Prediction of sensory properties of Brazilian Arabica roasted coffees by headspace solid phase microextraction-gas chromatography and partial least squares

Volatile compounds in fifty-eight Arabica roasted coffee samples from Brazil were analyzed by SPME-GC-FID and SPME-GC-MS, and the results were compared with those from sensory evaluation. The main purpose was to investigate the relationships between the volatile compounds from roasted coffees and certain sensory attributes, including body, flavor, cleanliness and overall quality. Calibration models for each sensory attribute based on chromatographic profiles were developed by using partial least squares (PLS) regression. Discrimination of samples with different overall qualities was done by using partial least squares-discriminant analysis (PLS-DA). The alignment of chromatograms was performed by the correlation optimized warping (COW) algorithm. Selection of peaks for each regression model was performed by applying the ordered predictors selection (OPS) algorithm in order to take into account only significant compounds. The results provided by the calibration models are promising and demonstrate the feasibility of using this methodology in on-line or routine applications to predict the sensory quality of unknown Brazilian Arabica coffee samples.According to the PLS-DA on chromatographic profiles of different quality samples, compounds 3-methypropanal, 2-methylfuran, furfural, furfuryl formate, 5-methyl-2-furancarboxyaldehyde, 4-ethylguaiacol, 3-methylthiophene, 2-furanmethanol acetate, 2-ethyl-3,6-dimethylpyrazine, 1-(2-furanyl)-2-butanone and three others not identified compounds can be considered as possible markers for the coffee beverage overall quality.     

Coffee aroma—Statistical analysis of compositional data

Solid-phase microextraction in headspace mode coupled with gas chromatography-mass spectrometry was applied to the determination of volatile compounds in 30 commercially available coffee samples. In order to differentiate and characterize Arabica and Robusta coffee, six major volatile compounds (acetic acid, 2-methylpyrazine, furfural, 2-furfuryl alcohol, 2,6-dimethylpyrazine, 5-methylfurfural) were chosen as the most relevant markers. Cluster analysis and principal component analysis (PCA) were applied to the raw chromatographic data and data processed by centred logratio transformation.     

Development of a solid-phase microextraction-gas chromatography-tandem mass spectrometry method for the analysis of chlorinated toluenes in environmental waters

In the present work, a simple and fast methodology has been developed for the analysis of chlorotoluenes in water samples using solid-phase microextraction (SPME) coupled to gas chromatography-tandem mass spectrometry (GC/MS/MS). A multifactorial experimental design strategy was used for studying the influence on extraction yield of factors such as fiber coating, extraction mode, temperature, and addition of sodium chloride. Quantitative recoveries (>/=84%) and satisfactory precision (relative standard deviations (RSD)相似文献   

Solid-phase extraction versus solid-phase microextraction for the determination of chlorinated paraffins in water using gas chromatography-negative chemical ionisation mass spectrometry

Solid-phase extraction (SPE) and solid-phase microextraction (SPME) were evaluated for the analysis of short-chain chlorinated paraffins (SCCPs) in water samples using gas chromatography coupled to negative chemical ionisation mass spectrometry (GC-NCI-MS). For SPE optimisation, four commercially available SPE cartridges were tested and several SPE parameters, such as the elution solvent, elution volume and breakthrough volume were studied. The best results were obtained with Varian Bond Elut-C18. In order to achieve a high selectivity in the determination of SCCPs, GC-NCI-MS was used. Quality parameters of the optimised SPE and SPME procedures were determined, and the best results were obtained for the SPE/GC-NCI-MS method with LODs of 5 and 20 ng l(-1) for tap and river water, respectively. This method was successfully applied to the analysis of SCCPs in river water samples at concentrations below the microg l(-1) level.     

Solid-phase microextraction-gas chromatographic-mass spectrometric analysis of garlic oil obtained by hydrodistillation

Garlic (Allium sativum L.) is highly consumed worldwide. This crop is mainly known for its flavor and odor, although the many medicinal properties that are attributed to it, including anticarcinogenic, antiatherosclerotic, and antithrombotic potential, among several others, have called the attention of scientists since very early times. It is known that sulfur-containing volatiles are the principal compounds responsible for such properties. The aims of this work were to develop a solventless extraction method for sulfur-containing volatiles from garlic, as well as their chemical characterization. Since garlic volatiles are rather thermolabile, low-pressure hydrodistillation was chosen as the extracting method. The analysis of all compounds was performed on an HP-FFAP chromatographic column mounted in a GC-MS system. For volatile transfer and injection method, solid-phase microextraction was selected, with the use of eight different fibers. The most abundant volatile compound was diallyl disulfide, followed by diallyl trisulfide. Among the 47 totally identified compounds, 18 were linear sulfur-containing volatile compounds, 6 were of non-sulfur nature, and the other 23 were cyclic compounds. However, linear sulfur volatiles accounted for 94% of the total amount.     

