2.3 Pump sampling
Indoor air was collected with a Gasprobenehmer GS312 pump sampler (Desaga, Heidelberg, Germany) equipped with a flowmeter from Kirchner GmbH (Hamburg, Germany). the PU foam cartridges each with a quartz filter mounted on top were placed 1 m above ground level and connected with a polyethylene hose to the pump sampler. Air was sucked through the filter at a flow of 10 L min-1 until a total volume of 1 m3 was reached. Thereafter, the pump was turned off and the filter was dismantled and stored in the original amber glass bottles until analysis in the laboratory on the same day. Each quartz filter was dismantled and the cartridge was spiked with 20 µL of the surrogate standard solution in toluene (1:10) and submitted to pressurized fluid extraction on a ASE™-350 instrument (Thermo Scientific, Karlsruhe, Germany) using a 22 mL cell equipped with an ASE extraction cellulose filters on the bottom (Thermo Scientific). The cells were heated to 100 °C for 10 min (static extraction) and cyclohexane/diethyl ether (95:5, v:v) was used as extraction solvent at 140 bar. The flush volume was 60%. Extracts were collected in 60 mL glass vials and concentrated to 1 mL under a stream of nitrogen and transferred to a GC vial. Each quartz filter was spiked and extracted in the same manner.