Date Published: March 28, 2018
Publisher: Springer Berlin Heidelberg
Author(s): Alexandra Schieweck, Jan Gunschera, Deniz Varol, Tunga Salthammer.
The substance group of very volatile organic compounds (VVOCs) is moving into the focus of indoor air analysis, facing ongoing regulations at international and European levels targeting on indoor air quality and human health. However, there exists at present no validated analysis for the identification and quantification of VVOCs in indoor air. Therefore, the present study targeted on the development of an analytical method in order to sample the maximum possible quantity of VVOCs in indoor air on solid sorbents with subsequent analysis by thermal desorption and coupled gas chromatography/mass spectrometry (TDS-GC/MS). For this purpose, it was necessary to investigate the performance of available sorbents and to optimize the parameters of GC/MS analysis. Stainless steel tubes filled with Carbograph 5TD were applied successfully for low-volume sampling (2–4 l) with minimal breakthrough (< 1%). With the developed method, VVOCs between C3 and C6 of different volatility and polarity can be detected even in trace quantities with low limits of quantitation (LOQ; 1–3 μg m−3). Limitations occur for low molecular weight compounds ≤C3, especially for polar substances, such as carboxylic acids and for some aldehydes and alcohols. Consequently, established methods for the quantification of these compounds in indoor air cannot be fully substituted yet. At least three different analytical techniques are needed to cover the large spectrum of relevant VVOCs in indoor air. In addition, unexpected reaction products might occur and need to be taken into account to avoid misinterpretation of chromatographic signals.
Determination of indoor air quality has become of increasing importance against the background of potential adverse effects on human health and well-being due to airborne pollutants . Specific measurement of chemical substances plays a role in many fields of indoor-related research such as sick building syndrome , microbial contamination , bioeffluents , odor evaluation , and indoor chemistry . The significance of material emission testing has just recently been outlined by the European Union (EU) Construction Products Regulation (CPR) which defines six basic requirements for construction works (BRCW) . The third basic requirement (BRCW 3) is dedicated to the aspects of hygiene, health, and environment and, therein, points out the protection of the health of building occupants and users as one main target of construction work. Among other things, the “giving-off of toxic gases” and “the emissions of dangerous substances, volatile organic compounds (VOC), greenhouse gases or dangerous particles into indoor or outdoor air” are included. This applies not only to buildings, but also as basic requirement to single materials, products, and furnishing contained in them. Thus, the limitation and prevention of airborne pollutants in indoor environments are explicitly identified and are consequently main conditions regarding the possible release of volatile substances from materials.
By using Carbograph 5TD (20/40 mesh) as solid sorbent and a medium polar GC column, it is possible to detect VVOCs between C3 and C6 of different volatility and polarity even in trace quantities. Limitations occur for some low molecular weight compounds ≤C3, especially for polar substances, such as carboxylic acids (formic acid, acetic acid) and some aldehydes. At least three different analytical techniques are therefore needed to cover the large spectrum of relevant VVOCs in indoor air (see Fig. 4). This allows a significantly broadening of the analytical spectrum ≤C6 beyond the C6–C16 window for VOCs as defined by ISO 16000-6 . Facing the definition of VVOCs in EN 16516 , it is important to highlight that this standard can only be applied to the specified GC column and analytical setup. As soon as the setup is changed, the definition is no longer valid. By using a medium polar GC column as in this study, substances which can fall within the class of VVOCs (regardless of the specific definition) will elute both before and after n-hexane (RI 534.38), e.g., isoprene (RI 516.12), 2-propanone (RI 532.02), methacroleine (RI 607.79), and methyl vinyl ketone (RI 631.49) (For calculation of retention indices and a list of retention indices of VVOC target substances, please see ESM and ). However, some of these substances are defined as VOCs according to EN 16516 (normative annex G), such as 2-methyl-2-propanol, n-butanal, and 2-methyl-1-propanol. Therefore, irrespective of any standard, a significant extension of the range of detectable and quantifiable volatile organics in indoor air was achieved in this study.Fig. 4Schematic overview of available analytical methods for the quantitative determination of a large spectrum of relevant VVOCs in indoor air