Monoterpene and sesquiterpene hydrocarbons of virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry

In the present article, a headspace solid-phase microextraction method coupled to GC/MS was developed and applied for the simultaneous determination of mono- and sesquiterpenic hydrocarbons in virgin olive oils of different olive variety and geographical origin. Analysis of various oils resulted in the simultaneous detection of 15 monoterpenes and 30 sesquiterpenes. Some of these hydrocarbons were previously reported to be constituents of virgin olive oil terpenoid fraction, although we also detected some terpenic hydrocarbons that have not previously been documented as present in virgin olive oil. Significant differences were detected in the proportion of terpenic compounds in oils obtained from different olive varieties grown in different geographical areas. The monoterpene, and particularly the sesquiterpene composition of olive oil may be used to distinguish samples from different cultivar and geographical areas.     

Analysis of virgin olive oil volatile compounds by headspace solid-phase microextraction coupled to gas chromatography with mass spectrometric and flame ionization detection

The efficiency of headspace solid-phase microextraction (SPME) was evaluated for the qualitative and semi-quantitative analysis of virgin olive oil volatile compounds. The behaviour of four fibre coatings was compared for sensitivity, repeatability and linearity of response. A divinylbenzene-Carboxen-polydimethylsiloxane fibre coating was found to be the most suitable for the analysis of virgin olive oil volatiles. Sampling and chromatographic conditions were examined and the SPME method, coupled to GC with MS and flame ionization detection, was applied to virgin olive oil samples. More than 100 compounds were isolated and characterised. The presence of some of these compounds in virgin olive oil has not previously been reported. The main volatile compounds present in the oil samples were determined quantitatively.     

Optimisation of wort volatile analysis by headspace solid-phase microextraction in combination with gas chromatography and mass spectrometry

The aim of this study was to create a simple, solventless technique without derivatisation in order to analyze a broad range of volatiles in beer wort. A method was developed using headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry. The procedure was optimised by selection of the appropriate fibre and optimisation of extraction temperature, extraction time, and salting-out. The detection limits were well below the actual wort concentrations of the selected volatiles, ranging from 12 ng/l for linalool to 0.53 microg/l for furfural. Moreover, the procedure showed a good linearity and was applied to the analysis of wort samples taken from a wort boiling process in an industrial brewery.     

Application of gas chromatography coupled to chemical ionisation mass spectrometry following headspace solid-phase microextraction for the determination of free volatile fatty acids in aqueous samples

Gas chromatography coupled to positive and negative ion chemical ionisation mass spectrometry was evaluated for the determination of free volatile fatty acids (VFAs) from aqueous samples by headspace solid-phase microextraction. Negative ion chemical ionisation in the selected ion monitoring mode using ammonia as reagent gas provided acceptable sensitivity and the highest selectivity for the determination of C2-C7 fatty acids using a polydimethylsiloxane-Carboxen fibre. Detection limits in the range of 150 microg l(-1) for acetic acid and from 2 to 6 microg l(-1) for the remaining carboxylic acids were achieved. The reproducibility of the method was between 9 and 16%. The developed analytical procedure was applied to the analysis of VFAs in raw sewage. The absence of interfering peaks provided a more accurate determination of acetic, propionic, butyric and isovaleric acids than a similar analytical scheme but using a flame ionisation detector.     

Determination of polycyclic aromatic hydrocarbons in olive oil by a completely automated headspace technique coupled to gas chromatography-mass spectrometry

A new and completely automated method for the determination of ten relevant polycyclic aromatic hydrocarbons (PAHs) in olive oil is proposed using an extraction by the headspace (HS) technique. Quantification and confirmation steps are carried out by gas chromatography-mass spectrometry (GC-MS) combining simultaneously selected-ion monitoring (SIM) and tandem mass spectrometry (MS/MS). This combination offers on one hand an increased sensitivity and on the other hand, selective and reliable qualitative information. Sample pretreatment or clean-up are not necessary because the olive oil sample is put directly into an HS vial, automatically processed by HS and introduced into the GC-MS instrument for analysis. Because of its high selectivity and sensitivity, a triple-quadrupole (QqQ) detector coupled with the gas chromatograph allows us to limit handling. Each sample is completely processed in approximately 63 min (45 min for HS isolation and 18 min for GC-MS determination), a reduced time compared with previously published methods. The chemical and instrumental variables were preliminarily optimized using uncontaminated olive oil samples spiked with 25 microg kg(-1) of each target compound. The final method was validated to ensure the quality of the results. The precision was satisfactory, with relative standard deviation (RSD) values in the range 3-9%. Recovery rates ranged from 96 to 99%. Limits of detection (LOD) were calculated as 0.02-0.06 microg kg(-1) and the limits of quantification (LOQ) were obtained as 0.07-0.26 microg kg(-1). It must be mentioned that the LOD and LOQ are much lower than the maximum levels established by the European Union (EU) in oils and fats intended for direct human consumption or for use as an ingredient in foods, which are set at 2 microg kg(-1). All the figures of merit are completely in accordance with the latest EU legislation. This fact makes it possible to consider the proposed method as a useful tool for the control of PAHs in olive oils.     

