Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul, 133-791, Korea.
Analyst. 2013 Sep 7;138(17):4922-32. doi: 10.1039/c3an00514c. Epub 2013 Jun 27.
A diffuser-incorporated transmission near-infrared (NIR) scheme that enables direct spectral collection of packed granular samples with reliable sample representation and reproducibility has been demonstrated. The analytical utility of this method has been evaluated for the determination of polyethylene (PE) pellet density and the discrimination of the geographical origin of rice samples. Based on the preliminary observation of transmission spectral features acquired from spherical polyoxymethylene (POM) packings composed of different particle sizes as well as packing thickness, a portion of the radiation was propagated through the void space in the packing without fully interacting with the POM pellets. This type of radiation, so-called non-fully interacted radiation (NFIR), adversely affected the sample representation as well as the reproducibility of transmission measurements. To maximize the interaction of NIR radiation with granular samples, a polytetrafluoroethylene (PTFE) diffuser was positioned in front of the sample packing to introduce isotropically diffused radiation into the sample. This diffuser-incorporated scheme resulted in highly reproducible transmission spectra for both packed granular samples. Consequently, the density determination of PE pellets as well as discrimination of rice samples according to geographical origin was more accurate using the proposed scheme.
一种结合了扩散器的透射近红外（NIR）方案已经被证明可以直接对颗粒状样品进行光谱采集，从而实现可靠的样品代表性和重现性。该方法的分析实用性已经通过测定聚乙烯（PE）颗粒密度和区分大米样品的地理来源得到了评估。基于对由不同粒径和填充厚度的球形共聚甲醛（POM）颗粒组成的填充颗粒的透射光谱特征的初步观察，一部分辐射在没有与 POM 颗粒完全相互作用的情况下通过填充颗粒的空隙传播。这种类型的辐射，称为非完全相互作用辐射（NFIR），会对样品代表性以及透射测量的重现性产生不利影响。为了使 NIR 辐射与颗粒样品的相互作用最大化，在样品填充之前放置一个聚四氟乙烯（PTFE）扩散器，将各向同性扩散的辐射引入样品中。这种结合了扩散器的方案导致填充颗粒样品的透射光谱具有高度的重现性。因此，使用该方案可以更准确地确定 PE 颗粒的密度以及根据地理来源区分大米样品。
