Vacuum-assisted Headspace Solid-phase Microextraction Research Articles

Vacuum-assisted headspace-solid phase microextraction of pesticides in grape samples

Vacuum-assisted headspace solid-phase microextraction (Vac-HS-SPME) could provide an alternative for extracting pesticides from grape samples. Vac-HS-SPME method is utilized to the simultaneous analysis of six pesticides from various classes, namely boscalid, quizalofop-p-methyl, oxyfluorfen, fluroxypyr-meptyl, metribuzin and epoxiconazole. In this study investigated and optimized the impact of independent variables, such as extraction temperature, extraction time, fiber coating, incubation time, salt effect, sample volume, air evacuation time, pH, desorption time with the objective of achieving lower detection limits (ranging from 0.11 to 0.61 µg mL-1) and effective analyte responses. Moreover, in this work a comparison was made between classical solid phase microextraction and vacuum-assisted solid phase microextraction for the extraction of pesticides in grape samples under the same parameters. The results clearly demonstrated that the combination of Vac-HS-SPME proved to be more appropriate and selective for the extraction of pesticides from grape samples.

Investigation of operational fundamentals for vacuum-assisted headspace high-capacity solid-phase microextraction and gas chromatographic analysis of semivolatile compounds from a model solid sample.

Vacuum-assisted headspace solid-phase microextraction (Vac-HS-SPME) is a technique used to enhance SPME sampling of semi-volatile organic compounds. Here, it was combined with a high-capacity SPME Arrow, which features a larger volume of extraction phase and a more rugged configuration than traditional extraction fibers. An in-depth assessment of the critical parameters was conducted to achieve optimal extraction of representative compounds from a model solid sample matrix (Ottawa sand). Operational fundamentals investigated included the types of seals needed to create a leak-free environment under vacuum conditions; the magnitude of the vacuum applied and time needed to activate the Vac kinetics; order of sample vial preparation methods (VPMs); and other standard variables associated with extract analysis by gas chromatography-mass spectrometry. When exploring the limits of sample VPMs, results indicated an ideal workflow requires the solid sample to be spiked before sealing the vial, allow the sample to rest overnight, then apply vacuum at a pressure of -677mbar (out of -789mbar maximum possible vacuum with pump and compressor used), exerted on the vial for 90 s. This work provides the necessary workflow for the optimization of Vac-HS-SPME sampling of analytes from solid matrices.

Vacuum-Assisted Headspace Solid-Phase Microextraction Sampling Method for the Extraction of Semi-Volatile Compounds: An Overview

Vacuum-assisted headspace solid-phase microextraction (Vac-HS-SPME) is an emerging sampling technique that enhances the extraction of semi-volatile compounds. The one extra step of pulling vacuum from the sampling vial pre-equilibrium increases the concentration of semi-volatiles in the headspace and allows for faster extraction times. This overview highlights the timeline, applications, and fundamentals of Vac-HS-SPME.

Enhance the Performance of Solid-Phase Microextraction by Exploiting Vacuum-Assisted Headspace and Multicumulative Trapping for Olive Oil Characterization

Headspace-solid-phase microextraction (HS-SPME) is a widely used technique for the analysis of volatile compounds from different kinds of samples and with multiple fields of applications. Despite of its applicability, it can require a long extraction time and it is limited by the volatility of the analytes of interest and the need for equilibrium conditions between the sample and the headspace. Recently, two additional approaches have been proposed to reduce the extraction time and broaden the coverage to less volatile compounds, namely vacuum-assisted HS-SPME and multi-cumulative trapping HS-SPME. This paper illustrates the principle of the two techniques and their potential for extending the applicability of HS-SPME, using them as alternatives or combined to characterize olive oil samples in terms of quality.

A simple and portable vacuum assisted headspace solid phase microextraction device coupled to gas chromatography based on covalent organic framework/metal organic framework hybrid for simultaneous analysis of volatile and semi-volatile compounds in soil

