“Insert-and-Go” Activated Carbon Electrode Tip for Heavy Metal Capture and In Situ Analysis by Microplasma Optical Emission Spectrometry

Abstract

The miniaturized optical emission spectrometry (OES) devices based on various microplasma excitation sources provide reliable tools for on-site analysis of heavy metal pollution, while the development of convenient and efficient sample introduction approaches is essential to improve their performances for field analysis. Herein, a small activated carbon electrode tip is employed as solid support to preconcentrate heavy metals in water and subsequently served as an inner electrode of the coaxial dielectric barrier discharge (DBD) to generate microplasma. In this case, heavy metal analytes in water are first adsorbed on the surface of the activated carbon electrode tip via a simple liquid–solid phase transformation during the sample loading process, and then, fast released to produce OES during the DBD microplasma excitation process. The corresponding OES signals are synchronously recorded by a charge-coupled device (CCD) spectrometer for quantitative analysis. This activated carbon electrode tip provides a new tool for sample introduction into the DBD microplasma and facilitates “insert-and-go” in subsequent DBD-OES analysis. With a multiplexed activated carbon electrode tip array, a batch of water samples (50 mL) can be loaded in parallel within 5 min. After drying the activated carbon electrode tips for 5 min, the DBD-OES analysis is maintained at a rate of 6 s per sample. Under the optimized conditions, the detection limits of 0.03 and 0.6 μg L–1 are obtained for Cd and Pb, respectively. The accuracy and practicability of the present DBD-OES system have been verified by measuring several certified reference materials and real water samples. This analytical strategy not only simplifies the sample pretreatment steps but also significantly improves the sensitivity of the DBD-OES system for heavy metal detection. By virtue of the advantages of high sensitivity, fast analysis speed, simple operation, low cost, and favorable portability, the upgraded DBD-OES system provides a more powerful tool for on-site analysis of heavy metal pollution.

Electrothermal Desolvation-Enhanced Dielectric Barrier Discharge Plasma-Induced Vapor Generation for Sensitive Determination of Antimony by Atomic Fluorescence Spectrometry

“…32,33 However, the enhancement of plasma energy density is a two-edged sword, which can improve the interaction of the plasma with the sample on the glass plate, but it can also lead to the dissociation of the generated molecular compounds in DBD-PIVG. 23,30,34,35 Therefore, the decreasing Sb signal with a decrease in the discharge gap was likely caused by the dissociation of the Sb volatile species. Finally, a discharge gap of 3 mm was employed for further experiments.…”

“…29 In 2021, Liu et al used a small activated carbon electrode tip as a solid support to preconcentrate Cd and Pb in water and subsequently as an inner electrode of the coaxial DBD to fast release and excite the elements in situ for analysis by OES. 30 All these studies indicate that plasma can achieve fast release/desorption of elements in dried residues, where a PIVG-like process might also occur. However, to the best of our knowledge, it has not been investigated, and direct vapor generation of Sb from dried solution residues by the plasmachemical process has not been reported.…”

“…In 2016, Marcus et al presented a proof-of-concept study using the liquid sampling atmospheric pressure glow discharge microplasma to volatilize and excite dried solution residues for the determination of heavy metals via optical emission spectroscopy (OES) . In 2021, Liu et al used a small activated carbon electrode tip as a solid support to preconcentrate Cd and Pb in water and subsequently as an inner electrode of the coaxial DBD to fast release and excite the elements in situ for analysis by OES . All these studies indicate that plasma can achieve fast release/desorption of elements in dried residues, where a PIVG-like process might also occur.…”

Atomic spectrometry update: review of advances in atomic spectrometry and related techniques

“…LODs ranged between 0.08 μg L −1 for Cd to 45 μg L −1 for As in a 10 μL sample. A similar set-up was described by Liu et al , 68 except that a DBD was used as the source and an activated carbon electrode tip doubled as both the sample collection device and the DBD inner electrode. Metals were preconcentrated from water samples onto the activated carbon tip, dried for 5 min, then fast released to produce OES during the DBD excitation process.…”

Direct and Sensitive Determination of Antimony in Water by Hydrogen-Doped Solution Anode Glow Discharge-Optical Emission Spectrometry Without Hydride Generation

“…In recent years, OES-based microplasma sources have received increasing attention because of their potential to be developed into compact, low-cost, and portable instruments. Different microplasma sources, for example, microwave-induced plasma, solution cathode glow discharge (SCGD), − low-power capacitively coupled plasma (CCP), dielectric barrier discharge (DBD), − point discharge (PD), atmospheric pressure glow discharge (APGD), − and solution anode glow discharge (SAGD), − have been developed, and some of them have also been employed for Sb measurement. In 2014, Frentiu et al evaluated the use of hydride generation (HG)-CCP-OES for the sensitive determination of Sb in soil samples.…”