Analysis of furan in coffee of different provenance by head-space solid phase microextraction gas chromatography–mass spectrometry: effect of brewing procedures

A simple, sensitive and accurate method for the analysis of furan in roasted coffee has been used based on headspace–solid-phase micro-extraction (HS–SPME) coupled to gas chromatography–mass spectrometry (GC–MS). The extraction was performed using 75-µm carboxen/polydimethylsiloxane fiber. Ionic strength, extraction time and temperature, and desorption time were assessed as the most important parameters affecting the HS–SPME procedure and d ₄-furan was used as the internal standard. The linearity range was in the range 0.0075–0.486 ng g^?1; the LOD and LOQ calculated using the signal-to-noise ratio approach were 0.002 and 0.006 ng g^?1, respectively. The inter- and intra-day precision was 8 and 10%, respectively. The concentration of furan found in batches of roasted coffee powder different producing countries ranged from 57.3 to 587.3 ng g^?1. The mean reduction in furan levels observed when brewing coffee by either infusion, using a moka pot or an expresso machine was 57, 67.5 and 63.3%, respectively.     

Ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric determination of phenolic compounds in cranberry products

An ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric (GC–MS) method has been developed for determination of phenolics in cranberry products. Prior to GC–MS separation and characterisation, the phenolics in samples were hydrolysed by hydrochloric acid with ultrasound-assistance, extracted with ethyl acetate, and derivatised with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TMCS) reagents. The application of ultrasonication significantly accelerated the acidic hydrolysation of the conjugated phenolics. A baseline separation of the 20 phenolics and internal standard was achieved in 25 min. Standard calibration curves were linear over the concentration range of 0.0–50 μg/mL and detection limits were 0.06–0.70 μg/mL. Twenty phenolics were identified in cranberry samples and all of them occurred mainly in conjugated forms. Of those, the benzoic acid, quercetin, and myricetin were most abundant phenolics. The total phenolics were 12.4 mg/g in cranberry fruits, 9.1 mg/mL in 100% cranberry juice, and 11.1 mg/g in cranberry sauces, respectively.     

Determination of volatile compounds formed in a glucose–selenomethionine model system by gas chromatography–atomic emission detector and gas chromatography–mass spectrometry

In order to gain a better understanding of the formation of organoselenium compounds in food system, the Maillard reaction of selenomethionine and glucose was studied in a model system. The effects of heating time and pH on the volatile compounds formed in a glucose–selenomethionine reaction were also investigated. Nine organoselenium compounds were identified. Pyrazines and dimethyldiselenide are major volatile compounds generated from the glucose–selenomethionine model system. A high pH level favours the formation of pyrazine and dimethyldiselenide. In unbuffered systems, a pH change of three or more pH units may occur, and this may significantly affect the formation of Maillard reaction products.     

Determination of trichothecenes in cereals and cereal-based products by liquid chromatography–tandem mass spectrometry

A sensitive, accurate and precise method for the simultaneous determination of nivalenol (NIV), deoxynivalenol (DON), T-2 toxin (T-2) and HT-2 toxin (HT-2) in different food matrices, including wheat, maize, barley, cereal-based infant foods, snacks, biscuits and wafers, has been developed. The method, using liquid chromatography coupled with atmospheric pressure chemical ionization triple quadrupole mass spectrometry (LC–APCI–MS/MS), allowed unambiguous identification of the selected trichothecenes at low µg per kg levels in such complex food matrices. A clean-up procedure, based on reversed phase SPE Oasis® HLB columns, was used, allowing good recoveries for all studied trichothecenes. In particular, NIV recoveries significantly improved compared to those obtained by using Mycosep® #227 columns for clean-up of the extracts. Limits of detection in the various investigated matrices ranged 2.5–4.0 µg kg^?1 for NIV, 2.8–5.3 µg kg^?1 for DON, 0.4–1.7 µg kg^?1 for HT-2 and 0.4–1.0 µg kg^?1 for T-2. Mean recovery values, obtained from cereals and cereal products spiked with NIV, DON, HT-2 and T-2 toxins at levels from 10 to 1000 µg kg^?1, ranged from 72 to 110% with mean relative standard deviation lower than 10%. A systematic investigation of matrix effects in different cereals and cereal products was also carried out by statistically comparing the slopes of standard calibration curve with matrix-matched calibration curve for each of the four toxins and the eight matrices tested. For seven of the eight matrices tested, statistically significant matrix effects were observed, indicating that, for accurate quantitative analysis, matrix-matched calibration was necessary. The method was applied to the analysis of 57 samples of ground wheat originated from South Italy and nine cereal food samples collected from retail markets.     

