Optimization and Calibration of Laser Ablation–Inductively Coupled Plasma Atomic Emission Spectrometry by Measuring Vertical Spatial Intensity Profiles

Abstract

Vertical spatial emission intensity profiles for ICP-AES were measured to optimize and calibrate laser ablation sampling. Laser ablation sampling and laser ablation plus liquid nebulization sampling were studied. The position of maximum ICP emission intensity above the rf load coil changes with gas flow rate for both cases, with the maximum position shifting to higher regions in the plasma at higher flow rates. The maximum emission intensity occurs at a flow rate of approximately 0.2–0.3 l min ^-1 and at approximately 5–10 mm above the load coil, which are significantly different to the values normally employed for liquid nebulization. In addition, by measuring the spatial emission profiles for laser ablation and nebulization sampling, solutions can be used as standards to calibrate the composition of the laser ablated mass. Calibrated Zn:Cu ratios were measured using UV nanosecond and picosecond laser pulses. Stoichiometric laser ablation sampling of a brass alloy was achieved only by using UV picosecond laser pulses at high power density.