Screening of Brazilian fruit aromas using solid-phase microextraction-gas chromatography-mass spectrometry

Manual headspace solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was used for the qualitative analysis of the aromas of four native Brazilian fruits: cupuassu (Theobroma grandiflorum, Spreng.), cajá (Spondias lutea. L.), siriguela (Spondias purpurea, L.) and graviola (Anona reticulata, L). Industrialized pulps of these fruits were used as samples, and extractions with SPME fibers coated with polydimethylsiloxane, polyacrylate, Carbowax and Carboxen were carried out. The analytes identified included several alcohols, esters, carbonyl compounds and terpernoids. The highest amounts extracted, evaluated from the sum of peak areas, were achieved using the Carboxen fiber.     

Characterization of three agave species by gas chromatography and solid-phase microextraction-gas chromatography-mass spectrometry

Steam distillation (SD) extraction-solid-phase microextraction coupled to GC-MS was developed for the determination of terpenes and Bligh-Dyer extraction-derivatization coupled with GC for the determination of fatty acids such as ethyl esters were used. It was found that the three different Agave species have the same profile of fatty acids; the quantity of these compounds is different in each Agave variety. On the other hand, different terpenes were identified in the three Agave plants studied: nine in A. salmiana, eight in A. angustifolia and 32 in A. tequilana Weber var. azul.     

Analysis of tetramethylene disulfotetramine in foods using solid-phase microextraction-gas chromatography-mass spectrometry

An automated solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method for the determination of tetramethylene disulfotetramine in foods was developed. A comparison of direct immersion (DI) and headspace (HS) extraction techniques using a 70microm carbowax/divinylbenzene (CW/DVB) fiber is presented. The optimized DI-SPME method provided an aqueous extraction limit of detection (LOD) of 9.0ng/g while the HS-SPME LOD was 2.7ng/g. In both SPME modes, recovery was highly matrix dependent and quantification requires standard addition calibrations. Analysis of foods using DI-SPME encountered many obstacles including fiber fouling, low recovery and poor reproducibility. HS-SPME was successfully applied to food analysis with minimal interferences. Standard addition calibration curves for foods gave high linearity (R2>0.98), reproducibility (RSD<12%) and sensitivity with LODs ranging from 0.9 to 4.3ng/g.     

Rapid validated method for the analysis of benzo[a]pyrene in vegetable oils by using solid-phase microextraction-gas chromatography-mass spectrometry

A solid-phase microextraction method coupled with comprehensive gas chromatography and time-of-flight mass spectrometry for the determination of polycyclic aromatic hydrocarbons in vegetable oils has recently been reported. The present paper tested the possibility to use the solid-phase microextraction method coupled with one-dimensional gas chromatography-mass spectrometry of the only benzo[a]pyrene. Furthermore, an in-house validation for benzo[a]pyrene, used as a marker, as requested by the European regulation no. 208/2005, was carried out. Statistical tests were performed to elaborate the data. Linearity was satisfactory (r(2)=0.999), between about 0.5 and 15 microg/kg. Detection limit and quantification limit were 0.17 and 0.46 microg/kg, respectively. In-day and inter-day repeatability were less than 6% in both cases.     

Characterization of the volatile profile of Antarctic bacteria by using solid-phase microextraction-gas chromatography-mass spectrometry

Bacteria belonging to the Burkholderia cepacia complex (Bcc) are significant pathogens in Cystic Fibrosis (CF) patients and are resistant to a plethora of antibiotics. In this context, microorganisms from Antarctica are interesting because they produce antimicrobial compounds inhibiting the growth of other bacteria. This is particularly true for bacteria isolated from Antarctic sponges. The aim of this work was to characterize a set of Antarctic bacteria for their ability to produce new natural drugs that could be exploited in the control of infections in CF patients by Bcc bacteria. Hence, 11 bacterial strains allocated to different genera (e.g., Pseudoalteromonas, Arthrobacter and Psychrobacter) were tested for their ability to inhibit the growth of 21 Bcc strains and some other human pathogens. All these bacteria completely inhibited the growth of most, if not all, Bcc strains, suggesting a highly specific activity toward Bcc strains. Experimental evidences showed that the antimicrobial compounds are small volatile organic compounds, and are constitutively produced via an unknown pathway. The microbial volatile profile was obtained by SPME-GC-MS within the m/z interval of 40-450. Solid phase micro extraction technique affords the possibility to extract the volatile compounds in head space with a minimal sample perturbation. Principal component analysis and successive cluster discriminant analysis was applied to evaluate the relationships among the volatile organic compounds with the aim of classifying the microorganisms by their volatile profile. These data highlight the potentiality of Antarctic bacteria as novel sources of antibacterial substances to face Bcc infections in CF patients.     

