Electrospun of functionalized mesoporous UiO-66 as the selective coating of solid phase microextraction Arrow for the determination of nine alkylphenols.

A solid-phase microextraction (SPME) Arrow and high-performance liquid chromatography-UV detector (HPLC-UV, detection at 225 nm) based method was developed for the selective determination of nine alkylphenols (APs) in milk. The functionalized mesoporous UiO-66 (4-meso-UiO-66) was utilized as the new coating material, which was synthesized by post-modification of pore-expanded UiO-66-NH2 by an esterification reaction with 4-pentylbenzoic acid. It was fully characterized by X-ray photoelectron spectroscopy (XPS), fourier transformation infrared spectrometry, nitrogen sorption-desorption test, scanning electron microscopy, transmission electron microscopy, and X-ray diffractometer. The characterization results showed the ester groups and benzene rings were introduced into the 4-meso-UiO-66, and the mesoporous structure was predominant in the 4-meso-UiO-66. The extraction mechanism of 4-meso-UiO-66 to APs is the synergistic effect of Zr-O electrostatic interaction and the size exclusion effect resulting from XPS, selectivity test, and nitrogen sorption-desorption test. The electrospinning technique was utilized to fabricate the 4-meso-UiO-66 coated SPME Arrow and polyacrylonitrile (PAN) was used as the adhesive. The mass rate of 4-meso-UiO-66 to PAN and the electrospinning time were evaluated. The extraction and desorption parameters were also studied. The linear range of this method was 0.2-1000 µg L-1 with a coefficient of determination greater than 0.9989 under the optimal conditions. The detection limits were 0.05-1 µg L-1, the inter-day and intra-day precision (RSD) were 2.8-11.5%, and the recovery was 83.6%-112%. The reusability study showed that the extraction performance of this new SPME Arrow could be maintained after 80 adsorption-desorption cycles. This method showed excellent applicability for the selective determination of APs in milk.

Oxidative stability differences of aqueous model systems of photoautotrophic n-3 LC-PUFA rich microalgae: The antioxidative role of endogenous carotenoids.

Microalgae rich in omega-3 long-chain polyunsaturated fatty acids (n-3LC-PUFA) have already shown their potential for developing functional food rich in these healthy fatty acids. Not only could they offer a more sustainable alternative for the fish stock that is currently relied upon but is unable to keep up with the demand, enrichment with certain microalgae also leads to oxidatively stable products. Although the reason for this stability has been attributed to the presence of endogenous carotenoids, further insight into their antioxidative role is missing and would be clarifying for selecting the proper microalgae for food enrichment. In trying to further accomplish this, a storage experiment (4 weeks, 37 °C) was set up with the parallel analysis of both oxidation products (primary and secondary) and carotenoids of two aqueous model systems of different (promising) microalgae (Nannochloropsis and Phaeodactylum). The results showed a clear difference in oxidative stability despite both microalgae containing endogenous carotenoids: Nannochloropsis led to oxidatively unstable and Phaeodactylum to oxidatively stable products. This was clearly confirmed by the analysis of n-3LC-PUFA throughout storage which showed a breakdown of half of the n-3LC-PUFA for Nannochloropsis. All carotenoids (violaxanthin, zeaxanthin and ß-carotene for Nannochloropsis, and fucoxanthin and ß-carotene for Phaeodactylum) acted as an antioxidant as shown by their degradation throughout storage, but the difference in oxidative stability pointed out an impact of carotenoid content and (possibly) type. The presence of a sufficient amount of carotenoids seems to be an important factor for perceiving oxidative stability. Phaeodactylum has shown to be more potent for food enrichment.

Isotope-labeling in situ derivatization and HS-SPME arrow GC-MS/MS for simultaneous determination of fatty acids and fatty acid methyl esters in aqueous matrices.

