Volatile Hydrocarbons in Contaminated Soil: Robustness of Fractional Quantification Using Headspace Gas Chromatography-Mass-Spectrometry

Fuel contamination of soils display complex and variable hydrocarbon mixtures with different volatility and toxicity characteristics. A recently suggested headspace procedure for the structure-based quantification of volatile hydrocarbons is evaluated regarding repeatability, reproducibility, and practical robustness. Three aliphatic and three aromatic fractions covering the boiling range between 69 and 216°C were defined as summation parameters by their respective equivalent carbon number ranges. A standard mixture of 35 aliphatic and aromatic hydrocarbons was used for calibration on basis of selected mass fragments specific for the aliphatics and aromatics, respectively. Two standard soils were fortified with the standard mixture or different fuels, respectively, and submitted to the analytical procedure. Limit of detection (LOD) and limit of quantification (LOQ) were for all fractions lower than 0.1 and 0.3 mg/kg, respectively. Analyte recovery was linear up to between 20 and 110 mg hydrocarbons/kg soil depending on the fraction. Hydrocarbon recovery ranged between 80% and 110% depending on the fraction and the repeatability was typically better than 10%. Finally, the impact of extraction solvent variation, column solid-phase polarity, and alternative summation of fractions were investigated. The procedure was applied to liner samples taken from a site contaminated with aviation fuel and its practicability is discussed.     

Circadian rhythmicity in emission of volatile compounds by flowers of Rosa hybrida L. cv. Honesty

Quantitative headspace analyses of rose flowers showed no significant differences in composition of emitted volatile compounds between flowers on the intact plant and cut flowers placed in vase water containing sucrose at 0, 15 or 30 g · l⁻¹. Volatile components emitted were geraniol, nerol, citronellol, E-citral, Z-citral, methylgeranylate, trans-caryophyllene, β-cubebene, dihydro-β-ionone, 2-phenylethanol, 2-phenylethylacetate, 3,5-dimethoxytoluene and hexylacetate. When exposed to a 12-h photoperiod these components showed maximum emission during the light period and a rhythmicity which differed for the individual compounds. The circadian nature of the rhythmicity was confirmed by the continuation of rhythmicity during continued darkness or light, and was characterized by `transient' and `free running' periods of 27 and 24 h, respectively, and a phase shift of 12 h in rhythmicity when a 24-h period of continuous darkness was followed by re-exposure to a 12-h photoperiod. Rhythmicity in emission was not observed when flowers were kept in darkness before flower bud opening, but started immediately upon exposure to a 12-h photoperiod. Received: 14 April 1998 / Accepted: 28 May 1998     

Assay for beta-glucuronidase utilizing headspace gas chromatography

An assay for beta-glucuronidase is described. The assay uses 1-(beta-D-glucopyranuronosyl)pyridinium hydroxide, inner salt, as substrate and the quantitative determination is performed with headspace gas chromatography, measuring one of the products, pyridine, in the gas phase. The assay has been developed utilizing commercially available beta-glucuronidase (EC 3.2.1.31.) from Escherichia coli, and has been applied to various sources of beta-glucuronidase. Crude homogenates can be assayed directly with a minimum of manipulative steps and the method is suited for automation.     

Behavioural and community ecology of plants that cry for help

Plants respond to insect herbivory with the production of volatiles that attract carnivorous enemies of the herbivores, a phenomenon called indirect defence or 'plants crying for help'. Plants are under selection to maximize Darwinian fitness, and this can be done by making the right 'decisions' (i.e. by responding to environmental stress in ways that maximize seed production). Plant decisions related to the response to herbivory in terms of the emission of herbivore-induced volatiles include 'to respond or not to respond', 'how fast to respond', 'how to respond' and 'when to stop responding'. In this review, the state-of-the-art of the research field is presented in the context of these decisions that plants face. New questions and directions for future research are identified. To understand the consequences of plant responses in a community context, it is important to expand research from individual interactions to multispecies interactions in a community context. To achieve this, detailed information on underlying mechanisms is essential and first steps on this road have been made. This selective review addresses the ecology of herbivore-induced plant volatiles (HIPVs) by integrating information on mechanisms and ecological functions. New questions are identified as well as challenges for extending current information to community ecology.     

Temporal variation of flower scent in Silene otites (Caryophyllaceae): a species with a mixed pollination system

Floral scent composition and emission are often related to olfactory abilities, preferences and activity times of pollinating agents. However, most studies have focused on species with one pollinator type, and little is known about species with mixed pollination systems. We investigated the temporal variation in flower visitor activity and flower scent emission of Silene otites (Caryophyllaceae), a species regarded as being nocturnal and pollinated by moths and mosquitoes. We found, however, that S. otites is not only visited at night by moths and mosquitoes, but also by a wide range of day‐active insects. Furthermore, both the intensity and composition of floral scent change during the course of the day. Total scent emission reached its maximum in the early hours of the night when compounds known to be attractants for moths and/or mosquitoes, such as lilac aldehyde, benzaldehyde, phenylacetaldehyde and 2‐phenylethanol, dominated the scent. However, although less intensive, emission continued during the day. In the early morning, α‐pinene, hotrienol, 2‐phenylethanol and δ‐3‐carene were the dominant scent compounds. (E)‐β‐Ocimene, hotrienol and benzyl alcohol contributed proportions of at least 10% before midday when flies, such as syrphids, were abundant flower visitors, whereas linalool and hotrienol contributed to the scent with at least 10% each in the afternoon when bees also contributed to flower visits. We conclude that, in S. otites, the changing emission patterns are ‘in tune’ with the olfactory abilities, preferences and activity times of its day‐ and night‐active potentially pollinating flower visitors. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 447–460.     

