SPME Fiber Research Articles

Solid-Phase Microextraction of Phthalate Esters from Aqueous Media by Functionalized Carbon Nanotubes (Graphene Oxide Nanoribbons) and Determination by GC–FID

Multiwalled carbon nanotubes were exposed to hydrothermal treatment for obtaining graphene oxide nanoribbons (GONRs). The fabricated graphene oxide nanoribbons have been morphologically and compositionally characterized via FE-SEM, XRD, and FT-IR techniques. The as-synthesized GONRs have been used as sorbent phase for headspace solid-phase microextraction of phthalate esters (PEs) from aqueous solutions. In this regard, the GC–FID analysis route has been used for quantification of PEs. The new SPME fiber shows remarkable analytical figures of merit including broad dynamic linear ranges, low limits of detection, as well as good stability and reasonable relative standard deviations for evaluation of PEs. The linearity of the method for analysis of PEs including DnBP, DnPP, DEHP, DEHA, BBP, and DMP was between the range of 0.05–100, 0.05–100, 0.1–100, 0.1–100, 0.2–100, and 0.5–100 μg L−1, respectively. The limits of detection (based on S/N = 3) and correlation coefficients were found to be in the range of 0.02–0.2 μg L−1 and 0.9907–0.9952, correspondingly. The prepared GONR-coated SPME fiber shows larger extraction yield in comparison to pristine MWNTs and commercial PDMS SPME fibers. Furthermore, real sample analysis showed that there is no significant matrix effect for evaluation of PEs from environmental water samples and proposed method could be used for evaluation and determination of PEs from aqueous samples in a precise and accurate manner. The existence of functional groups, π–π interactions, as well as hydrogen bonding between adsorbent phase and PE analytes could be the reason for observing such a high extraction yield.

Solvent-Free Synthesis of Phenolic Hydroxyl Enriched Ordered Mesoporous Polymer as an Efficient Solid-Phase Microextraction Coating for the Determination of Trace Phenols in Food Samples

The determination of trace phenols in food samples is of great significance, but it is still very challenging due to the low concentration and complex matrix. A robust method was developed to determine trace phenols in food sample by combining headspace-solid phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS). The hydroxylated ordered mesoporous polymer (OMP-OH) synthesized by solvent-free strategy possessed ordered mesoporous structure and high specific surface area and was used as SPME fiber coating. Factors affecting the extraction efficiency were optimized, including extraction time, extraction temperature, pH value, salt effect, and desorption conditions. Under the optimal conditions, OMP-OH coating exhibited a high capability for the enrichment of phenols, which was 2~8 times that of commercial SPME coating. Moreover, the coating can be reused for more than 150 times without a significant change in performance. Linear ranges of this method were 0.5~10000 ng L−1, of which 5~10000 ng L−1 for 2-nitrophenol and 1~10000 ng L−1 for 2, 4-dichlorophenol. The limits of detection (LODs) for phenols in tomato and grape are 0.19~2.13 ng L−1 and 0.21~2.41 ng L−1, respectively. High enrichment factors (439~1851), good precision (RSD< 8.87%), and superior reproducibility (RSD< 10.0%) were obtained. Ultimately, the established method was successfully applied to quantify the phenols in real food samples, i.e., tomato and grape. The results demonstrated that the established method was very promising for the determination of trace phenols in food samples with complex matrix.

Investigation of sorption and diffusion of hydrocarbons into polydimethylsiloxane in the headspace-solid phase microextraction sampling process via inverse gas chromatography