Determination of anethole in serum samples by headspace solid-phase microextraction-gas chromatography-mass spectrometry for congener analysis

A rapid headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method has been developed for the determination of anethole in serum samples. Anethole is a characteristic marker for the consumption of aniseed spirits. This method enabled the detection of anethole with a limit of detection (LoD) of 3.6 ng/ml and a limit of quantification (LoQ) of 5.3 ng/ml in serum samples with a good degree of precision intraday (2.8%) and interday (4.5%). Experiments were conducted with one volunteer, in which the subject consumed the alcoholic drink ouzo on 3 different days under controlled conditions. At defined intervals, blood samples were taken from the subject. Using these blood samples, the concentration-time profiles for anethole were determined. In blood samples taken from 50 drivers who claimed to have consumed drinks containing anethole (ouzo, raki and the German aniseed liqueur "Küstennebel") before the taking of the blood sample, anethole was detected in the serum in concentrations of between 5.4 and 17.6 ng/ml in 10 cases. This is the first report describing the qualitative and quantitative determination of a beverage-characteristic aroma compound - in this case anethole - in serum samples after consumption of alcoholic beverages.     

Development of headspace solid-phase microextraction-gas chromatography-mass spectrometry methodology for analysis of terpenoids in Madeira wines

A dynamic headspace solid-phase microextraction methodology was developed for analysis of varietal aroma compounds in must and Madeira wine samples, a spirit wine with an ethanol content of 18% (v/v). The factors with influence in the headspace solid-phase microextraction efficiency such as: fibre coating, extraction time and temperature, pH, ionic strength, ethanol content, desorption time and temperature, were optimised and the method validated. The best results were obtained for a 85 μm polyacrylate fibre, with a 60 min headspace for must and 120 min for wine samples, in a 2.4 ml sample at 40 °C with 30% of NaCl. The extract is injected in the splitless mode in a GC-MS Varian system, Saturn III, and separated on a Stabilwax capillary column. The linear dynamic range of the method covers the normal range of occurrence of analytes in wine with typical r² between 0.985 (β-ionone) and 0.998 (linalool) for musts and between 0.980 (α-terpineol) and 0.999 (linalool) for must and wine samples, respectively. For must samples the reproducibility ranges from 2.5% (citronellol) to 14.4% (nerolidol) (as R.S.D.), and from 4.8% (citronellol) to 14.2% (nerolidol) for wine samples. The analysis of spiked samples has shown that matrix effects do not significantly affect method performance. Limits of detection obtained are in low μg l⁻¹ range for all compounds analysed in this study.     

Screening of protein-ligand interactions using dynamic protein-affinity chromatography solid-phase extraction-liquid chromatography-mass spectrometry

A novel methodology is shown enabling the screening of mixtures of compounds for their affinity to a receptor protein. The system presented, dynamic protein-affinity chromatography solid-phase extraction (DPAC-SPE), overcomes the limitations of the existing methods by performing an incubation of the His-tagged protein with a mixture of possible ligands, which are still in their native conditions. This is followed by a fully automated affinity trapping step, coupled on-line to an LC-MS system in order to detect and identify the bound ligands. The system has been optimized using a commercially available on-line SPE system, using the estrogen receptor alpha (ERalpha) as model protein. A representative range of ligands with sub-nanomolar to millimolar affinities has been identified successfully from a mixture. The weakest binder that can be identified is norethindrone (approximately K(d)=0.1-1mM). The same setup also provides the possibilities to measure EC50 curves of both weak and strong binders.     

