Use of headspace mulberry paper bag micro solid phase extraction for characterization of volatile aromas of essential oils from Bulgarian rose and Provence lavender

In this study, a new sampling method called headspace mulberry paper bag micro solid phase extraction (HS-MPB-μ-SPE) combined to gas chromatography-mass spectrometry has been applied for the analysis of volatile aromas of liquid essential oils from Bulgarian rose and Provence lavender. The technique uses an adsorbent (Tenax TA) contained in a mulberry paper bag, minimal amount of organic solvent. Linearities for the six-points calibration curves were excellent. LOD values were in the rage from 0.38 ng mL⁻¹ to 0.77 ng mL⁻¹. Overall, precision and recovery were generally good. Phenethyl alcohol and citronellol were the main components in the essential oil from Bulgarian rose. Linalyl acetate and linalool were the most abundant components in the essential oils from true lavender or lavandin. Additionally, the relative extraction efficiencies of proposed method have been compared with HS-SPME. The overall extraction efficiency was evaluated by the relative concentration factors (CF) of the several characteristic components. CF values by HS-MPB-μ-SPE were lower than those by headspace solid phase microextraction (HS-SPME). The HS-MPB-μ-SPE method is very simple to use, inexpensive, rapid, requires small sample amounts and solvent consumption. In addition, this method allowed combining of extraction, enrichment, and clean-up in a single step. HS-MPB-μ-SPE and GC/MS is a promising technique for the characterization of volatile aroma compounds from liquid essential oils.     

Carbon nanocones/disks as new coating for solid-phase microextraction

In this article, the potential of carbon nanocones/disks as coating for solid-phase microextraction has been evaluated for the first time. The nanostructures were immobilized on a stainless steel needle by means of an organic binder. The fiber coating obtained was ca. 50 μm of thickness and 35 mm in length. The evaluation of the sorbent capacity was carried out through the determination of toluene, ethylbenzene, xylene isomers and styrene in water samples following the headspace sampling modality (15 min, 30 °C). The fiber was then transferred to a 10 mL vial which was sealed and heated at 110 °C for 15 min in the headspace module of the instrument to achieve the thermal desorption of the analytes. Then 2.5 mL of the headspace generated were injected in the gas chromatograph-mass spectrometer for analytes separation and quantitation. The detection and quantitation limits obtained for 10 mL of sample were 0.15 and 0.5 ng mL⁻¹ (0.6 and 2 ng mL⁻¹ for toluene). The optimized procedure was applied to the determination of the selected volatile compounds in waters collected from different locations. The recovery values obtained (average recovery ca. 92%) demonstrated the usefulness of the carbon nanocones/disks as sorbent material in solid-phase microextraction.     

Headspace solid-phase microextraction–gas chromatography–mass spectrometry for profiling free volatile compounds in Cabernet Sauvignon grapes and wines

The complex aroma of wine is derived from many sources, with grape-derived components being responsible for the varietal character. The ability to monitor grape aroma compounds would allow for better understanding of how vineyard practices and winemaking processes influence the final volatile composition of the wine. Here, we describe a procedure using GC–MS combined with headspace solid-phase microextraction (HS-SPME) for profiling the free volatile compounds in Cabernet Sauvignon grapes. Different sample preparation (SPME fiber type, extraction time, extraction temperature and dilution solvent) and GC–MS conditions were evaluated to optimize the method. For the final method, grape skins were homogenized with water and 8 ml of sample were placed in a 20 ml headspace vial with addition of NaCl; a polydimethylsiloxane SPME fiber was used for extraction at 40 °C for 30 min with continuous stirring. Using this method, 27 flavor compounds were monitored and used to profile the free volatile components in Cabernet Sauvignon grapes at different maturity levels. Ten compounds from the grapes, including 2-phenylethanol and β-damascenone, were also identified in the corresponding wines. Using this procedure it is possible to follow selected volatiles through the winemaking process.     

Determination of aliphatic amines in water by gas chromatography using headspace solvent microextraction

The possibility of applying headspace microextraction into a single drop for the determination of amines in aqueous solutions is demonstrated. A 1 μl drop of benzyl alcohol containing 2-butanone as an internal standard was suspended from the tip of a micro syringe needle over the headspace of stirred sample solutions for extraction. The drop was then injected directly into a GC. The total chromatographic determination was less than 10 min. Optimization of experimental conditions (sampling time, sampling temperature, stirring rate, ionic strength of the solution, concentration of reagents, time of extraction and organic drop volume) with respect to the extraction efficiency were investigated and the linear range and the precision were also examined. Calibration curves yielded good linearity and concentrations down to 2.5 ng ml⁻¹ were detectable with R.S.D. values ranging from 6.0 to 12.0%. Finally, the method was successfully applied to the extraction and determination of amines in tap and river water samples. This system represents an inexpensive, fast, simple and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at trace levels.     

