Sampling of Trace Volatile Metal(loid) Compounds in Ambient Air Using Polymer Bags: A Convenient Method Karsten Haas and Jo 1 rg Feldmann* Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen, AB24 3UE, Aberdeen, Scotland, U.K. The sampling of volatile metal(loid) compounds (VOMs) such as hydrides, methylated, and permethylated species of arsenic, antimony, and tin is described using Tedlar bags. Advantages as well as limitations and constraints are discussed and compared to other widely used sam- pling techniques within this area, namely, stainless steel canisters, cryotrapping, and solid adsorbent cartridges. To prove the suitability of Tedlar bags for the sampling of volatile metal(loid) compounds, series of stability tests have been run using both laboratory synthetic and real samples analyzed periodically after increasing periods of storage. The samples have been stored in the dark at 20 °C and at 50 °C. Various volatile arsenic species (AsH 3 , MeAsH 2 , Me 2 AsH, Me 3 As), tin species (SnH 4 , MeSnH 3 , Me 2 SnH 2 , Me 3 SnH, Me 4 Sn, BuSnH 3 ), and antimony spe- cies (SbH 3 , MeSbH 2 , Me 2 SbH, Me 3 Sb) have been gener- ated using hydride generation methodology and mixed with moisturized air. Three static gaseous atmospheres with concentrations of 0.3 -18 ng/ L for the various compounds have been generated in Tedlar bags, and the stability of the VOMs has been monitored over a period of 5 weeks. Sewage sludge digester gas samples have been stored only at 20 °C for a period of 48 h. Cryotrapping GC/ ICPMS has been used for the determination of the VOMs with a relative standard deviation of 5 % for 1 0 0 pg. After 8 h, the recovery rate of all the compounds in the air atmospheres was better than 95% at 20 and 50 °C, whereas the recovery after 2 4 h was found to be between 8 1 and 9 9 % for all VOMs at 2 0 and 5 0 °C except for Me 3 Sb and Me 3 As. These species show a loss between 48 and 73% at both temperatures. After 5 weeks at 20 °C, a loss of only 2 5 -5 0 % for arsine and stibine and the above-mentioned tin compounds was determined. Only Me 3 Sb, Me 3 Bi, and Me 2 Te were present in the digester gas sample. After 2 4 h, losses of 44, 10, and 12%, respectively, could be determined. Given these results, Tedlar bags could even be used, with some limitations, for long-term sampling of air containing traces of VOMs. The loss is more pronounced at higher temperatures. Sampling is the first step within an analytical investigation. Clearly, the process of sampling can have a strong influence on the correctness and quality of any analytical results. Factors such as representativeness, homogeneity, and stability have to be considered. 1 Many sampling devices using different strategies have been employed for the analysis of volatile organic compounds (VOCs). Several articles give a detailed overview of all possible methods described in the literature, under which certain are fairly general whereas others are focused on light hydrocarbons. 2-5 Volatile metal(loid) compounds (VOMs) have been identified in various anthropogenic gases such as landfill gas and sewage sludge digester gas. 6 In terms of their physical and chemical properties, volatile metal(loid) compounds and volatile organic compounds cannot be totally lumped together. Most VOMs are thermodynamically unstable, thus being prone to degradation of any kind. This feature is important for the choice of an appropriate sampling technique. Possible phenomena causing analyte loss are diffusion, oxidation, hydrolysis, photodecomposition, adsorption, absorption, and heterogeneous surface-catalyzed breakdown. Volatile compounds in general can be sampled using a variety of equipment and techniques. Whole air sampling can be carried out using balloons, in the simplest form, cylinders with inlet and exit valves, internally polished stainless steel canisters, or plastic bags made out of an inert polymer material. Polymer bags (usually Teflon or Tedlar) and stainless steel containers are the most widely used sampling vessels. 7,8 Sophis- ticated coating techniques have increased the field of application for canisters as well as the range of analytes that can be collected. 9 Sampling methods involving preconcentration of the analytes use liquid absorbents, cryotrapping, 10-12 adsorbent cartridges, 13 or impregnated surfaces or fibers (solid-phase microextraction) to * Corresponding author: (e-mail) j.feldmann@ abdn.ac.uk. (1) Osberghaus, U.; Helmers, E. In Sampling and sample preparation: A practical guide for analytical chemists; Stoeppler, Ed.; Springer: Berlin, 1997; p 72. (2) Dewulf, J.; van Langenhove, H. J. Chromatogr., A 1999 , 843, 163-177. (3) Camel, V.; Caude, M. J. 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