Magnetic field enhancement for femtosecond-laser-ablation mass spectrometry in ambient environments

Abstract

To improve the sensitivity of open-air femtosecond-laser-ablation mass spectrometry (fs-LA-MS), an external magnetic field was introduced to confine the propagation of the plasma, reduce the plasma neutralization rates, and drive charged particles towards the MS orifice. Signal-to-noise ratios (SNRs) of trace elements, including Al, Si and Pb, in standard NIST samples were obviously improved. The SNR enhancement depends strongly on the direction of the magnetic fields. The maximum enhancement factors were obtained when directing the magnetic fields towards the orifice of the mass spectrometer. The enhancement factors (EFs) of 8.30, 8.22 and 8.50 were achieved for ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb in pure lead. The limits of detection (LODs) of ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb were lowered from 9.75, 32.9 and 8.19 ppm to 2.32, 6.02 and 1.98 ppm, respectively.