顶空气相色谱法测定胡芦巴总皂苷中树脂残留物的研究

采用顶空气相色谱法,对胡芦巴(FLB)总皂苷中树脂残留物正庚烷、苯、正癸烷、甲苯、二甲苯、苯乙烯、二乙烯基苯与乙基苯乙烯进行检测,8种树脂残留物被完全分离,其峰面积与浓度在所考察浓度范围内具有良好的线形关系,R为0．99996～1．00000,平均回收率97．59％～103．58％,精密度的RSD均小于6％。本实验建立的色谱方法灵敏、准确,适用于胡芦巴总皂苷中树脂残留物的检测。     

Micropropagation of Santolina canescens Lagasca and in vitro volatiles production by shoot explants

Shoot-tips of Santolina canescens, an aromatic species producing a novel diacetylene derivative, were in vitromultiplied on Murashige-Skoog basal medium (MS) containing different concentrations of 6-benzyladenine (BA) and kinetin (KIN). Rooting phase was performed on media supplemented with different auxins: 3-indoleacetic acid (IAA), 3-indolebutyric acid (IBA) and 1-naphthaleneacetic acid (NAA). The best axillary-bud proliferation was recorded on MS medium containing 1.33 M BA plus 0.32 M NAA. Plantlets rooted easily on the different tested media, but more abundant and stronger roots occurred on media containing 2.68 M NAA. The composition of oil obtained through the cultured explants was analyzed by headspace gas chromatography (HS-GC), and santolindiacetylene (SDA) in vitro production was tested. In order to stimulate the production of this product, different concentrations of linoleic acid were supplemented to the media. The best santolindiacetylene production was obtained when the rooting media was supplemented with 0.36 M linoleic acid.     

HS-GC/MS法分析乌龙茶挥发性成分

本试验旨在采用静态顶空-气相色谱/质谱法(HS-GC/MS)建立起一种快速测定分析以金观音为代表的乌龙茶中挥发物的方法。本方法利用单因素试验结合L9(34)正交试验,以出峰个数和总峰面积为考察指标,确定了顶空平衡温度、平衡时间、茶/Na Cl以及加样量4种因素的最佳萃取条件,并以此方法对金观音的挥发性成分进行了分析。结果表明,平衡温度对出峰个数和总峰面积的影响最大,而平衡时间的影响最小。试验得出的顶空进样的最优条件为:平衡温度80℃,平衡时间60 min,茶/Na Cl为1∶2,加样量为0. 5 g。在此萃取条件下能够得到104种物质,这些物质能更真实地反映金观音香气成分的化学构成,为以金观音为代表的乌龙茶的开发利用提供有价值的数据。     

Profiles of the Essential Oils and Headspace Analysis of Volatiles from Mandragora autumnalis Growing Wild in Tunisia

Mandragora autumnalis Bertol . (Solanaceae family), synonym of M. officinalis Mill ., occurs in North Africa and grows natively in Northern and Central Tunisia, in humid to sub‐arid climates. The ripe fruits of mandrake are odiferous with a particular, indescribable, specific odor, shared, to a lesser extent, by the leaves and roots. We carried out an investigation of the essential oils (EOs) and of the aromatic volatiles emitted by fresh leaves, roots and ripe fruits of M. autumnalis growing wild in Central Tunisia. The EOs were obtained from freshly collected plant material by hydrodistillation, while the volatile emissions from the powdered M. autumnalis tissues were sampled by headspace solid phase microextraction (HS‐SPME); both types of samples were analyzed by gas chromatography‐mass spectrometry (GC/MS). Fifty‐one compounds representing 96.2–98.6 % of the total oil compositions were identified in the three tissues and belonged to different chemical classes specifically in 16 esters, 12 alcohols, 12 hydrocarbons, 6 ketones, 3 aldehydes and 3 acids. The main constituents were pentadecanoic acid (34.2 %) and hexadecanol (26.3 %). A total of 78 volatile compounds emanating from M. autumnalis tissues, representing 94.1–96.4 % of the total volatile compositions, were identified: 22 esters, 11 alcohols, 9 aldehydes, 14 ketones, 7 nitrogen, 10 hydrocarbons, 2 lactones, 1 sulfur and 2 ethers. Ethyl hexanoate (12.3 %) and 1,3‐butanediol (12.3 %) were at the highest relative percentages. This study characterizes and distinguishes M. autumnalis from Tunisia and attributes the compounds responsible for the intoxicating and particular odor of fruits. Chemosystematic of Mandragora autumnalis based on the identification of essential oils and headspace volatiles of each of its organ can be used to characterize this species according to its geographic distribution.