Determination of amphetamine and methamphetamine in serum via headspace derivatization solid-phase microextraction-gas chromatography-mass spectrometry

This study evaluates solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to determine trace levels of amphetamine and methamphetamine in serum. Headspace post-derivatization in a laboratory-made design with heptafluorobutyric anhydride vapor following SPME was compared with that without derivatization SPME. The SPME experimental procedures to extract amphetamine and methamphetamine in serum were optimized with a relatively non-polar poly(dimethylsiloxane) coated fiber at pH 9.5, extraction time for 40 min and desorption at 260 degrees C for 2 min. Experimental results indicate that the concentration of the serum matrix diluted to a quarter of original (1:3) ratio by using one volume of buffer solution of boric acid mixed with sodium hydroxide and two volumes of water improves the extraction efficiency. Headspace derivatization following SPME was performed by using 6 microl 20% (v/v) heptafluorobutyric anhydride ethyl acetate solution at an oil bath temperature of 270 degrees C for 10 s. The precision was below 7% for analysis for without derivatization and below 17% for headspace derivatization. Detection limits were obtained at the ng/l level, one order better obtained in headspace derivatization than those achieved without derivatization. The feasibility of applying the methods to determine amphetamine and methamphetamine in real samples was examined by analyzing serum samples from methamphetamine abused suspects. Concentrations of the amphetamine and methamphetamine ranged from 6.0 microg/l (amphetamine) to 77 microg/l (methamphetamine) in serum.     

Comparison of comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry and gas chromatography-mass spectrometry for the analysis of tobacco essential oils

A sample of tobacco essential oil was analyzed using gas chromatography-mass spectrometry (GC/MS) and comprehensive two-dimensional gas chromatography coupled to a time-of-flight mass spectrometry (GC × GC/TOFMS), respectively. In the GC/MS analysis, serially coupled columns were used. By comparing the GC/MS results with GC × GC/TOFMS results, many more components in the essential oil could be found within the two-dimensional separation space of GC × GC. The quantitative determination of components in the essential oil was performed by GC × GC with flame ionization detection (FID), using a method of multiple internal standards calibration.     

The extraction and analysis of 1,4-dioxane from water using solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry

In this study, two methods are developed for the extraction of 1,4-dioxane (dioxane) from water using 80-microm carboxen-polydimethylsiloxane solid-phase microextraction fibers followed by either gas chromatography (GC)-flame ionization detection (FID) or GC-mass spectrometry (MS). With GC-FID, the lower limit of detection (LOD) for 1,4-dioxane is 2.5 microg/L (ppb) with a linear range of 5 to 10,000 microg/L, obtained by immersing the fiber in the sample for 20 min with agitation. Using GC-MS, the lower limit of quantitation is 0.5 microg/L, and the LOD is 0.25 microg/L. The upper linear range limit is 100 microg/L. Samples are extracted in 20 min using either heated headspace with agitation or direct immersion with agitation.     

Fast analysis of volatile organic compounds and disinfection by-products in drinking water using solid-phase microextraction-gas chromatography/time-of-flight mass spectrometry

A fast method was developed for the extraction and analysis of volatile organic compounds, including disinfection by-products (DBPs), with headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) techniques. A GC/time-of-flight (TOF)-MS instrument, which had fast acquisition rates and powerful deconvolution software, was used. Under optimum conditions total runtime was 45s. Volatile organic compounds (VOCs), including purgeable A and B compounds (listed in US Environmental Protection Agency method 624), were identified in standard water samples. Extraction times were 1min for more volatile compounds and 2min for less volatile compounds. The method was applied to the analysis of water samples treated under different disinfection processes and the results were compared with those from a liquid-liquid extraction method.     

Quality assessment of Flos Chrysanthemi Indici from different growing areas in China by solid-phase microextraction-gas chromatography-mass spectrometry

Flos Chrysanthemi Indici is a common traditional Chinese medicine (TCM). In this paper, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was developed for quality assessment of Flos Chrysanthemi Indici from different growing areas in China. SPME parameters such as extraction fibers, extraction temperature, extraction time and sample mass were investigated to achieve identical results to those obtained by the steam distillation (SD). The selected SPME conditions were as follows: SPME fiber coated with 65-microm PDMS/DVB, extraction temperature of 60 degrees C, extraction time of 30 min and sample mass of 1.0 g. Furthermore, four active compounds (eucalyptol, camphor, borneol and bornyl acetate) presented in the TCM were applied to evaluating the quality of Flos Chrysanthemi Indici from 20 various areas. The quality assessment was successfully performed to compare the similarity value (S) between different sample vector of Flos Chrysanthemi Indici and the standard profile vector (SPV). The results showed that the proposed HS-SPME-GC-MS was an alternative technique for quality assessment of Flos Chrysanthemi Indici samples.     