Fatty acids (FAs) and fatty acid methyl esters (FAMEs) co-occur in many samples, and analysis of both substance classes is frequently of high interest. To this end, this study introduces the first method for simultaneous determination of FAs and FAMEs including fully automated solvent-free solid-phase microextraction (SPME) arrow headspace extraction combined with isotope-labeling in situ FA derivatization with deuterated methanol (CD3OD). By using the chromatographic isotope effect (ΔRt = 0.03 min) and the + 3 m/z mass shift, FAs can be selectively differentiated from the FAMEs during gas chromatography tandem-mass spectrometry (GC-MS/MS) operated in the multiple reaction monitoring (MRM) aquisition mode. Additionally, an approach is presented to predict the retention times of deuterated compounds. Optimization of the derivatization conditions was accomplished by design of experiments and found to be 20 min, 50 °C, 4 v/v% CD3OD, and pH 2.1. During method validation, FAs and FAMEs were calibrated in different concentration ranges by standard addition in five real matrices and ultrapure water leading to good linearities and method detection limits for FAs ranging from 1-30 µg L-1 and for FAMEs from 0.003-0.72 µg L-1. FAs and FAMEs were detected in real samples from surface water, wastewater treatment plant effluent, and three different bioreactor samples and could be quantified in concentrations ranging from 2-1056 µg L-1 for FAs and 0.01-14 µg L-1 for FAMEs.

A New Perspective on SPME and SPME Arrow: Formaldehyde Determination by On-Sample Derivatization Coupled with Multiple and Cooling-Assisted Extractions.

Formaldehyde (FA) is a toxic compound and a human carcinogen. Regulating FA-releasing substances in commercial goods is a growing and interesting topic: worldwide production sectors, like food industries, textiles, wood manufacture, and cosmetics, are involved. Thus, there is a need for sensitive, economical, and specific FA monitoring tools. Solid-phase microextraction (SPME), with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA) on-sample derivatization and gas chromatography, is proposed for FA monitoring of real-life samples. This study reports the use of polydimethylsiloxane (PDMS) as a sorbent phase combined with innovative commercial methods, such as multiple SPME (MSPME) and cooling-assisted SPME, for FA determination. Critical steps, such as extraction and sampling, were evaluated in method development. The derivatization was performed at 60 °C for 30 min, followed by 15 min sampling at 10 °C, in three cycles (SPME Arrow) or six cycles (SPME). The sensitivity was satisfactory for the method's purposes (LOD-LOQ at 11-36 ng L-1, and 8-26 ng L-1, for SPME and SPME Arrow, respectively). The method's linearity ranges from the lower LOQ at trace level (ng L-1) to the upper LOQ at 40 mg L-1. The precision range was 5.7-10.2% and 4.8-9.6% and the accuracy was 97.4% and 96.3% for SPME and SPME Arrow, respectively. The cooling MSPME set-up applied to real commercial goods provided results of quality comparable to previously published data.

Natural Appetite Control: Consumer Perception of Food-Based Appetite Regulating Aromas.

According to the WHO, the number of overweight people (BMI ≥ 25) and obese people (BMI ≥ 30) is constantly growing. On the other hand, the number of elderly people (≥60 years old) in 2020 reached 1.4 billion worldwide. Both mentioned groups demonstrate their individual and characteristic appetite disorders. In light of the side effects of appetite stimulating drugs, which interfere with diabetics, hypertension and thrombosis medicines or diet supplements with doubtful effectiveness in reducing appetite, new and natural alternatives are highly demanded. Therefore, the present study focusses on the search for natural food aromas, which may have potential for appetite regulation. A survey was carried out among consumers with excess body weight (BMI ≥ 25) and the elderly (≥60 years old). Food products and meals pointed out by the survey participants were subjected to volatile analysis by HS-SPME Arrow followed by GC-MS. As a result, a group of volatiles and their odor characteristic were determined for appetite stimulation or reduction, which may suggest that the actual composition of food aroma is more significant than the character of the aroma. Those results may be a basis for designing appetite regulating agents, in which the mechanism of action will be based only on olfaction activity.

A comparative study on flavor trapping techniques from the viewpoint of odorants of hot-pressed rapeseed oil.

