Laser Ablation ICP Mass Spectrometry
The laser ablation microprobe located in the Bruneau Centre for Research & Innovation consists of the Finnigan ELEMENT XR ICPMS, Finnigan Neptune Multicollector ICPMS and a GEOLAS 193 nm excimer laser system. The system operates by ablating material from a sample with the laser, ionizing the chemical atoms of the ablated material in an inductively coupled plasma of argon, focusing and accelerating the produced ions in a beam, and measuring the relative abundances of the ions after separating them on the basis of mass in a magnetic field.
Laser ablation of polished samples takes place in a sealed cell filled with helium. The ablated material consists of gas and particulates which are transported in a helium gas stream to the ICP. The ablation site on the sample surface is viewed through a camera, which permits precise positioning of the laser spot.
The ablation system utilizes an argon-fluorine gas laser emitting at the 193 nm wavelength. Deep-ultraviolet ablation greatly improves the coupling of laser energy to the sample surface, therefore increasing sampling efficiency. The laser system is flexible with regard to repetition rate, i.e., rate of firing, and laser beam spot size, which permits very controlled ablation rates and spatial resolution of sampling.
Sampling resolution down to about 10 micrometres can be achieved, although ablation pits on the order of 30 – 50 micrometres are usually used, when grain size allows, to provide better precision and detection limits.