Trace analysis of alkaline flavors in cut tobacco by heart‐cutting multidimensional GC–GC–MS

Tobacco is a complex chemical matrix. The analysis of trace alkaline flavors in tobacco is very difficult because of the limited peak capacity of monodimensional GC. In the present study, a home‐assembled twin‐oven GC–GC–MS system, with MS detection in both dimensions, has been applied to the analysis of 20 alkaline volatiles in a variety of cut‐tobacco samples. By transferring nine and six heart‐cuts from the first apolar column to the second polar column in two separate runs, the potential mutual interference of adjacent isomeric targets and the complex matrix could be removed. For comparative purposes, a systematic comparison of both quantification and qualification results for the cut‐tobacco sample as quality control was conducted between GC–GC–MS and GC–MS. The results showed that GC–GC–MS provided higher accuracy in peak assignment and quantification. And in GC–MS, the interferences of co‐elution had caused both low matched similarity in peak assignment and false‐negative/‐positive results in quantification for some targets. Advantages of the developed GC–GC–MS method in the analysis of alkaline flavors are its high resolving power, reliability, and simplicity.     

全二维气相色谱/飞行时间质谱(GC×GC/TOFMS)用于烟叶中挥发、半挥发性碱性化合物的组成研究

建立了烟叶中挥发性、半挥发性碱性化合物组成研究的全二维气相色谱/飞行时间质谱(GC×GC/TOFMS)分析方法, 并用所建立的方法对香料烟中碱性化合物进行了表征. 对比了一维气相色谱和全二维色谱方法用于烟叶碱性组分组成分析的效果. 一维色谱质谱方法共鉴定出45种碱性化合物. 用所建立的全二维气相色谱方法, 采用TOFMS谱图库检索结合全二维特有的包含结构信息的二维谱图, 通过族分离和结构谱图鉴定, 鉴定出了香料烟中挥发性、半挥发性碱性组分共92种. 包括吡咯类化合物6种, 吡啶类化合物39种, 吡嗪类化合物10种, 苯胺类化合物11种, 喹啉类化合物11种, 吲哚类4种和其他类化合物11种. 同时对不同类别的化合物在二维气相色谱上的分布模式进行了研究. 研究结果表明, 全二维色谱飞行时间质谱的高分辨率和特有的定性手段适合于烟叶这类复杂植物体系的化学组成研究.     

全二维气相色谱/飞行时间质谱用于烟叶中酸性成分的分离与分析

建立了烟叶中酸性化合物(挥发性、 半挥发性羧酸类和酚类)组成研究的全二维气相色谱/飞行时间质谱(GC×GC-TOFMS)分析方法, 并用此方法对香料烟中的酸性化合物进行了表征. 用同时蒸馏萃取样品的前处理方法, 采用TOFMS谱图库检索结合全二维特有的包含结构信息的二维谱图, 通过族分离和结构谱图, 鉴定出了香料烟中143种挥发性及半挥发性酸性组分, 包括10种酸酐和呋喃二酮, 43种有机酸和90种酚类化合物. 同时对不同类别的化合物在二维气相色谱上的分布模式进行了研究. 结果表明, 全二维气相色谱飞行时间质谱的高分辨率非常适合于烟叶这类复杂体系的分离分析.     

卷烟主流烟气粒相物中中性化学成分的全二维气相色谱飞行时间质谱(GC×GC-TOF MS)谱图特征识别

建立了全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)分析卷烟主流烟气中中性化学成分的方法。以较长的弱极性柱HP-5MS(50 m×0.2 mm i.d.×0.33μm)作为第一维柱,较短的薄液膜中等极性柱DB-17MS(1.7 m×0.1 mm i.d.×0.1μm)作为第二维柱,对优质烟叶单料卷烟烟气的中性成分进行定性分析,经过人工纠错等分析初步鉴定出匹配度大于700的1 464种成分,重点讨论了中性香味羰基化合物全二维点阵的谱图特征,为烟气和复杂体系的深入研究提供了方法学基础。     

Application of comprehensive two-dimensional gas chromatography mass spectrometry and different types of data analysis for the investigation of cigarette particulate matter

