Analysis of volatiles from Spanish honeys by solid-phase microextraction and gas chromatography-mass spectrometry

Headspace solid-phase microextraction (SPME), followed by gas chromatography (GC)-mass spectrometry (MS) determination, has been used for the analysis of honey volatiles. Two SPME fibers were employed to study the composition of volatiles from various types of Spanish honeys. The best results were obtained with the Carboxen/PDMS fiber, using a homogenization time of 1 h at 70 degrees C and a sampling period of 30 min. A total of 35 compounds were detected, most of them identified by GC-MS and quantified using external standards. Differences in the composition of honey volatiles were obtained, and these results allowed the differentiation of honeys. However, further studies are necessary to confirm the utility of this technique as an alternative tool for the characterization of the floral origin of honeys.     

Analysis of diacetyl in wine using solid-phase microextraction combined with gas chromatography-mass spectrometry

Analytical difficulties in the rapid and accurate determination of diacetyl (DA), an important flavor compound in wine, at low concentrations have been overcome by the use of solid-phase microextraction (SPME) with deuterated diacetyl-d(6) (d6-DA) as an internal standard followed by gas chromatography-mass spectrometry (GC-MS). The GC-MS analyses showed that the values of the ion response ratio of DA to d6-DA were consistent regardless of the conditions of SPME headspace and were not influenced by the presence of sulfur dioxide in wine. The quantitation value of DA was represented as the concentration of free plus bound with sulfur dioxide forms of DA. The detection limit of DA in wine was as low as 0.01 microg/mL with linearity through to 10 microg/mL.     

Analysis of benzothiazole in Italian wines using headspace solid-phase microextraction and gas chromatography-mass spectrometry

Benzothiazoles are a part of the molecular structure of a large number of natural products, biocides, drugs, food flavors, and industrial chemicals. They also appear in the environment mainly as a result of their production and use as rubber vulcanization accelerators. A new headspace solid-phase microextraction (HS-SPME) method for analysis of benzothiazole (BTH) in wine is described. This method is fast, inexpensive, and does not require solvents. The detection limit of BTH in wine was 45 ppt with linearity up to 100 ppb. The quantification of BTH is performed by the standard additions method and does not require the use of an internal standard. We have analyzed 12 wines from different grape varieties grown in several regions, using SPME extraction and gas chromatography-mass spectrometry (GC-MS) detection. Under these experimental conditions, benzothiazole was found in all wines analyzed. Concentration levels in samples varied from 0.24 microg/L (Vermentino) to 1.09 microg/L (Franciacorta).     

Ester variability in apple varieties as determined by solid-phase microextraction and gas chromatography-mass spectrometry

Solid-phase microextraction (SPME) with a polydimethylsiloxane fiber coupled with gas chromatography-mass spectrometry (GC-MS) was applied to the study of variability in volatiles released by 13 apple varieties. The relative amounts of 40 esters and alpha-farnesene were determined. Principal component analyses of these results clustered the apples into three groups according to skin color: red, green, and red-green. Total ester contents were highest with the red cluster apples, and the green cluster apples had the highest alpha-farnesene levels. This technology was also applied to the monitoring of changes in volatiles for apples removed from controlled-atmosphere storage with subsequent storage at 4 degrees C and room temperature. Total ester contents increased 25-fold, with the greater increases coming at room temperature, whereas alpha-farnesene levels increased only 5-fold. For apples stored at room temperature, after 11 days, the amount of increase was inversely proportional to the size of the ester: levels of smallest esters (molecular weight 116) increased 12.5-fold, and the largest esters (molecular weight 228) increased approximately 1.3-fold.     

Analysis of pesticides in honey by solid-phase extraction and gas chromatography-mass spectrometry

An analytical method for the simultaneous determination of 51 pesticides in commercial honeys was developed. Honey (10 g) was dissolved in water/methanol (70:30; 10 mL) and transferred to a C(18) column (1 g) preconditioned with acetonitrile and water. Pesticides were subsequently eluted with a hexane/ethyl acetate mixture (50:50) and determined by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM). Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. Pesticides were confirmed by their retention times, their qualifier and target ions, and their qualifier/target abundance ratios. Recovery studies were performed at 0.1, 0.05, and 0.025 microg/g fortification levels for each pesticide, and the recoveries obtained were >86% with relative standard deviations of <10%. Good resolution of the pesticide mixture was achieved in approximately 41 min. The detection limits of the method ranged from 0.1 to 6.1 microg/kg for the different pesticides studied. The developed method is linear over the range assayed, 25-200 microg/L, with determination coefficients of >0.996. The proposed method was applied to the analysis of pesticides in honey samples, and low levels of a few pesticides (dichlofluanid, ethalfluralin, and triallate) were detected in some samples.     

