SPME Fiber Research Articles

Quantitative analysis of volatile flavor components in Korean alcoholic beverage and Japanese sake using SPME-GC/MS.

Quantitative analysis of the volatile flavor components in Korean alcoholic beverages (makgeolli and yakju) and Japanese sake was carried out using SPME-GC/MS. Fusel oils (n-butyl alcohol, isobutyl alcohol, isoamyl alcohol, and phenethyl alcohol), ethyl esters (ethyl acetate, isoamyl acetate, ethyl caproate, ethyl caprylate, and ethyl caprate) and aldehydes (furfural and benzaldehyde) were analyzed quantitatively by an 85 μm SPME fiber (carboxen/polydimethylsiloxane) using internal standards (1-pentanol-1-13C and methyl nonanoate). Phenethyl alcohol (85-216 ppm) and isoamyl alcohol (38-115 ppm) constituted the majority of fusel oils in all the samples. Acetic acid was detected in sour makgeolli at a high level (0.02-0.14 ppm) compared with yakju and sake. A very high level of total ethyl esters (ethyl acetate, isoamyl acetate, ethyl caprate, and phenethyl acetate), having fruit and flower flavor, was found in makgeolli. Processing the volatile flavor data by multivariate partial least squares discriminant analysis, makgeolli, yakju, and sake showed cluster separation.

Direct tissue sampling of diazepam and amitriptyline using mixed-mode SPME fibers: A feasibility study

Here, we report on the applicability of the C18/SCX fiber (containing both C18 and strong cation exchange groups) as a direct sampling tool in tissue. An agarose gel model was used as semi-solid tissue surrogate, to mimic changes in matrix tortuosity as expected in tissue. Pork muscle was used as tissue source and was loaded with diazepam or amitriptyline using 24h incubation in spiked phosphate-buffered saline (PBS). Diazepam is neutral and its behavior is predictable based on the octanol–water partition coefficient (Kow). Amitriptyline is >99% positively charged at pH 7.4, and is likely to behave differently in both agarose gel and tissue compared to neutral compounds. The proposed SPME method yielded detectable fiber concentrations after direct sampling in agarose gel and loaded tissue, including short sampling times and different loading concentrations in tissue. Sorption affinity of both diazepam and amitriptyline is decreased when sampling from agarose gel compared to PBS, due to the presence of different binding groups in agarose. Sorption affinities from tissue are even further decreased compared to agarose gel. This indicates that tissue contains even more binding sites for these compounds compared to agarose gel. Interestingly, for both compounds, equilibration in tissue occurred faster than equilibration in agarose gel or PBS, most likely caused by direct fiber contact or through facilitated transport. Although more research is needed to obtain good quantitative results, these results show that the C18/SCX fiber is a sensitive tool to determine tissue concentrations of neutral and cationic compounds.

Inter-laboratory validation of automated SPME-GC/MS for determination of pesticides in surface and ground water samples: sensitive and green alternative to liquid–liquid extraction

An automated solid-phase microextraction gas chromatography/mass spectometry (SPME-GC/MS) method was developed for the determination of semi-volatile pesticides from several classes with a wide range of polarities in an environmental matrix, and validated according to the rigorous standards of a large commercial laboratory reporting data requiring regulatory acceptance with the purpose of being used as a standard test protocol. The target analytes showed a detection limit of 0.05–1 μg L−1, good calibration linearity (R2 > 0.99) with a wide linear range of 0.05–20 μg L−1, and accuracy in the range of 80–110 at three levels of calibration with relative standard deviation below 7% by commercial polydimethylsiloxane/divinylbenzene (PDMS/DVB) SPME fiber. An extensive study between SPME and liquid–liquid extraction as a reference US EPA method was performed from several analytical aspects including sensitivity, accuracy, repeatability, and greenness. The SPME method was validated through split blind analyses of 16 fortified surface and ground water samples within 4 months at Maxxam Analytics, the reference laboratory, and the University of Waterloo. Both methods were shown to be very accurate, with the highest frequency of results falling in the 70–130% accuracy range. The SPME method was shown to be more sensitive than the LLE, while requiring a lower volume of sample.

