The spatial resolved analysis of trace elements offers a deeper understanding of solid samples and thus of processes that lead to formation or transformation of e.g. geological samples. Since small spot sizes improve the resolution a high sensitive detection is key for this kind of applications. With the high sensitivity ICP-MS allows the use of smaller spot-sizes to improve the resolution and precision. The Tandem LA – LIBS instrument provides the unique capability of combining the analytical benefits of both LA-ICP-MS (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry) and LIBS (Laser Induced Breakdown Spectroscopy). LIBS can be used for the analysis of H – Pu, which includes non-metals such as H, N, O, and halogens that are difficult or impossible to analyze by a conventional ICP-MS instrument. When coupled with an ICP-MS instrument, it can perform LA-ICP-MS measurements focusing on trace elemental and isotopic ratio compositions. The abstract should give the motivation for the study, a brief statement on the state of the knowledge, the open question that was addressed, eventually a hypothesis, the methodological approach taken to answer the question and/or thest the hypothesis, the main result(s) and the conclusion with respect to the new knowledge gained and eventual implications for application on further research.
Instrumentation
Operating Parameters ICP-MS
ƒ. Time resolved data acquisition
ƒ. Peak hopping: 49Ti+, 65Cu+, 66Zn+, 137Ba+, 139La+, 140Ce+, 208Pb+, 232Th+, and 238U+
ƒ. Synchronized communication triggering with the LA – LIBS instrument
Operating Parameters Tandem LA-LIBS
ƒ. 213 nm Nd: YAG laser (ns) and an ICCD detector
ƒ. 85 μm crater diameter (spot size)
ƒ. Flex sample chamber with helium gas flow
ƒ. Laser sampling grid with a total of 400 locations over a 4 mm x 4 mm area using 50 laser pulses per location
Sample analysis
The mineral sample was used to assess the ability of the tandem instrument in combination with the high sensitive ICP-MS. A 16 mm2 area was analyzed using laser spot size of 85 μm (diameter) and spacing of 115 μm between locations.
Conclusion
LIBS was demonstrated as a means for detecting fluorine and oxygen in REE-rich mineral samples. These are analytes that are difficult or impossible to detect through other atomic spectroscopy techniques. Interfacing the tandem instrument with high sensitive ICP-MS enabled more complete elemental mapping of the investigated mineral. Elemental mapping of the sample using the data analysis software allowed for easy integration of the LIBS and LA data to create contour plots as shown in the aforementioned sections. The high sensitivity ICP-MS was ideal for trace level elemental and isotopic mapping analysis, since LA-ICP-MS often involves very small quantity of sampled mass, especially when high spatial resolution is desired.