Rapeseed oil, as one of the three major vegetable oils in the world, its matrix effect makes the decoding flavor a challenge. Solid-phase microextraction (SPME), SPME-Arrow, headspace stir bar sorptive extraction (HSSE), direct thermal desorption (DTD), and solvent-assisted flavor evaporation (SAFE) were compared based on the odorants in hot-pressed rapeseed oil. Besides, methodological validation for 31 aroma standards was conducted to compare reliability and robustness of these approaches. DTD showed the largest proportion of acids, while the other techniques extracted a majority of nitriles. The highest number of odorants was detected by SAFE (31), followed by HSSE (30), SPME-Arrow (30), SPME (24), and DTD (14). SPME-Arrow showed the best performance in linearity, recovery, and reproducibility followed by SPME, HSSE, DTD, and SAFE. Results reveal the advantages and limitations of diverse methodologies and provide valuable insights for the selection of extraction methods in an oil matrix and flavor decoding.

Exploring the Effect of Different Storage Conditions on the Aroma Profile of Bread by Using Arrow-SPME GC-MS and Chemometrics.

In the present feasibility study, SPME Arrow-GC-MS method coupled with chemometric techniques, was used for investigating the impact of two different storage conditions, namely freezing and refrigeration, on volatile organic compounds (VOCs) of different commercial breads. The SPME Arrow technology was used as it is a novel extraction technique, able to address issues arising with traditional SPME fibers. Furthermore, the raw chromatographic signals were analysed by means of a PARAFAC2-based deconvolution and identification system (PARADISe approach). The use of PARADISe approach allowed for an efficient and rapid putative identification of 38 volatile organic compounds, including alcohols, esters, carboxylic acids, ketones, and aldehydes. Additionally, Principal Component Analysis, applied on the areas of the resolved compounds, was used to investigate the effects of storage conditions on the aroma profile of bread. The results revealed that the VOC profile of fresh bread is more similar to the one of bread stored in the fridge. Furthermore, there was a clear loss of aroma intensity in frozen samples, which could be explained by phenomena related to different starch retrogradation that occurs during freezing and refrigeration. However, considering the limited number of investigated samples, this study must be considered as a proof of concept; a more statistically representative sampling and further examinations of other properties, such as bread texture, need to be performed to better understand whether samples destined for eventual analysis should be frozen or refrigerated.

Analysis of Furan and Its Derivatives in Food Matrices Using Solid Phase Extraction Coupled with Gas Chromatography-Tandem Mass Spectrometry.

The objective of this study was to develop a simultaneous analysis method of furan and its 10 derivatives in different food commodities. The results indicated that furan and its 10 derivatives could be separated within 9.5 min by using a HP-5MS column and gas chromatography-tandem mass spectrometry (GC-MS/MS) with multiple reaction monitoring mode for detection. Furthermore, this method could resolve several furan isomers, such as 2-methyl furan and 3-methyl furan, as well as 2,3-dimethyl furan and 2,5-dimethyl furan. The most optimal extraction conditions were: 5 g of the fruit or juice sample mixed with 5 mL of the saturated NaCl solution, separately, or 1 g of the canned oily fish sample mixed with 9 mL of the saturated NaCl solution, followed by the equilibration of each sample at 35 °C for 15 min, using a carboxen-polydimethylsiloxane SPME arrow to adsorb the analytes for 15 min at 35 °C for subsequent analysis by GC-MS/MS. For method validation of all the analytes in the different food matrices, the recovery was 76-117% and the limit of the quantitation was 0.003-0.675 ng/g, while the relative standard deviation (RSD%) of the intra-day variability range from 1-16%, and that of the inter-day variability was from 4-20%. The method validation data further demonstrated that a reliable method was established for the analysis of furan and its 10 derivatives in commercial foods.

Croatian Native Grapevine Varieties' VOCs Responses upon Plasmopara viticola Inoculation.