Modified HS-SPME for determination of quantitative relations between low-molecular oxygen compounds in various matrices

Similar quantitative relations between individual constituents of the liquid sample established by its direct injection can be obtained applying Polydimethylsiloxane (PDMS) fiber in the headspace solid phase microextraction (HS-SPME) system containing the examined sample suspended in methyl silica oil. This paper proves that the analogous system composed of sample suspension/emulsion in polyethylene glycol (PEG) and Carbowax fiber allows to get similar quantitative relations between components of the mixture as those established by its direct analysis, but only for polar constituents. It is demonstrated for essential oil (EO) components of savory, sage, mint and thyme, and of artificial liquid mixture of polar constituents. The observed differences in quantitative relations between polar constituents estimated by both applied procedures are insignificant (Fexp < Fcrit). The presented results indicates that wider applicability of the system composed of a sample suspended in the oil of the same physicochemical character as that of used SPME fiber coating strongly depends on the character of interactions between analytes-suspending liquid and analytes-fiber coating.

Utilization of highly robust and selective crosslinked polymeric ionic liquid-based sorbent coatings in direct-immersion solid-phase microextraction and high-performance liquid chromatography for determining polar organic pollutants in waters

Several crosslinked polymeric ionic liquid (PIL)-based sorbent coatings of different nature were prepared by UV polymerization onto nitinol wires. They were evaluated in a direct-immersion solid-phase microextraction (DI-SPME) method in combination with high-performance liquid chromatography (HPLC) and diode array detection (DAD). The studied PIL coatings contained either vinyl alkyl or vinylbenzyl imidazolium-based (ViCnIm- or ViBCnIm-) IL monomers with different anions, as well as different dicationic IL crosslinkers. The analytical performance of these PIL-based SPME coatings was firstly evaluated for the extraction of a group of 10 different model analytes, including hydrocarbons and phenols, while exhaustively comparing the performance with commercial SPME fibers such as polydimethylsyloxane (PDMS), polyacrylate (PA) and polydimethylsiloxane/divinylbenzene (PDMS/DVB), and using all fibers under optimized conditions. Those fibers exhibiting a high selectivity for polar compounds were selected to carry out an analytical method for a group of 5 alkylphenols, including bisphenol-A (BPA) and nonylphenol (n-NP). Under optimum conditions, average relative recoveries of 108% and inter-day precision values (3 non-consecutive days) lower than 19% were obtained for a spiked level of 10µgL−1. Correlations coefficients for the overall method ranged between 0.990 and 0.999, and limits of detection were down to 1µgL−1. Tap water, river water, and bottled water were analyzed to evaluate matrix effects. Comparison with the PA fiber was also performed in terms of analytical performance. Partition coefficients (logKfs) of the alkylphenols to the SPME coating varied from 1.69 to 2.45 for the most efficient PIL-based fiber, and from 1.58 to 2.30 for the PA fiber. These results agree with those obtained by the normalized calibration slopes, pointing out the affinity of these PILs-based coatings.

Development of the mass spectral fingerprint by headspace-solid-phase microextraction-mass spectrometry and chemometric methods for rapid quality control of flavoring essence

Based on non-separative headspace-solid-phase microextraction-mass spectrometry (HS-SPME-MS) method and multivariate statistical analysis, we describe in this paper a reliable and rapid technique capable of controlling the quality and verifying the authenticity of flavoring essences. Two similar types of essences corresponding to formula A and formula B were extracted and concentrated by the HS-SPME method. Subsequently, the constituents adsorbed on SPME fiber were thermally desorbed in the chromatographic injection port and directly transferred to mass spectrometer without prior chromatographic separation. Thus, a unique mass spectral fingerprint of essence was formed. Three multivariate statistical processes were carried out to distinguish the samples and analyze the results. Firstly, similarity analysis based on correlation coefficient was used to evaluate the resemblance of the essences. The results indicated that the correlation coefficients of formula A and B from different batches were more than 0.980 and 0.920, respectively. In addition, principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) were employed to provide a visual comparison of the two types of flavoring materials. We demonstrated that the PLS-DA method can establish a discrimination rule to predict the “belongingness” of new samples and further screen out the main ionic markers, which might be suitable for recognizing and monitoring the quality of flavoring essences.

