Quantitative Simultaneous Elemental Determinations in Alloys Using Laser-Induced Breakdown Spectroscopy (LIBS) in an Ultra-High Vacuum

Abstract

Laser-induced breakdown spectroscopy (LIBS) in an ultra-high vacuum is used in simultaneous quantitative elemental analysis of NIST transition metal alloy samples. A plasma is formed by focusing a Nd:YAG laser onto the sample's surface inside a vacuum chamber. UV-visible emission from excited species is monitored with the use of an optical multichannel analyzer (OMA). Linear calibration curves are shown for the elements (percent composition) Al (0.2–1.2%), Cu (0.021–0.49%), Fe (4.5–51.0%), Ni (30.8–80.3%), and Zn (6–12.8%) with the use of nonresonant lines. Detection limits (signal-to-noise = 3) vary with sample composition complexity from 0.0001% for Ni in a simple copper alloy (SRM 1111) to 0.16% for Al in a complex granular sample (SRM 349a). Absolute detection limits are estimated to be in the 20–200 μg/g range for the elements of interest. Simultaneous mass spectra were taken by sweeping the magnetic field of a mass spectrometer. Preliminary results showed the magnet could not be swept fast enough for multielement analysis. The use of a position-sensitive ion detection system is proposed.