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A Look at Isotope Ratio Mass Spectrometry

Dr. Paula Rose discusses her work with IRMS in a new lab at Texas A&M University.

Rachel Muenz

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Dr. Paula Rose is an associate research scientist in the Department of Physical and Environmental Sciences at Texas A&M University-Corpus Christi. She runs the Isotope Core Laboratory (ICL), a new lab located in the university’s Natural Resources Center. The ICL currently supports the research of several other labs on campus. Dr. Rose earned her master’s and PhD degrees in marine sciences at the School of Marine and Atmospheric Sciences at Stony Brook University in New York and was a National Research Council Postdoctoral Fellow with the Naval Research Laboratory in Washington, D.C. before she came to Texas A&M-Corpus Christi.

Q: What does your lab do? What do you use mass spectrometry for in your work?

A: We prepare and analyze biological and environmental samples for stable isotope analysis using an isotope ratio mass spectrometer [IRMS]. I started my research career in radioisotopes using gamma-ray spectrometry about 15 years ago and expanded to stable isotopes and IRMS about six years ago.

Q: Your lab is still fairly new, having recently celebrated its first anniversary. Can you tell me a bit more about that?

A: We finished the installation of an elemental analyzer, a gas chromatograph, and a gas bench that all feed into the IRMS last year and, over this past year, we’ve analyzed thousands of samples. Most of those have been biological samples—folks looking at food web dynamics.

Q: Do things ever get a bit crazy when working with so many different labs?

A: I think it really just requires a great deal of organization.

Q: What features are most important to have in a mass spectrometry system for the work you do?

A: It would be nice to be able to focus the source easier. That’s not an easy task with an isotope ratio mass spectrometer. It seems to be a bit of black magic.

Q: What are the key challenges you face?

A: Some of the key challenges that I face are proper sample preparation and introduction and also instrument stability.

Q: How do you deal with those challenges?

A: Honestly, with patience. It takes time to figure out what’s actually the issue and then more time is needed to solve the problem.

Q: What are the specific issues with sample prep that make it such a challenge?

A: It is both time and making sure the sample preparation is correct. For example, introducing samples into an elemental analyzer, which is interfaced with the isotope ratio mass spec, requires that the samples be very well prepared so that they don’t get stuck in the autosampler. That means making sure that they don’t have little tags hanging off of them; that they’re the right shape and the right size. The samples can be very small so sample handling is also very difficult.

Q: What important trends do you think your lab will see in mass spec in the future?

A: Developing methods for compound-specific stable isotope analysis, that’s where I see the lab going. That would allow us to expand our research capabilities here at the university and also expand our client base. We are currently working with university folks, but we could possibly then expand to collaborate not only with other universities but also with industry.

Q: What do you enjoy most about working with an isotope ratio mass spectrometer?

A: When [the instrument] produces good data. Actually, the precision of the instrument is quite remarkable and that, as a chemist, gives me great joy.

Q: Of all that your lab has achieved in the past year, what would you say you’re proudest of?

A: It’s two things that I’m proudest of: the number of samples that we’ve analyzed in the past year and the quality of the data produced by the lab.