Au-coated ZnO nanorods on stainless steel fiber for self-cleaning solid phase microextraction-surface enhanced Raman spectroscopy

Solid phase microextraction-surface enhanced Raman spectroscopy (SPME–SERS), combining the pretreatment and determination functions, has been successfully used in environmental analysis. In this work, Au-coated ZnO nanorods were fabricated on stainless steel fiber as a self-cleaning SERS-active SPME fiber. The ZnO nanorods grown on stainless steel fiber were prepared via a simple hydrothermal approach. Then the obtained nanostructures were decorated with Au nanoparticles through ion-sputtering at room temperature. The obtained SERS-active SPME fiber is a reproducible sensitivity sensor. Taking p-aminothiophenol as the probe molecule, the RSD value of the SERS-active SPME fiber was 8.9%, indicating the fiber owned good uniformity. The qualitative and quantitative detection of crystal violet and malachite green was also achieved. The log–log plot of SERS intensity to crystal violet and malachite green concentration showed a good linear relationship. Meanwhile, this SERS-active SPME fiber can achieve self-cleaning owning to the excellent photocatalytic performance of ZnO nanorods. Crystal violet was still successfully detected even after five cycles, which indicated the high reproducibility of this SERS-active SPME fiber.

Volatile components and sensory characteristics of Thai traditional fermented shrimp pastes during fermentation periods.

Headspace-volatile components and sensory characteristics, including color, Maillard reaction products and free amino acid profiles, of two types of Thai traditional fermented shrimp paste, Kapi Ta Dam and Kapi Ta Deang, were investigated during the fermentation periods up to 6months. The results showed that the colors of both products were changed with a decrease in CIELAB values over the fermentation period, except for yellowness of Kapi Ta Deang. Essential amino acids such as lysine and leucine and non-essential amino acids such as glutamic acid and alanine were found to be predominant free-amino acids in the products. After headspace volatile component extraction of the product was carried out using a SPME fiber coated with DVB/CAR/PDMS and analyzed by GC-MS, the main compounds responsible for distinct volatiles in the products were N-containing compounds, especially pyrazines which give roasted nutty odor. The results of sensory evaluation from panelists also suggest that fermentation period had an effect on sensory characteristics of the fermented shrimp pastes. Moreover, the sensory perceptions of the products would associate with their color, the Maillard reaction products, amino acid profiles and volatile compounds.

Extracting Emissions from Air Fresheners Using Solid Phase Microextraction Devices

Families all over the world commonly use air fresheners indoors. In this investigation, needle trap samplers (NTS), which are environmentally friendly analytical devices, are used to sample the gaseous products from three types of lavender fresheners-liquid, granular and oil. NTS are prepared using 60-80 mesh divinylbenzene (DVB) particles in 22 gauge stainless steel needles and utilized to extract indoor organic compounds. This investigation compares the extraction efficiency of NTS with that of commercially available 100-μm polydimethylsiloxane solid phase microextration (PDMSSPME) fiber samplers, when used to sample gaseous emission products from fresheners. The experimental results revealed that 60-80 mesh DVB-NTS outperformed SPME fibers during a 1-hr sampling period, and the main compounds that are extracted by NTS were ethanol, benzene, toluene, ethylbenzene, xylenes, dichloromethane, butenes and pentane. The potential use of small badge-sized or pen-sized NTS for indoor atmospheric and occupational hygiene applications is thoroughly evaluated.

Zeolitic imidazole framework templated synthesis of nanoporous carbon as a novel fiber coating for solid-phase microextraction.