Characterization of the volatile profile of thistle honey using headspace solid-phase microextraction and gas chromatography–mass spectrometry

In this study, a headspace solid-phase microextraction method was developed for the characterization of the volatile fraction of thistle honey and compared with a dynamic headspace extraction method. A DVB/CAR/PDMS fibre was used. The effects of extraction time, equilibration time and salt addition on extraction yield were evaluated. The volatile fraction of seven Italian thistle honey samples was extracted under the optimized conditions and analyzed by gas chromatography–mass spectrometry. Characterization of the volatile profile was performed in terms of nature and relative amount of the extracted compounds. A total of 40 compounds, belonging to different chemical classes, were identified. The relative amounts of 16 compounds found in all the analyzed thistle honeys, i.e. nonanal, furfural, decanal, 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran, benzaldehyde, α-linalool, lilac aldehyde (isomer IV), hotrienol, phenylacetaldehyde, 4-oxoisophorone, benzyl alcohol, 2-phenylethanol, a not identified compound, octanoic acid, nonanoic acid and methyl anthranilate, were calculated and submitted to statistical analysis, in order to define for each compound a typical range. On the basis of the obtained data, a characteristic set of values was defined for thistle honey volatile fingerprint. The developed model proved to be effective in recognizing the botanical origin of thistle honey.     

Characterization of Arabica and Robusta volatile coffees composition by reverse carrier gas headspace gas chromatography–mass spectrometry based on a statistical approach

Food Science and Biotechnology - Nineteen samples of Arabica and 14 of Robusta coming from various plantation were analysed by dynamic headspace capillary gas chromatography–mass spectrometry...     

Determination of alkylphenol residues in breast and commercial milk by solid-phase extraction and gas chromatography–mass spectrometry

This study presents a feasible and sensitive method to determine alkylphenol residues (i.e., 4-t-octylphenol (4-t-OP) and the isomers of 4-nonylphenols (4-NPs)) in breast milk samples and commercial cow milk products. The matrix interference associated with the constituents in the milk was reduced by extraction with n-hexane and dilution with 50% methanolic solution (v/v, methanol/water), then followed by the Oasis-HLB SPE extraction. The analytes were determined by a GC–MS system in full-scan and selected ion monitoring modes simultaneously. Limit of quantitation was less than 0.05 ng/g in a 20 g (wet weight) milk sample. The 4-NPs were detected in 19 of the 20 breast milk samples at concentrations ranging from 1.7 to 11.6 ng/g, while 4-t-OP was detected in 8 samples at concentrations ranging from 0.4 to 1.1 ng/g. The 4-NPs were detected in all the testing commercial cow milk products at concentrations ranging from 2.9 to 8.8 ng/g.     

An isotope dilution headspace method with gas chromatography–mass spectrometry for determination of propylene oxide in food

A method based on isotope dilution headspace and gas chromatography–mass spectrometry was developed for the determination of propylene oxide in foods. Optimum method sensitivity was achieved by the addition of NaCl in water at saturation and with the sample solution incubated at 90°C. The method had good repeatability with relative standard deviations of 6.0, 7.6 and 2.2% at 5, 20 and 40 µg l^?1, respectively. The method was used to determine propylene oxide in 36 selected food composite samples from the 2007 Canadian total diet study. Propylene oxide was not detected in any samples analyzed with an average method detection limit of 0.5 ng g^?1. Hydrolysis of propylene oxide in water was observed as a first-order reaction with a half-life of 15 h at room temperature and less than 10 min at 90°C. This confirms that it is very unlikely to find propylene oxide in foods as consumed due to its volatility and reaction with water.     

