Comparative study of the adsorption performance of a multi-sorbent bed (Carbotrap, Carbopack X, Carboxen 569) and a Tenax TA adsorbent tube for the analysis of volatile organic compounds (VOCs)

A comparison between two types of adsorbent tubes, the commonly used Tenax TA and a multi-sorbent bed (Carbotrap, Carbopack X, Carboxen 569) tube developed in our laboratory, has been done to evaluate their usefulness in the analysis of VOCs in ambient air. Duplicate indoor and outdoor samples of Tenax TA and multi-sorbent tubes of 10, 20, 40, 60 and 90 l were taken in Barcelona city (Spain) on July and October of 2009. Breakthrough values (defined as %VOCs found in the back tube) were determined for all sampling volumes connecting two sampling tubes in series. The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry detector (MSD). Significant differences between the concentrations obtained-from multi-sorbent bed and Tenax TA tubes are observed for the very volatile compounds (56 °C < boiling point < 100 °C and 4 kPa < vapour pressure (20 °C) < 47 kPa) (e.g. acetone, isopropanol, n-hexane) and for alcohols and chlorinated compounds (e.g. 1-butanol, carbon disulphide, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene), being the concentrations found higher in multi-sorbent bed than in Tenax TA tubes. On the other hand, mainly all compounds with boiling points higher than 100 °C (except α-pinene, chlorinated and polar compounds) do not show significant differences between the obtained multi-sorbent bed and Tenax TA tube concentrations. For the concentrations obtained (5 ppt to 100 ppb), Tenax TA present high breakthrough values (from 0 to 77%) for mainly all compounds and sampling volumes studied. On the other hand, multi-sorbent bed tubes do not exhibit important breakthrough values for these compounds, except the VVOCs ethanol (for all sampled volumes), and acetone, dichloromethane and isopropanol (for sampling volumes over 40 l). The concentration differences observed between Tenax TA and multi-sorbent bed tubes are directly related to the high breakthrough values determined for Tenax TA adsorbent.     

Trace Analysis of Hydrocarbons in Air Using Standard Gas Chromatographic and Personal Sampling Equipment

Abstract

Unmodified standard gas chromatographs are reported to be useful for the determination of a large number of ambient hydrocarbons. Packing of standard injector glass liners with an adsorbent permits thermal desorption in the injector on to the chromatographic column. Coupling to a personal sampling pump permits exposure-related sampling. The potential of the technique is illustrated by applications with the Tenax GC adsorbent. Precautions required to avoid artifacts when working in the subnanogram range are described.     

Solid-phase microcolumn extraction and gas chromatography-mass spectrometry identification of volatile organic compounds emitted by paper

A rapid non-destructive sampling technique for the analysis of volatile organic compounds (VOCs) emitted by paper sheets is described. A capillary, which is connected to a microcolumn packed with Tenax TA, is inserted between two sheets at the centre of a paper stack encapsulated inside a PET/Al/PE composite foil. The other end of the microcolumn is connected to a gas-tight syringe and an appropriate volume of gaseous phase is aspirated. The microcolumn is then thermally desorbed in a modified GC inlet (modification is presented) and analysed by gas chromatography-mass spectrometry (GC-MS). In the chromatogram from the analysis of artificially aged paper sample 21 compounds were identified. Advantages of the method including the short sampling time (1 min), simplicity and economic aspect are discussed.     

气相色谱法测定环境空气中的微量丙烯腈

 建立了测定环境空气中丙烯腈的Tenax GC吸附-热解吸气相色谱法。方法的回收率为85.6%～105.4%,RSD为4.5%～6.2%。当采样体积为2 L时,最低检测限为0.01 mg/m3 。     

热解吸-气相色谱-质谱法测定烟草中的低沸点组分

以气相色谱／质谱法为主要检测手段,选择对香气组分有良好富集作用的吸附材料及有效的富集方法,考察了香气成分分析的影响因素,建立了合理的热解吸实验方案,从而实现对烟草中香气组分的定性分析．该方法无需任何样品前处理,尤其适用于测定烟草中的低挥发性组分,可以弥补其它烟草处理方法的不足．     

The stability of Tenax TA thermal desorption tubes in simulated field conditions on the HAPSITE® ER

Due to the growing need to monitor aircraft cabin, cockpit and breathing-line air quality, functional assessment of sampling equipment for the specialised field conditions of flight need to be established for both in-flight and ground safety. In this article, we assess the reliability of Tenax TA thermal desorption tubes to perform under various relevant field sampling conditions, such as storage temperature, loading temperature, vibrational velocity, gravitational force (G Force) and altitude pressure with semi-real-time gas chromatograph-mass spectrometer (GC-MS) analysis on the field portable HAPSITE^® ER (Hazardous Air Pollutants on Site Extended Range) instrument. First, we show that Tenax TA thermal desorption tubes can handle storage under extreme environmental conditions, 4–77°C, over numerous analytical test cycles. Next, we confirm that extreme loading temperature, both hot (77°C) and cold (4°C), does not affect the analytical reliability of Tenax TA thermal desorption tubes. Then, we illustrate that G Force may have a significant (p ≤ 0.0364) effect on Tenax TA performance while vibrational velocity (p ≤ 0.7265) and low ambient air pressure (p ≤ 0.1753), such as that found at high altitude, do not. Finally, several Tenax TA thermal desorption tubes were flight-tested, demonstrating that the durability of these tubes maybe insufficient for use on military cargo aircraft (p = 0.0107). The results presented here provide a rationale for additional testing of Tenax TA thermal desorption tubes for flight suitability.     

Sorbent material characterization using in‐tube extraction needles as inverse gas chromatography column

In‐tube extraction is a full automated enrichment technique that consists of a stainless‐steel needle, packed with sorbent material for the extraction of volatile and semivolatile compounds. In principle, all particulate sorbents used for enrichment in air or headspace analysis can be used. However, the selection of the sorbents is merely based on empirical considerations rather than on experimental data, which is caused by a lack of knowledge about the relevant physicochemical properties of the sorbent. Especially, the knowledge of hydrostatic, advective, diffusive, and dispersion mechanisms in addition to sorption enthalpies are important for combined transport and sorption models. To provide these missing parameters, we developed and evaluated a method in which an ordinary in‐tube extraction needle was employed directly as column for sorbent characterization by inverse gas chromatography. As probe compounds, benzene, ethyl acetate, and 3‐methyl‐1‐butanol were used to determine thermodynamic parameters such as sorption enthalpy, partitioning constant between the solid and gas phase, and kinetic parameters such as the diffusion coefficient, dispersion coefficient, and apparent permeability, exemplarily. As sorbent, three commercially available phases were characterized to demonstrate the applicability of the method.