Aroma analysis of fresh and preserved onions and leek by dual solid-phase microextraction-liquid extraction and gas chromatography-mass spectrometry

The lachrymatory factor (thiopropanal-S-oxide) was directly analysed on fresh onion (Allium cepa) juice by solid-phase microextraction (polyacrylate fibre) using a fast routine GC-MS method on a 10 m x 0.32 mm I.D. (4 microm thick polydimethylsiloxane film) column with splitless mode injection. The identification and quantification of thiosulphinates and zwiebelanes were obtained on the same juice extracted by diethyl ether after 80 min maceration using the same GC-MS method. Selected ion recording enhanced the differentiation possibilities and the detection limits. This dual method was used to evaluate flavour differences between onion and shallot varieties as it provides accurate profiles of all initially formed compounds. Moreover, this method allowed us to compare qualitatively and quantitatively transformed products: frozen, freeze-dried powders and sterilised products. Excepting the lachrymatory factor, frozen onion compounds were similar compared to those of fresh onion sample. Conversely, the other transformed samples have lost most of the initially formed compounds and produced mainly di- and trisulphides corresponding to the degradation of thiosulphinates and zwiebelanes. These dramatic changes can explain the very different flavours of these manufactured products compared to fresh material.     

Classification of Nebbiolo-based wines from Piedmont (Italy) by means of solid-phase microextraction-gas chromatography-mass spectrometry of volatile compounds

Sixty-eight samples of wines from Piedmont (Italy) were analysed to determine their content of volatile compounds, using the solid-phase microextraction (SPME) technique coupled with gas chromatography-mass spectrometry (GC-MS). Samples were from five groups of wines: Barolo, Barbaresco, Nebbiolo d'Alba, Roero and Langhe Nebbiolo, all produced from the Nebbiolo grape in the Langhe and Roero areas (province of Cuneo, Piedmont) but differing in vintage (respectively, 3 years, 2 years, 1 year, 8 months and few months) and production zone. Thirty-five analytes were identified; peak area data, corrected for internal standard, were used for pattern recognition treatments. Principal components analysis, hierarchical cluster analysis, Kohonen self organising map, stepwise linear discriminant analysis and soft independent modelling of class analogy were applied to the data, revealing a good separation between the five groups. A main factor, strictly connected to wine vintage, was identified and found to be related to some analytes.     

Analysis of volatile compounds emitted from fresh Syringa oblata flowers in different florescence by headspace solid-phase microextraction-gas chromatography-mass spectrometry

In this study, a simple and solvent-free method was developed for determination of the volatile compounds from fresh flowers of Syringa oblata using headspace solid-phase microextraction and gas chromatography-mass spectrometry. The SPME parameters were studied, the optimum conditions of a 65 μm polydimethylsiloxan/divinylbenezene (PDMS/DVB), extraction temperature of 25 °C and extraction time of 30 min were obtained and applied to extraction of the volatile compounds emitted from fresh flowers of S. oblata. The volatile compounds released from fresh flowers of S. oblata were separated and identified by GC-MS. Lilac aldehyde A, lilac aldehyde B, lilac aldehyde C, lilac aldehyde D, lilac alcohol A, lilac alcohol B, lilac alcohol C, lilac alcohol D, α-pinene, sabinene, β-pinene, myrcene, d-limonene, eucalyptol, cis-ocimene, benzaldehyde, terpinolene, linalool, benzene acetaldehyde, α-terpineol, p-methoxyanisole, p-anisaldehyde, (Z,E)-α-farnesene and (E,E)-α-farnesene were the most abundant volatiles released from fresh flowers of S. oblata var. alba. The relative contents of main volatile fragrance were found to be different in emissions from two varieties of S. oblata flowers (white or purple in color). The four isomers of lilac alcohol and four isomer lilac aldehyde were the characteristic components of the scent of fresh flowers of S. oblata. The main volatile fragrance from fresh flowers of S. oblata var. alba in different florescence ((A) flower buds; (B) at the early stage of flower blooming; (C) during the flower blooming; (D) at the end of flower blooming; (E) senescence) were studied in this paper. The results demonstrated that headspace SPME-GC-MS is a simple, rapid and solvent-free method suitable for analysis of volatile compounds emitted from fresh flowers of S. oblata in different florescence.     

