Tenax tubes

Lab method using glass-fibre/Tenax tube sampling and high performance liquid chromatography Field method using acid hydrolysis, diazotization, coupling and spectrophotometry... 

The amount of hydrocarbons present in the fire effluents have been measured in two different ways 1) amount of non-burnt hydrocarbons 2) soot was separated from gas with a glassfilter and latei extracted with cyclohexane. After the porous filter an absorbent glass-tube was connected with either charcoal or Tenax GC as the absorbent. Charcoal tubes were later extracted with carbon disulfide for analysis and Tenax tubes directly thermally desorbed t( a gas chromatograph and a mass spectrometer. 

The ROPs include sampling, sample preparation, and analysis instructions for low-volume Tenax and XAD-2 air samples. Only the preparation of an XAD-2 low-volume air sample is presented in this article, while the thermal desorption of a Tenax tube is described in the context of gas chromatographic analysis see Chapter 10). Active charcoal is such a strong adsorbent that it requires more effective extraction methods than XAD-2 resin or Tenax tubes. Thus, the recoveries of CWC-related chemicals tend to be lower from active charcoal than from other air sampling materials. Furthermore, active charcoal is not usually used for the collection of organophosphorus chemicals. The sample preparation methods for active charcoal samples have not been validated in international round-robin or proficiency tests. 

Determination of the intact CW agents in urine or blood may proceed by the methods commonly applied to water samples. Extraction with an organic solvent and subsequent cleanup with a Florisil column is a well-established procedure. Rather volatile, scheduled compounds can often be successfully recovered and purified from biological materials by means of dynamic headspace stripping and subsequent adsorption on Tenax tubes these tubes are then subjected to GC/MS analysis. 

Additional cleaning of Tenax tubes was standardized by heat desorption at 200 C for 30 min in the oven of the D.C.I. System. 

Preliminary experiments, the results of which are summarized briefly under Results and Discussion, led to the following optimized sampling method. Volatile collection was carried out for 30 min at the cold storage temperature (4 c) and with a vacuum pump flow rate of 50 mL/min. Then, the sampled Tenax tubes were removed, capped and ready for GC analysis the same day. 

One of the auxiliary Tenax tubes (1) was placed inside the desorption oven (2), located upstream of the fixed Tenax trap (3) (0,2 g Tenax GC, 60-80 mesh, packed into a 7 cm by 2 mm i.d. stainless steel tube). At controlled temperature (lOO C) and low pressure (1,5 psl) the oven was flushed by a 25 mL/min flow of Helium for 10 min. Desorbed and diluted in scavenging gas (a), the volatiles were then concentrated and trapped in the Tenax trap, cooled to -30°C by circulation of liquid nitrogen. By switching a rotary valve (4), carrier gas (b) flowed through the trap... 

The conditions of chromatographic analysis (desorption of volatiles from the Tenax tube and their adsorption on the Fixed... 

Homes 30 Finland Tenax tubes Thermal desorption (flash desorption) GC-FID GC-MS [31]... 

To redress problems caused by the different approaches to TVOC estimation, a uniform procedure was proposed [2,12]. The procedure, which is based on sampling of VOCs on Tenax tubes followed by thermal desorption and GC/MS analysis (with nonpolar columns), proposed that TVOC be defined as... 

Figure 1.1-1. Breakthrough of volatile substances on Tenax TA. Terpene concentrations in the backup tubes during sampling of 12 1 of air through a Tenax tube (Uhde, 1999).

Figure 1.2-2. Different types of sampling devices for aldehydes, phenols and MDI, 1 = Tenax tube with gas meter and pump 2 = DNPH cartridge 3 = MDI cartridge 4 = Muencke absorber with gas meter and pump.

Air samples were collected on Tenax TA (60-80 mesh) (0.5-1.0 1 total volume at a flow rate of 50 ml/min). The analysis of Tenax tubes was carried out using a GC/ MS-system (Hewlett-Packard 6890) or a GC/FID-system (Hewlett-Packard 5890) with a 25-m HP-5 column, each equipped with a thermal desorber - cold trap injector (Perkin Elmer ATD 400). Identification of the compounds was based on a PBM library search. Moreover, mass spectra and retention data were compared with those of reference compounds. The monoterpenes and sesquiterpenes were sampled on active charcoal (NIOSH standard, SKC 226-01, 60-80 1 total volume at a flow rate of 0.5 1/min). The terpenes were extracted by use of carbon disulfide under constant shaking for 1 h and analyzed via GC/FID. Aldehydes were trapped on filter cartridges coated with dini-trophenylhydrazine (DNPH) (Macherey Nagel). The dinitrophenylhydrazone derivatives were extracted with acetonitrile and analyzed via HPLC/UV. 

These samples are analyzed for certain compounds identified in previous surveys and for unknowns. Bulk air samples, coupled with Concentration Mass Spectroscopy (MS/MS), can be used for the detection and identification of volatile inorganics and organics. Unknown volatile organics can also be identifiedusing Tenax tubes with subsequent thermal desorption and Gas Chromatography/Mass Spectroscopy (GC/MS) analysis. 

Experimental variables (sampling volume, desorption time, desorption temperature and headspace pressure) were mathematically modelled and quantitatively assessed with a view to optimisation. Van Eldik et al. [985] applied solid polymer PT analysis for the screening of the outgassing behaviour of 61 styrenic samples (ABS, HIPS, PPO/PS), containing a variety of BFRs (such as DBBP, DBDPO, OBB, TBBP-A, TBPE, etc.), taken from used TV sets, computer housings and printers, and 13 polyamides (PA6, PA6.6) for electrotechnical applications in relation to health and safety for the user. The analytes were collected on a Tenax tube, cryofocused and analysed by means of TD-GC-MS. 

Adsorptive tubes are sometimes used to take samples for analysis for VOCs. A 4 mm diameter hard glass or stainless steel tube is filled with granular adsorbent (e.g. Tenax tubes). The air to be sampled is pumped through the tube using a small battery powered piunp and the VOCs in the air are adsorbed and condensed. The tube is then sent to a laboratory for analysis. 

Crespo et a/. [18]. Mycobacterium avium and Mycobacterium kansasii, and a non-pathogenic fast growing species, Mycobacterium smegmatis, in Middlebrook M7H9 culturing media were followed online. To aid in the identification volatiles were collected in Tenax tubes and analysed with a gas chromatograph equipped with a flame photometric detector. Identification of VOCs was also based on isotopic ratios and CID results. 

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