Laser Ablation Inductively Coupled Plasma

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is one of the most successful direct solid sampling techniques for major, minor and trace element analysis. However, this technique still suffers from matrix dependent ablation characteristics, which makes quantification very difficult. Furthermore, the laser sampled material alters its composition from the sample to the detector. Therefore, various approaches were carried out to gain detailed knowledge about the function of laser energy, laser wavelength, transport system and excitation source. This work presents LA-ICP-MS investigations on four main topics: 1. Developments of different laser ablation systems 2. Studies on the ablation characteristics of different wavelengths 3. Description and reduction of sources of elemental fractionation 4. Trace element analysis in glass samples and element fingerprinting of sapphires A high power (40 J cm−2) homogenized 266 nm Nd:YAG laser ablation system shows improved crater morphology, signal structure and reduced fractionation behavior in comparison to commercially available 266 nm laser ablation systems. However, elemental fractionation still remained and the ablation characteristics never reached the quality of a homogenized 193 nm excimer laser ablation system for silicates. Therefore, an all solid state 193 nm Nd:YAG laser ablation system was developed using an optical parametric oscillator to generate from one laser source the most common wavelengths 266 nm, 213 nm and 193 nm used in laser ablation ICP-MS. Investigated ablation rates shows the wavelength dependence of LA. The shortest wavelength (193 nm) has equal ablation rates in samples with different absorption behavior and similar matrix. In contrast, 266 nm was found to have different ablation rates on the same silicate samples. Particle size distribution measurements using identical parameters (except wavelength) showed that 266 nm produces larger particles than 193 nm when ablating silicates. 213 nm was found to give intermediate behavior i.e. producing larger particles for the more transparent samples and almost only small particles below 300 nm for the more opaque samples, which is similar to 193