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.     

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.     

SPME/GC-MS测定水中痕量二苯氯胂

采用衍生化固相微萃取/气相色谱-质谱(GC-MS),对水中痕量二苯氯胂进行测定,考察了衍生化试剂、萃取纤维、萃取时间等因素对方法灵敏度的影响。测定二苯氯胂的线性范围为1.8~216μg/L,检出限为0.3μg/L(S/N=3),相对标准偏差为7.63%,回收率为95%~103%。     

Solid-phase microextraction coupled with high-performance liquid chromatography for the determination of phenylurea herbicides in aqueous samples

Solid-phase microextraction coupled with high-performance liquid chromatography was successfully applied to the analysis of nine phenylurea herbicides (metoxuron, monuron, chlorotoluron, isoproturon, monolinuron, metobromuron, buturon, linuron, and chlorbromuron). Polydimethylsiloxane-divinylbenzene (PDMS-DVB, 60 microm) and Carbowax-templated resin (CW-TPR, 50 microm) fibers were selected from four commercial fibers for further study because of their better extraction efficiencies. The parameters of the desorption procedure were studied and optimized. The effects of the properties of analytes and fiber coatings, carryover, duration and temperature of absorption, pH, organic solvent and ionic strength of samples were also investigated. External calibration with an aqueous standard can be used for the analysis of environmental samples (lake water) using either PDMS-DVB or CW-TPR fibers. Good precisions (1.0-5.9%) are achieved for this method, and the detection limits are at the level of 0.5-5.1 ng/ml.     

Solid-phase microextraction coupled with microcolumn liquid chromatography for the analysis of amitriptyline in human urine

Summary Solid-phase microextraction (SPME) is a solvent-free sample-preparation technique that enables isolation and pre-concentration of analytes from a sample on a thin film coating a fused-silica fiber. In this study SPME coupled with microcolumn liquid chromatography (micro LC) has been used for the determination of four tricyclic antidepressants (amitriptyline, imipramine, nortriptyline, and desipramine) in human urine. SPME conditions which affect extraction efficiency were optimized, and under the optimum conditions the system was a few hundred times more sensitive than direct LC analysis without SPME. For amitriptyline the detection limit was 3 ng mL⁻¹ and the calibration curve was linear in the range of 5–500 ng mL⁻¹. The SPME-micro LC method has been applied to the analysis of amitriptyline in patient’s urine.     

Solid-phase microextraction for the gas chromatography mass spectrometric determination of oxazole fungicides in malt beverages

This paper describes a method for the sensitive, selective, and solvent-free determination of six oxazole fungicide residues (hymexazol, drazoxolon, vinclozolin, chlozolinate, oxadixyl, and famoxadone) in malt beverages. Direct immersion solid-phase microextraction (DI-SPME) coupled to gas chromatography with mass spectrometry in the selected ion monitoring mode, GC-MS(SIM), is used. A comparison of the optimal fiber used, a polar carbowax-divinylbenzene 70-microm fiber, and a nonpolar polydimethylsiloxane 100-microm fiber was carried out. Optimal extraction conditions were 60 degrees C and an extraction time of 30 min under continuous stirring. Desorption was carried out at 250 degrees C for 5 min. Detection limits ranged from 0.006 to 0.3 microg L(-1) at a signal to noise ratio of 3, depending on the compound. The proposed method was successfully applied to malt beverages including malt, beer, and whisky, and none of the samples contained residues higher than detection limits.     

Solid-phase microextraction/capillary gas chromatography for the profiling of confiscated ecstacy and amphetamine

Summary Impurity profiling of ecstacy and amphetamine seizures was accomplished by solid-phase microextraction (SPME) combined with capillary gas chromatography (GC). Samples were dissolved in 0.1 M aqueous acetate buffer (pH 5.0) as the only manual operation and subsequently subjected to SPME-GC. Ecstacy tablets were analyzed by head-space SPME to avoid contamination of SPME fibers with insoluble tablet components, while illicit amphetamine powders were exposed to immersed SPME. A SPME fiber of polydimethylsiloxane-divinylbenzene was found to provide excellent extraction of both polar and non-polar impurities. For both illicit ecstacy and amphetamine, complex impurity profiles were obtained by SPME providing a high information content. For ecstacy, profiles (relative peak areas) were repeatable within 2.2 to 12.6% RSD (n=6) while similar data on amphetamine varied between 2.0 and 10.9% RSD (n=6). No carry-over was observed although each fiber was used for 50 to 100 extractions.     