Inverse gas chromatography was employed to investigate the sorption and diffusion of hydrocarbons into polydimethylsiloxane (PDMS) in the headspace-solid phase microextraction (HS-SPME) sampling process. Six hydrocarbons as molecular probes and two types of non-cross-linked PDMS with different average molecular weights as stationary phases were used in this study. Experimental measurements with columns containing a PDMS stationary phase were carried out to obtain specific retention volumes, molar enthalpies of sorption, interaction parameters, diffusion coefficients, and activation energies of diffusion of hydrocarbon probes over temperatures ranging from 60 to 90°C. The primary driving force of the hydrocarbon sorption into the PDMS SPME fibers was found to be the molar enthalpy of sorption, which depended on the molecular size of the hydrocarbons. As the molecular size of the hydrocarbon increased, the molar enthalpies of sorption became more exothermic. Interaction parameters and diffusion coefficients indicated that both n-heptane and n-octane were diffused into the PDMS matrix and localized to form clusters or aggregates, which were responsible for more negative molar entropies of sorption. However, the diffusivities of n-nonane and aromatic probes were limited due to their large molecular size and lack in the structural flexibility, respectively. The molar enthalpies of hydrocarbon sorption were independent of the average molecular weight of PDMS. However, specific retention volumes, interaction parameters, diffusion coefficients, and activation energies of diffusion of the hydrocarbons depended on the molecular weight of PDMS as well as the molecular weights and structures of hydrocarbons, as shown by the results of the Wilcoxon signed-rank test.

Plant Extract and Herbal Products as Potential Source of Sorbent for Analytical Purpose: An Experimental Study of Morphine and Codeine Determination Using HPLC and LC-MSMS.

Solid-phase microextraction (SPME) is an analytical method for microextraction of analytes, in which the analytes bind to the sorbent on the surface of the SPME fiber. Many types of chemical agents are used as sorbent; however, many of these sorbents cause secondary contamination or are not cost-effective. Here, aqueous extract of Ferula gummosa was evaluated as potential source of sorbent for simultaneous microextraction of morphine and codeine. For this purpose, multiwalled carbon nanotubes were carboxylated with H2SO4/HNO3 (3:1) and then functionalized with aqueous extract of F. gummosa. Functionalization was confirmed by Fourier transform infrared and Raman spectroscopy measurements as well as scanning electron microscopy analysis. Porous polypropylene hollow fibers were filled with the functionalized carbon nanotubes (CNTs) and used for analyte extraction in urine sample at 40°C and pH6 for 2min. Reversed-phase high-performance liquid chromatography (RP-HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed that the fiber could preconcentrate 1ng/mL of morphine and 0.75ng/mL codeine in urine sample and was successfully used for 30 times with no significant loss in the extraction efficiency. Limit of detection (LOD) and limit of quantification (LOQ) for morphine were 1 and 3.3ng/mL, respectively. LOD and LOQ for codeine were determined 0.75 and 2.47ng/mL, respectively. Recovery of the fiber was 80% and 93% for morphine and codeine, respectively. SPME fiber using extract of F. gummosa plant was used for the detection of a small amount of morphine in urine sample. Therefore, plants can be considered as abundant and cheap sources of sorbent for various analytical purposes.

Carbon aerogel-based solid-phase microextraction coating for the analysis of organophosphorus pesticides.

The current study is focused on the in situ synthesis of a carbon aerogel (CA)-based solid-phase microextraction (SPME) fiber coating on stainless steel wire and evaluation of the suitability of CAs as SPME coating materials for the analysis of selected organophosphorus pesticides (OPPs) contained in environmental samples. A CA-based coating was obtained by pyrolyzing organic aerogels, which were prepared by the sol-gel polymerization of formaldehyde and 5-methylresorcinol, an oil shale processing by-product. The results demonstrated, for the first time, the in situ synthesis of a CA-based SPME fiber coating on stainless steel wire and its suitability for the extraction and preconcentration of six OPPs. Main parameters affecting the extraction efficiency were investigated and optimized. The direct immersion (DI)-SPME procedure combined with gas chromatography-mass spectrometry (GC-MS) for the simultaneous analysis of selected OPPs was successfully applied to the efficient and sensitive determination of analytes of interest in environmental matrices of honey and natural water samples. The developed CA-coated SPME fiber showed good linearity (R2 = 0.981-0.994), low detection limits (0.11-0.83 μg L-1) and satisfactory single fiber and fiber-to-fiber reproducibilities (8.8-12.3%, n = 5 and 11.4-17.2%, n = 3). The performance of the CA-coating was compared with that of commercially available SPME fiber coatings.

