and greenhouse conditions, as well as the identification of transformation products (TPs) and coformulants, performing suspect screening analysis. Analyses were performed by ultra-high-performance liquid and gas chromatography coupled to quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-MS and GC-Q-Orbitrap-MS). In all cases, chlorantraniliprole was fitted to a biphasic kinetic model, with R2 values greater than 0.99. Dissipation was noticeably faster in greenhouse studies, in which even 96% dissipation was achieved over 53 days. One TP, IN-F6L99, was tentatively identified in both greenhouse and laboratory studies and was semiquantified by using chlorantraniliprole as the analytical standard, yielding a top value of 354 µg/kg for laboratory studies, whereas values for greenhouse studies fell under the limit of quantitation (LOQ). Finally, a total of 15 volatile coformulants were identified by GC-Q-Orbitrap-MS.

Dissipation of penconazole formulation in horticultural crops by ultrahigh performance liquid chromatography-high resolution mass spectrometry: From the active substance to metabolites.

The present study describes the dissipation and metabolism of penconazole in horticultural products by a method based on ultra-high performance liquid chromatography-quadrupole-orbitrap (UHPLC-Q-Orbitrap). Targeted and suspected analysis were carried out. Two independent trials were performed under laboratory conditions (on courgette samples), and under greenhouse conditions (on tomatoes) during 43 and 55 days, respectively. In both studies, a pesticide formulation (TOPAS® EW) containing penconazole was used. The results showed that penconazole was relatively short-lived (<30 days) in horticultural products. The proposed method allowed for the tentative identification and semi-quantification of nine metabolites. In addition, the potential toxicity of these metabolites was evaluated, observing that some of them are even more toxic than penconazole, as triazole lactic acid. This research may provide a starting point for understanding the dissipation process of penconazole, the formation pathways of its main metabolites, their concentrations and toxicity to ensure food safety and the environmental protection.

Untargeted 1H NMR-based metabolomics and multi-technique data fusion: A promising combined approach for geographical and processing authentication of thyme by multivariate statistical analysis.

Thyme is a culinary herb highly susceptible to increasing mislabeling occurring in the spice industry. In this study, proton nuclear magnetic resonance spectroscopy (1H NMR) combined with multivariate statistics was successfully applied with two authenticity purposes: (1) tracing thyme metabolic differences among three relevant geographical regions (Morocco, Spain, and Poland), and (2) assessing the influence of sterilization processing on the metabolic fingerprint. Multivariate data analysis provided six and seven key geographical and processing markers, respectively, including thymol, organic acids, chlorogenic acid, and some carbohydrates (e.g., sucrose). Additionally, for the first time, a mid-level data fusion approach was tested for thyme authenticity combining three complementary and synergic analytical platforms: gas and liquid chromatography coupled with high-resolution mass spectrometry, and 1H NMR spectroscopy, providing a comprehensive metabolomics insight into the origin and processing effects on thyme fingerprinting, and opening the path to new metabolomics approaches for quality control in the spice industry.

Comprehensive Dissipation of Azadirachtin in Grapes and Tomatoes: The Effect of Bacillus thuringiensis and Tentative Identification of Unknown Metabolites.

Neem oil is a biopesticide normally applied together with Bacillus thuringiensis (Bt). However, neither its dissipation nor the influence of Bt has been previously evaluated. In this study, dissipation of neem oil was investigated when it was applied alone or together with Bt at 3 and 22 °C. A methodology involving solid-liquid extraction and liquid chromatography-high-resolution mass spectrometry was developed for that purpose. The method was validated obtaining recoveries from 87 to 103%, with relative standard deviations lower than 19% and limits of quantification from 5 to 10 µg/kg. Azadirachtin A (AzA) dissipation was fit to a single first order, being faster when neem oil was applied together with Bt and at 22 °C (RL50 = 12-21 days) than alone and at 3 °C (RL50 = 14-25 days). Eight related compounds were found in real samples with similar dissipation curves compared to AzA, and five unknown metabolites were identified in degraded samples, with increasing concentrations during parent compound degradation.

Unified Method for Target and Non-Target Monitoring of Pesticide Residues in Fruits and Fruit Juices by Gas Chromatography-High Resolution Mass Spectrometry.