An interior needle electropolymerized pyrrole-based coating for headspace solid-phase dynamic extraction

A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography-mass spectrometry (GC-MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the scanning electron microscopy (SEM).The developed method was applied to the trace level extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample. In order to enhance the extraction efficiency and increase the partition coefficient of analytes, the stainless steel needle was cooled at 5 °C, while the sample solution was kept at 80 °C. Optimization of influential experimental conditions including the voltage of power supply, the time of PPy electrodeposition, the extraction temperature, the ionic strength and the extraction time were also investigated. The detection limits of the method under optimized conditions were in the range of 0.002-0.01 ng mL⁻¹. The relative standard deviations (R.S.D.) at a concentration level of 0.1 ng mL⁻¹ were obtained between 7.54 and 11.4% (n = 6). The calibration curves of PAHs showed linearity in the range of 0.01-10 ng mL⁻¹. The proposed method was successfully applied to the extraction of some selected PAHs from real-life water samples and the relative recoveries were higher than 90% for all the analytes.     

Rapid analysis of Achillea tenuifolia Lam essential oils by polythiophene/hexagonally ordered silica nanocomposite coating as a solid-phase microextraction fibre

In this work, a highly porous fibre coated with polythiophene/hexagonally ordered silica nanocomposite (PT/SBA-15) was prepared and used for extraction of essential oils with microwave-assisted distillation headspace solid phase microextraction (MA-HS-SPME) method. The prepared nanomaterials were immobilised on a stainless steel wire for fabrication of the SPME fibre. Using MA-HS-SPME followed by GC-MS, 24 compounds were separated and identified in Achillea tenuifolia, which mainly included limonene (28.6%), α-cadinol (12.7%), borneol (6.7%), caryophyllene oxide (3.2%), bornyl acetate (4.3%), camphene (3.2%) and para-cymene (2.3%). The experimental results showed that the polythiophene/hexagonally ordered silica nanocomposite fibres were suitable for the semi-quantitative study of the composition of essential oils in plant materials and for monitoring the variations in the volatile components of the plants.     

Headspace solvent microextraction: a very rapid method for identification of volatile components of Iranian Pimpinella anisum seed

At the present study, a new and rapid headspace solvent microextraction (HSME), for the extraction and pre-concentration of the volatile components of plant sample into a microdrop was applied. The extraction occurred by suspending a microliter drop of the solvent from the tip of a microsyringe to the headspace of a ripen and powdered dry fruit sample (Iranian Pimpinella anisum seed) in a sealed vial for a preset extraction time, then the microdrop was retracted back into the microsyringe and injected directly into a GC injection port. The chemical composition of the HSME extracts were confirmed according to their retention indexes and mass spectra (EI, 70 eV); and quantitative analysis was performed by GC-FID.Parameters such as the nature of the extracting solvent, particle size of the sample, temperatures of the microdrop and sample, volume of sample and the extraction time were studied and optimized, and the method's performance was evaluated. The optimized conditions were: sample particle size, 1 mm; sample volume, 5 ml (in a 15 ml vial); sample temperature, 60 °C; microsyringe needle temperature, 0 °C; and extraction time, 10 min. Finally, accordingly, the percentage of trans-anethole (the major compound of P. anisum) and the relative standard deviation for extraction and determination of trans-anethole (seven-replicated analysis) were determined to be 90% and 3.9%, respectively.     

Inhibiting sorbent stripping by designing a sorbent‐packed porous probe for headspace solid‐phase microextraction

To prevent the stripping of coating sorbents in headspace solid‐phase microextraction, a porous extraction probe with packed sorbent was introduced by using a porous stainless steel needle tube and homemade sol–gel sorbents. The traditional stainless‐steel needle tube was punched by a laser to obtain two rows of holes, which supply a passageway for analyte vapor during extraction and desorption. The sorbent was prepared by a traditional sol–gel method with both poly(ethylene glycol) and hydroxy‐terminated silicone oil as coating ingredients. Eight polycyclic aromatic hydrocarbons and six benzene series compounds were used as illustrative semi‐volatile and volatile organic compounds in sequence to verify the extraction performance of this porous headspace solid‐phase microextraction probe. It was found that the analysis method combining a headspace solid‐phase microextraction probe and gas chromatography with mass spectrometry yielded determination coefficients of no less than 0.985 and relative standard deviations of 4.3–12.4%. The porous headspace solid‐phase microextraction probe showed no decrease of extraction ability after 200 uses. These results demonstrate that the packed extraction probe with porous structure can be used for headspace solid‐phase microextraction. This novel design may overcome both the stripping and breakage problems of the conventional coating fiber.     