Essential oil composition of sachalinmint from Norway detected by solid-phase microextraction and gas chromatography-mass spectrometry analysis

The essential oil of leaves and flowers of sachalinmint [Mentha sachalinensis (Briq.) Kud?] grown in Norway (Trondheim) has been studied by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry analysis (GC-MS). The essential oil content increased linearly in acropetal direction from 1.08% (0-20 cm plant height) to 1.75% (60-80 cm; young leaves and flowers). The steam-distilled samples showed a minor complex matrix with a very high menthol and a much lower menthone content (87.89 and 4.05%, respectively). From testing of HS-SPME unequilibrated exposure times ranging from 10 s to 5 min, an extraction time of 30 s was found to be sufficient to detect both low- and high-eluting compounds. Comparison of HS-SPME and steam-distilled samples established that the same tendencies of increasing menthol/menthone content in the basipetal/acropetal direction could be detected by both analysis methods. With regard to the extraction efficiency, HS-SPME gave additional detailed information about less important terpenic compounds.     

Headspace solid-phase microextraction gas chromatography-mass spectrometry analysis of volatiles in orujo spirits from a defined geographical origin

A headspace solid-phase microextraction (HS-SPME) and gas chromatography-selective ion monitoring/mass spectrometry (GC-SIM/MS) method was optimized for analysis of 22 volatile compounds in orujo spirit samples from the Geographic Denomination "Orujo de Galicia/Augardente de Galicia". HS-SPME experimental conditions, such as fiber coating, extraction temperature, extraction and pre-equilibrium time, sample volume, and the presence of salt, were studied to improve the extraction process. The best results were obtained using a 65 microm Carbowax-divinylbenzene fiber during a headspace extraction at 40 degrees C with constant magnetic stirring for 15 min and after a 5 min period of pre-equilibrium time. The sample volume was 6 mL of orujo containing 25% of NaCl, placed in 12 mL glass vials equipped with a screw cap and PTFE/silicone septum. Desorption was performed directly in the gas chromatograph injector port for 5 min at 250 degrees C using the splitless mode. The proposed method is sensible (with detection limits between 0.0045 and 0.2399 mg/L), precise (with coefficients of variation in the range 0.99-8.18%), and linear over more than 1 order of magnitude. The developed method presented recoveries comprised between 76.0 and 112.4%. The applicability of the new method was demonstrated by determining the considered 22 volatile compounds in nine orujo commercial samples with quality and origin brands.     

Analysis of cooking oil fumes by ultraviolet spectrometry and gas chromatography-mass spectrometry

This paper investigated the components, especially aldehydes, in the fume condensates from four kinds of cooking oil using ultraviolet (UV) spectrometry and gas chromatography-mass spectrometry (GC-MS). It was observed that there was a great change of the UV absorption spectra from the results of the unheated oil to the results of the fume after heat treatment (190-200, 230-240, and 270-280 degrees C). There was a strong peak within the wavelength range of 260-270 nm in each condensate sample. From the GC-MS results, it was tentatively deduced that there were some 2,4-dialkylenaldehydes and other conjugated compounds in the condensates. The results showed there were large amounts of hexanal and 2-heptenal in the cooking oil fume and that the total aldehyde peak areas of the condensates from four kinds of oil were around 30-50% of the total peak area at 270-280 degrees C.     

Determination of 24 pesticide residues in fortified wines by solid-phase microextraction and gas chromatography-tandem mass spectrometry

The present work describes a solid-phase microextraction (SPME) gas chromatography-tandem mass spectrometry (MS/MS) method to quantify 24 pesticides in fortified white wine and fortified red wine. In this study "fortified wine" refers to a wine in which fermentation is arrested before completion by alcohol distillate addition, allowing sugar and alcoholic contents to be higher (around 80-100 g/L total sugars and 19-22% alcohol strength (v/v)). The analytical method showed good linearity, presenting correlation coefficients (R(2)) ≥ 0.989 for all compounds. Limits of detection (LOD) and quantitation (LOQ) in the ranges of 0.05-72.35 and 0.16-219.23 μg/L, respectively, were obtained. LOQs are below the maximum residue levels (MRL) set by European Regulation for grapes. The proposed method was applied to 17 commercial fortified wines. The analyzed pesticides were not detected in the wines tested.     

