Preconcentration of middle oxyethylated nonylphenols from water samples on magnetic solid phase

Magnetic solid phase extraction (MSPE) is proposed as a simple and fast method for the preconcentration of free middle oxyethylated nonylphenols (NPs) from water. Middle oxyethylated NPs were extracted by MSPE from different water samples (10 and 500 ml samples of distilled, potable, well, river and pond water in concentrations of 30 and 0.6 μg ml⁻¹) using magnetically modified polyphenyleneoxide, Tenax TA and Tenax GR as magnetic adsorbents. Recoveries were 80–100% and relative standard deviations were less than 10%.     

Migration of organic compounds from a multilayer plastic–paper material intended for food packaging

This paper deals with the study of the kinetic migration of a series of organic compounds representative of potential contaminants in packaging materials and used as surrogates (o-xylene, acetophenone, dodecane, naphthalene, 2,3,4-trichloroanisole, benzophenone, isomeric mix of diisopropylnaphthalene, diisobutyl phthalate and methyl stearate). Migration to one side of a solid simulant, Tenax, also referred to as MPPO (modified polyphenylene oxide), was investigated in this study. One spiked sample of multilayer material was used to optimise the extraction procedures for the multilayer paper-based material and the Tenax as well as to perform kinetic migration studies. Three sequential extractions using ethanol were necessary for the strips of the multilayer material but only one extraction was necessary for the solid simulant to obtain >70% recovery of the surrogates. These results enabled us to specify the extraction requirements of the multilayer sample and the solid simulant and as well as those of the migration tests at high temperature using Tenax as solid simulant. The matrix effect associated with the extraction of the contaminants from the multilayer sample is also discussed.     

Development and validation by accuracy profile of a method for the analysis of monoterpenes in indoor air by active sampling and thermal desorption-gas chromatography-mass spectrometry

The technique of thermal desorption (TD)-GC/MS was evaluated for the measurement of monoterpenes in indoor air. The validation strategy was intentionally oriented towards routine use and the reliability of the method rather than extreme performance. For this reason, validation by accuracy profile was chosen. The accuracy profile procedure, which is based on the concept of total error (bias + standard deviation), guarantees that a known proportion of future results obtained with the method will be within acceptance limits. For all the compounds tested in the present study, α-pinene, α-terpineol, β-pinene, d-limonene, Δ³-carene, camphene, 1,8-cineole, p-cymene, linalool, but not in the case of carvone, the accuracy profile procedure established that at least 95% of the future results obtained would be within the ±15% acceptance limits of the validated method over the whole defined concentration range. Other parameters, such as selectivity, recovery, repeatability, stability of the molecules of interest and the effect of temperature, were also determined. The performance of the described method was finally evaluated by the analysis of indoor air from new timber frame constructions.     

Identification of volatile (micro) biological compounds from household waste and building materials by thermal desorption–capillary gas chromatography–mass spectroscopy

Volatile compounds from biodegradable household waste and infected building materials have been studied by dynamic or equilibrium headspace sampling and concentration on Tenax TA followed by thermal desorption and HRGC-MS. Equilibrium headspace sampling was also used to study vegetables stored for 14–18 days at ambient temperature. Over 200 compounds were tentatively identified. The concentration of organic sulfur compounds from garden waste was high enough to contribute to respiratory problems of waste handling personnel. Nitriles, alkyl nitro compounds, and alkyl nitrates were isolated from radish and carrot samples at low concentrations (10–50 ppb). Air monitoring in waste handling working environments may be required to ensure the safety of personnel. Branched aliphatic aldehydes, carboxylic acids, esters, and 2-alkanones were found in the headspace of the infected building materials, indicating that volatile compounds may be useful for detection of microbial growth in buildings.     

On-line solid phase extraction - thermal desorption for introduction of large volumes of aqueous samples into a gas chromatograph

A new approach to the introduction of large aqueous samples into a gas chromatograph, solid phase extraction - thermal desorption, is presented. Carrier gas pushes the sample through a packed liner mounted in a programmed temperature vaporizer; analytes retained by the packing material are thermally desorbed after drying of the adsorbent. The sorption properties and thermal stability of some packing materials have been studied off-line. Tenax GC®, and octyl-modified silica silylated with diphenyltetramethyldisilazane to improve its thermal stability, appeared to be suitable materials. The drying period and the desorption temperature are critical for satisfactory performance of the method. When Tenax GC® is used as packing material, thermal desorption at 250°C for 15 min gives quantitative recovery for methyl esters up to hexacosanoic acid methyl ester. With the silylated octyl-modified silica, the application range is limited to the methyl esters of decanoic to octadecanoic acids.     