Various microextraction methods have demonstrated a positive effect when assisted by vacuum. However, working with such systems is often laborious, they often require expensive and non-portable vacuum pumps, and may even suck off some sample vapor or solid particles during the evacuation process. To address these issues, a simple, and affordable vacuum-assisted headspace solid-phase microextraction (HS-SPME) device was developed in this study. The device, named In Syringe Vacuum-assisted HS-SPME (ISV-HS-SPME), utilizes an adjustable 40 mL glass syringe as a vacuum provider and sampling vessel. A new fiber coating, made from a hybrid of covalent triazine-based frameworks and metal-organic frameworks (COF/MOF), was prepared and characterized by Fourier transform infrared spectrometry, field emission scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis, and Brunauer–Emmett–Teller techniques for use in the ISV-HS-SPME. By optimizing parameters such as extraction temperature, extraction time, desorption temperature, desorption time, and, humidity using a simplex method, the ISV system was found to increase the extraction efficiency of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in solid samples by up to 175%. The determinations were followed by GC-FID measurements. Compared to three commercially available fibers, the ISV-HS-SPME device with the COF/MOF (2DTP/MIL-101-Cr) fiber exhibited significantly higher peak areas for PAHs and BTEX. The linear dynamic ranges for BTEX and PAHs were 7.1–9000 ng g−1 and 0.23–9000 ng g−1, respectively, with limits of detection ranging from 2.1–5 ng g−1 for BTEX and 0.07–1.6 ng g−1 for PAHs. The relative standard deviation of the method was 2.6–7.8% for BTEX and 1.6–6.7% for PAHs. The ISV-HS-SPME was successfully used to simultaneously determine PAHs and BTEX in polluted soil samples with recoveries ranging from 80.4 to 108%.

Determination of Biomarkers in Multifloral Honey by Vacuum-Assisted Headspace Solid-Phase Microextraction

Determination of Biomarkers in Multifloral Honey by Vacuum-Assisted Headspace Solid-Phase Microextraction

A sustainable approach for the reliable and simultaneous determination of terpenoids and cannabinoids in hemp inflorescences by vacuum assisted headspace solid-phase microextraction

• Headspace solid phase microextraction can be adopted for the recovery of terpenoids and cannabinoids from Cannabis sativa inflorescences. • Vacuum conditions in the Cannabis headspace ensure the recovery of cannabinoids with low sampling temperature and time. • The adoption of mild conditions allows to not discriminate volatile and semivolatile fractions. • The adoption of mild conditions decreases the formation of artefacts. • The separation of terpenoid and cannabinoids markers can be obtained in less than 30 min with short narrow bore columns. Cannabis sativa L. is an intriguing plant that has been exploited since ancient times for recreational, medical, textile and food purposes. The plant's most promising bioactive constituents discovered so far belong to the terpenoid and cannabinoid classes. These specialised metabolites are highly concentrated in the plant aerial parts and their chemical characterisation is crucial to guarantee the safe and efficient use of the plant material irrespective of which use it is. This study investigates for the first time the use of vacuum assisted HS-SPME as a sample preparation process in an analytical protocol based on HS-SPME combined to fast GC-MS analysis that aims at comprehensively characterising both the terpenoid and cannabinoid profiles of Cannabis inflorescences in a single step. The results proved that vacuum in the HS should be preferred over atmospheric pressure conditions as it ensures the fast recovery of cannabinoid markers at relatively lower sampling temperatures (i.e., 90°C) that do not discriminate the most volatile fraction nor cause the formation of artefacts when the sampling time is minimised.

Vacuum-assisted headspace solid-phase microextraction and gas chromatography coupled to mass spectrometry applied to source rock analysis

Abstract Vacuum-assisted headspace solid phase microextraction (Vac-HSSPME) with high temperature of extraction was used for source-rock analysis. Optimization of extraction conditions was performed by Doehlert experimental design (DD) in gas chromatography coupled to mass spectrometer detector (GC–MS). Samples from the same oil well were mixed to obtain a mean stratigraphic characteristic for extraction optimization. Source-rock samples were analyzed in the DD optimal conditions and the proposed Vac-HSSPME+GC–MS method was compared to the classical procedure (SARA). The identification of important biomarkers like steranes and pentacyclic terpanes was possible. Fingerprint comparison between both methods shows similarity for steranes profile of overall chromatographic signal and compounds distribution. Also, it was possible to assess theoretical kinetic considerations for the system, as it differs from most conditions reported in literature. Furthermore, no organic solvent was used during the extraction or analysis with Vac-HSSPME. Classifying the procedure as a green methodology, while being faster and cheaper for oil bearing source-rock analyses.

Quantification of trace transformation products of rocket fuel unsymmetrical dimethylhydrazine in sand using vacuum-assisted headspace solid-phase microextraction.

