Full-range analysis of ambient volatile organic compounds by a new trapping method and gas chromatography/mass spectrometry

This study investigated the feasibility of analyzing a full range of ambient volatile organic compounds (VOCs) from C(3) to C(12) using gas chromatograph mass spectrometry (GC/MS) coupled with thermal desorption. Two columns were used: a PLOT column separated compounds lighter than C(6) and a DB-1 column separated C(6)-C(12) compounds. An innovative heart-cut technique based on the Deans switch was configured to combine the two column outflows at the ends of the columns before entering the MS. To prevent the resolved peaks from re-converging after combining, two techniques were attempted (hold-up vs. back-flush) to achieve the intended "delayed" elution of heavier components. Thus, the resulting chromatogram covering the full range of VOCs is a combination of two separate elutions, with the heavier section following the lighter section. With the hold-up method, band-broadening inevitably occurred for the delayed C(6)-C(7) DB-1 compounds while the light compounds eluted from the PLOT column. This broadening problem resulted in peak tailing that was largely alleviated by adding a re-focusing stage while the DB-1 compounds were back-flushed, and this modified technique is referred to as the back-flush method. With this modification, the separation of the C(6)-C(7) compounds improved dramatically, as revealed by the decrease in peak asymmetry (As) and increase in resolution. Linearity and precision for these peaks also improved, yielding R(2) and RSD values better than 0.9990 and 2.8%, respectively.     

Analysis of volatile organic compounds in polymers by dynamic headspace and gas chromatography/mass spectrometry

An experimental method for the analysis of volatile organic compounds in polymers is described. The technique involves dynamic headspace sampling, collection, and concentration of the volatiles in a cold trap, followed by capillary column gas chromatography/mass spectometry. Flow switching is carried out by the Deans switching technique. Four technical polymers used as pharmaceutical packaging materials have been analyzed in order to demonstrate the method.     

Determination of volatile halogenated organic compounds in soils by purge-and-trap capillary gas chromatography with atomic emission detection

Nine volatile halogenated organic compounds (VHOCs), including four trihalomethanes (THMs), were determined in soils by capillary gas chromatography with microwave induced-plasma atomic emission spectrometry (GC-AED), using a purge-and-trap system (PT) for sample preconcentration. Analytes were previously extracted from the soil sample in methanol and the extract was preconcentrated before being chromatographed. Element-specific detection and quantification were carried out monitoring two wavelength emission lines, corresponding to chlorine (479 nm) and bromine (478 nm). Each chromatographic run took 21 min, including the purge step. The method showed a precision of 1.1-7.2% (R.S.D.) depending on the compound. Detection limits ranged from 0.05 to 0.55 ng ml⁻¹, for chloroform and dichloromethane, respectively, corresponding to 3.3 and 36.0 ng g⁻¹ in the soil samples. The chromatographic profiles obtained showed no interference from co-extracted compounds. Low levels of dichloromethane and chloroform ranging from 0.04 to 1.13 μg g⁻¹ were found in samples obtained from small gardens irrigated with tap water. The method is reliable and can be used for routine monitoring in soil samples.     

Detection of volatile organic sulfur compounds in water by headspace gas chromatography and membrane inlet mass spectrometry

Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic conductivity detector) are compared in tlie analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethyl-methyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC-ELCD method and four decades with the GC-FID and MIMS methods. Detection limits were at low (μg/1 levels with the two gas chromatographic methods and clearly below μg/1 level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC-ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.     

Importance of enhanced mass resolution in removing interferences when measuring volatile organic compounds in human blood by using purge-and-trap gas chromatography/mass spectrometry

The number of volatile organic compounds (VOCs) that can be purged from human blood is so great that they cannot be separated completely by capillary gas chromatography. As a result, the single-mass chromatograms used for quantitating the target compounds by mass spectrometry have many interferences at nominal (integer) mass resolution of a quadrupole mass spectrometer. The results of these interferences range from small errors in quantitation to completely erroneous results for the target VOCs. By using a magnetic sector mass spectrometer, these interferences at nominal mass can be removed at higher resolution by lowering the ion chromatogram windows around the masses of interest. At 3000 resolution (10% valley definition), unique single-ion chromatograms can be made for the quantitation ions of the target VOCs. Full-scan mass data are required to allow the identification of unknown compounds purged from the blood. By using isotope-dilution mass spectrometry, most target VOCs can be detected in the low parts per trillion range for a 10-mL quantity of blood from which the VOCs have been removed by a purge-and-trap method.     

