Vapor generation and analyte atomization integrated into a single dielectric barrier discharge reactor: Reagent-free...

Traditional sample introduction strategies in trace element analysis include either liquid nebulization or chemical vapor generation (CVG). Recently, plasma-mediated vapor generation (PMVG) has emerged as an elegant alternative, producing volatile species through plasma interaction with liquid sample, without the need for reagents. Both CVG or PMVG generate volatile species, usually molecular structured, which require atomization for atomic spectrometry detection. Conventionally, the generation of volatile species and their subsequent atomization are two separate processes, performed in different devices: the volatile species generator and the atomizer.

A laboratory-built PMVG reactor based on dielectric barrier discharge was constructed including its power supply source. Using the atomic absorption spectrometry as a detector, the reactor was optimized to generate volatile As species and to atomize them in a single device. The experimental parameters were optimized, including the discharge gas composition and flow rate (200 mL min^-1 He + 10 mL min^-1 H₂), discharge voltage (4.1 kV), sample volume (18 μL), and sample matrix composition (HCl or HNO₃). The limit of detection of 9 μg L^-1 was achieved, meeting the criteria for environmental sample analysis. The sensitivity observed in long-term measurements for PMVG (0.43 s ng^-1) was comparable to the conventional CVG. The efficiency of volatile As species generation and atomization was estimated to be close to 100%.

The concept of a single device serving both for As vapor generation and atomization in situ within the optical axis of the spectrometer was successfully demonstrated for the first time. The method developed can compete in terms of sensitivity, volatile species generation and atomization efficiencies with conventional CVG systems - without the use of any reagents.