Quantification of unsymmetrical dimethylhydrazine transformation products in solid samples is an important stage in monitoring of environmental pollution caused by heavy rockets launches. The new method for simultaneous quantification of unsymmetrical dimethylhydrazine transformation products in sand samples using vacuum-assisted headspace solid-phase microextraction without addition of water followed by gas chromatography-mass spectrometry is proposed. Decreasing air evacuation time from 120 to 20 s at 23 °C resulted in increased responses of analytes by 25-46% and allowed obtaining similar responses as after evacuation at -30 °C. The best combination of responses of analytes and their relative standard deviations (RSDs) was achieved after air evacuation of a sample (m = 1.00 g) for 20 s at 23 °C, incubation for 30 min at 40 °C, and 30-min extraction at 40 °C by Carboxen/polydimethylsiloxane(Car/PDMS) fiber. The method was validated in terms of linearity (R2=0.9912-0.9938), limits of detection (0.035 to 3.6 ng g-1), limits of quantification (0.12-12 ng g-1), recovery (84-97% with RSDs 1-11%), repeatability (RSDs 3-9%), and reproducibility (RSDs 7-11%). It has a number of major advantages over existing methods based on headspace solid-phase microextraction-lower detection limits, better accuracy and precision at similar or lower cost of sample preparation. The developed method was successfully applied for studying losses of analytes from open vials with model sand spiked with unsymmetrical dimethylhydrazine transformation products. It can be recommended for analysis of trace concentrations of unsymmetrical dimethylhydrazine transformation products when studying their transformation, migration and distribution in contaminated sand.

Sub-ambient temperature sampling of fish volatiles using vacuum-assisted headspace solid phase microextraction: Theoretical considerations and proof of concept

The extraction of volatiles from perishable food at a sub-ambient temperature using headspace solid-phase microextraction (HS-SPME) has not been considered in the past due to the corresponding loss in sensitivity. We propose HS-SPME sampling under vacuum (Vac–HS–SPME) to compensate problems of sensitivity loss and achieve substantial improvement in extraction efficiencies whilst sampling at temperatures as low as 5 °C. The approach was applied to fish samples, representing a highly vulnerable perishable food sample. The theoretical considerations explaining the performance of Vac–HS–SPME at sub-ambient temperatures are discussed and related to the increase in gas diffusivities when sampling under vacuum. A comparative study between Vac- and regular HS-SPME for the extraction of 18 compounds from salmon was carried out at different temperatures (5, 30 and 40 °C) and sampling times (10–60 min). For the majority of the compounds, Vac–HS–SPME at 5 °C yielded similar or superior extraction efficiencies than regular HS-SPME even when sampling at 40 °C. However, four compounds were better extracted at 1 atm presumably due to the intensification of competitive adsorption of analytes on the SPME fiber under vacuum or the partial losses of more volatile analytes during air-evacuation in the presence of the frozen samples. Sub-ambient temperature sampling (5 °C) combined with Vac–HS–SPME was also applied to monitor the changes in the 18 compounds present in salmon, redfish, and cod refrigerated for up to five days. The results were compared to those obtained with regular HS-SPME at 40 °C. Overall, Vac–HS–SPME sampling at 5 °C represents a new and powerful approach for the analysis of volatiles in refrigerated foods, and has a great potential for future studies in quality control and freshness assessment.

Rapid quantification and screening of nitrogen-containing rocket fuel transformation products by vortex assisted liquid-liquid microextraction and gas chromatography – high-resolution Orbitrap mass spectrometry

Existing and newly developed technologies for clean-up of wastewaters and soils contaminated with rocket fuel unsymmetrical dimethylhydrazine (UDMH) are based on the oxidative treatment, as well as gasification in supercritical water. Being easily transformed by a radical mechanism, UDMH is capable of producing an extremely wide range of potentially hazardous nitrogen-containing products. Their identification and simultaneous quantification at low concentrations in water samples by gas chromatography is a challenging task requiring a matrix change. We proposed a combination of dispersive vortex-assisted liquid-liquid microextraction (VALLME) of analytes followed by gas chromatography – Orbitrap mass spectrometry allowing simultaneous target analysis and non-targeted screening. Dichloromethane and chloroform provided rapid (10 min) and effective extraction of most of UDMH transformation products. The maximum recoveries were achieved by alkalizing and saturating the aqueous samples with ammonium sulfate. The use of pyridine‑d5 as an internal standard allowed developing an approach to the simultaneous determination of 24 compounds of various classes with detection limits for the most analytes in the range 0.02–1.1 μg L−1 and accuracy of 81–117% with low-cost, simple, and rapid sample preparation procedure. Extraction with a 100 µL of chloroform allowed further increasing sensitivity up to one order of magnitude and attaining LOD values for 20 compounds in the range of 0.002–0.1 μg L−1 comparable with that obtained by vacuum-assisted headspace solid-phase microextraction. The developed method was validated and tested for the analyses of real samples – degraded aqueous solution of rocket fuel, products of UDMH treatment in supercritical water and aqueous extract of soil from the place of carrier rocket accidental crash. Twenty-nine compounds that were not previously described as UDMH transformation products were tentatively identified.

