Detection of gold alloy elements by target-enhanced orthogonal triple-pulse laser-induced breakdown spectroscopy with improved sensitivity and minimal sample ablation

Abstract

In order to realize more sensitive elemental analysis of precious samples under minimal sample ablation, target-enhanced orthogonal triple-pulse laser-induced breakdown spectroscopy (TEOTP-LIBS) was first developed. In this technique, a pre-ablation laser with adequate interpulse delay was introduced in reheating target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS); the pre-ablation laser was collinearly propagated with the reheating laser and both interacted with a solid KHCO3 target. 5–7 folds signal enhancement caused by the pre-ablation laser could be observed. A maximum of 256 folds total signal enhancement has been achieved for Au I 267.595 nm transition line while analyzing an 18 K gold sample, if comparing TEOTP-LIBS with single-pulse LIBS using equal pulse energy for the ablation laser. 5.4–11.3 folds total improvement on the signal-to-noise ratio could be observed. The mechanism of the signal enhancement contributed by the pre-ablation laser was also discussed. It was demonstrated that TEOTP-LIBS was able to provide a better solution on the sensitive elemental analysis of precious samples under minimal sample ablation than TEODP-LIBS.