The Plasmopara viticola pathogen causes one of the most severe grapevine diseases, namely downy mildew. The response to P. viticola involves both visible symptoms and intricate metabolomic alterations, particularly in relation to volatile organic compounds, and depends on the degree of resistance of a particular variety. There are numerous native grapevine varieties in Croatia, and they vary in susceptibility to this oomycete. As previously reported, in vitro leaf disc bioassay and polyphenolic compound analysis are complementary methods that can be used to separate native varieties into various resistance classes. This research used the Solid Phase Microextraction-Arrow Gas Chromatography-Mass Spectrometry method to identify the early alterations in the VOCs in the leaves after P. viticola inoculation. Based on the absolute peak area of sesquiterpenes, some discrepancies between the sampling terms were noticed. The presence of certain chemical compounds such as humulene, ylangene, and α-farnesene helped distinguish the non-inoculated and inoculated samples. Although specific VOC responses to P. viticola infection of native varieties from various resistance classes could not be identified, the response of less susceptible native varieties and resistant controls was associated with an increase in the absolute peak area of several compounds, including geranylacetone, ß-ocimene, and (E)-2-hexen-1-ol.

Antioxidative capacity of microalgal carotenoids for stabilizing n-3LC-PUFA rich oil: Initial quantity is key.

The health-beneficial long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA) are easily affected by the undesired process of lipid oxidation in fish oil, while being stable in the lipid extracts of photoautotrophic microalgae. The current research investigates the role of carotenoids by evaluating the oxidative stability of mixtures of fish oil with total lipid extracts of two different microalgae (Phaeodactylum and Isochrysis) throughout an accelerated storage experiment of 4 weeks at 37 °C. A clear separation between oxidatively stable and oxidatively unstable mixtures was observed for which the initial amount of carotenoids relative to the amount of n-3LC-PUFA was a good indicator. The lipid class composition, clearly differing between the two algae, was probably of minor influence. The antioxidative role of fucoxanthin, and diatoxanthin and ß-carotene as minor carotenoids, was illustrated by their gradual degradation throughout storage. However, when their initial contents were too low, this role could not be exerted leading to thorough lipid oxidation.

Optimization and automation of rapid and selective analysis of fatty acid methyl esters from aqueous samples by headspace SPME arrow extraction followed by GC-MS/MS analysis.

The analysis of fatty acid methyl esters (FAMEs) is of high relevance for monitoring and control of various industrial processes and biological systems. In this study, a novel, green analytical approach for the determination of 24 FAMEs from aqueous samples is proposed, which is based on a headspace solid-phase microextraction (SPME) arrow followed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). The method was substantially accelerated to a run time of 44 min per sample by thorough optimization and automation of the relevant parameters. The limiting parameters, mostly based on expediting equilibrium attainment, were found to be parameters of extraction: material, pH, time, and temperature, which were optimized to divinylbenzene polydimethylsiloxane (DVB-PDMS), pH 2, 20 min, and 70 °C, respectively. The optimization and automation of the method led to low method detection limits (9-437 ng L-1) and high selectivity. Evaluation of the method on real samples was done by analyzing the aqueous phase of a bioreactor, whereby the matrix effect could be greatly reduced due to dilution and headspace sampling. The rapid, sensitive, selective, and matrix-reduced approach is found to be not only a novel method for water analysis but is promising for further applications, e.g., with solid and gaseous samples containing FAMEs.

Improved Analytical Method for Determination of Furan and Its Derivatives in Commercial Foods by HS-SPME Arrow Combined with Gas Chromatography-Tandem Mass Spectrometry.

Owing to the presence of significant levels of toxic furan compounds reported globally in commercial foods by various food authorities, the objectives of this study were to develop an analytical method for determination of furan and its 10 derivatives in commercial foods using headspace-solid phase microextraction (HS-SPME)-Arrow coupled with gas chromatography-tandem mass spectrometry. Furan and its 10 derivatives were separated within 10 min by employing an HP-5MS capillary column with d4-furan as the internal standard for quantitation. The most optimal sample weight and extraction time for various commercial food samples, respectively, ranged from 1 to 5 g and 10-15 min depending on the sample variety. For extraction, carboxen/poly(dimethylsiloxane) (CAR/PDMS) cellulose was used with the temperature at 30 °C, equilibration time of 15 min, and desorption time of 3 min. The limit of detection ranged from 0.001 to 1.071 ng/g, while the limit of quantitation ranged from 0.003 to 3.571 ng/g. A high precision and accuracy were obtained for this method. The total furan content in commercial foods ranged from nd to 40 725.85 ng/g, in which the mean contents were the highest for brewed coffee (35 082.26 ng/g) and canned coffee (25 152.22 ng/g), while the lowest were for potato chip and cookies (0.57-1.48 ng/g), donut (1.50 ng/g), milk (0.34-30.38 ng/g), and oat (6.56 ng/g).

