Laser Ablation ICP-MS
Laser ablation ICP-MS is a technique used for direct analysis of solid samples and is widely becoming a technique commonly used to measure trace elements in marine calcifiers.
At UC-Davis, I helped develop the lab protocol for analyzing foraminifera and worked with students and other researchers to analyze trace elements in oysters, otoliths, speleothems, mussels, olivella shells, and tree cores. The image at the left is an example of a laser ablation depth profile of a foram I analyzed using the LA-ICP-MS system at UCD. This is an amazing technique for linking growth conditions to shell geochemistry. For example, in the specimen below (Orbulina universa) the foraminifer was grown in seawater with elevated Ba/Ca ratios (4x ambient) during the day and ambient seawater at night. By using a low repetition rate and low energy density we are even able to resolve thin inner calcite banding (data between 2-10 seconds). These inner calcite Mg bands occur across a few microns of calcite. This shell was analyzed as part of a culture study where we modified light conditions to assess controls on the Mg/Ca banding in this species (in prep). Learn more about laser ablation techniques and why a 'foram standard' is useful for within and between analytical sessions here. Are you using the laser for sample analyses? LA Tools is a free, online program for reducing laser data. The program greatly reduces the time it takes to analyze data, generate data tables, AND (importantly) provides a handy mechanism for zipping your data for sharing with your publication. Access LA tools HERE. A few highlighted studies that relied on LA for the trace element data: 2017: We used LA-ICP-MS to analyze shells cultured for assess mechanisms responsible for diurnal Mg-banding in N. dutertrei and have developed a new model for how this species adds calcite throughout its ontogeny. (Published in Nature Communications) 2020: We published a paper comparing laser-based and solution-based TE/Ca analyses (results focus on Mg and Sr data only). We demonstrate that laser based and solution analyses compare quite well, but for multi chambered foraminifera, it is important to analyze ALL of the chambers in order to generate mean trace element averages that agree with the solution based data. In a separate manuscript, OSU graduate student Theresa Fritz-Endres used LA to assess the effects of cleaning on trace elements in the non-spinose foraminifera. (These studies were published in G-cubed) 2022: OSU PhD student Theresa Fritz-Endres use LA to analyze foraminifera to establish the utility of Ba/Ca ratios in non-spinose foraminifera as a proxy for paleoproductivity. |
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