Magnetic field enhanced detection of heavy metals in soil using laser induced breakdown spectroscopy

A combination of magnetic field and Laser Induced Breakdown Spectroscopy (LIBS) has been used to improve the detection limit of heavy elements in different Soil samples. The plasma plume was generated by a focused Nd: YAG laser (532 nm) beam on the surface of soil samples in air and the emission spectra were registered in the presence and absence of an external magnetic field (0.3 T) using a set of four spectrometers. The magnetic field is applied transverse to the plasma plume. The emission intensity enhancement factor up to about 8 has been observed and the limit of detection (LOD) of Cr has been improved from 18.2 mg/kg to 7.7 mg/kg in the presence of magnetic field. The effects of magnetic field on the plasma parameters have been studied. The emission intensity enhancement is attributed to magnetic confinement of the laser-generated plasma. The spatial and temporal behavior reveals that the electron number density and electron temperature decreases nearly exponentially in the presence of magnetic field due to the deceleration of the plasma plume.