A new solid-phase microextraction (SPME) fiber coating material, a zeolitic imidazole framework-67 (ZIF-67) templated nanoporous carbon, Co-NPC, was fabricated by one-step direct carbonization of ZIF-67 without using any other carbon precursors. The prepared Co-NPC was then coated onto a functionalized stainless steel wire by a simple physical coating method to prepare SPME fibers. By coupling the Co-NPC coated fiber based SPME with gas chromatography/micro-electron capture detection (GC/μECD), the developed method exhibited low limits of detection (0.07-0.45 ng g(-1)) and a wide linearity (0.30-50 ng g(-1)) for the determination of five organochlorine pesticides (OCPs) in vegetable samples. The method was applied to the analysis of cabbage, cucumber and celery cabbage samples, and the recoveries of the analytes were in the range of 87.9-103.9% with the relative standard deviations (RSDs) ranging from 5.1% to 10.4% (n = 5). Single fiber repeatability and fiber-to-fiber reproducibility values expressed as RSDs were in the range of 4.9-9.6% and 5.8-11.0%, respectively. The method was simple, convenient and feasible for the determination of OCPs in real samples.

A nanoporous carbon material derived from pomelo peels as a fiber coating for solid-phase microextraction

A novel nanoporous carbon derived from a biomass source was prepared and used as an SPME fiber coating.

Flow-Assisted Electro-Enhanced Solid-Phase Microextraction for the Determination of Haloethers in Water Samples

Haloethers represent a special class of disinfection byproducts which pose serious harms to humans and are carcinogenic at parts per billion levels. Flow-assisted electro-enhanced solid-phase microextraction (FA-EE-SPME) method was developed for the determination of 4-chlorophenyl phenyl ether (CPPE) and 4-bromophenyl phenyl ether (BPPE) in large volumes of water samples. Within the extraction system, different commercial SPME fibers were exposed into a 100 mL sample flowing at a rate of 50 mL min−1 via direct immersion mode for extraction of target analytes. The major factors affecting the extraction efficiency such as absorption time, pump flow rate, ionic strength, applied potential, sample pH and SPME fiber type were optimized using one factor at-a-time approach. After extraction, the SPME fiber was desorbed in the injector port of gas chromatography–mass spectrometry (GC–MS). The proposed method combines advantages of electrical potential and flow system together to enhance extraction efficiency of SPME. Quantification was carried out over a concentration range of 0.5–100 µg L−1 and good linearity was obtained with detection limits of 0.05 and 0.07 µg L−1, respectively, for CPPE and BPPE. The relative standard deviation of the calibrations was in the range of 1.1 and 3.6 %. Application of FA-EE-SPME was tested for various drinking and tap water samples collected from Eastern Province of Saudi Arabia and the method performance was compared with reported literature values.

Solid phase microextraction Arrow for the sampling of volatile amines in wastewater and atmosphere

A new method is introduced for the sampling of volatile low molecular weight alkylamines in ambient air and wastewater by utilizing a novel SPME Arrow system, which contains a larger volume of sorbent compared to a standard SPME fiber. Parameters affecting the extraction, such as coating material, need for preconcentration, sample volume, pH, stirring rate, salt addition, extraction time and temperature were carefully optimized. In addition, analysis conditions, including desorption temperature and time as well as gas chromatographic parameters, were optimized. Compared to conventional SPME fiber, the SPME Arrow had better robustness and sensitivity. Average intermediate reproducibility of the method expressed as relative standard deviation was 12% for dimethylamine and 14% for trimethylamine, and their limit of quantification 10μg/L and 0.13μg/L respectively. Working range was from limits of quantification to 500μg/L for dimethylamine and to 130μg/L for trimethylamine. Several alkylamines were qualitatively analyzed in real samples, while target compounds dimethyl- and trimethylamines were quantified. The concentrations in influent and effluent wastewater samples were almost the same (∼80μg/L for dimethylamine, 120μg/L for trimethylamine) meaning that amines pass the water purification process unchanged or they are produced at the same rate as they are removed. For the air samples, preconcentration with phosphoric acid coated denuder was required and the concentration of trimethylamine was found to be around 1ng/m3. The developed method was compared with optimized method based on conventional SPME and advantages and disadvantages of both approaches are discussed.