Characterization of the volatile organic compounds of Italian 'Fossa' cheese by solid-phase microextraction gas chromatography/mass spectrometry

Fossa cheese is an Italian hard cheese, ripened for up to 3 months in underground pits dug into tuffaceous rock. During this period, the cheese develops a unique flavour and intense and somewhat piquant aroma. Solid-phase microextraction gas chromatography/mass spectrometry (SPME-GC/MS) was utilized to characterize the volatile organic compounds (VOCs) of Fossa cheese. A total of 75 VOCs were separated and identified; in particular, the major class of compounds found in the cheeses ripened in the pits were the esters of fatty acids. Discriminant analysis of volatile profiles allowed us to distinguish between cheeses in different stages of seasoning (60-day-old cheese and cheese ripened an additional 90 days in and out of the pits).     

Identification of volatile organic compounds emitted by a naturally aged book using solid-phase microextraction/gas chromatography/mass spectrometry

Solid-phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) has been applied to the analysis of volatile organic compounds emitted from a naturally aged groundwood pulp paper originating from an old book in order to access the products produced through the decomposition reactions occurring in paper upon ageing. Two different extraction methods were developed and compared: headspace SPME and contact SPME. The influence of few extraction parameters were tested in order to define the best extraction conditions. An optimised non-destructive contact SPME method was elaborated and allowed the characterisation of more than 50 individual constituents.     

Analysis of volatile compounds in Herba Asari by single-drop micro-extraction gas chromatography mass spectrometry

A rapid headspace single-drop micro-extraction(mix) gas chromatography mass spectrometry(SDMEGC -MS) for the analysis of the volatile compounds in Herba Asari was developed in this study.A mixed solvent of n-tridecane and butyl acetate(1:1) was finally used for the extraction at 70 C for 15 min with sample amount of 0.750 g and 100 mesh particle size.Under the determined conditions,the pound samples of Herba Asari were directly applied for the analysis.SDME-GC-MS,SPME-GC-MS and SD-GCMS methods were compared and the results showed that SDME-GC-MS method was a simple, inexpensive and effective way to measure the volatile compounds in Herba Asari and could be used for the analysis of volatile compounds in complex samples.     

Monitoring the emission of volatile organic compounds from flowers of Jasminum sambac using solid-phase micro-extraction fibers and gas chromatography with mass spectrometry detection

Solid-phase micro-extraction (SPME) was studied as a solvent free alternative method for the extraction and characterization of volatile compounds in intact and plucked flowers of Jasminum sambac at different day time intervals using gas chromatography (GC-FID) and gas chromatography-quadrupole mass spectrometry. The analytes identified included alcohols, esters, phenolic compounds, and terpenoids. The main constituents identified in the flower aroma using different fibers were cis-3-hexenyl acetate, (E)-beta-ocimene, linalool, benzyl acetate, and (E,E)-alpha-farnesene. The benzyl acetate proportion decreased from morning to afternoon and then increased in evening collections. PDMS fiber showed a high proportion of (E,E)-alpha-farnesene in jasmine floral aroma. Among other constituents identified, cis-3-hexenyl acetate, linalool, and benzyl acetate were major aroma contributors in plucked and living flowers extracts using PDMS/DVB, Carboxen/PDMS, and DVB/Carboxen/PDMS fibers. PDMS/DVB recorded the highest emission for benzyl acetate while the (E)-beta-ocimene proportion was highest in DVB/Carboxen/PDMS when compared with the rest. The highest linalool content, with increasing proportion from morning to noon, was found using mixed coating fibers. Almost negligible volatile adsorption was recorded for the polyacrylate fiber for intact flower aroma, whereas it was most effective for benzyl acetate, followed by indole under plucked conditions. Moreover, the highest amounts extracted, evaluated from the sum of peak areas, were achieved using Carboxen/PDMS, and DVB/Carboxen/PDMS. Introduction of a rapid, and solvent free SPME method for the analysis of multicomponent volatiles can be successfully employed to monitor the extraction and characterization of flower aroma constituents.     

Analysis of volatile organic compounds using gas chromatography

The focus of this review is the analysis of volatile organic compounds (VOCs) by gas chromatography (GC) in the field of environmental, food, flavour and fragrance, medical and forensic sciences. New trends in sample injection, separation and detection are covered, including multi-dimensional and high-speed GC. Attention is drawn to a growing interest in quality assessment. From the review, it is clear that it remains a challenge to generate multi-component gaseous standards of VOCs at ppbv and pptv.     

