Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa.
Anal Chim Acta. 2012 Jun 12;730:71-9. doi: 10.1016/j.aca.2011.11.013. Epub 2011 Nov 15.
Atmospheric polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants, which may be present both in the gaseous phase and adsorbed onto the surface of particles. Denuders are sampling devices which have been effectively employed in such partitioning applications. Here we describe and characterise a novel miniature denuder consisting of two multi-channel silicone rubber traps (each 178 mm long, 6 mm o.d. containing 22 silicone tubes), separated by a quartz fibre filter for particle phase collection. The denuder only requires a small portable personal sampling pump to provide sampling flow rates of ∼0.5 L min(-1). Theoretical considerations indicated that the air flow through the denuder was expected to be laminar, and the linear velocity arising from longitudinal diffusion was found to be negligible. The calculated particle transmission efficiency through the denuder was found to be essentially 100% for particles>50 nm, whilst the experimental overall efficiency, as determined by CPC and SMPS measurements, was 92 ± 4%. The size resolved transmission efficiency was <60% for particles below 20 nm and 100% for particles larger than 200 nm. Losses could have been due to diffusion and electrostatic effects. Semi-volatile gaseous analytes are pre-concentrated in the silicone of the trap and may be thermally desorbed using a commercially available desorber, allowing for total transfer and detection of the collected analytes by GC-MS. This enhances detection limits and allows for lower sampling flow rates and shorter sampling times, which are advantageous for studies requiring high temporal resolution.
大气多环芳烃是普遍存在的环境污染物，可能存在于气相和颗粒表面吸附态。吸收管是一种采样装置，已被有效地应用于这种分配应用中。在这里，我们描述并表征了一种新型的微型吸收管，它由两个多通道硅橡胶管（每个长 178mm，外径 6mm，包含 22 根硅橡胶管）组成，通过石英纤维滤膜分离用于颗粒相采集。吸收管仅需要一个小型便携式个人采样泵即可提供约 0.5L/min 的采样流速。理论考虑表明，预计吸收管内的空气流动是层流的，并且由于纵向扩散产生的线性速度可以忽略不计。通过计算发现，对于大于 50nm 的颗粒，穿过吸收管的颗粒传输效率基本上为 100%，而通过 CPC 和 SMPS 测量确定的实验总效率为 92±4%。对于小于 20nm 的颗粒，尺寸分辨传输效率<60%，对于大于 200nm 的颗粒，传输效率为 100%。损失可能是由于扩散和静电效应造成的。半挥发性气态分析物被预浓缩在陷阱的硅橡胶中，并且可以使用市售的解吸器进行热解吸，从而允许通过 GC-MS 对收集的分析物进行完全转移和检测。这提高了检测限，并允许使用更低的采样流速和更短的采样时间，这对于需要高时间分辨率的研究是有利的。