Investigating the Potential of an In-Situ Method for Monitoring the Malting of Barley Using Solid Phase Microextraction with a Portable Gas Chromatography Mass Spectrometry Instrument

An improved understanding of the malting process could have a significant impact on the efficient production of quality malt for the brewing industry. Analysis of volatile organic compounds produced during the malting process is one approach towards achieving this goal. In-situ methods avoid the possibility of contamination and chemical changes occurring during sample transport and storage. This paper describes the investigation of an in-situ sampling method for the detection of volatile organic compounds produced during the malting of barley. Solid Phase Microextraction Gas Chromatography Mass Spectrometry (SPME-GC/MS) was used to identify compounds. The investigated method involved the direct exposure of an SPME fiber in the kiln during barley malting. Using this method, compounds including aldehydes, ketones, and esters were detected. Some changes in volatile organic compound composition were observed during the production of pale malt at a commercial malting house.

Comparing different extraction methods for the investigation of red pepper (Capsicum annuum L.) volatiles

ABSTRACT Different SPME fibres and distillation techniques (steam distillation and simultaneous distillation extraction) were applied to extract the volatile constituents of special quality sweet, ground red pepper. Preparation methods produced substantially different scent aromagrams recorded with GC-MS. Each procedure showed individual character. Distillation methods were the most effective ones considering the number and sum of peak intensities. Esters, terpenes, carotenoid derivatives and benzene components were the most intense volatiles. Among the SPME fibres PDMS-DVB showed the highest general sensitivity in those chemical classes that are crucial from varietal characterization and quality description aspects. In case of lactones and furans of high smell activities and fruity/sweet nuance, Carboxen-PDMS fiber seemed acceptably good. PDMS fibre was not really proper for paprika scent analysis and Polyacrylate practically could not be used at all. Comparison of SPME and distillation results permits to recognize and circumscribe the artefacts are induced by the distillation steps of the sampling procedure.

OPTIMIZATION OF SOLID-PHASE MICROEXTRACTION CONDITIONS OF MILK CHOCOLATE

In the current study, the Central Composite Design was applied to optimize HS-SPME extraction in order to detect 2,3,5,6 tetramethyl pyrazine in isomalt contaning milk chocolate. The optimal conditions for the three experimental responses influencing SPME efficiency were 10 min, 40 min and 57 °C for equilibration time, extraction time and extraction temperature, respectively. SPME fibers coated with 100 m polydimethylsiloxane coating, 65 µm polydimethylsiloxane/divinylbenzene coating, 75 µm carboxen/polydimethylsiloxane coating and 50/30 µm divinylbenzene/carboxen/polydimethylsiloxane on a StableFlex fiber were investigated. The preparation conditions of the chocolate samples were also evaluated by measuring their effects on the coating composition of the head space. The SPME fiber coated with 50/30 µm divinylbenzene/carboxen-polydimethylsiloxane provided the highest extraction efficiency, especially when the samples were extracted at 60 °C for 30 min under dry conditions. Eighty-one blends were extracted and experimentally detected most of which have been formerly stated as odor-active components.

Copper ferrite nanoparticles as novel coating appropriated to solid-phase microextraction of phthalate esters from aqueous matrices

The prepared CuFe2O4 nanoparticles (NPs) resulting from a facile citrate–nitrate combustion method were adhesived on stainless steel wire with epoxy glue as a novel fiber coating. A direct immersion solid-phase microextraction (DI-SPME) method based on the prepared coating was established through sensitively detecting four phthalate esters (PAEs) from aqueous media with gas chromatography-flame ionization detection (GC-FID). The effects of various parameters on the efficiency of SPME process such as extraction time, extraction temperature, pH, ionic strength, desorption time, and desorption temperature were studied. Under optimized conditions, the limit of detections (LODs) and quantifications (LOQs) for the phthalate esters varied in the range of 0.12–0.40 μg·L−1 and 0.40–1.33 μg·L−1, respectively. The inter-day and intra-day relative standard deviations for these varied phthalate esters at 10 μg·L−1 concentration level (n = 6) using a single fiber were 3.9–12.4% and 6.6–15.1%, respectively. The fiber to fiber repeatabilities (n = 3), expressed as relative standard deviation (RSD%), were between 9.9% and 16.5% at 10 μg·L−1 concentration levell, and the the linear ranges varied between 1 and 500 μg·L−1. The prepared fiber can be repeatedly used to exceed 80 times, revealing a long lifetime and good stability. The method was successfully applied to analysis of the mineral water samples with recoveries from 81.1 to 103.7%. This work also provided an interesting insight for stable SPME fiber prepared by spinel materials for efficient extraction of PAEs.