Full automation of derivatization--solid-phase microextraction-gas chromatography-mass spectrometry with a dual-arm system for the determination of organometallic compounds in aqueous samples

The determination of organometallic compounds in aqueous samples by in-vial derivatization and headspace solid-phase microextraction (SPME)-gas chromatography (GC)-mass spectrometry (MS) has been fully automated using a Twin PAL dual-arm robotic system. Linearity, accuracy, sensitivity for a series of n-methyl, n-ethyl, and n-phenyl metal substituted chloride compounds of tin, lead, and mercury were investigated. The automated method was compared to similar manual methods and improved precision, speed and throughput was achieved. By originally programming the Twin PAL dual-arm system with the supplier's software (Cycle Composer, Version 1.5.0) the arms on the robot were only able to work in sequence. However, in order to have a flexible system and exploit time efficiently the robotic arms must work simultaneously. This was accomplished by programming the robot with the new software package called Cruise Control 4-2 for Twin PALs. Compared to Cycle Composer, Cruise Control 4-2 enhanced the speed and throughput of the automated system further. In addition, with a built-in crash prevention protocol and an improved user interface a more user-friendly system was obtained.     

Quality control of Schizonepeta tenuifolia Briq by solid-phase microextraction gas chromatography/mass spectrometry and principal component analysis

The chemical composition of Schizonepeta tenuifolia Briq. (Sch.t.Briq.) is mainly composed of several volatile substances that affect multiple pharmacological targets and provide clinical efficacy. In this work, a headspace/solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS) method was developed to evaluate the profiles of volatile compounds in Sch.t.Briq. The optimization of SPME conditions was carried out using four kinds of fiber, extraction time and temperature, desorption temperature and time, and sample amount. The GC/MS analysis allowed the tentative identification of 21 compounds, with similarities higher than 85%, in accordance with the NIST/Wiley mass spectral library. Major components such as (+)-menthone (14.32%), (−)-pulegone (47.73%), 2-hydroxy-2-isopropenyl-5-methylcyclohexane (5.97%), cis-pulegone oxide (4.12%), and schizonal (5.36%) were identified by comparison of retention time and mass spectral data of standards isolated from Sch.t.Briq. The contents of these compounds were about above 78% against total amounts of volatile compounds extracted from Sch.t.Briq. Based on optimized SPME method, 19 different Sch.t.Briq. samples collected from markets in Korea and China were analyzed to obtain the profiling data of volatile compounds. In addition, principal component analysis (PCA) was performed on the profiling data in order to classify the samples collected from the different regions. PCA could possibly visualize the grouping tendencies of the studied varieties of herbal samples, as well as the identification of the volatiles responsible for discriminating the groups.     

Headspace solid-phase microextraction-gas chromatography-quadrupole mass spectrometric methodology for the establishment of the volatile composition of Passiflora fruit species

Dynamic headspace solid-phase microextraction (HS-SPME) followed by thermal desorption gas chromatography-quadrupole mass spectrometry analysis (GC-_qMS), was used to investigate the aroma profile of different species of passion fruit samples. The performance of five commercially available SPME fibres: 65 μm polydimethylsiloxane/divinylbenzene, PDMS/DVB; 100 μm polydimethylsiloxane, PDMS; 85 μm polyacrylate, PA; 50/30 μm divinylbenzene/carboxen on polydimethylsiloxane, DVB/CAR/PDMS (StableFlex); and 75 μm carboxen/polydimethylsiloxane, CAR/PDMS; was evaluated and compared. Several extraction times and temperature conditions were also tested to achieve optimum recovery. The SPME fibre coated with 65 μm PDMS/DVB afforded the highest extraction efficiency, when the samples were extracted at 50 °C for 40 min with a constant stirring velocity of 750 rpm, after saturating the sample with NaCl (17%, w/v — 0.2 g). A comparison among different passion fruit species has been established in terms of qualitative and semi-quantitative differences in volatile composition. By using the optimal extraction conditions and GC-qMS it was possible to tentatively identify seventy one different compounds in Passiflora species: 51 volatiles in Passiflora edulis Sims (purple passion fruit), 24 in P. edulis Sims f. flavicarpa (yellow passion fruit) and 21 compounds in Passiflora mollissima (banana passion fruit). It was found that the ethyl esters comprise the largest class of the passion fruit volatiles, including 82.8% in P. edulis variety, 77.4% in P. edulis Sims f. flavicarpa variety and 39.9% in P. mollissima.The semi-quantitative results were then submitted to principal component analysis (PCA) in order to establish relationships between the compounds and the different passion fruit species under investigation.     