In tobacco research, the comparison of different tobacco blends as well as the puff-dependent behaviour of cigarettes is a matter of particular interest. For the investigation of smoke characteristics, GC x GC offers different ways for data analysis, namely, compound target analysis, automated peak-based compound classification and comprehensive pixel-based data analysis. This study will show the application as well as the pros and cons of these types of data analysis for very complex matrices like cigarette particulate matter. In addition, new aspects about the recently discovered puff-dependent behaviour of compounds in cigarette smoke will be presented. Automated peak-based compound classification including mass spectrometric pattern recognition is used for the classification of tobacco particulate matter samples and the puff-dependent investigation of different compound classes. This compound group specific analysis is further reinforced by applying an even more comprehensive pixel-based analysis. This kind of analysis is used to generate fingerprints of different types of cigarettes. The combination of fast feature reduction methods like analysis of variance (ANOVA) and t-test with multivariate feature transformation methods like partial least squares discriminate analysis (PLSDA) for feature selection provides a powerful tool for a detailed inspection of different types of cigarettes.     

Enantiomeric analysis of beta-pinene and limonene by direct coupling of reversed phase liquid chromatography and gas chromatography using absorbents as packing materials

A method based on the use of absorbents as packing materials inside the interface of the online coupling between RPLC and GC is proposed for the enantiomeric analysis of beta-pinene and limonene in essential oils. For that purpose, a comparison of the RSD, detection limit and recovery provided by two absorbents and one adsorbent is included in this study. The results found in this work proved the validity of absorbents as packing materials in online RPLC-GC to determine minor compounds in complex matrices. In particular, PDMS seemed to be specially useful to analyse nonpolar compounds, such as beta-pinene and limonene, since it provided higher sensitivity for this kind of compounds. The developed method was applied to the evaluation of the natural and non-natural character of commercial essential oils by means of the determination of the enantiomeric composition of beta-pinene and limonene.     

Qualitative supercritical fluid extraction coupled to capillary gas chromatography

The usefulness and ease of utilizing supercritical fluid extraction (SFE) directly coupled to capillary gas chromatography (GC) as quantitative or qualitative analytical problem-solving tools will be demonstrated. As an alternative to conventional liquid solvent extractions, SFE presents itself as a means to achieve high extraction efficiencies of different compounds in complex solid matrices in very rapid tims frames. Moreover, SFE has an additional advantage of being able to achieve distinct extraction selectivities as a function of the solubilizing power of the supercritical fluid extracting phase. For on-line SFE/GC, the extraction effluent is directly transferred to the analytical chromatograph. On-line SFE/GC involves the decompression of pressurized extraction effluent directly into a heated, unmodified capillary split injection port of the GC. In this respect, SFE introduction into GC can be used as an alternative means of GC injection, comparable to such modes of injection as pyrolysis and thermal desorption. This paper will show applications of SFE/GC where mass spectrometric detection together with flame ionization detection was used for component identification from environmental, tobacco, and petroleum matrices.     

Coupled LC‐GC‐NPD for Determination of Carbazole‐Type PANH and Its Application to Personal Exposure Measurement

A coupled LC‐GC method for the analysis of carbazole‐type PANH has been developed and evaluated. Group separation and isolation of carbazoles from interfering acridines in a complex sample matrix was accomplished by using a back‐flush technique and an in situ end‐capped dimethylaminopropyl silica column in the HPLC part of the system. On‐line injection of the carbazole fraction into the GC column was performed with a loop‐type interface utilizing concurrent solvent evaporation technique. An LOD of 1–3 pg of individual carbazole compounds was achieved by nitrogen selective detection using an NPD. The method is shown to be robust and is demonstrated by application to personal exposure measurement in an aluminum reduction plant.     

Analysis of polycyclic aromatic hydrocarbons in solid sample material using a desorption device coupled to a GC/MS system

Summary Polycyclic aromatic hydrocarbons (PAH) today are ubiquitous detectable constituents of recent sediments. The compounds are adsorbed on particulate emissions and are thus transferred to the environment. To date the analysis of PAH in sediments, dust samples and plant material is based mainly on the application of solvent-extraction methods followed by liquid chromatography and/or gas chromatographic separation of the extracts.An alternative approach for the analysis of PAH in solid samples such as coal, sediments, dust samples and plant waxes is shown in this contribution. A commercially available device for the analysis of volatile compounds present in solid matter is connected on-line to a GC/MS system. The device enables the thermal desorption of hydrocarbons at a temperature of 320°C. Subsequently, the hydrocarbons trapped on the initial part of the capillary column are analyzed by GC/MS. The application of mass chromatography provides the possibility of detection and quantitation of PAH in complex mixtures even when they coelute with other compounds. The sample amount required varies between 1 and 10 mg depending on the hydrocarbon content.     