The Potential of Phaeodactylum as a Natural Source of Antioxidants for Fish Oil Stabilization.

Worldwide, fish oil is an important and rich source of the health-beneficial omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). It is, however, troubled by its high susceptibility towards lipid oxidation. This can be prevented by the addition of (preferably natural) antioxidants. The current research investigates the potential of Phaeodactylum carotenoids in this regard. The oxidative stability of fish oil and fish oil with Phaeodactylum addition is evaluated by analyzing both primary (PV) and secondary (volatiles) oxidation products in an accelerated storage experiment (37 °C). A first experimental set-up shows that the addition of 2.5% (w/w) Phaeodactylum biomass is not capable of inhibiting oxidation. Although carotenoids from the Phaeodactylum biomass are measured in the fish oil phase, their presence does not suffice. In a second, more elucidating experimental set-up, fish oil is mixed in different proportions with a Phaeodactylum total lipid extract, and oxidative stability is again evaluated. It was shown that the amount of carotenoids relative to the n-3 LC-PUFA content determined oxidative stability. Systems with a fucoxanthin/n-3 LC-PUFA ratio ≥ 0.101 shows extreme oxidative stability, while systems with a fucoxanthin/n-3 LC-PUFA ratio ≤ 0.0078 are extremely oxidatively unstable. This explains why the Phaeodactylum biomass addition did not induce oxidative stability.

Photo-Oxidative Stability of Aqueous Model Systems Enriched with Omega-3 Long-Chain Polyunsaturated Fatty Acid-Rich Microalgae as Compared to Autoxidative Stability.

Several species of microalgae are promising as an alternative source of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). Photoautotrophic species show the greatest potential, since incorporating them into food products leads to oxidatively stable products; however, the presence of photosensitizers could reduce the shelf-life due to the appearance of photo-oxidation on exposure to light. This study investigated the oxidative impact of illumination for aqueous model suspensions enriched with Phaeodactylum (phototrophic microalgae─containing potential photosensitizers) and Schizochytrium (heterotrophic microalgae─lacking photosensitizers) during storage for 28 days at 37 °C. Primary (peroxide value) and secondary (volatiles with gas chromatography (GC)-mass spectrometry) oxidation products, n-3 LC-PUFA content (GC), and pigments (high-pressure liquid chromatography) were assessed. The results showed that photo-oxidation did not cause oxidative instability for Phaeodactylum samples compared with strong autoxidation in Schizochytrium samples. For the Phaeodactylum-enriched suspensions, only minimal photo-oxidation could be detected and the n-3 LC-PUFA content remained stable throughout storage regardless of illumination.

Untargeted analysis of microbial metabolites and unsaturated fatty acids in salmon via hydrophilic-lipophilic balanced solid-phase microextraction arrow.

The ability to detect spoilage and the nutrient content of salmon is critical for ensuring food safety and determining market value. In this paper, we document the development of a hydrophilic-lipophilic balanced solid-phase microextraction arrow that offers better extraction performance than two other commercial devices. The devices were also compared using two operational models: headspace microextraction and direct immersion. The multidimensional statistical analysis and heatmap analysis for the headspace microextractions showed that the content levels of volatile metabolites including hydrocarbons, alcohols, ketones, acids, amino acids, and ethers increased with longer storage times, indicating an increase in the activity of spoilage-associated bacteria, such as gram-negative bacteria. For the direct immersion tests, important nutrients, including lipids, sterols, and squalene, were directly extracted from the salmon fillets with high efficiency. Thus, the developed method provides a simple and easy time-domain monitoring strategy for testing the freshness and quality of salmon for consumers.

Optimization of SPME-Arrow-GC/MS Method for Determination of Free and Bound Volatile Organic Compounds from Grape Skins.

