Spatially and Temporally Resolved Detection of Arsenic in a Capillary Dielectric Barrier Discharge by Hydride Generation High-Resolved Optical Emission Spectrometry

Abstract

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.

Design of Fluorescence-Enhanced Silver Nanoisland Chips for High-Throughput and Rapid Arsenite Assay

“…Arsenic contamination in the environment, including water, foods, and air, is a critical threat to public health worldwide. 1 − 3 In drinking water, the limitation of total arsenic is 10 ppb (μg·L –1 ), as prescribed by WHO. 4 Among the arsenic species, inorganic arsenite (As(III)) is highly stable in the environment and extremely toxic to humans.…”

In Situ Dielectric Barrier Discharge Trap for Ultrasensitive Arsenic Determination by Atomic Fluorescence Spectrometry

“…As a typical gas discharge of nonthermal plasma (NTP), dielectric barrier discharge (DBD) has been widely applied to various fields, because of ambient-temperature operation, miniaturization, simplicity, and low expense/energy consumption. Due to availability of plasma, free radicals and other activated particles, DBD can also be implemented as ionization source for mass spectrometry, , as atomizer for AAS and AFS, , as chemical vapor generator (CVG), , or as an excitation source for OES. , Zhu et al − used it as an atomizer of hydride-forming elements or plasma-assisted CVG for AAS/AFS. Hou et al attempted to utilize a tungsten coil electrothermal vaporizer (ETV) coupled to a DBD atomizer for Cd and Zn detection.…”

“…Due to availability of plasma, free radicals and other activated particles, DBD can also be implemented as ionization source for mass spectrometry, 2,3 as atomizer for AAS and AFS, 4,5 as chemical vapor generator (CVG), 6,7 or as an excitation source for OES. 8,9 Zhu et al 10−13 used it as an atomizer of hydride-forming elements or plasma-assisted CVG for AAS/AFS. Hou et al 14 attempted to utilize a tungsten coil electrothermal vaporizer (ETV) coupled to a DBD atomizer for Cd and Zn detection.…”

Alternating-Current-Driven Microplasma for Multielement Excitation and Determination by Optical-Emission Spectrometry

“…Microplasma is produced by confining the dimension of plasma to 1 mm or less . Currently, various configurations of microplasma have been applied for optical emission, including glow discharge (GD), − microhollow-cathode discharge (MHCD), , dielectric-barrier discharge (DBD), − point discharge (PD), , capacitively coupled microplasma (μCCP), microfabricated inductively coupled plasma (mICP), and microwave-microstrip plasma (MSP) . Compared with conventional inductively coupled plasma (ICP) as the excitation source, microplasma possesses a series of excellent characteristics, including simplicity, a small size, a nonthermal source, and low power and gas consumption .…”

“…Initially, various gaseous species can be directly introduced into the microplasma for excitation and OES detection . Various species in aqueous media should be volatilized as “pure” and “dry” species for their excitation and detection by the microplasma–OES system, such as with chemical-vapor generation ,,,− or electrothermal vaporization, − in order to avoid concomitant products and residual moisture. Although gaseous introduction avoids the decrease in the excitation capability or even the extinguishing of microplasma resulting from the presence of a large amount of water molecules, the multielement-analysis capability of OES itself has to be highly dependent on the gaseous species produced or the electrothermal-vaporization device.…”