Nanostructured octadecylsilica chemically coated stainless-steel fiber for vacuum-assisted HS-SPME sampling of PAHs in soil

An efficient and robust solid-phase microextraction (SPME) fiber was developed for vacuum-assisted sampling of polycyclic aromatic hydrocarbons (PAHs) in solid samples. The surface of a stainless-steel fiber was first oxidized and then coated with nanostructured n-octadecylsilica using the Stöber method, by hydrolysis and condensation of tetraethylorthosilicate in the presence of octadecyltrichlorosilane through a sol–gel strategy. The synthesized sorbent was characterized using scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and Fourier transform infrared spectroscopy (FT-IR). The developed vacuum-assisted headspace SPME (VA-HS-SPME) procedure was coupled with GC-FID and optimized for the analysis of PAHs in soil, using multivariate statistical analysis, based on Box-Behnken design. The calibration graphs for seven PAHs were linear (R2 > 0.995) over 0.001–4000 ng g−1. The limits of detection were found to be 0.1–0.9 pg g−1. The relative standard deviations for six repeated analyses of 100 ng g−1 of the PAHs (using a single fiber) were calculated 3.2–8.7% and fiber-to-fiber reproducibility (n = 6) obtained 5.2–12.34%. The nanostructured octadecylsilica was shown to be substantially robust and durable. It was utilized for ultrasensitive VA-HS-SPME/GC analysis of the PAHs in different polluted soil samples and satisfactory results were obtained, with low matrix effects.

Exploiting the versatility of vacuum-assisted headspace solid-phase microextraction in combination with the selectivity of ionic liquid-based GC stationary phases to discriminate Boswellia spp. resins through their volatile and semivolatile fractions.

The frankincense resins, secreted from Boswellia species, are an uncommon example of a natural raw material where every class of terpenoids is present in similar proportions. Diterpenoids (serratol, incensole, and incensole acetate) are used to discriminate samples from different species and origins. Headspace solid-phase microextraction has been used for frankincense analysis, although it requires long sampling time for medium- to low-volatility markers; headspace solid-phase microextraction under vacuum can overcome this limit. Gas chromatography is used for analysis but the separation of incensole and serratol needs polar stationary phases. In this study, we develop a method to discriminate frankincenses based on vacuum-assisted headspace solid-phase microextraction combined with fast gas chromatography-mass spectrometry with ionic liquid-based stationary phases. The optimized conditions for solid samples were: air evacuation below 0°C, 15min of incubation time, and 15min of extraction time. Losses of volatiles due to vial air-evacuation in the presence of the sample were minimized by sample amount above 100mg and low sample temperature. Fast gas chromatography provides the baseline separation of all markers in 20min. By applying vacuum sampling and fast gas chromatography, the total analysis was reduced to 50min compared to 120min (60min sampling plus 60min analysis) as previously reported. The method was successfully applied to commercial frankincense samples.

A multifaceted investigation on the effect of vacuum on the headspace solid-phase microextraction of extra-virgin olive oil

Headspace solid-phase microextraction (HS-SPME) is an easy, effective, and selective technique for the extraction of volatiles and semi-volatiles compounds. For the latter, longer equilibration times are needed, which are typically shortened by applying agitation or heating the sample. A less explored way to improve the extraction kinetics of analytes with a low-affinity for the headspace is to sample under vacuum conditions. The methodology that evolved from this approach was termed “vacuum-assisted HS-SPME” (Vac–HS–SPME) and was mainly used for water- and solid-based samples.The aim of this work was to investigate the effect of vacuum when dealing with non-aqueous liquid samples. For this purpose, the volatile profile of extra virgin olive oil was analyzed using a divinylbenzene/carboxen/polydimethylsiloxane fiber followed by gas chromatography-mass spectrometry. The effects of extraction temperature and sampling time were investigated using traditional one-variable at a time approach and a two-variable central component design for both Vac–HS–SPME and regular HS-SPME. The results showed an important enhancement in the extraction of semi-volatile compounds when using Vac–HS–SPME, and improved the information gained for the olive oil aroma fingerprint. A theoretical formulation of the underlying process was proposed, providing new insights into the SPME extraction theory. Lowering the sampling pressure effectively reduced gas-sided limitations and accelerated extraction kinetics. However, for viscous samples such as olive oils, the liquid-phase resistance played an important role and delayed extraction. Overall, applying heating (i.e. reducing the viscosity of the oily sample and increasing headspace concentrations) next to reducing the total pressure in the headspace is the best analytical HS-SPME strategy for obtaining fast a rich volatile profile from the oily samples.