A new polyvalent wide-scope analytical method, valid for both raw and processed (juices) fruits, combining target and non-target strategies, has been developed and validated to determine low concentrations of 260 pesticides, as well as many potential non-target substances and metabolites. The target approach has been validated according to SANTE Guide requirements. Trueness, precision, linearity, and robustness values were validated in raw fruit (apple) and juice (apple juice) as representative solid and liquid food commodities. Recoveries were between 70-120% and two ranges of linearity were observed: 0.5-20 µg kg-1 (0.5-20 µg L-1 apple juice) and 20-100 µg kg-1 (20-100 µg L-1 apple juice). The limits of quantification (LOQs) reached were lower than 0.2 µg kg-1 in apple (0.2 µg L-1 apple juice) in most cases. The developed method, based on QuEChERS extraction followed by gas chromatography-high resolution mass spectrometry (GC-HRMS), achieves part-per-trillions lower limits, which allowed the detection of 18 pesticides in commercial samples. The non-target approach is based on a retrospective analysis of suspect compounds, which has been optimized to detect up to 25 additional compounds, increasing the scope of the method. This made it possible to confirm the presence of two pesticide metabolites which were not considered in the target screening, phtamlimide and tetrahydrophthalimide.

Grain Germination Changes the Profile of Phenolic Compounds and Benzoxazinoids in Wheat: A Study on Hard and Soft Cultivars.

Pre-harvest sprouting is a frequent problem for wheat culture that can be simulated by laboratory-based germination. Despite reducing baking properties, wheat sprouting has been shown to increase the bioavailability of some nutrients. It was investigated whether wheat cultivars bearing distinct grain texture characteristics (BRS Guaraim, soft vs. BRS Marcante, hard texture) would have different behavior in terms of the changes in phytochemical compounds during germination. Using LC-Q-TOF-MS, higher contents of benzoxazinoids and flavonoids were found in the hard cultivar than in the soft one. Free phytochemicals, mainly benzoxazinoids, increased during germination in both cultivars. Before germination, soft and hard cultivars had a similar profile of matrix-bound phytochemicals, but during germination, these compounds have been shown to decrease only in the hard-texture cultivar, due to decreased levels of phenolic acids (trans-ferulic acid) and flavonoids (apigenin) that were bound to the cell wall through ester-type bonds. These findings confirm the hypothesis that hard and soft wheat cultivars have distinct behavior during germination concerning the changes in phytochemical compounds, namely the matrix-bound compounds. In addition, germination has been shown to remarkably increase the content of benzoxazinoids and the antioxidant capacity, which could bring a health-beneficial appeal for pre-harvested sprouted grains.

Understanding the Metabolism and Dissipation Kinetics of Flutriafol in Vegetables under Laboratory and Greenhouse Scenarios.

Flutriafol is a systemic triazole fungicide that is used to control diseases in various crops. A study was developed to evaluate the metabolism and dissipation of flutriafol in two different scenarios: laboratory and greenhouse conditions. Courgette and tomato samples treated with a commercial product (IMPACT® EVO) at the manufacturer recommended dose were analyzed, and courgette samples were also treated at double dose. Ultra-high-performance liquid chromatography coupled with Q-Orbitrap mass spectrometry (UHPLC-Q-Orbitrap-MS), performing targeted and non-targeted approaches (suspect screening and unknown analysis), were used to analyze the samples. The dissipation of flutriafol was fitted to a biphasic kinetic model, with a persistence, expressed as half-life (t1/2), lower than 17 days. During suspect screening, three metabolites (triazole alanine, triazole lactic acid and triazole acetic acid) were tentatively identified. Unknown analysis led to the identification of four additional metabolites (C16H14F2N4, C16H14F2N4, C19H17F2N5O2 and C22H23F2N3O6). The results revealed that the proposed methodology is reliable for the determination of flutriafol and its metabolites in courgette and tomato, and seven metabolites could be detected at low concentration levels. The highest concentration of metabolites was found in the laboratory conditions at 34.5 µg/kg (triazole alanine). The toxicity of flutriafol metabolites was also evaluated, and some of them could be more toxic than the parent compound.

Critical Evaluation of Analytical Methods for the Determination of Anthropogenic Organic Contaminants in Edible Oils: An Overview of the Last Five Years.

Anthropogenic contaminants, as pesticides, polycyclic aromatic hydrocarbons (PAHs) and monochloropropanediols (MCPDs), have become important to be controlled in edible oils, since their regular occurrence. In fact, alerts from the Rapid Alert System for Food and Feed (RASFF) in oils normally include these compounds. From a critical point of view, tools used to control these compounds in the last 5 years will be discussed, including sample preparation, analysis and current regulations. Extraction and analysis methods will be discussed next, being liquid-liquid extraction (LLE) and QuEChERS, with or without clean-up step, as well as chromatographic methods coupled to different analyzers (mainly mass spectrometry), the most commonly used for extraction and analysis respectively. Occurrence in samples will also be reviewed and compared with the legal maximum residue limits (MRLs), observing that 4%, 20% and 60% of the analyzed samples exceed the legal limits for pesticides, MCPDs and PAHs respectively.

UHPLC-QTOF-HRMS metabolomics insight on the origin and processing authentication of thyme by comprehensive fingerprinting and chemometrics.