Universal and discriminative detection using a miniaturized pulsed discharge detector in comprehensive two-dimensional GC

A miniaturized pulsed discharge detector (Mini-PDD) has been successfully demonstrated for comprehensive 2-D GC (GC x GC) analysis of pyrolysis gasoline and the pyrolysis GC x GC analysis of a polyethylene copolymer. The detector cell volume of the Mini-PDD is reduced to 25% of the Valco plug-in PDD D-3. An n-C11 peak width at base is 96 ms for the Mini-PDD, about 23% larger than a peak width of 78 ms detected by a flame ionization detector (FID). The Mini-PDD has sufficient response time for most GC x GC applications. When Mini-PDD is operated in helium photoionization mode (Mini He-PDD), it is a universal detector for both inorganic and organic compounds. This is especially useful when detection of water is needed in GC x GC applications. When krypton is doped in the helium discharge gas (Mini Kr-PDD), it can suppress signals of compounds having higher ionization potentials and enhance relative signal intensities of aromatic compounds. The determination of aliphatic to aromatic hydrocarbon ratios is essential to the operation of petroleum crackers. Comparison of the signal from two modes of the Mini-PDD is a simple and fast way to verify the location of aromatics in comprehensive 2-D gas chromatograms.     

烟梗中的中性致香成分定性定量分析

采用带MS Vent装置的气质联用仪,同时实现MS定性和FID定量,对烤烟烟梗中性致香成分进行定性定量分析,共分离鉴定出40种成分.方法回收率介于85.69%～100.39%之间,精密度达到0.28%.结果表明,该方法简便、快捷、可靠,为全面评价烟草质量提供一种有效的分析手段.     

制备气相色谱在挥发性成分分离中的应用研究进展北大核心CSCD

分析型气相色谱仪对低沸点易挥发的有机化合物展现出优异的分离性能,通过在其色谱柱末端加装馏分收集装置,建立了现代制备气相色谱(Prep GC)技术,该技术可用于挥发性成分的快速分离富集。制备气相色谱仪是由分析型气相色谱仪改装而来,其进样系统、分离系统、检测系统、馏分收集系统也在不断地优化升级,以提高目标化合物的回收效率和纯度。Prep GC与现代波谱技术(如紫外可见吸收光谱、红外吸收光谱、拉曼光谱、质谱、X射线衍射、核磁共振波谱)耦合,可对分离富集得到的目标化合物的结构进行精准确证。近年来,与Prep GC在各种挥发性成分分离中的应用相关的报道逐渐增多,展现出良好的应用前景。然而,Prep GC在分离过程中也存在着无法制备热敏性化合物、分离成本高、易引入外源性污染等问题。该文根据近年来国内外研究学者的相关研究工作,对制备气相色谱仪的结构及其在精油单体化合物、昆虫信息素、食品和植物挥发性成分、地质生物标志物及持久性环境污染物的分离等领域的应用研究进展进行综述。最后,还对Prep GC在挥发性成分分离中的应用进行了总结与展望,旨在为拓展Prep GC应用领域提供参考。     

Identification of Abnormal Urinary Organic Acids in Inherited Metabolic Diseases by Gas Chromatography-Mass Spectrometry

A gas chromatography/mass spectrometry (GC/MS) coupled system has been established for the confirmatory identification of abnormal urinary organic acids in inherited metabolic diseases. Samples of patient urines were extracted with an organic solvent and trimethylsilylated (TMS). A mass spectra of gas chromatographically separated TMS derivatives can be obtained using the GC/MS coupled system with a single analytical run. Those compounds with close methylene units (e.g., 4-hydroxyphenylacetaic acid and phenylpyruvic acid) in the gas chromatograph can be identified by their specific mass spectra. The results indicate that this GC/MS system is a powerful method for identifying abnormal urinary organic acids. These acids can be identified by comparison with authentic mass spectra established in our laboratories or with mass spectra files from other sources or they can be directly identified by analysis of the mass spectrum. By using this system, we were able to make positive identification of several inherited metabolic diseases found in Chinese patients, including phenylketonuria, propionic acidemia, and methylmalonic aciduria. This GC/MS system is a powerful tool for the diagnosis of inherited metabolic diseases.     