(1) Background: Solid phase microextraction (SPME)-Arrow is a new extraction technology recently employed in the analysis of volatiles in food materials. Grape volatile organic compounds (VOC) have a crucial role in the winemaking industry due to their sensory characteristics of wine.; (2) Methods: Box-Behnken experimental design and response surface methodology were used to optimise SPME-Arrow conditions (extraction temperature, incubation time, exposure time, desorption time). Analyzed VOCs were free VOCs directly from grape skins and bound VOCs released from grape skins by acid hydrolysis.; (3) Results: The most significant factors were extraction temperature and exposure time for both free and bound VOCs. For both factors, an increase in their values positively affected the extraction efficiency for almost all classes of VOCs. For free VOCs, the optimum extraction conditions are: extraction temperature 60 °C, incubation time 20 min, exposure time 49 min, and desorption time 7 min, while for the bound VOCs are: extraction temperature 60 °C, incubation time 20 min, exposure time 60 min, desorption time 7 min.; (4) Conclusions: Application of the optimized method provides a powerful tool in the analysis of major classes of volatile organic compounds from grape skins, which can be applied to a large number of samples.

Accelerated Solvent Extraction of Terpenes in Cannabis Coupled With Various Injection Techniques for GC-MS Analysis.

The cannabis market is expanding exponentially in the United States. As state-wide legalization increases, so do demands for analytical testing methodologies. One of the main tests conducted on cannabis products is the analysis for terpenes. This research focused on implementation of accelerated solvent extraction (ASE), utilizing surrogate matrix matching, and evaluation of traditional vs. more modern sample introduction techniques for analyzing terpenes via gas chromatography-mass spectrometry (GC-MS). Introduction techniques included Headspace-Syringe (HS-Syringe), HS-Solid Phase Microextraction Arrow (HS-SPME Arrow), Direct Immersion-SPME Arrow (DI-SPME Arrow), and Liquid Injection-Syringe (LI-Syringe). The LI-Syringe approach was deemed the most straightforward and robust method with terpene working ranges of 0.04-5.12 µg/mL; r 2 values of 0.988-0.996 (0.993 average); limit of quantitation values of 0.017-0.129 µg/mL (0.047 average); analytical precisions of 2.58-9.64% RSD (1.56 average); overall ASE-LI-Syringe-GC-MS method precisions of 1.73-14.6% RSD (4.97 average); and % recoveries of 84.6-98.9% (90.2 average) for the 23 terpenes of interest. Sample workflows and results are discussed, with an evaluation of the advantages/limitations of each approach and opportunities for future work.

Comparison of headspace solid-phase microextraction high capacity fiber coatings based on dual mass spectrometric and broadband vacuum ultraviolet absorption detection for untargeted analysis of beer volatiles using gas chromatography.

Despite the same basic ingredients used in brewing, there is a significant variation in beer styles. With the rapid increase in craft brewing, beer styles have become even more numerous and complex in the recent past. A GC-MS/VUV (post-column split for dual detection) instrument with headspace high capacity SPME was used to investigate 21 different beers which represent three beer styles - India pale ales, blondes, and hefeweizens. Since results from untargeted studies can be affected by the sorbent material used, the extraction performances of three high capacity SPME fibers, i.e., polydimethylsiloxane, polydimethylsiloxane/carbon wide range, and polydimethylsiloxane/carbon wide range/divinylbenzene, were evaluated. Good reproducibility (<10% RSD) was obtained for each high capacity fiber using both detectors. The tandem MS/VUV detection coupled with GC separation proved to be particularly valuable for compound identification, especially for isomers and compounds with similar structures. The evaluation of VUV detection for untargeted analysis led to similar performances as MS detection. Both the VUV and the MS were able to effectively differentiate between beer styles using principal component analysis. In addition, the use of 3 different statistical approaches, one-way ANOVA (p-value < 0.05), partial least square discriminant analysis, and random forest, universally identified 12 of the components most influential in distinguishing the three beer styles (e.g., ß-myrcene, linalool, isopentyl acetate, 2,4-di-tert-butylphenol). This is the first reported evaluation of VUV detection and the first comparison of simultaneous VUV and MS detection for untargeted classification of complex mixtures using GC.

Determination of selected volatile terpenes in fish samples via solid phase microextraction arrow coupled with GC-MS.

