Hi Chris,

One strategy to add to the good advice from the rest of the community:

In dual gas mode on the 252 with the Kiel, lower the reference gas pressure (refill time can be reduced in the methods) so the voltage at 50% bellows expansion matches the voltage generated by the average 15-20 µg calcite sample.  The mass spec will spend less time balancing sample and ref major ion beam and get on with analysis before the sample bleeds away.

Test working standards at a variety of weights and refill times to get the right voltage range.

Stanley H. Ambrose, Professor
Environmental Isotope Paleobiogeochemistry Laboratory
Department of Anthropology
University of Illinois
109 Davenport Hall
607 South Mathews Avenue
Urbana, IL, 61801, USA
Phone 217 244-3504
http://www.anthro.illinois.edu/people/ambrose

From: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>> on behalf of Christopher Maupin <[log in to unmask]<mailto:[log in to unmask]>>
Reply-To: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>>
Date: Wednesday, October 25, 2017 at 9:30 AM
To: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>>
Subject: [ISOGEOCHEM] Carbonates under 20 micrograms? Under 10 micrograms?

Dear Isogeofolks, a broad, community query here:

I’m curious what your successes and/or failures running extremely small carbonate samples have been like. Seeing the uptick in individual foram papers in recent years as piqued my curiosity to reach out to the broader iso-sphere.

What instrument/peripherals have you tried/are you using?
What are the smallest masses of CaCO3 you are able to successfully measure?
What precision are you routinely achieving on these successful measurements?
What is your “recipe” for success?

Many thanks!
________________________________________________
Chris Maupin, Ph.D.
http://christophermaupin.strikingly.com<https://urldefense.proofpoint.com/v2/url?u=http-3A__christophermaupin.strikingly.com&d=DwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=_6nQiB6g13JM3XaZ9wJrIZ1TqXa8aAQHXaZtr_hhShQ&m=6LdTzXd5IL5Ts4kR4Pe5cA4aNXHKJkCkOwyghr9RN9c&s=oYRe308XVtDhlZsQqoJUE1LvcZC726ef8wN4wNRB_tI&e=>
Research Associate and Facilities Manager
Stable Isotope Geosciences Facility (SIGF)
Geography Department
Texas A&M University
405 Eller O&M Building 3147 TAMU
College Station, TX 77843 USA
Email: [log in to unmask]<mailto:[log in to unmask]>, [log in to unmask]<mailto:[log in to unmask]>
Mobile: (512) 810-8437