Trace metal detection by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been widely pursued for tra ce elemental determination in gases, solids, and liquids. Application to li quids has proved problematic due to high spatial confinement of the LIES pl asma and rapid quenching of the excited-state emission. This work presents an alternative approach to trace metal determination in liquids in which 1. 0 mL of liquid is deposited onto a carbon planchet and then evaporated, thu s transforming the liquid analysis to a solid surface analysis. Using optim ized excitation and detection conditions, we have identified spectral regio ns for sensitive detection of 15 metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni , Cu, Zn, As, Cd, Hg, Ph). The limit of detection (LOD) for the technique r anged from 10 ppb to 10 ppm for these elements. A 100 ppb LOD represents de tection of 130 picograms of metal (approximately 2 picomoles) in a single m easurement calculated from the laser spot size on the sample. Scanning elec tron microscopy (SEM) images and energy-dispersive X-ray (EDX) spectra of t he samples provide insight into the observed reproducibility and linearity of the technique for several of the metals studied.