Analysing Construction Product Emissions using Novel Micro-Chamber Technology with Thermal Desorption-GC–MS

Caroline Widdowson, Markes International Ltd, Gwaun Elai Medi Science Campus, Llantrisant, UK.

Introduction

Many construction products (e.g., paints, sealants, plasterboard, flooring and wood panelling) are responsible for the release of harmful chemicals, specifically volatile organic compounds (VOCs) and formaldehyde, to indoor air and the environment. Some Chinese plasterboard products, for example, have been found to emit high levels of VOCs, semi-VOCS (SVOCs) and sulphur compounds, which can adversely affect the health of building occupants.¹ In response to growing concerns, regulations are being implemented (e.g., the Construction Products Regulation),² which require the production of low emission, 'green' building materials. Similarly, the German AgBB scheme³ is a product approval standard, which names a variety of VOCs that need to be monitored due to their potential impact on toxicity in consumers.

To develop compliant products and routinely monitor product quality, most manufacturers will want the ability to screen product emissions in-house. Emissions testing for product approval is performed by accredited laboratories and involves incubating materials in an enclosed chamber at (near) ambient temperature under a flow of clean, humidified gas; vapours are exhausted for several days. Emitted vapours are then collected onto a sorbent tube, followed by thermal desorption (TD)-GC–MS for VOC analysis,⁴ or onto a DNPH cartridge with HPLC for formaldehyde analysis. TD is an automated sample extraction/concentration technique, used to increase the sensitivity of VOC analysis by GC–MS. To simplify and speed up in-house emissions screening for manufacturers, novel micro-chamber technology has been developed. Such equipment is compact, robust and able to process several samples each hour. The emissions data obtained have been shown to correlate with longer term reference tests and can be used to maintain factory production (quality) control and to enhance new product development.^5–8 Figure 1 shows a schematic of a micro-chamber for material emissions sampling.

Figure 1: Schematic of a micro-chamber.

A sample of plasterboard was obtained for emissions screening using the micro-chamber–TD-GC–MS system to test the suitability for analysis of a complex sample.

Experimental Conditions

A representative amount of plasterboard (44 mm diameter circle) was placed into one of the chambers of the Micro-Chamber/Thermal Extractor (Markes International Ltd, UK). The chamber was set to 50 °C and a flow of gas (100 mL/min) was applied. A slightly higher than ambient temperature was used to compensate for the relatively small sample size and speed up equilibration (30 minutes) while not significantly affecting the emission profile. The vapour exhausted was collected for 12 minutes onto a 3.5" 6.4 mm OD stainless steel tube (Markes International) packed with quartz wool, Tenax TA (Buchem BV, The Netherlands) and Carbograph 5 TD (Lara Laboratori, Italy).

The tube was then thermally desorbed on a UNITY 2 TD system (Markes International) with subsequent GC–MS analysis (Agilent 6890/5975) under the following conditions:

Tube desorption: 5 min, 300 °C

TD split: 25:1

Focusing trap: Materials emissions trap (Markes International) U-T12ME-2S

Trap low temp: 0 °C

Trap high temp: 300 °C

Column: 30 m × 0.25 mm × 0.5 µm DB-5 phase

Results

The chromatogram obtained was processed using ClearView software (ALMSCO International Ltd, UK) to remove background interference and improve compound identification. The original data file is retained (e.g., for total VOC calculations).

The conditions used during vapour sampling were chosen to provide an emissions profile representative of the plasterboard under normal use. The sorbents and temperatures used for TD were selected to retain the widest possible range of analytes emitted. This method resulted in a complex total ion chromatogram (TIC), comprising a very high number of VOCs and SVOCs, and a wide range of analyte concentrations, illustrating the versatility and efficiency of the combined analytical system (Figure 2).

Figure 2: Drywall emission profile post-ClearView (original profile is shown inset).

Table 1 lists some of the most significant volatile and semi-volatile compounds in the TIC. Benzene, a known carcinogen, along with phenol and toluene, which affect the central nervous system and kidneys, were detected. In addition, with the new building product regulations in mind, several compounds of particular interest were found in the plasterboard emission profile; a number of VOCs specified by the AgBB scheme which were detected are highlighted with an asterisk in Table 1.

Table 1

Screening data can be used by manufacturers to confirm product conformity, and develop new low-emission, higher-value products. It can also be useful for pre-screening samples going for third party tests and for evaluating emission profile variations across a product range.

Conclusions

Recent innovations in micro-chamber technology allow manufacturers to screen emissions for their products in-house. The generation of a comprehensive chemical profile, as shown here, has resulted in the detection of a wide range of VOCs and SVOCs emitted by the sample. In addition, several compounds targeted under key construction product test protocols were identified. This demonstrates that the micro-chamber–TD-GC–MS methodology can be used to obtain useful emissions data from chemically complex building products. Such data will enable a company to routinely test their products to comply with regulations and to develop new low emission materials, thus protecting their business, the consumer and the environment.

References

1. L.E. Saltzmann, US Consumer Product Safety Commission staff summary of contractor's indoor air quality assessment of homes containing Chinese drywall (2009).

2. EC Construction Product Regulation (CPR) http://ec.europa.eu/enterprise/sectors/construction/construction-products/index_en.htm

3. AgBB Scheme: Health-related evaluation of emissions of volatile organic compounds (VOC and SVOC) from building products (2010).

4. Markes International TDTS Note 89: Thermal desorption technology for testing chemical emissions from construction products and consumer goods (2010)

5. T. Schripp et al., Analytical and Bioanalytical Chemistry, 387(5), 1907–1919 (2007).

6. PARD report: G.J. Williams and M. Pharaoh, Correlation between the VDA 276 test and micro-chamber testing. Issued by WMG, University of Warwick, UK (2009).

7. Markes International TDTS Note 67: Introducing the Micro-Chamber/Thermal Extractor (µ-CTE) for rapid screening of chemicals released (emitted) by products and materials (2010).

8. Markes International TDTS Note 68: Using Markes emission screening technology to simplify compliance with the latest construction product regulations (2010).

Markes International Ltd

Gwaun Elai Medi Science Campus, Llantrisant CF72 8XL, UK

tel. +44 1443 230935 fax +44 1443 231531

Website: www.markes.com