Limonene concentration in lemon (Citrus volkameriana) peel oil as a function of ripeness

The dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish-yellow, and yellow-orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC-MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kováts retention indexes (determined using a non-logarithmic scale on capillary columns coated with both polar (DB-Wax) and non-polar (DB-1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish-yellow coloration.     

Photooxidation of aqueous trichloroethylene using a buoyant photocatalyst with reaction progress monitored via micro-headspace GC/MS

Although photooxidation has previously been shown to be successful in removing organic contaminants from water, methods combining the rapid photooxidation of the desired contaminant with easy catalyst manipulation and removal are few and far between. In the absence of an easy means of catalyst removal, the photooxidation process becomes more costly and time consuming, and photocatalysis cannot be employed as an in situ method for the remediation of aqueous organic contaminants. In this study, the photocatalyst was added to an aqueous trichloroethylene (TCE) solution in the form of TiO₂-coated buoyant microspheres. The solution, placed in a flow-cell photoreactor along with the buoyant catalyst, was irradiated with a UV-filtered Xenon light source. Limited sample sizes necessitated the development of a low-cost headspace GC/MS analysis method, utilizing a standard direct-injection autosampler. This analytical technique aptly monitored reaction progress and indicated that aqueous TCE concentration decreases by nearly 90% in the first hour of irradiation. Subsequent solvent extraction GC/MS analysis indicated that the TCE is initially sorbed by the photocatalyst spheres, but as irradiation continued, TCE is removed from the catalyst spheres surfaces. During the course of irradiation, the expected TCE mineralization product hydrochloric acid appeared, as indicated by a decrease in pH and ion chromatography analysis. The microsphere-born catalyst was easily removed from the treated solution by filtration. Thus, it is possible that a method for effective, low-cost in situ photooxidation of aqueous organic contaminants will be realized in the near future.     

Separation and determination of m-phenoxybenzaldehyde reaction products by capillary gas chromatography

A capillary GC method employing an internal standard has been developed and successfully used for quantitative determination both of the raw materials used for the manufacture of m-phenoxybenzaldehyde and for the components of the reaction mixtures obtained at various stages of the development of the process. A complete analysis can be performed in a single temperature programmed run.     

乌骨鸡磷脂侧链脂肪酸的GC-MS分析

用氯仿:甲醇(2:1)超声提取乌骨鸡总磷脂,丙酮脱油精制后,经皂化、甲酯化处理,应用GC-MS联用技术对其侧链脂肪酸组成进行分析,并以面积归一法,计算各脂肪酸的相对百分含量.结果显示,乌骨鸡总磷脂中含有硬脂酸27.46%、花生四烯酸21.39%、油酸18.22%、亚油酸16.67%、棕榈酸12.13%、二十二碳六烯酸(DHA) 2.26%、二十碳三烯酸1.71%、棕榈油酸0.16%.不饱和脂肪酸和多不饱和脂肪酸的含量分别为60.41%和42.03%.乌骨鸡磷脂侧链脂肪酸中高比例的多不饱和脂肪酸和花生四烯酸含量是乌骨鸡磷脂的显著特征.     

GC/MS分析新疆大麻烟中的大麻类物质

大麻类物质是大麻制品及大麻植物的主要成分。本文采用GC／MS技术分析了新疆大麻烟中的大麻类物质。在莎车的麻烟中检测到16种大麻类组分，如CBD-C3、CBT、Δ^9THCV、CBL、CBD-C4、CBC、CBV、CBD、CBCR、Δ^10sTHC、CBE、Δ^3THC、Δ^9THC、DCBF、CBG和CBN。按照GC／MS鉴定的通用法则，推定了它们的结构。     

Preparation and evaluation of nickelmesogen for micropacked gas chromatography

The preparation and mesomorphic properties of a substituted bis(dithiolene)nickel complex derived from 4, 4'-dimethoxybenzil are reported. The phase transition temperatures were based on data obtained by polarized light microscopy and differential scanning calorimetry. The mesogenic phase existed over the temperature range from 77 to 175 degrees C. A novel micropacked column (1.5 or 3 m x 1 mm i.d.) prepared from the slurry of bis[1,2-bis(4-n-undecyloxyphenyl)ethane-1,2-dithiolene] nickel(II) (5%, w/w), coated on Chromosorb W was applied for the separation of dialkyl sulfides. The non-linearity (discontinuity) of Van't Hoff plots suggests that the liquid crystal property existed even in the coated phase. Factors affecting the retention and the sample selectivity on the prepared column were examined by using a flame photometric detector (FPD). The separation might be based on the mechanism of ligand exchange, shape selectivity and polarity interaction besides the vapor pressure. LOD for the determination of dialkyl sulfides was below 1 ng for most of the analytes.     

GC-MS与GC-FTIR联合测定C9烃馏分组成

混合碳九组成复杂,估计为环状烯烃、芳烃、多环烃、烷烃等,目前该产品主要用于生产石油树脂。随着我国乙烯生产能力的不断扩大,其产量也在不断增加,为充分利用碳九资源,研究开拓其新的应用领域非常必要。而此研究的首要条件在于对其组成进行较为全面、准确地分析。传统的分析方法不能对其组成提供详尽的数据资料,直接影响了对碳九进行综合利用研究。GC-MS兼有GC的高效分离能力与MS很好的定性功能,且灵敏度较高,是分析有机混合物十分有效的手段。本文将GC-MS应用于碳九组成的定性分析中。但由于碳九组分中含有较多的同分异构体如三甲苯与二甲苯等,同分异构体的质谱图几乎相同,GC-MS对其不易鉴别,而红外(FTIR)对有机物同分异构体尤其苯系物的异构体具有非常好的鉴别能力。因此本文将GC-MS与GC-FTIR联合使用,对碳九组成进行定性分析,样品定量采用色谱氢火焰检测器峰面积归一化法得到的各组分峰面积相对百分含量,较好地解决了碳九组分的定性定量问题,为开发碳九新的应用领域提供依据。     

GC-MS测定人血清中酞酸酯类环境污染物

为了解酞酸酯类环境污染物在人血清中的含量水平。采用毛细管柱气相色谱-质谱联用法的选择离子检测(GC-MS-SIR)技术,结合有机溶剂提取,高速离心去蛋白和低温浓缩的方法测定103份健康人血清中酞酸二丁酯(di--nbutyl phthalate,DBP)和酞酸二异辛酯[di-(2-ethyl-hexyl)phthalate,DEHP]。测定结果提示酞酸酯类环境污染物已进入人血清,DBP约为7.10 mg.L-1,DEHP约为6.78 mg.L-1,大部分人体内已有一定的污染负荷。     

MDGC–MS: A powerful tool for enantioselective flavor analysis

This paper reports the differentiation between the enantiomers of theaspiranes and theaspirones, potent flavor compounds widely used in the flavor industry. Optically pure reference compounds of isomeric theaspiranes were obtained by enantioselective synthesis. Enantiomerically pure reference theaspirones were isolated from quince fruit; their absolute stereochemistry was assigned by CD spectroscopy. For both types of compounds the order of elution was elucidated by using authentic reference compounds. These data enabled the determination of the enantiomeric distribution of both types of compounds in a variety of plant tissues. Because of the complexity of the natural flavor isolates, compounds were identified by mass spectrometry after multidimensional gas chromatography employing a Sichromat 2 double oven chromatograph. After separation of the target compounds on the first, achiral, column (DB-5), they were transferred to a chiral column (C-Dex B) for determination of the enantiomeric distribution. Multiple ion detection (MID) enabled the determination of the enantiomeric distribution even for complex mixtures containing the target compounds at extremely low levels.