The metabolic composition of thyme, one of the most used aromatic herbs, is influenced by environmental and post-harvest processing factors, presenting the possibility of exploiting thyme fingerprint to assess its authenticity. In this study, a comprehensive UHPLC-QTOF-HRMS fingerprinting approach was applied with a dual objective: (1) tracing thyme from three regions of production (Spain, Morocco, and Poland) and (2) evaluating the metabolic differences in response to processing, considering sterilized thyme samples. Multivariate statistics reveal 37 and 33 key origin and processing differentiation compounds, respectively. The findings highlighted the remarkable "terroir" influence on thyme fingerprint, noticing flavonoids, amino acids, and peptides among the most discriminant chemical classes. Thyme sterilization led to an overall metabolite enrichment, most likely due to the facilitated compound accessibility as a result of processing. The findings provide a comprehensive metabolomics insight into the origin and processing effect on thyme composition for product traceability and quality assessment.

An untargeted strategy based on UHPLC-QTOF-HRMS metabolomics to identify markers revealing the terroir and processing effect on thyme phenolic profiling.

Thyme is one of Europe's most consumed aromatic herbs and represents a matrix susceptible to intentional mislabelling and food frauds. In this study, a phenolic profiling approach based on UHPLC-QTOF-HRMS untargeted metabolomics was used to trace its geographical origin, as well as to assess the effect of post-harvest processing by comparing sterilized vs non-sterilized thyme. Both unsupervised and supervised statistics led to reliable sample clustering, high-quality model parameters, as well as the identification of a total of 45 differential compounds (markers) for discrimination purposes. The phenolic signature was markedly affected by environmental conditions related to the region of production, leading to an overall higher abundance of flavonoids in Moroccan thyme (from Fez), flavanols in Polish one (from Lublin), and tyrosols and other phenolics in thyme cultivated in Spain (from Castilla-La Mancha). The processing was also shown to play an important role in phenolic profiling, noticing not only the decrease of thermolabile phenolics (such as flavonoids) but also the enhancement of other phenolic subfamilies in response to sterilization. This study opens the path to novel metabolomics-based strategies to support the integrity of thyme and possibly other spices, scarcely studied so far.

Non-targeted analysis of co-formulants in antifungal pesticide formulations by gas chromatography-tandem high resolution mass spectrometry.

In the present study, six commercial pesticide formulations with antifungal activity were characterized. Thus, two complementary injection methods based on gas chromatography were employed: direct injection (DI) and headspace (HS), both coupled to high resolution mass spectrometry (GC-Q-Orbitrap-MS). The combination of both injection modes allowed the tentatively identification of potential co-formulants. Available analytical standards were acquired for their confirmation, and 21 compounds were successfully confirmed. Finally, the concentration of these co-formulants was calculated, finding the highest value in one of the pesticide formulation, at 218.22 g L-1 for cyclohexanone. Results clearly show that this methodology is suitable for the reliable identification of co-formulants in pesticide formulations, offering high sensitivity, and highlighting that five co-formulants were detected by both injection techniques (DI and HS). Moreover, one of the main advantages of the proposed methods was the great capacity for the elucidation of compounds with similar molecular formula, bearing in mind that up to 8 co-formulants with the same molecular formula C10H14, were well differentiated by retention times between 8.46 (1-methyl-3-propylbenzene) and 10.98 min (1,2,3,4- tetramethylbenzene) in one of the pesticide formulation. Toxicity to human health and the environment has been evidenced for the co-formulants detected, finding compounds with relatively high toxicity, as naphthalene and cyclohexanone.

Fingerprinting based on gas chromatography-Orbitrap high-resolution mass spectrometry and chemometrics to reveal geographical origin, processing, and volatile markers for thyme authentication.

Thyme is an aromatic herb traditionally used for food purposes due to its organoleptic characteristics and medicinal properties, which is highly susceptible to food fraud. In this study, GC-HRMS-based fingerprinting was applied for the first time to determine the geographical traceability of thyme based on different origins (Spain, Poland, and Morocco), as well as to assess its processing by comparing sterilized vs. non-sterilized thyme. Unsupervised chemometric methods (PCA and HCA) revealed a predominant influence of the geographical origin on thyme fingerprints rather than processing effects. Supervised PLS-DA and OPLS-DA were used for discrimination purposes, revealing high predictive ability for further samples (100%), and allowing the identification of differential compounds (markers). A total of 24 markers were putatively identified (13 metabolites were confirmed) belonging to different classes: monoterpenoids, diterpenoids, sesquiterpenoids, alkenylbenzenes, and other miscellaneous compounds. This study outlines the potential of combining untargeted analysis by GC-HRMS with chemometrics for thyme authenticity and traceability.