Rapid white truffle headspace analysis by proton transfer reaction mass spectrometry and comparison with solid-phase microextraction coupled with gas chromatography/mass spectrometry

The gastronomic relevance and high price of white truffle are related mainly to its unique aroma. Here we evaluate, for the first time, the possibility of characterizing in a rapid and non-destructive way the aroma of white truffles based on proton transfer reaction mass spectrometry (PTR-MS). We indicate that anonymous PTR-MS fingerprinting allows sample classification and we also compare qualitatively and quantitatively PTR-MS data with measurements made by solid-phase microextraction gas chromatography (SPME-GC) of the same samples under the same conditions. PTR-MS fragmentation data of truffle-relevant compounds are also published here for the first time. Most of the sulfur-containing compounds detected by GC and relevant for white truffle aroma have a high positive correlation with single PTR-MS peaks. Our work indicates that, after preliminary comparison with GC data, PTR-MS is a new tool for the rapid, quantitative and non-invasive characterization of white truffle by direct headspace injection without any pre-concentration.     

Determination of volatile organic acids in oriental tobacco by needle-based derivatization headspace liquid-phase microextraction coupled to gas chromatography/mass spectrometry

A method coupling needle-based derivatization headspace liquid-phase microextraction with gas chromatography-mass spectrometry (HS-LPME/GC-MS) was developed to determine volatile organic acids in tobacco. The mixture of N,O-bis(trimethylsilyl)trifluoroacetamide and decane was utilized as the solvent for HS-LPME, resulting that extraction and derivatization were simultaneously completed in one step. The solvent served two purposes. First, it pre-concentrated volatile organic acids in the headspace of tobacco sample. Second, the volatile organic acids extracted were derivatized to form silyl derivatives in the drop. The main parameters affecting needle-based derivatization HS-LPME procedure such as extraction and derivatization reagent, microdrop volume, extraction and derivatization time, and preheating temperature and preheating time were optimized. The standard addition approach was essential to obtain accurate measurements by minimizing matrix effects. Good linearity (R(2)> or =0.9804) and good repeatability (RSDs< or =15.3%, n=5) for 16 analytes in spiked standard analytes sample were achieved. The method has the additional advantages that at the same time it is simple, fast, effective, sensitive, selective, and provides an overall profile of volatile organic acids in the oriental tobacco. This paper does offer an alternative approach to determine volatile organic acids in tobacco.     

Quantification of 13 priority polycyclic aromatic hydrocarbons in human urine by headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants in both living and working environments. The aim of this study was the development of a headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry (HS-SPME/GC-IDMS) method for the simultaneous quantification of 13 PAHs in urine samples. Different parameters affecting PAHs extraction by HS-SPME were considered and optimized: type/thickness of fiber coatings, extraction temperature/time, desorption temperature/time, ionic strength and sample agitation. The stability of spiked PAHs solutions and of real urine samples stored up to 90 days in containers of different materials was evaluated. In the optimized method, analytes were absorbed for 60 min at 80 °C in the sample headspace with a 100 μm polydimethylsiloxane fiber. The method is very specific, with linear range from the limit of quantification to 8.67 × 10³ ng L⁻¹, a within-run precision of <20% and a between-run precision of <20% for 2-, 3- and 4-ring compounds and of <30% for 5-ring compounds, trueness within 20% of the spiked concentration, and limit of quantification in the 2.28-2.28 × 10¹ ng L⁻¹ range. An application of the proposed method using 15 urine samples from subjects exposed to PAHs at different environmental levels is shown.     

Development of gas chromatography/mass spectrometry following headspace solid-phase microextraction for fast determination of asarones in plasma

Asarones (alpha-asarone and beta-asarone) are the active components in the traditional Chinese medicine (TCM) of Acorus tatarinowii Schott, which has been used to treat epilepsy for several thousand years. To perform the pharmacokinetics (PK) study of alpha- and beta-asarone from the TCM essential oil, a simple, rapid and sensitive method was developed for the determination of asarones from the TCM in rabbit plasma, based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography/mass spectrometry (GC/MS) with electron ionization (EI). The extraction parameters of headspace volume, fiber coating, sample temperature, extraction time, stirring rate and ion strength were systemically optimized. Furthermore, the method linearity, detection limit and precision were also investigated. It was shown that the proposed method provided a good linearity (0.02-20 microg/mL, R(2) > 0.99), low detection limit (<2.0 ng/mL) and good precision (RSD < 7.0%). Finally, HS-SPME followed by GC/MS was applied to fast determination of alpha- and beta-asarone in rabbit plasma at different time points after oral adminstration of the essential oil from A. tatarinowii. The experimental results suggest that the proposed method provides an alternative approach to the PK studies of volatile compounds in TCMs.     