Analysis of acrylamide in green tea by gas chromatography-mass spectrometry

Optimization of the solid-phase extraction cleanup procedure enabled the GC-MS analysis of acrylamide in tea samples without the interference of bromination by tea catechins. Although polyvinylpolypyrrolidone (PVPP) is available for removing tea catechins from tea extract, the peaks derived from PVPP had the same retention time as brominated acrylamide in mass chromatograms obtained by GC-MS. A considerable amount of acrylamide was formed at roasting temperatures of > or =120 degrees C; the highest acrylamide level was observed when tea samples were roasted at 180 degrees C for 10 min. Higher temperatures and longer processing times caused a decrease in the acrylamide content. Furthermore, an analysis of 82 tea samples showed that rather than the reducing sugar content, the asparagine content in tea leaves was a significant factor related to acrylamide formation in roasted products. The acrylamide level in roasted tea products was controlled by asparagine in the presence of reducing sugars.     

Analysis of glycated and ascorbylated proteins by gas chromatography-mass spectrometry

Proteins or poly-L-lysine which were incubated in the presence of ascorbic acid, dehydroascorbic acid (ascorbylation), or various sugars (glycation) were analyzed by gas chromatography-mass spectrometry (GC-MS). To also detect more labile reaction products, the Maillard modified proteins or poly-L-lysine were enzymatically hydrolyzed and reacted with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide to form the N(O)-tert-butyldimethylsilyl (tBDMS) derivatives prior to GC analysis. Under these conditions, the known Maillard products N (epsilon)-(carboxymethyl)lysine (1), oxalic acid mono-N (epsilon)-lysinylamide (2), and N (epsilon)-(carboxyethyl)lysine (3) could be simultaneously detected and quantified in glycated and ascorbylated proteins. Additionally, N (epsilon)-(1-carboxy-3-hydroxypropyl)-L-lysine (4) was identified for the first time as a Maillard product of proteins. Under the conditions applied here, 4 was found only in ascorbylated proteins or poly-L-lysine, but not in glycated proteins. Maillard-modified poly-L-lysine was further subjected to high-performance liquid chromatography (HPLC) analysis after enzymatic hydrolysis and formation of the phenyl isothiocyanate derivatized amino acids. Using this method, N (epsilon)-formyl-L-lysine (5), which cannot be distinguished from 2 by GC-MS analysis, was identified for the first time as a glycation product. Compound 5 is mainly formed from ribose, lactose, and fructose. The indicated Maillard products were quantified in beta-lactoglobulin (GC-MS) or poly-L-lysine (HPLC) which were glycated or ascorbylated using different precursors.     

Analysis of aldehydes in beer using solid-phase microextraction with on-fiber derivatization and gas chromatography/mass spectrometry

A new, fast, sensitive, and solventless extraction technique was developed in order to analyze beer carbonyl compounds. The method was based on solid-phase microextraction with on-fiber derivatization. A derivatization agent, O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA), was absorbed onto a divinyl benzene/poly(dimethylsiloxane) 65-microm fiber and exposed to the headspace of a vial with a beer sample. Carbonyl compounds selectively reacted with PFBOA, and the oximes formed were desorbed into a gas chromatograph injection port and quantified by mass spectrometry. This method provided very high reproducibility and linearity. When it was used for the analysis of aged beers, nine aldehydes were detected: 2-methylpropanal, 2-methylbutanal, 3-methylbutanal, pentanal, hexanal, furfural, methional, phenylacetaldehyde, and (E)-2-nonenal.     