A high-efficiency enrichment method is required for determination of trace-level volatile terpenes in fish tissue, since the presence of such compounds in fish at elevated levels may induce bad sensory acceptance of fish meat, thus degrading its customer acceptance and consequently, its market value. In this study, a solid-phase microextraction (SPME) arrow configuration using a thick sorbent coating (120 µm, PDMS/CWR) was applied to enrich selected terpenes, namely α-pinene, limonene, linalool, and citronellol, in fish tissue (Oreochromis niloticus). Due to the thicker coating of the SPME arrow, a longer extraction time of 60 min was required to reach equilibrium extraction in comparison to the traditional fiber configuration. SPME conditions such as extraction temperature (60 °C), desorption temperature (250 °C), and salt effect (10% NaCl) were optimized for the developed application using the arrow configuration. The developed method exhibited good linearity at a concentration range of 5.0-500.0 µg L-1 for α-pinene and limonene, and 50.0-500.0 µg L-1 for linalool and citronellol. In addition, the coefficients of determination (R2) for all terpenes ranged from 0.9990 to 0.9999. The developed method was shown to be robust with good inter-day reproducibility in the range of 3.6-8.3%. Method sensitivity was assessed in terms of limits of detection (LODs) and limits of quantification (LOQs), with higher sensitivity achieved for α-pinene and limonene (LODs of 1.7 µg L-1) in comparison to linalool (LOD, 5.0 µg L-1) and citronellol (LOD, 17.0 µg L-1). Theoretical calculations verified that the increased coating thickness afforded by the arrow configuration can enable higher method sensitivity and widen the range of detected compounds for the headspace SPME.

Development and validation of an improved, thin film solid phase microextraction based, standard gas generating vial for the repeatable generation of gaseous standards.

This work presents the development and validation of novel thin film solid phase micro extraction (TF-SPME) based standard gas generating vials suitable for repeatable generation of gaseous standards for GC-MS analysis and quality control. The vials were developed using carbon mesh membranes loaded with pure polydimethylsiloxane (PDMS), divinylbenzene (DVB/PDMS), hydrophilic-lipophilic balance (HLB/PDMS), and carboxen (Car/PDMS) sorbents that were then spiked with modified McReynolds standards including benzene, 2-pentanone, 1-nitropropane, pyridine, 1-pentanol, octane, dodecane, and hexadecane. Sorbent strength was determined to follow the aforementioned order, with pure PDMS presenting the weakest sorption capabilities and Car/PDMS the strongest. While the weaker, pure PDMS based gas generating vials transferred an instrument-overloading amount of McReynolds probes to the 1.1 mm DVB/PDMS SPME arrows used for extraction, vials prepared using Car/PDMS TF-SPME as a sorbent failed to provide consistently detectable amounts of analytes less volatile than 1-nitropropane. The DVB/PDMS and HLB/PDMS based vials were found to maintain optimal sorption capabilities for the tested analytes, providing a sorption strength strong enough to not exhibit any depletion in 10 replicate runs, while still delivering a consistent amount of all the regular McReynolds components. Moreover, with intra-vial%RSDs of 5% or less for all analytes tested, these HLB and DVB vials were found to deliver very good repeatability. After purposely submitting vials to 200 accelerated depletion extractions (1.1 mm DVB/PDMS arrow at 55 °C for 3 min), vials prepared with DVB/PDMS were found to deplete by 33%, 38%, 34%, 33%, 40%, and 33% while vials prepared with HLB/PDMS were found to deplete by 21%, 16%, 12%, 31%, 16% and 0% for benzene, 2-pentanone, 1-nitropropane, pyridine, 1-pentanol, and octane, respectively. When user typical extractions conditions were used instead (50/30 µm DVB/Car/PDMS SPME fiber at 35 °C for 1 min), no depletion could be observed from the HLB/PDMS based vial while%RSDs ranged from 1.1-3.0% after the 300 extraction/desorption cycles. Finally, in efforts to demonstrate its real world applicability, the DVB/PDMS vial was used to evaluate the inter-fiber repeatability of commercial DVB/PDMS SPME arrows, with results demonstrating that arrows from a single package were statistically similar (ANOVA at 95% confidence).