Concurrent quantification of light and heavy sulphur volatiles in wine by headspace solid-phase microextraction coupled with gas chromatography/mass spectrometry

A new method based on headspace solid-phase microextraction coupled with gas chromatography/mass spectrometry (HS-SPME-GC/MS) to analyse 13 light and heavy volatile sulphur compounds in the same run was established. For the successful application of the procedure, various adsorption process parameters were optimised. In particular the nature of the adsorptive phase, the temperature, the ionic strength of the sample solutions and the equilibration time were considered. The best extraction conditions, in terms of the maximum signal obtainable for each compound, were obtained with a carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) 2 cm long coating fibre. The choice of suitable internal standards and the matrix effect were studied and the proposed method was validated by determining linearity, precision and accuracy, evaluating the critical, detection and quantification limits. This method is fast, sensitive and precise and easy to transfer to wine quality control. Finally, the proposed method was applied to the determination of the aforementioned sulphur compounds in 32 red and white wines.     

Trace level determination of trichloroethylene in biological samples by headspace solid-phase microextraction gas chromatography/negative chemical ionization mass spectrometry

A gas chromatography/negative chemical ionization mass spectrometry (GC/NCIMS) method using headspace solid-phase microextraction (HS-SPME) was developed for the determination of trichloroethylene (TCE) in blood, liver, kidney, lung and brain. The method was optimized with respect to several parameters including extraction time, extraction temperature, desorption time and salt addition. The method showed good linearity over the range of 0.025-25 ng/mL in blood and 0.075-75 ng/g in tissues with correlation coefficient (R2) values higher than 0.99. The precision and accuracy for intra-day and inter-day measurements were less than 10%. The relative recoveries of all matrices were greater than 52%. Samples showed no significant loss during 8 h in the autosampler and following three freeze/thaw cycles. Validation results demonstrated that selected-ion monitoring of the 35Cl and 37Cl isotopes using NCI resulted in reliable and sensitive quantitation. This validated method was successfully applied to study the toxicokinetics of TCE following oral administration of extremely low doses of this potential human carcinogen to small test animals (rats).     

Volatile fingerprints of artemisinin-rich Artemisia annua cultivars by headspace solid-phase microextraction gas chromatography/ mass spectrometry

The cultivar Anamed (A3) is a hybrid of Artemisia annua with a high content of the secondary metabolite artemisinin, a well-known antimalarial drug. Here we report for the first time the volatile profile of fresh leaves of this hybrid in comparison with that of Artemisia annua L. wild-type species. Evaluation and comparison of the volatile profiles of A. annua genotypes with different content in artemisinin were carried out by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography/mass spectrometry (GC/MS) that was performed on fresh leaves of the plants under investigation using a polydimethylsiloxane (PDMS) fiber. The chromatograms obtained from hybrids with a high content of artemisinin (A. annua cv. Anamed A3 and A. annua cv. Artemis F2) reveal the total absence of artemisia ketone, one of the major and characteristic compounds of the wild-type A. annua L., along with a significantly lower variety of volatile compounds. In conclusion, HS-SPME coupled with GC/MS is a very useful, non-destructive and efficient method to describe the volatile pattern of Artemisia annua cultivars. It represents a rapid screening method for the evaluation of volatile biomarkers like artemisia ketone, whose absence is typical of artemisinin-rich A. annua cultivars.     

Detection of perfluorocarbons in blood by headspace solid-phase microextraction combined with gas chromatography/mass spectrometry.

A new method of detection of perfluorocarbon molecules (PFCs) in blood sample has been established. After an extraction and pre-concentration step performed by headspace solid-phase microextraction (HS-SPME), the PFCs are detected by gas chromatography-mass spectrometry (GC/MS) with an ion trap mass spectrometer in MS and MS/MS modes. The influence of different parameters on the SPME process is discussed. The limit of detection and the linearity of the procedure have been determined for two PFCs.     

