Archive for May 23rd, 2017

Isotope analysis by TIMS is FUN

May 23rd, 2017

Chapel Hill, NC – Wooster Geologists have been hard at work preparing samples for isotope analysis. Now that sample preparation is complete, the next step is to analyze them on the thermal ionization mass spectrometer (TIMS). In the TIMS, a sample heats up until it ionizes, created a beam of charged particles.

The charged particles are sent through a mass spectrometer, which accelerates the ions through a curved path in a magnetic field. The ions separate based on their mass to charge ratio. The separated beams of ions are sent to collectors that convert the ions into an electrical signal that can be used to determine the sample’s isotopic composition. Figure from Revesz et al. (2001).

For a complete overview of how the TIMS works, check out this website at SERC.

 

Our tiny samples get loaded onto tiny filaments that heat up in the instrument. The filaments are stored in neat, orderly rows in a cabinet in the TIMS lab. If you look closely, you’ll see the flat ribbon onto which we’ll mount our samples.

You can imagine that the filament loading process is as meticulous as the sample preparation work. Here, Ben Kumpf (’18) pipettes a sample onto the filament.

This is what our sample looks like before we heat up the filament. It’s a single drop.

The filaments will get loaded into the TIMS instrument. This is one of the TIMS instruments here at the University of North Carolina Chapel Hill that we’ll use to analyze for strontium (Sr).

This is the exciting part, when we hope that all of our hard work as paid off. It’s a lot of effort for a single data point, but we know it’s well worth it.

References

Revesz, K.M., Landwehr, J.M., and Keybl, J. 2001. Measurement of bigsymbol13C and bigsymbol18O Isotopic Ratios Of CaCO3 using a Thermoquest Finnigan GasBench II Delta Plus XL Continuous Flow Isotope Ratio Mass Spectrometer with Application to Devils Hole Core DH-11 Calcite: USGS Open-File Report 01-257. US Government Printing Office.