Magnetic Field-Accelerated Nonthermal Plasma Digestion for Field Pretreatment and Determination of Heavy Metals in Biological Samples

Abstract

Field analysis of heavy metals in biological samples is essential for assessing their potential threats to human health. The development of portable pretreatment and detection devices is crucial to address this challenge. Herein, a magnetic field-accelerated nonthermal plasma digestion device using dielectric barrier discharge (DBD) is designed for the rapid and environmentally friendly pretreatment of biological samples and subsequently combined with point discharge-optical emission spectrometry (PD-OES) for sensitive determination of heavy metals. With the assistance of a magnetic field, the DBD plasma digestion of a batch of six samples using a H₂O + H₂O₂ + HNO₃ system can be completed within 25–40 min, achieving the digestion efficiencies of 92–99%. The application of magnetic field enhances the electron density, excitation temperature, discharge current, and power of the DBD plasma, thereby reducing the digestion time by 40–69%. The determination of heavy metals in the digestion solution is directly performed using a miniature injection-detector based on hydride generation-PD-OES. Under the optimized conditions, the detection limits for Pb, Sb, Sn, and Bi are 2.4–8.2 μg L^–1 (0.048–0.16 mg kg^–1), with precisions of <5%. The accuracy and practicability of the present device are verified by measuring several certified reference materials, including GBW10023 (laver) and GBW10044 (rice), and real rice, laver, fish, milk, and blood samples. With its advantages of environmental sustainability, short digestion time, compact size, and lightweight design, the present device provides a simple and efficient tool for field analysis of toxic elements in biological samples.