Porous Membrane-Assisted Purge and Trap Sampling for Determination of VOCs in Gas Chromatography with Needle-Type Extraction Device

An analytical method using a porous polytetrafluoroethylene (PTFE) membrane that passes through gas while repelling water, and a needle-type extraction device was developed for purge-and-trap (PT) extraction followed by gas chromatography–mass spectrometric (GC–MS) determination of volatile organic compounds (VOCs) in water samples. The PTFE membrane was fixed in a solid-phase extraction glass cartridge, and 10 mL of water sample and sodium chloride were added. Then, a needle-type extraction device was inserted into the cartridge headspace, and the headspace gas was collected. Due to decompression on the inside of the cartridge, purge gas was introduced from the bottom side of the cartridge through the PTFE membrane. After the sample extraction, VOCs were thermally desorbed by inserting the needle into the heated GC injection port. The limit of quantification of the proposed method for 23 investigated VOCs was less than 0.5 μg/L, and the upper limit of the calibration curve was 500 μg/L for dichloromethane and 1000 μg/L for other compounds. The relative standard deviations of the relative peak area for 23 investigated VOCs were less than 15% (n = 5). The method was used to determine VOCs in tap water samples.