Trace determination of airborne polyfluorinated iodine alkanes using multisorbent thermal desorption/gas chromatography/high resolution mass spectrometry

A novel gas chromatography/high resolution mass spectrometry method coupled with multisorbent thermal desorption cartridges has been developed for the determination of volatile neutral polyfluorinated iodine alkanes (PFIs) in airborne samples. It allows, for the first time, simultaneous analysis of four mono-iodized perfluorinated alkanes, three diiodized perfluorinated alkanes and four mono-iodized polyfluorinated telomers in ambient air samples. 3.75 L air sample was passed through a sorbent tube packed with 150 mg of Tenax TA and 200 mg of Carbograph 1TD for analyte adsorption. Important factors during the analysis procedures, such as safe sampling volume, air sampling rate, analyte desorption and transfer strategies, were optimized and good thermal desorption efficiencies were obtained. The method detection limit (MDL) concentration ranged from 0.04 pg/L for 1H,1H,2H,2H-perfluorododecyl iodide to 1.2 pg/L for perfluorohexyl iodide, and instrument response of a seven-point calibration was linear in the range of 10–1000 pg. Travel spike recoveries ranged from 83% to 116%. Small variabilities of less than 36% were obtained near the MDLs and the differences between triplicates were even smaller (2.1–7.3%) at 200 pg spiked level. The method was successfully applied to analyze ambient air samples collected near a point source, and five PFIs were identified (10.8–85.0 pg/L), with none of the analytes detectable at the background site.     

热解吸/化学发光联用技术检测空气中痕量苯

自组装一种新型的热解吸/化学发光的仪器系统,据此建立了一种测定空气中痕量苯的新方法,并对比研究了不同吸附剂对苯的吸附性能.实验表明,Tenax-TA(2,6-二苯基对苯醚的多孔聚合物)对空气中低浓度的苯具有较好吸附效果.当从吸附剂解吸的苯蒸汽通过氧化钇(Y2O3)粉体表面时,其催化发光强度与苯浓度在相当宽的范围内呈良好的线性关系,其线性范围为0.44～44 mg/m3(r=0.9991,n=9),检出限为0.1 mg/m3(S/N=3); 对浓度为0.44 mg/m3的苯气体平行测定了9次,其相对标准偏差为4.45%;Tenax-GR(2,6-二苯并呋喃聚合物树脂加上30%石墨碳)对低浓度苯的吸附效果更好,其线性范围为0.22～22 mg/m3(r=0.9922,n=9); 检出限为0.07 mg/m3(S/N=3).本方法耗时短、简便快速,成功实现了对苯的实时在线检测.     

Evaluation of the suitability of sampling on Tenax TA and polydimethylsiloxane for the analysis of combustion gases

Two sorbents commonly employed for air sampling were selected for the evaluation of their suitability for the analysis of combustion gases namely Tenax TA as adsorbent and polydimethylsiloxane (PDMS) as absorbent. Target compounds were selected among the gaseous combustion products of polyurethane foam and fire-retarded polystyrene. The combustion gases were generated by burning test materials in the flame of a Bunsen burner. Gaseous combustion products were sampled simultaneously with the two sorbents using a two-way adapter, thereby exposing each sorbent to the same combustion gas atmosphere. Special attention was given to the deterioration encountered in the Tenax TA performance upon repeated combustion gas exposure, limiting its use for sampling reactive atmospheres.     

Gas-chromatographische Bestimmung von Piracetam in Serum und biologischem Material

Zusammenfassung Eine einfache und zuverlässige Methode zur Bestimmung von Piracetam in Körperflüssigkeiten und Hirnhomogenaten wird beschrieben.

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Estimation of piracetam in serum and biological material by gas chromatography

Summary A simple and reliable method for the determination of piracetam in serum and brain homogenates is presented.

     

Determination of gas phase nicotine and 3-ethenylpyridine,and particulate phase nicotine in environmental tobacco smoke with a collection bed – capillary gas chromatography system

A combined sampling and analysis technique for the determination of gas phase nicotine and 3-ethenylpyridine, and of particulate phase nicotine in environmental tobacco smoke with capillary gas chromatography is reported. The major advantage of the technique is that all of the collected particulate phase material is analyzed by thermal desorption of the collected material rather than by analysis of only a fraction of the sample extracted from the collection medium. A Teflon filter microtube is used to collect particulate phase nicotine. This microtube is follwed by a small Tenax sorbent bed to collect gas phase nicotine and 3-ethenylpyridine. After sampling, the Teflon filter is transferred to a clean glass tube and the tube becomes an insert for a modified packed column injector port where the material collected on the filter is heat desorbed to a cold capillary tubing trap. Gas phase nicotine and 3-ethenylpyridine are also transferred from the Tenax to the GC column by thermal desorption from the Tenax sorbent bed. Gas phase nicotine and 3-ethenylpyridine, and particulate phase nicotine are each determined by GC analysis of the desorbed material. Nicotine and 3-ethenylpyridine are quantitated by the use of external standards. This technique is straightforward and can be used for semi-real time determination of both gas and particulate phase compounds in environmental tobacco smoke. The results obtained by this technique compare well with those obtained by sampling with annular diffusion denuders.