Analysis of Volatile Compounds from Wheat Flour in the Heating Process

Abstract Volatile profiling was carried out during heating through vacuum-assisted headspace solid-phase microextraction combined with gas chromatography-mass spectrometry to better understand the flavor forming mechanism of flour products. Ninety-two volatile compounds were detected and identified, including aldehydes (25), ketones (15), alcohols (9), nitrogen- and sulfur-containing compounds (6), benzene derivatives (15), furans (10), and acids and esters (12). The formation temperature of each volatile was also determined. Results showed that temperature played an important role in the formation and content of volatile compounds. In the low-temperature range (60 °C–100 °C), the flavor composition of flour was mainly composed of C6–C10 volatile aldehydes and alcohols. At temperatures exceeding 100 °C, especially at 120 °C, many long carbon chain aldehydes and alcohols, furans, acids, esters, nitrogen- and sulfur-containing compounds were formed. The formation rate of most identified volatile compounds increased during heating, especially from 90 °C to 130 °C.

Room temperature and sensitive determination of haloanisoles in wine using vacuum-assisted headspace solid-phase microextraction

Headspace solid-phase microextraction (HSSPME) is a widespread technique used to extract trace amounts of haloanisoles from wine samples. A major challenge to overcome is the high ethanol content in wines that affects the solubilities of haloanisoles and reduces their headspace abundance. To overcome this obstacle and meet sensitivity requirements, reported HSSPME procedures typically suggest heating the wine samples and/or sampling for extended times. The present work proposes the use of vacuum-assisted HSSPME (Vac-HSSPME) to accelerate the extraction kinetics whilst sampling at room temperature. Although ethanol affected the physico-chemical properties of the target analytes, these changes were not sufficient to prevent the positive effect of vacuum on HSSPME sampling. To demonstrate the benefits of adopting the vacuum approach, Vac-HSSPME and regular HSSPME methods were independently optimized and the results were compared at all times. The effect of ethanol under each pressure condition was also discussed. Under the optimum conditions found, Vac-HSSPME sampling for 30 min at room temperature at 25 °C yielded lower detection limits (0.13 to 0.19 ng L−1) than those obtained with regular HSSPME sampling for 30 min at 55 °C (0.26 to 0.76 ng L−1). The proposed Vac-HSSPME method was successfully applied to quantify haloanisoles in bottled red wines and a discussion on the effect of wine volatiles was included. The standard addition method was used to minimize matrix effects. The increase in total pressure due to the presence of ethanol and other volatile wine components did not reduce the positive effect of vacuum on HSSPME. Nonetheless, in accordance to past HSSPME methods, the limits of detection and quantification were affected due to the noise level increase and analyte interaction with matrix. The proposed Vac-HSSPME procedure was applied to twelve bottled red wines and one sample was found positive on 2,4,6-trichloronanisole.

Определение продуктов трансформации несимметричного диметилгидразина в водных экстрактах из почвы на основе вакуумной парофазной твердофазной микроэкстракции

Quantification of transformation products of unsymmetrical dimethylhydrazine (UDMH) in soil requires tedious, time- and labor-consuming sample preparation. The simple and fast method for quantification of transformation products of UDMH in aqueous extracts from soil using vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) was optimized in this work. The method is based on extraction of analytes from soil with water followed by Vac-HSSPME of the obtained aqueous extracts, and gas chromatography-mass spectrometry analysis. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. The effect of a sample pH on responses of target analytes was studied. It was negligible, and no pH adjustment was recommended before a subsequent extraction. The water amount was optimized to provide the best combination of analytes responses and their precision. Extraction by adding 7.00 mL of water to 2.0 g of soil ensured linear dependence of responses of the analytes on their concentrations in soil. The optimized method provided detection limits of target analytes in soil in the range from 0.2 to 9 ng/g. The spike recoveries obtained for model samples were in the range 90-103%. The developed method can be recommended for application in laboratories conducting routine analyses of soil samples potentially contaminated by rocket fuel residuals.

