Banded Samples: Coral, Speleothems, Teeth, Otoliths
LA-ICP-MS can analyze the isotopic and chemical signatures of many banded samples. By scanning the sample under the laser beam and continually monitoring isotopes with the ICP-MS, it is possible to reveal fascinating insights into the structure of the specimen. Such information can, among other things, help to explore ancient climates from the isotope ratios recorded in modern and ancient corals and speleothems. Teeth can also record the chemical environment of their owner, and otoliths can reveal the progeny and intricacies of the host fish's lifespan.
The RESOlution instrument is ideally suited for the analysis of banded samples:
The physical size of banded structure can sometimes be very small. To detect this variation, the spot size needs to be commensurate with the physical structure being measured. Making a round laser spot very small will achieve this, but unfortunately it will reduce the amount of material collected to below the detection limit of the ICP. To circumvent this limitation it is very advantageous to use a rectangular laser spot, with the short axis aligned to the direction of travel. Using the rectangular slit in this way allows high resolution in the direction of interest, while still retaining sufficient sampling volume. Since natural samples rarely feature perfectly parallel bands of material, it is necessary to rotate the aperture as the stage moves, thus maintaining the desired geometry. Read More »
Some samples, such as corals and speleothems, do not polish well, or are prone to contamination. In these circumstances the laser can be used to shave a thin layer from the surface of the sample. The RESOlution software, GeoStar, has advanced features to facilitate surface cleaning. This approach is sometimes called "Pre-Ablation" and can be easily configured in the software.
During regular ablation, all of the analyte is sent to the ICP-MS, regardless of whether the signal is of interest or not. RESOlution instruments are equipped with a diversion valve for switching the analyte away from the ICP. This allows the user to discard the material collected during cleaning, and thus increase the service interval on the ICP-MS, which ultimately means less cone cleaning is required!