Optimization of a headspace solid-phase microextraction method for the gas chromatography-mass spectrometry analysis aroma compounds of Litsea mollis Hemsl. immature fruit

Abstract This study optimized using a headspace solid-phase microextraction (HS-SPME) method for extracting volatile aroma compounds, terpenoids in particular, from Litsea mollis Hemsl. immature fruit (LMIF). Gas chromatography-mass spectrometry was used to separate and identify volatile terpenoids in LMIF. The types of SPME fiber coating, salt addition, and desorption time were optimized by single factor-experiments to determine the range of extraction temperature. Built on insights from the single factor-experiments, the response surface methodology was further used to optimize the extraction temperature, extraction time, and equilibrium time of HS-SPME. The results showed that the optimal HS-SPME conditions for extracting volatile terpenoids from LMIF were: 50/30 μm of DVB/CAR/PDMS SPME fiber, 2.0 g of added sodium chloride, desorption at a temperature of 250 °C for 3 min, extraction and equilibrium temperature of 46 °C, extraction time of 36 min, and equilibrium time of 20 min. Under the above conditions, the predicted value of extraction was 66.92, while the experimental value was 65.78. The prediction value matched well with the experimental value with good repeatability. The designed model was proven to be valid, which can be applied for future extraction of aroma compounds from IMIF.

Characterisation of volatile compounds associated to sensory changes during the storage of traditional sorghum beer by HS-GC/FID and SPME-GC/MS

The study was carried out to analyse volatile compounds (VOCs) associated to sensory changes during the storage of traditional sorghum beer at ambient temperature and 4 °C. Tchapalo samples were collected and stored at ambient temperature (27–30 °C) for four days and at 4 °C for six days. Volatile and sensory changes were monitored during the storage period. VOCs were extracted and detected using HS-GC/FID and SPME-GC/MS. These methods allowed to identify 68 volatile compounds. The use of SPME fiber permitted to obtain 63 volatile compounds, while simple headspace (HS) was able to extract only 10 compounds. The proportions of isoamyl alcohol, phenylethyl alcohol, ethyl lactate, isoamyl acetate, ethyl hexanoate, ethyl DL-leucate, ethanol, diethyl succinate, phenethyl acetate and benzene acetaldehyde observed significant variation during the storage at ambient temperature. For Tchapalo stored at 4 °C, the proportions of ethanol, ethyl lactate, isoamyl acetate, ethyl hexanoate, ethyl octanoate and phenylethyl alcohol presented significant variation. Principal component analysis based on quantitative changes of these volatile compounds showed three groups among Tchapalo samples which reflected to the differences observed during the sensory evaluations.

In vivo quantification of volatile organoselenium compounds released by bacteria exposed to selenium with HS-SPME-GC-MS. Effect of selenite and selenium nanoparticles

Quantification of volatile organoselenium species released by Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), after their growth in the presence of 1 and 2 mg Se·L-1 as both selenite and chitosan-modified selenium nanoparticles (Ch-SeNPs), was achieved by the application of a method based on headspace solid-phase microextraction (HS-SPME) and in-fiber internal standardization, combined with gas chromatography coupled to mass spectrometry (GC-MS). This method consisted of an initial extraction of the released volatile organoselenium compounds on the SPME fiber, followed by the extraction of internal standard (IS), deuterated dimethyl sulfide (d6-DMS), on the same fiber before its desorption at the injection port of GC-MS. The results showed that the biotransformation of selenite and Ch-SeNPs into volatile organoselenium compounds was dependent on both the type of bacterial species and the chemical form of selenium (Se) administered. In this sense, E. coli was able to biotransform both selenite and Ch-SeNPs into dimethylselenium (DMSe) and dimethyldiselenium (DMDSe) while S. aureus, biotransformed selenite into DMSe and DMDSe and, Ch-SeNPs only into DMDSe. Additionally, the formation of a volatile mixed sulfur/selenium compound, dimethyl selenenyl sulfide (DMSeS), from Se in nanoparticulated form has been detected for the first time.

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., β-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.

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).