Determination of transformation products of unsymmetrical dimethylhydrazine in water using vacuum-assisted headspace solid-phase microextraction

A new, sensitive and simple method based on vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) followed by gas chromatography-mass-spectrometry (GC–MS), is proposed for the quantification of rocket fuel unsymmetrical dimethylhydrazine (UDMH) transformation products in water samples. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. For these analytes and within shorter sampling times, Vac-HSSPME yielded detection limits (0.5–100 ng L−1) 3–10 times lower than those reported for regular HSSPME. Vac-HSSPME sampling for 30 min at 50 °C yielded the best combination of analyte responses and their standard deviations (<15%). 1-Formyl-2,2-dimethylhydrazine and formamide were discarded because of the poor precision and accuracy when using Vac-HSSPME. The recoveries for the rest of the analytes ranged between 80 and 119%. The modified Mininert valve and Thermogreen septum could be used for automated extraction as it ensured stable analyte signals even after long waiting times (>24 h). Finally, multiple Vac-HSSME proved to be an efficient tool for controlling the matrix effect and quantifying UDMH transformation products.

A comparison study on a sulfonated graphene-polyaniline nanocomposite coated fiber for analysis of nicotine in solid samples through the traditional and vacuum-assisted HS-SPME

A simple, rapid, and reliable headspace solid-phase microextraction (HS-SPME) procedure, reinforced by applying vacuum in the extraction vial, was developed. It was applied for the extraction of nicotine in solid samples prior to determination by gas chromatography-flame ionization detection (GC-FID). First, the surface of a narrow stainless steel wire was made porous and adhesive by platinization to obtain a durable, higher surface area, and resistant fiber. Then, a thin film of sulfonated graphene/polyaniline (Sulf-G/PANI) nanocomposite was synthesized and simultaneously coated on the platinized fiber using the electrophoretic deposition (EPD) method. It was demonstrated that the extraction efficiency remarkably increased by applying the reduced-pressure condition in the extraction vial. To evaluate the conventional HS-SPME and vacuum-assisted HS-SPME (VA-HS-SPME) platforms, all experimental parameters affecting the extraction efficiency including desorption time and temperature, extraction time and temperature and moisture content of sample matrix were optimized. The highest extraction efficiency was obtained at 60°C, 10min (extraction temperature and time) and 280°C, 2min (desorption condition), for VA-HS-SPME strategy, while for conventional HS-SPME the extraction and desorption conditions found to be 100°C, 30min and 280°C, 2min, respectively. The Sulf-G/PANI coated fiber showed high thermal stability, good chemical/mechanical resistance, and long lifetime. For analysis of nicotine in solid samples using VA-HS-SPME-GC-FID, linear dynamic range (LDR) was 0.01–30μgg−1 (R2=0.996), the relative standard deviation (RSD%, n=6), for analyses of 1μgg−1 nicotine was calculated 3.4% and limit of detection (LOD) found to be 0.002μgg−1. The VA-HS-SPME-GC-FID strategy was successfully carried out for quantitation of nicotine in hair and tobacco real samples.

Simple, Low-Cost and Reliable Device for Vacuum-Assisted Headspace Solid-Phase Microextraction of Volatile and Semivolatile Compounds from Complex Solid Samples

A new simple, low-cost, reliable vacuum-assisted headspace solid-phase microextraction (VA-HS-SPME) device was fabricated and evaluated considering the strengths and weaknesses of previously reported systems. The device can be applied for analysis of solid and liquid samples without sample loss or vacuum loss during the evacuation process, in contrast to similar setups. Additionally, it is simpler, lower cost, and more operator friendly for direct extraction of volatiles and semivolatiles from complicated solid matrices. It was coupled with gas chromatography-flame ionization detection (GC-FID) and applied for direct extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in polluted soil samples, without any sample preparation steps. Parameters affecting the performance of the developed method, such as extraction temperature and time, vacuum level, volumes of vacuum chamber and sample vial, and desorption condition, were investigated and optimized. Under the optimal conditions, calibration curves were linear over the range of 0.01–2 μg g−1 (R 2 > 0.996). The limits of detection (LODs) were found to lie in the range of 0.3–0.8 ng g−1, while the relative standard deviations (RSDs) for six replicate analyses were 5.3–7.1%. The developed VA-HS-SPME/GC-FID procedure was used for ultrasensitive determination of PAHs in contaminated soil samples; the results were statistically in agreement with those obtained using a validated ultrasonic solvent extraction (USE) method.