Screening of volatile composition from Portuguese multifloral honeys using headspace solid-phase microextraction-gas chromatography-quadrupole mass spectrometry

The volatile composition from four types of multifloral Portuguese (produced in Madeira Island) honeys was investigated by a suitable analytical procedure based on dynamic headspace solid-phase microextraction (HS-SPME) followed by thermal desorption gas chromatography-quadrupole mass spectrometry detection (GC-qMS). The performance of five commercially available SPME fibres: 100 μm polydimethylsiloxane, PDMS; 85 μm polyacrylate, PA; 50/30 μm divinylbenzene/carboxen on polydimethylsiloxane, DVB/CAR/PDMS (StableFlex); 75 μm carboxen/polydimethylsiloxane, CAR/PDMS, and 65 μm carbowax/divinylbenzene, CW/DVB; were evaluated and compared. The highest amounts of extract, in terms of the maximum signal obtained for the total volatile composition, were obtained with a DVB/CAR/PDMS coating fibre at 60 °C during an extraction time of 40 min with a constant stirring at 750 rpm, after saturating the sample with NaCl (30%). Using this methodology more than one hundred volatile compounds, belonging to different biosynthetic pathways were identified, including monoterpenols, C₁₃-norisoprenoids, sesquiterpenes, higher alcohols, ethyl esters and fatty acids. The main components of the HS-SPME samples of honey were in average ethanol, hotrienol, benzeneacetaldehyde, furfural, trans-linalool oxide and 1,3-dihydroxy-2-propanone.     

Quantitative analysis of acetates in cigarette tobacco using solid-phase microextraction and gas chromatography-mass spectrometry

A method incorporating solid-phase microextraction (SPME) and gas chromatography-mass spectrometry for the headspace analysis of selected volatile organic compounds present in cigarette tobacco is developed and evaluated. Quantitative information on methyl, ethyl, n-propyl, isopropyl, isopropenyl, vinyl, and butyl acetates present in 29 different flavor variants (full, light, and ultra-light) of the top ten selling brands in the United States is presented. The concentrations of the various acetate analytes range from the low nanaogram to microgram levels per cigarette. Clear differences are observed in the concentrations of various acetates when comparing the levels in brands from different manufacturers. The SPME technique provides a method that allows high sample throughput, requires little sample preparation, and yields useful analytical information. High precision is obtained on multiple measurements of cigarettes from an individual pack, but lower precision levels are observed in general when comparing results obtained on the analysis of cigarettes from different packs of the same brand. The higher pack-to-pack variations may be due in part to product aging with a proportionate amount of evaporative loss of the relatively volatile acetates.     

Characterisation of lavender essential oils by using gas chromatography-mass spectrometry with correlation of linear retention indices and comparison with comprehensive two-dimensional gas chromatography

Nine samples of lavender essential oil were analysed by GC–MS using low-polarity and polar capillary columns. Linear retention indices (LRI) were calculated for each component detected. Characterisation of the individual components making up the oils was performed with the use of an mass spectrometry (MS) library developed in-house. The MS library was designed to incorporate the chromatographic data in the form of linear retention indices. The MS search routine used linear retention indices as a post-search filter and identification of the “unknowns” was made more reliable as this approach provided two independent parameters on which the identification was based. Around 70% of the total number of components in each sample were reliably characterised. A total of 85 components were identified. Semi-quantitative analysis of the same nine samples was performed by gas chromatography (GC) with flame ionisation detection (FID). The identified components accounted for more than 95% of each oil. By comparing the GC–MS results with the results from the GC×GC–FID analysis of a lavender essential oil, many more components could be found within the two-dimensional separation space.