IDENTIFICATION OF ODOR COMPONENTS OF AGARWOOD

This article presents the use of Z-score in assessing the significant chemical compounds extracted by head space solid phase microextraction (HS-SPME) and gas chromatography – mass spectrometry (GC-MS) analysis of an agarwood oil obtained from Melaka, Malaysia. Two types of SPME fiber; polydimethylsiloxane (PDMS) and divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) were used. During the extraction analysis, the results showed that at least 27 and 29 compounds were identified using PDMS and DVB-CAR-PDMS fiber, respectively. DVB-CAR-PDMS fiber was found to be more efficient in terms of selectivity of compounds extraction. The application of Z-score showed that eight and eleven marker compounds were determined in PDMS and DVB-CAR-PDMS fibers, respectively. 4-Phenyl-2-butanone, a-guaiene, β-agarofuran, a-bulnesene, a-agarofuran and 10-epi-g-eudesmol were some of the compounds selected and were often reported significantly in agarwood oils as key odor compounds. The information gathered will be used for compound selection towards grading of agarwood oils by sensor technology.

The development of a SPME-GC/MS method for the analysis of VOC emissions from historic plastic and rubber materials

Analytical methods have been developed for the analysis of VOC emissions from historic plastic and rubber materials using SPME-GC/MS. Parameters such as analysis temperature, sampling time and choice of SPME fibre coating were investigated and sampling preparation strategies explored, including headspace sampling in vials and in gas sampling bags. The repeatability of the method was evaluated. It was found that a 7d accumulation time at room temperature, followed by sampling using a DVB/CAR/PDMS fibre, with a sampling time of 60min at room temperature was a suitable strategy for the detection of VOC emissions from a wide range of historic plastic and rubber artefacts. For 20ml vials, a sample size of 50mg was found to be appropriate and grinding the samples improved the repeatability of the analysis and yielded higher levels of emissions. A non-destructive adaptation of the method that could be used directly on historic objects in a museum environment is also presented. The detected emissions improve understanding of ongoing degradation processes within historic plastic and rubber materials, in addition to providing information on material composition.

Modified application of HS-SPME for quality evaluation of essential oil plant materials

The main limitation in the standard application of head space analysis employing solid phase microextraction (HS-SPME) for the evaluation of plants as sources of essential oils (EOs) are different quantitative relations of EO components from those obtained by direct analysis of EO which was got in the steam distillation (SD) process from the same plant (EO/SD). The results presented in the paper for thyme, mint, sage, basil, savory, and marjoram prove that the quantitative relations of EO components established by HS-SPME procedure and direct analysis of EO/SD are similar when the plant material in the HS-SPME process is replaced by its suspension in oil of the same physicochemical character as that of SPME fiber coating. The observed differences in the thyme EO composition estimated by both procedures are insignificant (Fexp<Fcrit). In relation to classical EO analysis involving the SD procedure, the application of the new HS-SPME procedure proposed in this paper substantially shortens the evaluation time of plant material quality and thus may improve the efficiency of analytical laboratories.

Detailed identification and quantification of the condensable species released during torrefaction of lignocellulosic biomasses

Torrefaction is a mild thermal pretreatment which improves biomass properties and releases condensable species. Condensable species released during torrefaction of pine, ash wood, miscanthus and wheat straw at 250, 280 and 300°C were investigated. A fixed-bed reactor was used for the laboratory scale experiments. A micro-GC, Karl Fischer titrator and GC-MS were used to analyse incondensable gases, water and other condensable species, respectively. The overall mass balance ranged from 96 to 103wt.%. The quantification rate of condensable species was on average 77wt.%. In addition to the major species usually reported in the literature – water, acetic acid, 2-propanone,1-hydroxy- – we show that large amounts of some anhydrosugars were produced. Additionally, 85 condensable species were identified. Among these species, many terpenes and terpenoids in pine were identified by adsorption on SPME fibre. Finally, the influence of temperature and of the nature of biomass on the yields of condensable species was highlighted.