Solid-phase microextraction for the analysis of short-chain chlorinated paraffins in water samples

A novel solid-phase microextraction (SPME) method coupled to gas chromatography with electron capture detection (GC-ECD) was developed as an alternative to liquid-liquid and solid-phase extraction for the analysis of short-chain chlorinated paraffins (SCCPs) in water samples. The extraction efficiency of five different commercially available fibres was evaluated and the 100-microm polydimethylsiloxane coating was the most suitable for the absorption of the SCCPs. Optimisation of several SPME parameters, such as extraction time and temperature, ionic strength and desorption time, was performed. Quality parameters were established using Milli-Q, tap water and river water. Linearity ranged between 0.06 and 6 microg l(-1) for spiked Milli-Q water and between 0.6 and 6 microg l(-1) for natural waters. The precision of the SPME-GC-ECD method for the three aqueous matrices was similar and gave relative standard deviations (RSD) between 12 and 14%. The limit of detection (LOD) was 0.02 microg l(-1) for Milli-Q water and 0.3 microg l(-1) for both tap water and river water. The optimised SPME-GC-ECD method was successfully applied to the determination of SCCPs in river water samples.     

固相微萃取-气相色谱法测定食品添加剂中有害有机挥发杂质

建立了固相微萃取（SPME）-气相色谱法（GC）测定食品添加剂中有害有机挥发杂质：二氯甲烷、三氯甲烷、苯、三氯乙烯和1、4-二n恶烷的方法。以聚二甲基硅氧烷（PDMS）涂层的萃取纤维萃取糖精钠、柠檬酸、苯甲酸钠溶液中的待测组分。以HP-5毛细管柱为分离柱，火焰离子化检测器（FID）定量测定。优化了固相微萃取条件：萃取纤维、萃取方式、萃取温度、平衡时间、pH及电解质浓度等。在优化的试验条件下，进行了方法的检出限、精密度、回收率试验。5种组分的回收率在97．3％～103．9％之间。     

Assessment of the degradation of polyurethane foams after artificial and natural ageing by using pyrolysis-gas chromatography/mass spectrometry and headspace-solid phase microextraction-gas chromatography/mass spectrometry

Polyurethane foams are widely present in museum collections either as part of the artefacts, or as a material for their conservation. Unfortunately many of PU foam artefacts are in poor condition and often exhibit specific conservation issues. Their fast thermal and photochemical degradations have been the aim of previous researches. It is now accepted that hydrolysis predominates for polyester-based polyurethane PU(ES) whereas oxidation is the principal cause of degradation for polyether-based polyurethane PU(ET) variety. Only a few studies have been devoted to volatile organic compounds (VOCs) emitted by polyurethanes and, to our knowledge, none were performed on polyurethane foams by using headspace-solid phase microextraction (HS-SPME). The objective of the work described here is to assess the impact of some environmental factors (humidity, temperature and daylight) on the degradation of PU foams by evaluating their volatile fractions. We investigated morphological changes, polymerized fractions and volatile fractions of (i) one modern produced PU(ES) foam and one modern PU(ET) foam artificially aged in different conditions as well as (ii) four naturally aged foams collected from various daily life objects and selected for the representativeness of their analytical data. Characterization procedure used was based on attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and non-invasive headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry (HS-SPME-GC/MS). In this paper, the formation of alcohol and acid raw products for PU(ES) and glycol derivatives for PU(ET) during natural and artificial ageing is confirmed. These main products can be considered as degradation markers for PU foams. Results show that artificial and natural ageing provide similar analytical results, and confirm that the dominant degradation paths for PU(ES) and for PU(ET) are hydrolysis and photo-oxidation, respectively. Lastly, we highlight that non-invasive HS-SPME-GC/MS analysis allows to distinguish between PU(ES) and PU(ET) at any point of their degradations.     

Use of multivariate analysis techniques for the characterization of analytical results for the determination of the mineral composition of kale

This paper describes the determination and evaluation of the mineral composition (calcium, magnesium, iron, manganese and zinc) of kale (Brassica oleracea L. var. acephala DC.) grown in soils within four cities in Bahia State, Brazil. The sampling process was performed during the summer and winter. Samples were digested with concentrated nitric acid and a digestion pump. Analyses were performed with inductively coupled plasma optical emission spectrometry (ICP OES) and the accuracy was confirmed with a certified reference material of apple leaves furnished by the National Institute of Standard and Technology. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed different mineral compositions of the samples collected in the summer and winter. Samples collected in the winter have a higher concentration of micronutrients (iron, zinc and manganese) and macronutrients (calcium and magnesium). The average contents (wet weight and mg per 100 g) for the winter and summer were 551 and 535 for calcium; 117 and 106 for magnesium; 2.13 and 1.48 for iron; 2.63 and 1.95 for zinc and 2.05 and 1.34 for manganese, respectively. These results are in agreement with values previously reported in the literature.