A new method for the determination of carbonyl compounds in wines by headspace solid-phase microextraction coupled to gas chromatography-ion trap mass spectrometry

A new analytical method for the determination of 18 carbonyl compounds [2,3-pentadione, hexanal, (E)-2-hexen-1-al, octanal, acetoin, (E)-2-octenal, furfural, decanal, (E)-2-nonenal, benzaldehyde, 5-methylfurfural, (E,E)-2-cis-6-nonadienal, β-damascenone, phenylacetaldehyde, acetophenone, (E,E)-2,4-decadienal, benzophenone, and vanillin] in wines using automated headspace solid-phase microextraction (HS/SPME) coupled to gas chromatography-ion trap mass spectrometry (GC-ITMS) was developed. Five fibers with different polarities were tested, and a study of the influence of various factors such as time and extraction temperature, desorption time and temperature, pH, and ionic strength and content in tannins, anthocyans, sucrose, SO(2), and alcoholic degree was conducted. These factors were optimized using a synthetic wine doped with the different analytes. The proposed method affords wide ranges of linearity, good linearity (r(2) > 0.998), values of repeatability and reproducibility lower than 5.5% of RSD, and detection limits ranging from 0.62 μg/L for β-damascenone to 129.2 μg/L for acetoin. Therefore, the optimized method was applied to the quantitative analysis of the aforementioned analytes in real samples of wines.     

Silylation of acrylamide for analysis by solid-phase microextraction/gas chromatography/ion-trap mass spectrometry

A method for quantitative analysis of acrylamide has been developed for use with headspace solid-phase microextraction (SPME). In the method, acrylamide undergoes silylation with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) to form the volatile N,O-bis(trimethylsilyl)acrylamide (BTMSA). Once formed, BTMSA is readily extracted from the headspace over the silylation reaction using a 100 microm poly(dimethylsiloxane) SPME fiber. A series of experiments was undertaken to optimize the amount of BSTFA, the silylation reaction temperature, the silylation reaction duration, and SPME sampling duration to maximize the analytical sensitivity for BTMSA. Acrylamide levels were quantified relative to a [13C3]-acrylamide internal standard using gas chromatography/ion-trap mass spectrometry (GC/MS) in the single ion monitoring mode. An analytical working curve was constructed and found to be linear over the 4 to 6700 ppb acrylamide range investigated with a limit of detection of 0.9 ppb. The native acrylamide levels of three commercial cereals were measured using the optimized analytical method. Quantitative standard additions of acrylamide to the cereal matrixes demonstrated complete recovery of the spiked acrylamide.     

Rapid screening of polar compounds in Brazilian propolis by high-temperature high-resolution gas chromatography-mass spectrometry

Methanol extracts of propolis from six different places, five in Rio de Janeiro state and one in S?o Paulo state, both in the Southeast of Brazil, were investigated using high-temperature high-resolution gas chromatography (HT-HRGC) and HT-HRGC-mass spectometry. The main purpose of the study was to establish the applicability of HT-HRGC as an analytical method for systematic studies of polar propolis fractions. Several compounds, including carbohydrates, phenolic acid derivatives, and high molecular weight compounds (e.g., wax esters of long chain fatty alcohols) could be readily characterized in the crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude polar extracts without cleanup.     

One-step derivatization and preconcentration microextraction technique for determination of bisphenol A in beverage samples by gas chromatography-mass spectrometry

A simple technique based on ultrasound-assisted emulsification microextraction in situ derivatization (USAEME-ISD) is proposed for the one-step derivatization, extraction, and preconcentration of bisphenol A (BPA) in beverage samples prior to gas chromatography-mass spectrometry (GC-MS) analysis. BPA was in situ derivatized with acetic anhydride and simultaneously extracted and preconcentrated by using USAEME. Variables affecting the extraction efficiency of BPA were evaluated. Under optimal experimental conditions, the detection limit (LOD) was 38 ng L(-1) with a relative standard deviation (RSD) value of 11.6%. The linear working range was 100-1250 ng L(-1), and the coefficient of estimation (r(2)) of the calibration curve was ≥0.9971. The robustness of the proposed methodology was probed by developing a recovery study at two concentrations (125 and 500 ng L(-1)) over different beverage samples. This study led to a satisfactory result achieving recoveries of ≥82%, which showed acceptable robustness for determination of nanograms per liter of BPA in samples of food safety interest.     