GC／MS检测信息的综合利用

从充分利用气相色谱／质谱（ＧＣ／ＭＳ）提供的信息来鉴定ＧＣ流出组分的目的出发，并以脂肪醇分析为例讨论了ＧＣ保留指数在ＭＳ谱图解析及ＭＳ鉴定结果的合理性检验方面的作用。总结了ＧＣ保留的同系物规律、极性规律、加和规律及异构物规律来指导ＭＳ谱图解析。提出了含氧化合物官能团相对于－ＣＨ２－质量数的保留指数附加贡献值辅助ＭＳ确定化合物的类别。同时采用了ＧＣ／ＭＳ中选择离子检测方法（ＳＩＭ）在分子离子峰受噪音干扰或太弱以至完全未观测到时来进一步佐证其相对分子质量。     

Identification of unknown compounds on the basis of retention index data in comprehensive two-dimensional gas chromatography

The identification of unknown compounds in complex samples is very difficult. Comprehensive two-dimensional gas chromatography (GC x GC) provides very good resolution and improved identification reliability. Mass spectrometry is a powerful identification tool and retention index data are another good approach to this end. In this study, a second-order polynomial was used to calculate retention index data based on n-alkanes beyond the region of the 'isovolatile' curve in GC x GC, and the results in the 2nd dimension were validated by using the same stationary phase column in one-dimensional GC. To test the usefulness of the method, volatile compounds in a tobacco leaf extract fraction were analyzed using GC x GC, and 60 compounds were identified on the basis of their retention indices.     

香芸火绒草精油化学成分研究

用毛细管气相色谱／质谱、毛细管气相色谱／付里叶红外联用技术对青海产香芸火绒草精油化学成分进行分离。共鉴定出１１９个化俣物，占全部峰面积的９６．８％。     

热脱附/冷阱聚焦/气相色谱/质谱法卷烟香气分析

利用热脱附装置(TDS)对烟丝粉末进行快速升温,模拟卷烟燃吸过程中蒸馏区的部分反应,用冷阱收集所脱附的物质,以GC/MS对进行定性分析.成功的分离出了有机酸、饱和烃、芳香烃、烯烃以及含氮、氧杂原子的化合物等系列超过100种有机化合物,并且还发现了典型的存在于环境中的化学污染物——邻苯二甲酸二丁酯.     

Comprehensive two-dimensional gas chromatography, retention indices and time-of-flight mass spectra of flavonoids and chalcones

The applicability of comprehensive two-dimensional gas chromatography (GC×GC) for flavonoids analysis was investigated by separation and identification of flavonoids in standards, and a complex matrix natural sample. The modulation temperature was optimized to achieve the best separation and signal enhancement. The separation pattern of trimethylsilyl (TMS) derivatives of flavonoids was compared on two complementary column sets. Whilst the BPX5/BPX50 (NP/P) column set offers better overall separation, BPX50/BPX5 (P/NP) provides better peak shape and sensitivity. Comparison of the identification power of GC×GC-TOFMS against both the NIST05 MS library and a laboratory (created in-house) TOFMS library was carried out on a flavonoid mixture. The basic retention index information on high-performance capillary columns with a non-polar stationary phase was established and database of mass spectra of trimethylsilyl derivatives of flavonoids was compiled. TOFMS coupled to GC×GC enabled satisfactory identification of flavonoids in complex matrix samples at their LOD over a range of 0.5-10 μg/mL. Detection of all compounds was based on full-scan mass spectra and for each compound a characteristic ion was chosen for further quantification. This study shows that GC×GC-TOFMS yields high specificity for flavonoids derived from real natural samples, dark chocolate, propolis, and chrysanthemum.     

Tracking juniper berry content in oils and distillates by spectral deconvolution of gas chromatography/mass spectrometry data

The complex nature of botanicals and essential oils makes it difficult to identify all of the constituents by gas chromatography/mass spectrometry (GC/MS) alone. In this paper, automated sequential, multidimensional gas chromatography/mass spectrometry (GC-GC/MS) was used to obtain a matrix-specific, retention time/mass spectrometry library of 190 juniper berry oil compounds. GC/MS analysis on stationary phases with different polarities confirmed the identities of each compound when spectral deconvolution software was used to analyze the oil. Also analyzed were distillates of juniper berry and its oil as well as gin from four different manufacturers. Findings showed the chemical content of juniper berry can be traced from starting material to final product and can be used to authenticate and differentiate brands.