Silicone glue coated stainless steel wire for solid phase microextraction

A new solid phase microextraction (SPME) fiber based on high-temperature silicone glue coated on a stainless steel wire is presented. The fiber coating can be prepared easily in a few minutes, it is mechanically stable and exhibits relatively high thermal stability (up to 260 °C). The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using both direct and headspace SPME modes coupled to gas chromatography-flame ionization detection. The effects of the extraction and desorption parameters including extraction and desorption time, sampling and desorption temperature, and ionic strength on the extraction/desorption efficiency have been studied. For both headspace and direct SPME the calibration graphs were linear in the concentration range from 0.5 μg L⁻¹ to 10 mg L⁻¹ (R² > 0.996) and detection limits ranged from 0.07 to 0.24 μg L⁻¹. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.8 and 21.5%, respectively. Finally, headspace SPME was applied to determine BTEX in petrol station waste waters with spiked recoveries in the range of 89.7-105.2%.     

Automated headspace solid-phase dynamic extraction to analyse the volatile fraction of food matrices

High concentration capacity headspace techniques (headspace solid-phase microextraction (HS-SPME) and headspace sorptive extraction (HSSE)) are a bridge between static and dynamic headspace, since they give high concentration factors as does dynamic headspace (D-HS), and are as easy to apply and as reproducible as static headspace (S-HS). In 2000, Chromtech (Idstein, Germany) introduced an inside-needle technique for vapour and liquid sampling, solid-phase dynamic extraction (SPDE), also known as "the magic needle". In SPDE, analytes are concentrated on a 50 microm film of polydimethylsiloxane (PDMS) and activated carbon (10%) coated onto the inside wall of the stainless steel needle (5 cm) of a 2.5 ml gas tight syringe. When SPDE is used for headspace sampling (HS-SPDE), a fixed volume of the headspace of the sample under investigation is sucked up an appropriate number of times with the gas tight syringe and an analyte amount suitable for a reliable GC or GC-MS analysis accumulates in the polymer coating the needle wall. This article describes the preliminary results of both a study on the optimisation of sampling parameters conditioning HS-SPDE recovery, through the analysis of a standard mixture of highly volatile compounds (beta-pinene, isoamyl acetate and linalool) and of the HS-SPDE-GC-MS analyses of aromatic plants and food matrices. This study shows that HS-SPDE is a successful technique for HS-sampling with high concentration capability, good repeatability and intermediate precision, also when it is compared to HS-SPME.     

Use of solid phase microextraction in diffusive sampling of the atmosphere generated by different essential oils

This work describes the development and optimisation of a complete headspace-solid phase microextraction (HS-SPME) procedure for qualitative and quantitative analysis of the equilibrium headspace generated by a number of essential oils (EOs) with potential applications in active packaging, including basil (Ocinum basilicum), clove (Sygyzium aromaticum), rosemary (Rosmarinus officinalis), citronella (Melissa officinalis), and cinnamon (Cinnamonum zeylanicum). The method consists of a combination of fully exposed HS-SPME for qualitative analysis and diffusive HS-SPME for quantitative determination.First, complete optimisation of a fully exposed HS-SPME procedure was carried out by means of a combination of a Plackett-Burman screening experimental design and response surface modelling (RSM). The results were used to fully describe the atmosphere generated by the EOs and to select the most relevant compounds for further consideration.The fibres were then calibrated (i.e. the uptake rate was calculated) by exposing them to known concentrations of terpenes in closed extraction vials. With a sampling time of 30 min at 20 °C, uptake rates ranged from 2.2 to 3.3 pg (min ppb_v)⁻¹. Results were checked by sampling over extended periods of times, with the observed variation being less than 5%, despite a 10-fold increase in extraction time. The results were further validated by comparing the calculated diffusion coefficients with theoretical data. The ratios of experimental:theoretical values varied between 0.85 and 1.05. The sensitivity of the uptake rate to headspace concentration was also investigated; variation of less than 10% was observed despite changes in concentration of four orders of magnitude. The new diffusive sampling method proved to give robust determinations of all the test analytes (by contrast, HS-SPME failed for camphene, camphor and cinnamaldehyde), providing repetitivity and intermediate precision lower than 9% (the values for HS-SPME were 10 and 12%, respectively).     

