Howard L. Hunter Chemical Laboratories, Department of Chemistry, Clemson University, Clemson, South Carolina 29634-1905.
Anal Chem. 1999 Aug 1;71(15):3061-9. doi: 10.1021/ac9901485.
The direct introduction of particulate matter into glow discharge atomic emission and mass spectrometry sources through a particle beam/momentum separator apparatus is described. Vacuum action through a narrow (0.0625 in. i.d.) stainless steel tube allows the introduction of discrete samples of NIST SRM 1648 urban particulate matter (UPM) and caffeine in powder form. Introduction of "ambient" airborne particulate matter is also possible. Particles passing through the aerodynamic momentum separator impinge on the heated (∼200-250 °C) inner surface of the glow discharge plasma volume and are flash-vaporized. The resultant atoms/molecules are subjected to excitation/ionization collisions within the low-pressure (0.5-5 Torr of He or Ar) plasma, producing characteristic photon emission and/or signature ionic species. In this way, atomic emission and mass spectrometry identification of particle constituents is possible. Basic design aspects of the apparatus are presented, and demonstrations of atomic emission detection of the constituents in the NIST SRM illustrate the general characteristics of the approach. Transient atomic emission signals are captured for the introduction of preweighed, discrete samples, with the integrated areas used to construct analytical response curves. Limits of detection using this relatively simple atomic emission system are on the order of tens of nanograms for sample masses of ∼50 μg. Mass spectrometric monitoring of introduced caffeine particles and a mixture of polycyclic aromatic hydrocarbons (PAHs) illustrates the ability of the glow discharge plasma to produce high-quality, library (electron impact) searchable mass spectra of molecular species while also yielding isotopic identification of elemental components of the UPM. Limits of detection for Fe in the NIST SRM are on the order of 175 ng of material, equivalent to ∼7 ng of analyte Fe. It is believed that the small size, low power consumption, ease of operation, and multimode sampling capabilities (AES/MS) of the particle beam-glow discharge (PB-GD) apparatus hold promise for applications in continuous monitoring and discrete particle sampling.
通过粒子束/动量分离器装置将颗粒物直接引入辉光放电原子发射和质谱源中。通过一根狭窄的（内径为 0.0625 英寸）不锈钢管实现真空作用，可将 NIST SRM 1648 城市颗粒物（UPM）和粉末状咖啡因的离散样品引入。也可以引入“环境”空气传播颗粒物。穿过空气动力动量分离器的颗粒撞击加热的（约 200-250°C）辉光放电等离子体体积的内表面，并被闪蒸蒸发。由此产生的原子/分子在低压（0.5-5 托的氦或氩）等离子体中经历激发/电离碰撞，产生特征光子发射和/或特征离子种类。通过这种方式，可以对颗粒物成分进行原子发射和质谱识别。介绍了该仪器的基本设计方面，并展示了 NIST SRM 中成分的原子发射检测，说明了该方法的一般特征。对于预先称重的离散样品的引入，捕获瞬态原子发射信号，并使用积分面积构建分析响应曲线。使用这种相对简单的原子发射系统，检测限约为数十纳克，样品质量约为 50 μg。引入的咖啡因颗粒和多环芳烃（PAH）混合物的质谱监测说明了辉光放电等离子体产生高质量、可用于库（电子碰撞）搜索的分子种类质谱的能力，同时还对 UPM 元素成分进行同位素鉴定。NIST SRM 中 Fe 的检测限约为 175 纳克物质，相当于约 7 纳克分析物 Fe。据信，粒子束-辉光放电（PB-GD）装置的小尺寸、低功耗、易于操作和多模式采样能力（AES/MS）有望在连续监测和离散颗粒采样中得到应用。
