Stable Isotope



Sample Preparation


Sample Submission

UC Davis Plant Sciences

Tips for Compound Specific Isotope Analysis (CSIA) by GC-C-IRMS

1) Avoid Over-tight Caps
We’ve received samples that leaked from vials because caps were over-tightened, causing the septa to get pinched out of the lids. Turn caps until snug, but not so far that septa start to pucker.

2) Use Internal Standards

We recommend using an internal standard (e.g., C19:0) if you intend to calculate concentration from peak area.

3) Inspect Chromatograms for Small Peaks and Overlapping Peaks

Please inspect your data. We provide data for all detectable peaks and let you decide which data points to keep and which ones to discard, rather than performing this step for you. In the results file, we make note of small peaks for which isotope results are less accurate. Very small peaks sometimes have suspicious values that should be ignored. Look for overlapping peaks. The isotope ratio may not be accurate for a small peak riding on a large peak, but the reading for the large peak is likely acceptable. As large peaks overlap each other, the readings for each approach the average of the two; the IRMS only measures CO2 and cannot discern the CO2 from either peak.

Important Information Regarding Compound-Specific Stable Isotope Analysis

e-mail: | phone: 530-752-8100 | fax: 530-752-4361
UC Davis Stable Isotope Facility | Department of Plant Sciences
One Shields Avenue | Davis, California, 95616 | USA