In Vitro and In Vivo Human Body Odor Analysis Method Using GO:PANI/ZNRs/ZIF−8 Adsorbent Followed by GC/MS

Among various volatile organic compounds (VOCs) emitted from human skin, trans-2-nonenal, benzothiazole, hexyl salicylate, α-hexyl cinnamaldehyde, and isopropyl palmitate are key indicators associated with the degrees of aging. In our study, extraction and determination methods of human body odor are newly developed using headspace-in needle microextraction (HS-INME). The adsorbent was synthesized with graphene oxide:polyaniline/zinc nanorods/zeolitic imidazolate framework-8 (GO:PANI/ZNRs/ZIF−8). Then, a wire coated with the adsorbent was placed into the adsorption kit to be directly exposed to human skin as in vivo sampling and inserted into the needle so that it was able to be desorbed at the GC injector. The adsorption kit was made in-house with a 3D printer. For the in vitro method, the wire coated with the adsorbent was inserted into the needle and exposed to the headspace of the vial. When a cotton T-shirt containing body odor was transferred to a vial, the headspace of the vial was saturated with body odor VOCs. After volatile organic compounds were adsorbed in the dynamic mode, the needle was transferred to the injector for analysis of the volatile organic compounds by gas chromatography/mass spectrometry (GC/MS). The conditions of adsorbent fabrication and extraction for body odor compounds were optimized by response surface methodology (RSM). In conclusion, it was able to synthesize GO:PANI/ZNRs/ZIF−8 at the optimal condition and applicable to both in vivo and in vitro methods for body odor VOCs analysis.     

Application of solid-phase microextraction to the analysis of volatile compounds in virgin olive oils

Solid-phase microextraction was used as a technique for headspace sampling of extra virgin olive oil and virgin olive oil samples with different off-flavours. A 100 microm coated polydimethylsiloxane fiber was used to extract volatile aldehydes, the sampling temperature was 45 degrees C and the fiber has been exposed to the headspace for 15 min. Nonanal and 2-decenal were present in all the olive oils with extraction off-flavours but were not in extra virgin olive oil sample.     

Rapid removal of selected volatile organic compounds from gaseous mixtures using a new dispersive vapor extraction technique: A feasibility study

A new dispersive vapor extraction (DVE) technique for rapid removal of selected volatile organic compounds (VOCs) from gaseous mixtures was investigated. In this technique, less than 1.0 mL of a volatile solvent was vaporized for 8 min in a 250-mL flask containing a gaseous mixture. The flask was then cooled under running tap water for 2-3 min to induce condensation of the vapor and co-extraction of the VOCs from the headspace. The technique was tested over a concentration range of 4-23 ppb, and resulted in extraction efficiencies ranging from 80 to 97% for the VOCs tested. Because of its simplicity and the relatively short sampling time, DVE could potentially lead to high sample throughput and rapid air analysis.     

Comparative study of the whisky aroma profile based on headspace solid phase microextraction using different fibre coatings

A dynamic headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to ion trap mass spectrometry (GC-(IT)MS) method was developed and applied for the qualitative determination of the volatile compounds present in commercial whisky samples which alcoholic content was previously adjusted to 13% (v/v). Headspace SPME experimental conditions, such as fibre coating, extraction temperature and extraction time, were optimized in order to improve the extraction process. Five different SPME fibres were used in this study, namely, poly(dimethylsiloxane) (PDMS), poly(acrylate) (PA), Carboxen-poly(dimethylsiloxane) (CAR/PDMS), Carbowax-divinylbenzene (CW/DVB) and Carboxen-poly(dimethylsiloxane)-divinylbenzene (CAR/PDMS/DVB). The best results were obtained using a 75 microm CAR/PDMS fibre during headspace extraction at 40 degrees C with stirring at 750 rpm for 60 min, after saturating the samples with salt. The optimised methodology was then applied to investigate the volatile composition profile of three Scotch whisky samples--Black Label, Ballantines and Highland Clan. Approximately seventy volatile compounds were identified in the these samples, pertaining at several chemical groups, mainly fatty acids ethyl esters, higher alcohols, fatty acids, carbonyl compounds, monoterpenols, C13 norisoprenoids and some volatile phenols. The ethyl esters form an essential group of aroma components in whisky, to which they confer a pleasant aroma, with "fruity" odours. Qualitatively, the isoamyl acetate, with "banana" aroma, was the most interesting. Quantitatively, significant components are ethyl esters of caprilic, capric and lauric acids. The highest concentration of fatty acids, were observed for caprilic and capric acids. From the higher alcohols the fusel oils (3-methylbutan-1-ol and 2.phenyletanol) are the most important ones.     

