Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The workflow of making calibration curves. Predetermined amounts of standards were directly added to centrifuging tubes containing 3 mL of extraction solvent with 13C-IS. The peak areas of the U-13C and monoisotopic (U-12C) metabolites were measured by MS/MS. 12C/13C ratios were plotted against their corresponding known amounts of naturally labeled standards on log3-log3 transformed liner calibration curves.
