Leibniz Institut für Analytische Wissenschaften-ISAS-e.V. , Bunsen-Kirchhoff-Str. 11 , 44139 Dortmund , Germany.
Institute of Analytical Chemistry , Czech Academy of Sciences , Veveří 97 , 60200 Brno , Czech Republic.
Anal Chem. 2018 Mar 6;90(5):3424-3429. doi: 10.1021/acs.analchem.7b05072. Epub 2018 Feb 22.
A new method for arsenic detection by optical emission spectrometry (OES) is presented. Arsine (AsH) is generated from liquid solutions by means of hydride generation (HG) and introduced into a capillary dielectric barrier discharge (DBD) where it is atomized and excited. A great challenge in OES is the reduction of the recorded background signal, because it negatively affects the limit of detection (LOD). In conventional DBD/OES methods, the signal intensity of the line of interest, in this case arsenic, is integrated over a long time scale. However, due to the pulsed character of the plasma, the plasma on-time is only a small fraction of the integration time. Therefore, a high amount of noise is added to the actual signal in each discharge cycle. To circumvent this, in the present study the emitted light from the DBD is collected by a fast gated iCCD camera, which is mounted on a modified monochromator. The experimental arrangement enables the recording of the emission signal of arsenic in the form of a monochromatic 2D-resolved picture. The temporal resolution of the iCCD camera in the nanosecond range provides the information at which point in time and how long arsenic is excited in the discharge. With use of this knowledge, it is possible to integrate only the arsenic emission by temporally isolating the signal from the background. With the presented method, the LOD for arsenic could be determined to 93 pg mL with a calibration curve linear over 4 orders of magnitude. As a consequence, the developed experimental approach has a potential for both mechanistic studies of arsine atomization and excitation in DBD plasmas as well as routine applications, in which arsenic determination at ultratrace levels is required.
一种通过原子发射光谱法（OES）检测砷的新方法。通过氢化物发生（HG）将液体溶液中的胂（AsH）生成，并将其引入毛细管介电阻挡放电（DBD）中，在那里将其原子化并激发。OES 中的一个重大挑战是降低记录的背景信号，因为它会对检测限（LOD）产生负面影响。在传统的 DBD/OES 方法中，感兴趣的线的信号强度，在这种情况下是砷，在很长的时间尺度上进行积分。然而，由于等离子体的脉冲特性，等离子体的通电时间只是积分时间的一小部分。因此，在每个放电周期中，大量的噪声都会被添加到实际信号中。为了解决这个问题，在本研究中，通过快速门控 iCCD 相机收集 DBD 发出的光，该相机安装在经过修改的单色仪上。实验装置能够以单色 2D 分辨图像的形式记录砷的发射信号。iCCD 相机在纳秒范围内的时间分辨率提供了关于在放电过程中何时以及多长时间激发砷的信息。利用这一知识，可以通过从背景中暂时隔离信号来仅积分砷的发射。使用这种方法，可以将砷的检测限（LOD）确定为 93 pg mL，校准曲线在 4 个数量级上呈线性。因此，所开发的实验方法具有用于研究 DBD 等离子体中胂原子化和激发的机制以及需要在痕量水平下测定砷的常规应用的潜力。
