OPTIMIZATION AND CALIBRATION OF LASER-ABLATION INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY BY MEASURING VERTICAL SPATIAL INTENSITY PROFILES

Vertical spatial emission intensity profiles for ICP-AES were measured to optimize and calibrate laser ablation sampling. Laser ablation sam pling and laser ablation plus liquid nebulization sampling were studie d. The position of maximum ICP emission intensity above the rf load co il changes with gas flow rate for both cases, with the maximum positio n shifting to higher regions in the plasma at higher flow rates. The m aximum emission intensity occurs at a flow rate of approximately 0.2-0 .31 min(-1) and at approximately 5-10 mm above the load coil, which ar e significantly different to the values normally employed for liquid n ebulization. In addition, by measuring the spatial emission profiles f or laser ablation and nebulization sampling, solutions can be used as standards to calibrate the composition of the laser ablated mass. Cali brated Zn:Cu ratios were measured using UV nanosecond and picosecond l aser pulses. Stoichiometric laser ablation sampling of a brass alloy w as achieved only by using UV picosecond laser pulses at high power den sity.