Headspace liquid-phase microextraction of methamphetamine and amphetamine in urine by an aqueous drop

This study developed a headspace liquid-phase microextraction (LPME) method by using a single aqueous drop in combination with high performance liquid chromatography (HPLC)-UV detection for the determination of methamphetamine (MAP) and amphetamine (AP) in urine samples. The analytes, volatile and basic, were released from sample matrix into the headspace first, and then protonated and dissolved in an aqueous H₃PO₄ drop hanging in the headspace by a HPLC syringe. After extraction, this drop was directly injected into HPLC. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the investigated concentration range of 1.0-1500 μg L⁻¹, repeatability of the extraction (R.S.D. < 5%, n = 6), and low detection limits (0.3 μg L⁻¹ for both analytes). Enrichment factors of about 400-fold and 220-fold were achieved for MAP and AP, respectively, at optimum conditions. The feasibility of the method was demonstrated by analyzing human urine samples.     

Effect of maturation in small oak casks on the volatility of red wine aroma compounds

Wood maturation of red wine produces complex interactions between oak extracted compounds and pre-existing components in wine. Wood contributes with some aroma volatiles; but the whole volatile fraction, including the volatiles extracted from grape or produced during fermentation, could be involved in interactions with the non-volatile fraction. Samples of red wine with increasing time of wood contact, matured in 25 l casks of new American oak, were analysed on their volatile composition both in solution and headspace, and phenolic components. There was an increase of acetic acid and acetate esters as the time of wood contact increased. On the other hand, ethyl esters decreased as the time in wood increased. Some volatiles showed different behaviour when comparing their relationship between headspace and solution from two different casks, even though they were treated as replicates. This different evolution among casks was also consistent with different evolution of phenolic compounds, suggesting that there was an interaction among the volatile fraction and phenolic components.     

Characterization of volatile compounds of <Emphasis Type="Italic">Daucus crinitus</Emphasis>Desf. Headspace Solid Phase Microextraction as alternative technique to Hydrodistillation

Background  

Traditionally, the essential oil of aromatic herbs is obtained using hydrodistillation (HD). Because the emitted volatile fraction plays a fundamental role in a plant's life, various novel techniques have been developed for its extraction from plants. Among these, headspace solid phase microextraction (HS-SPME) can be used to obtain a rapid fingerprint of a plant's headspace. Daucus crinitus Desf. is a wild plant that grows along the west coast of Algeria. Only a single study has dealt with the chemical composition of the aerial part oils of Algerian D. crinitus, in which isochavicol isobutyrate (39.0%), octyl acetate (12.3%), and β-caryophyllene (5.4%) were identified. Using GC-RI and GC-MS analysis, the essential oils and the volatiles extracted from separated organs of D. crinitus Desf. were studied using HS-SPME.     

Corrosion problem in headspace gas chromatography with phase reaction conversion technique

This paper reports a corrosion problem in the headspace sampling needle when using a phase reaction conversion headspace gas chromatographic method in Agilent headspace auto-sampler. The examination by microscopy shows that corrosion mainly takes place on the surface of the outer wall of the needle that is exposed to the air during each headspace sampling. Since it was proven that the helium flushing is effective in minimizing the pit type of corrosion on the stainless needle material, a custom-made surface flushing device was proposed for corrosion inhibition.     

Preparation and characterization of fragrance by extracting the essential oils from different raw materials

The extraction is a simple process and it is widely used to extract the fragrances in fragrance industries from essential oils. There are number of compounds (i.e. flowers, oils, leaves etc.) from which we can prepare the fragrance by extracting the essential oils from them. In this work, we have prepared the fragrance from the essential oils by the liquid-liquid extraction process, where the essential oil presented as the concentrated hydrophobic liquid containing volatile aroma compounds. We used the combination of Gas chromatography and Mass spectrometry (GC/MS) characterization techniques to make our product more useful, convenient and compitative with the other fragrance available in the market. This study would be helpful to understand the preparation of the fragrance from the concentrated hydrophobic liquid type essential oils which contains volatile aroma compounds by using a significant liquid-liquid extraction process.