Development of a standard gas generating vial comprised of a silicon oil–polystyrene/divinylbenzene composite sorbent

In this work, a highly reproducible standard gas generating vial is proposed. The vial is comprised of a silicon diffusion pump oil spiked with an appropriate calibration compound, such as modified McReynolds probes (benzene, 2-pentanone, pyridine, 1-nitropropane, 1-pentanol, and n-octane), and then mixed with polystyrene/divinylbenzene (PS/DVB) particles. The concentrations of these compounds in gaseous headspace were found to substantially decrease in comparison to previously developed hydrocarbon pump oil based vials; hence, the amount of standard loaded onto SPME fibers was at most, half that of the previous vial design. Depletion for all compounds after 208 successive extractions was shown to be less than 3.5%. Smaller quantities of standards being used resulted in a vial that depleted slower while remaining statistically repeatable over a wider number of runs. Indeed, it was found that depletion could be largely predicted by using a mass balance theoretical model. This behavior allowed a further increase in the number of loadings that could be performed repeatedly. At a 95% level of confidence, the ANOVA test demonstrated that the prepared vials were statistically identical, with no significant intra- or inter-batch differences. In addition, it was found that vials stored under different conditions (e.g. under light exposure, room temperature, and within a refrigerator) were stable over 10 weeks. Silicon based vials proved to be ideal for performing instrument quality control and loading of internal standards onto fibers, both of which are of great importance when performing on-site analysis using portable GC–MS instrumentation and high throughput determinations in laboratory.

Optimization of headspace solid phase microextraction for the analysis of microbial volatile organic compounds emitted by fungi: Application to historical objects

The main goal of this work was to optimize the SPME sampling method for measuring microbial volatile organic compounds (MVOCs) emitted by active molds that may deteriorate historical objects. A series of artificially aged model materials that resemble those found in historical objects was prepared and evaluated after exposure to four different types of fungi. The investigated pairs consisted of: Alternaria alternata on silk, Aspergillus niger on parchment, Chaetomium globosum on paper and wool, and Cladosporium herbarum on paper. First of all, a selection of the most efficient SPME fibers was carried out as there are six different types of fibers commercially available. It was important to find a fiber that absorbs the biggest number and the highest amount of MVOCs. The results allowed establishing and selecting the DVB/CAR/PDMS fiber as the most effective SPME fiber for this kind of an analysis. Another task was to optimize the time of MVOCs extraction on the fiber. It was recognized that a time between 12 and 24h is adequate for absorbing a high enough amount of MVOCs. In the last step the temperature of MVOCs desorption in the GC injection port was optimized. It was found that desorption at a temperature of 250°C allowed obtaining chromatograms with the highest abundances of compounds. To the best of our knowledge this work constitutes the first attempt of the SPME method optimization for sampling MVOCs emitted by molds growing on historical objects.

Chlorophenol’s ultra-trace analysis in environmental samples by chitosan–zinc oxide nanorod composite as a novel coating for solid phase micro-extraction combined with high performance liquid chromatography

In this study, a simple, novel, and efficient preconcentration method has been developed for the determination of some chlorophenols (4-chlorophenol, 2,5-dichlorophenol, 2,3-dichlorophenol, and 2,4,6-trichlorophenol) using a direct solid phase microextraction (D-SPME) based on chitosan–ZnO nanorod composite combined with high performance liquid chromatography (HPLC). A one step-novel hydrothermal method was demonstrated on the fabrication of ZnO nanorods arrayed on the fused silica fiber in the chitosan hydrogel solution (CZNC) as a new coating of SPME fiber. The coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) instruments. The CZNC coating has combined the merits of both ZnO nanorods and chitosan hydrogel; it has several improvements such as increased extraction efficiency of chlorophenols and longer life time (over 80 cycles of D-SPME-HPLC operation). Experimental design method was used for optimization of extraction conditions and determination of four chlorophenols in water samples by SPME-HPLC-UV method. The calibration curves were linear from 5 to 1000µgL−1 for analytes, and the limits of detection were between 0.1 and 2µgL−1. Single fiber repeatability and fiber-to-fiber reproducibility were in the range of 5.8–10.2% and 8.8–14.5%, respectively. The spiked recoveries at 50µgL−1 for environmental water sample were in the range of 93–102%.