ANALYSIS OF VOLATILE ORGANIC COMPOUNDS IN INDOOR AIR

Michail Kokonoglou and Lorraine Gibson

University of Strathclyde

INTRODUCTION Volatile organic compounds (VOCs) are a cause of concern for human health due to their increased presence in the indoor environment. They are responsible for a phenomenon known as the sick building syndrome (SBS). Air monitoring is being used to assess indoor pollution. Solid phase extraction (SPE) procedures are used extensively for trapping and removing VOCs from indoor air. AIM The aim of this work is to develop a method for the determination of the VOCs toluene , ethylbenzene , o-xylene and cumene (TEXC) in air. VOCs are extracted using solid phase extraction cartridges and the extracts are then analysed and quantified using a gas chromatograph with flame ionisation detection (GC-FID). Figure 1 : A schematic diagram of the SPE apparatus. SPE Procedure The cartridge was conditioned and washed with 3 mL of methanol. The system was then equilibrated with 3 mL of 50:50 solution methanol:water. 3 mL of a standard solution containing 100 µg mL-1 of all analytes in methanol:water were loaded onto the cartridge. The analytes were eluted with 3 mL of dichloromethane (DCM) into a 5 mL volumetric flask. 100 µL of a dichlorobenzene (DCB) external solution was added to the extract giving a DCB concentration of approximately 80 µg mL -1. The extract was analysed and quantified using GC-FID. The cartridges that were used during the SPE method were Waters C18 cartridges and Anasorb CSC coconut shell charcoal cartridges. INSTRUMENTATION PERKIN - ELMER 8500 Gas Chromatograph PERKIN - ELMER GP - 100 graphics printer RESULTS AND DISCUSSION Standard solutions of different concentrations containing all analytes and DCB in DCM were prepared in order to investigate the linear calibration range. The GC response was found to be linear up to 400 µg mL -1. The minimum elution volume of DCM required to desorb all of the analytes from the sorbent was found to be 3 mL Figure 3: Recoveries for analytes using Activated Charcoal cartridges in different elution volumes. Figure 4: Recoveries for analytes using C18 cartridges in different elution volumes. The SPE method was found to be precise at the optimum conditions by performing 4 replicate extractions. Table 1: Recoveries for all analytes using C18 cartridges. Analytes % Recoveries Toluene 91 92 88 92 Ethylbenzene 93 91 90 94 o-Xylene 98 91 96 96 Cumene 92 92 96 94 Cartridges were found to be reliable even after repeated use. Recoveries of approximately > 90 % for each analyte were obtained for cartridges used 10 times previously. After each experiment cartridges were cleaned by washing with DCM. Stability of the VOCs retained in the SPE cartridges was investigated over time. Immediately after preparation, the analyte recoveries were approximately 95 % and 85 % for C18 and activated charcoal cartridges, respectively. In room temperature significant loss of analytes was obtained for both cartridges. Even when the cartridges were stored at -4°C, recoveries of approximately 60 % were obtained after 30 days suggesting that new methods of storage will have to be developed. Table 2 : Recoveries of analytes for cartridges stored in -4°C. % Recoveries   C18 Cartridges Activated Charcoal Cartridges Analytes after 1 day after 2 days after 30 days after 1 day after 2 days after 30 days Toluene 92 88 56 72 64 47 Ethylbenzene 95 90 63 76 68 51 o-Xylene 99 95 65 60 58 43 Cumene 100 96 75 80 73 60 Table 3 : Recoveries of analytes for cartridges stored in room Temperature. % Recoveries   C18 Cartridges Activated Charcoal Cartridges Analytes after 1 day after 2 days after 1 day after 2 days Toluene 85 81 54 48 Ethylbenzene 89 83 58 57 o-Xylene 93 91 45 44 Cumene 94 92 62 60 CURRENT AND FUTURE WORK The SPE procedure developed in this work is currently being assessed for analytes in the vapour phase. An environmental chamber has been constructed to obtain VOC contaminated air, and an active sampling pump is used to drew the air over the C18 and activated charcoal cartridges. Remedial technologies are also being addressed. New crystalline silicates are being designed , synthesised and tested for the removal of VOCs from contaminated air.

Michail Kokonoglou (*), Lorraine Gibson Department of Pure and Applied Chemistry University of Strathclyde 295 Cathedral Street Glasgow, G1 1XL, UK E-mail: mkokonoglou@hotmail.com (*): Author to whom correspondence may be addressed

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