Fast volatile organic compound recovery from soil standards for analysis by thermal desorptio gas chromatography

摘要

the developmetn of high-throughput environmental screening assays are needed to meet high-specification data quality objectives (DQOs) that require large numbes of samples ot be taken and analysed rapidely.The acquisition and stabilisation of the sample is a key technical adn operational challenge in analytical sequences associated with and stabilisation of the sample is a key technical and operational challenge in analytical sequences associated with and determination of volatile organic compound (VOC) contamination of soils.Further the development of miniaturised and embedded analytical systems for environmental conditioning monitoring requires the development of new sampling techniques.A proof-of-concept study is described that shows how pressurised gas,in this case carbon dioxide,may be used to recover reversibly-bound VOCs from soil into an adsorbent sampler,and then analysed by thermal desorption-gas chromatography.The effects of the volume of the pressurised gas,the gas flow rate and the mass of the soil sample onth recovery efficiency and breakthrough from the adsorbent trap were investigated in a preliminary characterisation study.twodistinct approaches were identified.The first trap were investigated in a preliminary chaaracterisation study.Two distinct approaches were identified.The first involved ventilation of the voids within th soil matrix to displace the soil-gas headspace,a rapid screening approach.The second involved a more prolonged purge of the matrix to strip reversibly bound species into the gas phase and hence pass them into the adsorbent trap,a purge and trap approach.The shortest possible sample processing tiem required to yield nalaytically useful responses was 5 s with the use of the headspace aproach.In this case n-octane,benzene and toluene were rcovered form conditioned spided soil samples at concnetrations in the range 42 to 1690 mg kg~-1.The limit of detection for the system was estimated to be no greater than 1.2 mg kg~-1.Using th epurge and trap variant enabled recovery efficiencies greater than 93% tobe achieved with liquid spikes of n-octane onto soil samples.These preliminary studies showed that a system based on this approach would need to balance recovery efficiency,time and analyte breakthrough from the adsorbent trap.