One-step microwave-assisted headspace solid-phase microextraction for the rapid determination of synthetic polycyclic musks in oyster by gas chromatography–mass spectrometry

A rapid, simple and solvent-free procedure was developed for the determination of synthetic polycyclic musks in oyster samples by using one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) and gas chromatography–mass spectrometry (GC–MS). Two commonly used synthetic polycyclic musks, galaxolide (HHCB) and tonalide (AHTN), were selected in the method development and validation. The parameters (microwave irradiation power, extraction time, amount of water added, pH value and addition of NaCl) affecting the extraction efficiency of analytes from oyster slurry were systematically investigated and optimised. The best extraction conditions were achieved when the oyster tissue mixed with 10-mL deionised water (containing 3 g of NaCl in a 40-mL sample-vial) was microwave irradiated at 80 W for 5 min. The limit of quantification (LOQ) was 0.1 ng/g in 5-g of wet tissue. The good precision and accuracy of one-step MA-HS-SPME coupled with GC–MS for the determination of trace level of AHTN in oyster samples was also demonstrated.     

Fast screening of pesticide residues in fruit juice by solid-phase microextraction and gas chromatography–mass spectrometry

A new vanguard–rearguard analytical method for determining 54 pesticide residues in different fruit juices (natural and commercial orange, peach and pineapple juices were tested) is proposed. For that, in a first step, a fast screening (vanguard) method is applied for detecting those samples containing pesticides at concentrations above a pre-established cut-off value. In a second step, those samples are re-analyzed by a conventional pesticide residue (rearguard) method that confirms the presence of the pesticides and quantifies them. The sample process is very simple, fast and semiautomatic and therefore, it reduces significantly the average time required per sample, increases precision and minimizing human mistakes. Only 1 mL of juice sample is required for analysis. Pesticides are quickly extracted with ethyl acetate in a test tube, transferred to a mixture water:acetone 9:1 (v/v), and isolated by solid-phase microextraction (SPME). The SPME screening method only requires 10 min of SPME extraction. The SPME confirming/quantifying method requires 55 min of SPME extraction. The instrumental determination is carried out by gas chromatography–mass spectrometry (GC–MS) using a full scan acquisition mode for the screening method (less than 17 min of chromatographic run) and a tandem mass spectrometry (MS/MS) acquisition mode for the quantifying/confirming method (less than 70 min of chromatographic run). The use of full scan MS and tandem MS for the detection increase significantly the certainty of the results. Also, the combination of a solvent and SPME extractions and GC–MS/MS offers a significant selectivity and sensitivity with a proven reduction of false positive and negative cases. The use of a vanguard–rearguard strategy can reduce the 50% of the total time required for determining routinely juices in a laboratory by a traditional strategy (identification, confirmation and quantitation of the pesticides in the samples by a conventional analytical method).     

Microwave pretreatment and gas chromatography–mass spectrometry determination of herbicide residues in onion

A rapid multi-residue method was developed for the determination of 16 herbicides in onion. The analytical procedure was based on preventing formation of sulfur-containing compounds in onion by microwave inactivation of the enzyme alliinase. The onion samples which had been pretreated were extracted with acetonitrile and cleaned by solid-phase extraction. The herbicide residues in onion were detected by gas chromatography/mass spectrometry with selected ion monitoring. The recoveries of 16 herbicides ranged from 69.2% to 105.0% with the relative standard deviations (RSD) below 10.7%. The limit of quantitation (LOQ) ranged from 0.003 to 0.015 mg kg⁻¹. The method was applied to the analysis of herbicide residues in onion samples.     

Ethyl-carbamate determination by gas chromatography–mass spectrometry at different stages of production of a traditional Brazilian spirit

Ethyl carbamate (EC), which is probably carcinogenic to humans, can be produced during the alcoholic fermentation of sugar-cane juice to give cachaça. The stages to produce cachaça are obtainment of sugar-cane juice, sugar-cane fermentation to wine, and obtainment of distilled fractions and residue. In order to investigate the presence of EC in the wine and in the fractions of the distillation process, as well as in the vinasse (the residue left after distillation), gas chromatography–mass spectrometry was employed. After the fermentation phase, the wine showed an average content of 122 mg L⁻¹ of EC. Average EC content in distilled fractions was 59.7 mg L⁻¹ for head, 52 μg·L⁻¹ for heart and 1.57 mg L⁻¹ for tail. EC content was 53.1 mg L⁻¹ for vinasse. The results showed that it is essential to separate the head and tail fractions to ensure cachaça quality, with respect to EC content.     