Analysis of terpenoids from hemlock (Tsuga) species by solid-phase microextraction/gas chromatography/ion-trap mass spectrometry

A sampling method for determining the volatile terpenoid composition from single needles of seven Tsuga species was developed using headspace solid-phase microextraction (SPME). A reproducible sampling method for the volatile components was generated by examination of sample storage, method of needle cutting, and headspace sampling duration. Following SPME collection of the volatile compounds from the seven Tsuga species, gas chromatography/ion-trap mass spectrometry was used to identify 51 terpenoids present in the needle headspace. A semiquantitative method was devised to express individual terpenoid amounts as a percentage of all of the identified peaks in the chromatogram. The semiquantitative results permitted facile interspecies comparison using principal component analysis. Two components were able to account for 90% of the variance and were interpreted as a "species" component and a "resistance/susceptibility" component. Three interspecies groupings were evident from the principal component analysis: (1) Tsuga canadensis and Tsuga caroliniana; (2) Tsuga chinesnsis, Tsuga diversifolia, Tsuga heterophylla, and Tsuga sieboldii; and (3) Tsuga mertensiana. The finding that T. mertensiana was grouped alone and far removed from the other species adds to the morphological evidence that this species should be segregated from other Tsuga.     

Chloramphenicol extraction from honey, milk, and eggs using polymer monolith microextraction followed by liquid chromatography-mass spectrometry determination

A rapid confirmatory method for monitoring chloramphenicol (CAP) residues in honey, whole milk, and eggs is presented. This method is based on the polymer monolith microextraction (PMME) technique and high-performance liquid chromatography (HPLC)-electrospray ionization mass spectrometry (MS). A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column was selected as the extraction medium. To obtain optimum extraction efficiency, several parameters related to PMME were investigated. After dissolution in 20 mM phosphate solution at pH 4.0 and centrifugation, honey, eggs, or milk samples were directly passed through the extraction tube. The LC-MS instrument was equipped with an electrospray ion source and a single quadrupole. The eluates were analyzed by LC-MS in the negative-ion mode and by monitoring a pair of isotopic ions for the target compound. The in-source collision-induced dissociation process produced confirmatory ions. The recoveries of CAP from real samples spiked at 0.1-10 ng/g (honey), 0.2-10 ng/mL (milk), and 0.2-10 ng/g (egg) were in the range of 85-102%, with relative standard deviations ranging between 2.1% and 8.9%. The limits of detection (S/N = 3) were 0.02 ng/g, 0.04 ng/mL, and 0.04 ng/g in honey, milk, and eggs, respectively. The proposed method was proved to be robust in monitoring CAP residue in honey, milk, and eggs.     

Simultaneous quantification of eight biogenic amine compounds in tuna by matrix solid-phase dispersion followed by HPLC-orbitrap mass spectrometry

A method for the extraction of agmatine, cadaverine, histamine, phenyethylamine, putrescine, tryptamine, tyramine, and urocanic acid from canned tuna and frozen tuna loin matrices by matrix solid-phase dispersion, followed by separation and quantification of these compounds by ultrahigh-performance hydrophilic interaction chromatography (UHPLC-HILIC) with orbitrap mass spectrometric detection, is described. Tuna samples are dispersed in a CN-silica sorbent and eluted with a mixture of aqueous ammonium formate buffer and acetonitrile. Separation and detection are carried out on an Agilent 1200 high-performance liquid chromatograph coupled to a Thermo Exactive orbitrap mass spectrometer, and metformin is used as the internal standard. Spike recoveries are determined across a range of 20-100 ppm for each compound, and the method is validated with respect to linearity, reproducibility, accuracy, and limits of quantitation and detection. The method is demonstrated to be suitable for use in quantifying these target compounds in the studied matrices.     

Analysis of ergosterol in single kernel and ground grain by gas chromatography-mass spectrometry

A method for analyzing ergosterol in a single kernel and ground barley and wheat was developed using gas chromatography-mass spectrometry (GC-MS). Samples were saponified in methanolic KOH. Ergosterol was extracted by "one step" hexane extraction and subsequently silylated by N-trimethylsilylimidazole/trimethylchlorosilane (TMSI/TMCS) reagent at room temperature. The recoveries of ergosterol from ground barley were 96.6, 97.1, 97.1, 88.5, and 90.3% at the levels of 0.2, 1, 5, 10, and 20 microg/g (ppm), respectively. The recoveries from a single kernel were between 93.0 and 95.9%. The precision (coefficient of variance) of the method was in the range 0.8-12.3%. The method detection limit (MDL) and the method quantification limit (MQL) were 18.5 and 55.6 ng/g (ppb), respectively. The ergosterol analysis method developed can be used to handle 80 samples daily by one person, making it suitable for screening cereal cultivars for resistance to fungal infection. The ability for detecting low levels of ergosterol in a single kernel provides a tool to investigate early fungal invasion and to study mechanisms of resistance to fungal diseases.