Center for Conservation Biology

FIRMS: TC/EA Instructions

1. All samples should be thoroughly dried and homogenized prior to weighing.
2. Getting the right sample weight is critical to good stable isotope measurements. It is always better to contact FIRMS before weighing samples so that we can help you arrive at the ideal sample size. For unusual samples, we can also develop a customized method on the mass spectrometer.
3. As a rough guide we suggest the following sample weights:
   1. Plant materials: 0.5 to 1 mg
   2. Normal soils: 1 mg
   3. Low C and low N soils: 2 mg
   4. Lake sediments: 1 mg
   5. Animal tissues: 0.5 mg
4. Samples must be encapsulated in silver capsules and placed into 96 well plates (on campus users can stop by FIRMS and borrow these plates). For most types of samples 3.5 x 5 capsules work best and they can be purchased from Costech Analytical Technologies (http://www.costechanalytical.com).
5. Weigh the samples on a balance with resolution of 0.1 milligram. FIRMS has two microbalances that can be used, at no charge, by customers submitting samples.
6. 6. Sample capsules must be compressed into tight spheres. Please see this web site for examples of properly prepared samples: http://stableisotopefacility.ucdavis.edu/ . This is very important as a poorly prepared capsule will result in the loss of data from two samples!
7. As samples are weighed the weights should be recorded, in mg to at least 1 decimal place (two decimal places is preferred), in an Excel spreadsheet. On the FIRMS website you will find our preferred spreadsheet for sample submittal. Note: FIRMS will weigh your samples for an additional charge – see the price structure on the website.
8. Each sample weight in the submittal spreadsheet should be accompanied by the following information:
   1. Position in 96 well plate (e.g., A1, A2, B1, B2 etc..)
   2. b. Sample code number. This cannot be the well plate position. FIRMS requires that each sample have a unique sample code number. A good approach is to use the investigator’s last name and a numeral: Jones001, Jones002, Jones003 etc.
9. Once a set of the samples are in the 96 well plates:
   1. Tape the lid of the plate securely to the base.
   2. Label the plate with the investigator’s name and contact information
   3. Make a printout of the submission spreadsheet and rubber-band it to the plate.
   4. E-mail the submission spreadsheet to FIRMS (dlucero@ucr.edu ) and make an appointment to drop off the samples in 2424 Geology Building
10. Our normal turnaround time is 4 weeks.