Determination of phthalate esters in wine using solid-phase extraction and gas chromatography–mass spectrometry

A method for the determination of six phthalate esters in wine samples has been developed. The phthalates were extracted from wine samples with an optimised solid-phase extraction method on C18 column and quantification was achieved via gas chromatography coupled with a mass spectrometer. The method was linear between 0.015 and 5.000 μg mL⁻¹ for DMP, DEP and DEHP and between 0.018 and 5.000 μg mL⁻¹ for iBP, DBP and BBP. The LOQs of DMP, DEP and DEH were 0.024 μg mL⁻¹ while those of iBP, DBP and BBP were 0.029 μg mL⁻¹. The intra-day method repeatability was between 10% and 15% RSD, whereas the inter-day method repeatability was between 13% and 21% RSD. A survey was performed on white and red wines (n = 62) from the market, winemakers and an experimental pilot plant. All the analysed samples were phthalate contaminated. Commercial wine showed higher detection frequency and level of total phthalate, DBP and BBP than those produced in a pilot plant. iBP and DEHP concentrations were similar in all the groups of samples. iBP concentration was higher in red wines than in white ones.     

Determination of polybromodiphenyl ethers (PBDEs) in milk cream by gas chromatography–mass spectrometry

An analytical method for polybromodiphenyl ethers (PBDEs) in milk cream has been optimized. The six PBDEs targeted were chosen on criteria of toxicity and occurrence in environmental matrices. Three methods of extraction were tested and compared in terms of lipid recovery yields and repeatability. The sample preparation process includes two steps: extraction by accelerated solvent extraction (ASE) and purification by solid phase extraction (SPE). The preferred method of extraction used a hexane/methylene chloride/methanol (5 : 2 : 1, v/v) solvent mixture. Three extraction cycles were carried out per sample at a temperature of 80°C and a pressure of 1500 psi. The method was validated on milk cream samples spiked with the specified PBDEs. Recoveries for the whole sample preparation process (extraction and cleanup) for cream samples spiked at 10 and 100 ng g^?1 were greater than 80% (ranging from 81 to 106%) at both concentrations for BDE-99, -100, -153 and 154. Recoveries were lower (ranging from 65 to 75%) for BDE-28 and BDE-47. PBDEs were quantified by GC/MS detection with selected ion monitoring (SIM) using three ions formed by electron capture. The method was successfully tested on real samples.     

Distribution and migration study of pesticides between peel and pulp in grape by online gel permeation chromatography–gas chromatography/mass spectrometry

A multi-residue method for the analysis of 175 pesticides was developed by online gel permeation chromatography–gas chromatography/mass spectrometry (GPC–GC/MS) to study pesticide distribution and migration between peel and pulp in grape. The separated peel and pulp samples were extracted by acetonitrile after fortified with chlorpyrifos-d₁₀ isotope internal standard. The extract was first purified by solid phase distribution sorbent of primary secondary amine (PSA) and then detected by online GPC–GC/MS. At the spiking levels of 10, 50 and 200 μg kg⁻¹, 73.7%, 94.3% and 98.9% of the pesticides, respectively, presented recoveries between 70% and 120%. The ratios were 91.4%, 94.9% and 92.0%, respectively, for the relative standard deviations (RSDs) bellow 15%. Limits of detection (LODs) for the pesticides in pulp were below 10 μg kg⁻¹. Pesticides were separated to four groups according to the distribution ratios (peel/whole grape) of 100%, 80–99.9%, 50–80% and 0–50% in peel. Relationship between the pesticide distribution and corresponding regulation of EU maximum residue level (MRL) was discussed. Six factors influencing the pesticides distribution and migration between peel and pulp were discussed. Weak linear correlation between the pesticide solubility in water (20 °C) and the distribution ratios (lowest and average) in peel was found for most of the detected pesticides with solubility less than 200 mg L⁻¹.     

Characterisation of sugars as the typical taste compounds in soy sauce by silane derivatisation coupled with gas chromatography–mass spectrometry and electronic tongue

A total of 214 taste compounds were identified in soy sauce by silane derivatisation coupled with gas chromatography–mass spectrometry (SD-GC-MS), including 74 kinds of sugars. The proportion of total sugars is highest from 37.24–77.24% among all taste compounds. In particular, rare sugars were detected and identified as the special compounds in soy sauce which come from the sugar metabolism. Rare sugars identified in soy sauce by traditional fermented technology were prominent than Japanese technology. Principal component analysis (PCA) investigation of these results showed that samples can be distinguished by sugars as the first principal component and the general evaluation index (GEI) of samples was consistent with the result of sensory evaluation. Meanwhile, sweetness had the maximum range (from −9.89 to 14.10) in all taste indexes by electronic tongue (E-tongue) analysis.