Overcoming matrix effects in the analysis of pyrethroids in honey by a fully automated direct immersion solid-phase microextraction method using a matrix-compatible fiber

Pyrethroids insecticides may constitute a major hazard to honeybees, leading to colony collapse disorder. However, the determination of pyrethroids in honey has remained a challenging undertaking for analysts to date due to the high complexity of this matrix as well as the MRLs. This paper presents a fully automated method to overcome matrix influences using matrix-compatible overcoated SPME fiber for quantitative analysis of pyrethroids in diluted honey by GC–MS. The developed method was optimized using a multivariate approach providing LOQ values much lower than the stablished MRL (0.10–10 ng/g), while granting satisfactory linearity (R2 > 0.998) in a wide linear range of 0.1–2000 ng/g, repeatability with RSDs < 10%, reproducibility RSDs < 20%, and accuracy ranging from 75 to 118% and from 82 to 120 % for inter-day and intra-day assays, respectively by using five replicates. The method herein proposed overcomes challenges presented by complex matrices while minimizing sample handling and the overall complexity of the procedure.

Comparison of volatile compounds in different parts of fresh Amomum villosum Lour. from different geographical areas using cryogenic grinding combined HS\u2013SPME\u2013GC\u2013MS

BackgroundThe essential oil is one of the main active ingredients of Amomum villosum Lour. However, volatile compounds are easily lost during the drying, storage and even sample preparation procedure. Therefore, using fresh samples can obtain more accurately data for qualitative and comparative analysis.MethodsIn this study, the volatile compounds in different parts of fresh A. villosum from different origins were systemic analyzed and compared by using cryogenic grinding combined HS–SPME–GC–MS for the first time. GC–MS analyses were performed on a 6890 Series GC instrument coupled to a 5973 N mass spectrometer. The volatile compounds were extracted by the SPME fiber (100 μm PDMS). Analytes separation was achieved on a HP-5MS capillary column. The oven temperature was initially programmed at 70 °C, then raised 4 °C/min to reach 125 °C and then programmed at 0.5 °C/min to 133 °C, then at 6 °C/min to 170 °C and finally, at 20 °C/min to 280 °C held for 2 min. The temperatures of the injection port, ion source and transfer line were set at 250 °C, 230 °C and 280 °C, respectively.ResultsForty-eight main compounds were identified in different parts of fresh A. villosum. The most abundant components in fresh fruit samples were camphor (3.91%), bornyl acetate (10.53%), caryophyllene (8.70%), β-bisabolene (11.50%), (E)-nerolidol (14.82%) and cubenol (10.04%). This is quite different with that of dried samples analyzed in our previous work. As different parts of the same plant, many common components with biological activities were detected in fruit and other parts. In principle components analysis (PCA) and hierarchical clustering analysis (HCA), four parts of A. villosum were divided into different groups clearly. Additionally, fruit and root samples also could be divided into two subgroups (HCA) in accordance with their regions.ConclusionThe developed method was successfully used for qualitative and comparative analysis of volatile compounds in fresh A. villosum samples. Additionally, using fresh samples can obtain much more information which is helpful for their performance in the fields of functional foods, agriculture and biomedical industry. Furthermore, our research is helpful for comprehensive utilization and quality control of A. villosum.

Breath analysis of smokers, non-smokers, and e-cigarette users

Solid phase micro extraction-Gas Chromatography/Mass Spectrometry (SPME-GC/MS) analysis was performed in exhaled breath samples of 48 healthy volunteers: 20 non-smokers, 10 smokers and 18 e-cigarette (EC, vape) users. Each volunteer provided 1 L of exhaled breath in a pre-cleaned Tedlar bag, in which an SPME fiber was exposed to absorb the emitted breath volatile organic compounds (VOCs). The acquired data were processed using multivariate data analysis (MDA) methods in order to identify the characteristic chemicals of the three groups. The results revealed that the breath of non-smokers demonstrated inverse correlation with a variety of molecules related to the breath from smokers including furan, toluene, 2-butanone and other organic substances. Vapers were distinguished from smokers by the chemical speciation of the e-liquids, such as that of esters (e.g. ethyl acetate), terpenes (e.g. α-pinene, β-pinene, d-limonene, p-cymene, etc.) and oxygenated compounds (e.g. 3-hexen-1-ol, benzaldehyde, hexanal, decanal, etc). Two classification models were developed (a) using principal component analysis (PCA) with hierarchical cluster analysis (HCA) and (b) using partial least squares-discriminant analysis (PLS-DA). Both models were validated using 8 new samples (4 vapers and 4 smokers), collected in addition to the 48 samples of the calibration set. The combination of GC/MS breath analysis and MDA contributed successfully in classifying the volunteers into their respective groups and highlighted the relevant characteristic VOCs. The respective dynamic combination (SPME-GC/MS and MDA) provides a means for long term non-invasive monitoring of the population’s health status for early detection purposes.