光皮木瓜果实中香气成分的GC-MS分析

以成熟光皮木瓜为试样,采用顶空固相微萃取与气质联用方法分析检测木瓜果实中的香气成分,共鉴定出43种香气成分,占总峰面积的92.89%。含量较高的依次为2-己烯醛、反式-2-甲基-环戊醇、(E,E)-2,4-己二烯醛、2-丁酮、(Z)-3-己烯醛、醋酸乙酯、(E)-3-己烯-1-醇、茶香螺烷等。其中C6化合物占总量的70%以上,因此可以确定C6化合物是构成光皮木瓜果实清香味的主要成分。     

Determination of phthalates and adipate in bottled water by headspace solid-phase microextraction and gas chromatography/mass spectrometry

The performance of three fibres for the headspace solid-phase microextraction (SPME) of di-2-ethylhexyl adipate (DEHA) and eight phthalates in water was investigated systematically under different extraction conditions. Good responses on the 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) SPME fibre were observed for DEHA and all phthalates. The polydimethylsiloxane (PDMS) SPME fibre had very poor responses for the lighter and slightly polar phthalates, dimethyl phthalate (DMP) and diethyl phthalate (DEP), while the divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) SPME fibre had very poor responses for the heavier and non-polar adipate and phthalates. The salt (NaCl) was found to increase the partitioning of DMP, DEP, diisobutyl phthalate (DiBP), di-n-butyl phthalate, and benzyl butyl phthalate (BBP) from water into the headspace, while partitioning of heavier adipate and phthalates from water into headspace was suppressed when the concentration of NaCl was above 10%. The automated headspace SPME methods were developed and validated under two different salting conditions (30% NaCl for DMP, DEP and BBP, and 10% for DEHA, DiBP, DBP, di-n-hexyl phthalate (DHP), di-2-ethylhexyl phthalate (DEHP), and di-n-octyl phthalate (DOP)). Linearity with R(2) values better than 0.9949 was observed for DEHA and eight phthalates over the range from 0.1 to 20 microg L(-1). Method detection limits ranged from 0.003 microg L(-1) for DOP to 0.085 microg L(-1) for BBP. Good repeatability was observed for DEHA and most phthalates with relative standard deviation (RSD) values less than 10%. The methods were used to analyse bottled water samples for DEHA and eight phthalates. DMP, DHP, BBP, DEHA and DOP were not detected in any samples. Concentrations of the other phthalates were low (around sub-ppb) except for DBP in the water from a polycarbonate bottle at 1.72 microg L(-1).     

Determination of aromatic hydrocarbons in asphalt release agents using headspace solid-phase microextraction and gas chromatography-mass spectrometry

The possibility of quantitative analysis of aromatic hydrocarbons in oil-based asphalt release agents was investigated using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). The target analytes studied were benzene, toluene, ethylbenzene, p-, m-, and o-xylene (BTEX) and 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene. Experimental parameters influencing HS-SPME efficiency were studied (equilibration time between sample and headspace and between headspace and SPME fiber, sample amount and sample matrice effects). A HS-SPME method using hexadecane as a surrogate matrice was developed. The detection limit was estimated as 0.03-0.08 ppm (w/w) for the target analytes investigated. Good linearity was observed (R2 > 0.999) for all calibration curves at high, medium and low concentration level. The repeatability of the method (RSD, relative standard deviation) was found to be less than 10% (generally less than 5%) in triplicate samples and approximately 2% at eight consecutive tests on one and the same sample. The accuracy of the method given by recovery of spiked samples was between 85 and 106% (generally between 95 and 105%). The HS-SPME method developed was applied to four commercially available asphalt release agents. External calibration and standard addition approaches were investigated regarding accuracy. The results showed that standard addition generates higher accuracy than external calibration. The contents of target aromatic hydrocarbons in the asphalt release agents studied varied greatly from approximately 0.1-700 ppm. The method described looks promising, and could be a valuable tool for determination of aromatic hydrocarbons in different types of organic matrices.     

Determination of diisopropylfluorophosphate in rat plasma and brain tissue by headspace solid-phase microextraction gas chromatography/mass spectrometry

A simple, sensitive and rapid method for the determination of diisopropylfluorophosphate (DFP) in rat plasma and brain tissue using headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. A 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was selected for sampling. The main parameters affecting the SPME process such as extraction and desorption temperature, extraction and desorption time, salt addition, and fiber preheating time were optimized in each matrix to enhance the extraction efficiency of the method. The lower limits of quantitation for DFP in plasma and brain tissue were 1 ng/mL and 3 ng/g, respectively. The method showed good linearity over the range from 1-100 ng/mL in plasma and 3-300 ng/g in brain tissue with correlation coefficient (R(2)) values higher than 0.995. The precision and accuracy for intra-day and inter-day were less than 10%. The relative recoveries in plasma and brain for DFP were greater than 50%. Stability tests including autosampler and freeze and thaw were also investigated. This validated method was successfully applied to study the neurobehavioral effects of low-level organophosphate exposures. Copyright (c) 2008 John Wiley & Sons, Ltd.