吹扫捕集气相色谱-质谱法测定土壤中54种挥发性有机物

建立了土壤中54种挥发性有机物的吹扫捕集气相色谱质谱分析方法.54种挥发性有机物检测限在0.20 ～0.72μg/kg之间,平均加标回收率为92.5％～112.1％,各组分相对标准偏差为1.4％～8.8％.本方法适用于批量样品的分析.     

Determination of volatile organic compounds in the dried leaves of Salvia species by solid-phase microextraction coupled to gas chromatography mass spectrometry

Salvia spp. are used throughout the world both for food and pharmaceutical purposes. In this study, a method involving headspace solid-phase microextraction combined with gas chromatography–mass spectrometry was developed, to establish the volatiles profile of dried leaves of four Iranian Salvia spp.: Salvia officinalis L., Salvia leriifolia Benth, Salvia macrosiphon Boiss. and two ecotypes of Salvia reuterana Boiss. A total of 95 volatiles were identified from the dried leaves of the five selected samples. Specifically, α-thujone was the main component of S. officinalis L. and S. macrosiphon Boiss. (34.40 and 17.84%, respectively) dried leaves, S. leriifolia Benth was dominated by β-pinene (27.03%), whereas α-terpinene was the major constituent of the two ecotypes of S. reuterana Boiss. (21.67 and 13.84%, respectively). These results suggested that the proposed method can be considered as a reliable technique for isolating volatiles from aromatic plants, and for plant differentiation based on the volatile metabolomic profile.     

Determination of specific volatile organic compounds synthesised during Tuber borchii fruit body development by solid-phase microextraction and gas chromatography/mass spectrometry

Fruit body development is a particular phase of the Tuber life cycle, characterised by the aggregation of different types of hyphae, i.e., vegetative hyphal cells and highly specialised reproductive hyphae (asci). In order to identify the volatile organic compounds (VOCs) produced in different stages of the Tuber borchii ripening fruit body, solid-phase microextraction with gas chromatography and mass spectrometry was used. The volatile organic compounds were extracted using a DVB/CAR/PDMS 50/30 microm fiber placed for 10 min at room temperature in the truffle headspace. The results obtained reveal 49 compounds each of which was present only in a particular stage of maturation. 1-octen-3-ol, aromadendrene, alpha-farnesene and other terpenoid compounds were of particular interest, and their possible biological roles are discussed. The production of aromadendrene in the completely unripe fruit body suggests the existence of communication events in the early stage of ascomata formation between the fungus and the host plant. alpha-Farnesene could represent a chemotactic attractant to saprophytic organisms in order to disperse the fungal spores in the environment. The identification of the VOCs produced by truffles during their maturation could give information about the processes underlying this phase of Tuber life cycle.     

化工废渣中半挥发性有机有害物的GC/MS分析

 参照美国环保局的８２７０方法，根据我国情况采用内标定量法对某化工废渣进行半挥发性有机物分析，使用内标法可消除系统和进样过程中带来的误差，提高数据的置信度。通过实验，测得废渣中含１０种美国环保局规定的优先监测污染物和１１种含氯化合物，含量在０．４～８０μｇ／ｇ之间。它们对人体有较大危害，必须进行严格处理才能排放。     

Determination of the volatiles from tobacco by capillary gas chromatography with atomic emission detection and mass spectrometry

A new gas chromatograph‐atomic emission detector (GC‐AED) coupled with Deans switching technique for analyzing volatiles from tobaccos were developed. The detector operating parameters (reagent gas pressure and make‐up gas flow rate) were optimized. The detection limits for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) ranged 0.05–0.2, 0.05–0.3 and 1–11 ng, respectively, depending on the compound. The sensitivity and linearity for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) decreased in the order O>H>C. Calibration curves were obtained by plotting peak area versus concentration, and the correlation coefficients relating to linearity were at least 0.9359. Elemental response factors measured on these channels, relative to the carbon 193‐nm channel, were hydrogen, 0.38–0.48 (mean %RSD=5.64), and oxygen, 0.085–0.128 (mean %RSD=14.9). The evaluation was also done for the new technique and for an established GC‐MS technique for the same real samples. The results of GC‐AED and GC‐MS showed that there was a relatively good agreement between the two sets of data.