The new silica-based coated SPME fiber as universal support for the confinement of ionic liquid as an extraction medium

The new silica-based SPME fiber coating is reported for the first time as universal support purposed to confinement of ionic liquid as an extraction medium. Fiber coating was prepared by the sol-gel process, using potassium silicate (K2SiO3) as a precursor and dimethylformamide (DMF) as a pore-forming medium. The concept of synthesis assumes obtaining a solid porous material on the surface of the glass rod and, being characterized by high porosity, mechanical strength, and uniformity of shape. In the course of the research, several parameters were optimized, like the type of silica precursor, drying steps, time and temperature of aging.Properties of obtained coatings were evaluated using optical and scanning electron microscopies and thermal adsorption/desorption measurements. Finally, the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate [C2C1IM][BF4] was immobilized in silica pores of the prepared fiber. The usefulness of the obtained SPME silica-IL fibers was investigated by its utilization in model analytical procedures. Robustness of produced fibers is supported by high fiber-to-fiber reproducibility (%) as well as by a long lifetime reaching over 50 extraction/desorption cycles.

Identification of Aroma Compounds in Freeze-dried Strawberries and Raspberries by HS-SPME-GC-MS

The objective of this study was to determine a method for the identification of aroma volatile compounds in freeze-dried (FD) strawberries and raspberries for quality purposes. The aroma profile was examined using headspace solid-phase micro-extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). FD strawberries and raspberries were extracted at four different times (10,15, 20 and 30 min) and three different temperatures (40 &amp;deg;C, 60 &amp;deg;C and 80 &amp;deg;C) using a SPME fiber coated with 50/30 &amp;micro;m divinylbenzene/carboxen on polydimethylsiloxane (DVB/CAR-PDMS) to determine optimum recoveries for aroma volatile compounds. The DVB/CAR-PDMS SPME fiber showed the best extraction of aroma volatile compounds from strawberry and raspberry at 60&amp;deg;C for 15 min. Twenty-nine volatile compounds were identified from the strawberry samples and 20 from the raspberry samples, including terpenes, aldehydes, esters, acids and alcohols. Select aroma compounds in FD strawberries and raspberries were quantitated using SPME and GC-MS. It is important to determine the desirable aroma active compounds in freeze-dried strawberries and raspberries for quality uses since they are becoming popular commercially.

An ultrasound-assisted pressure-regulated solid-phase microextraction setup for fast and sensitive analysis of volatile pollutants in contaminated soil.

Release of analytes from their native matrix and diffusion into the gas phase is the rate-limiting step for the sampling of volatiles in complex solid samples. This limitation is more serious in the solvent-less and solvent-free microextraction sampling strategies. In this research, a three-stage reinforced sampling strategy including high-pressure/sonication/low-pressure was introduced for fast and efficient release of analytes in soil samples. For this purpose, a novel ultrasound-assisted pressure-regulated solid-phase microextraction (UA-PR-SPME) device was developed. It was coupled with gas chromatography-flame ionization detection (GC-FID) and carried out for the determination of benzene, toluene, ethylbenzene, and xylenes (BTEX, as the model analytes) in complex solid samples. Graphene oxide/3-aminopropyltriethoxysilane (GO-APTES) nanocomposite was synthesized and used as the SPME fiber coating. Under optimal conditions, the limits of detection (LODs) were obtained 0.1-0.4 ng/g. The calibration curves were linear over the range of 2.4-5000 ng/g. Relative standard deviations (RSDs%) were calculated 5.1-7.0% (n = 6). The developed technique was employed for the analysis of BTEX in contaminated soil samples.