Related Experiment Video
Updated: Aug 12, 2026

LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics
Published on: April 9, 2017
Delayed separation and the plasma amino acids arginine and ornithine
K L Nuttall1, M Chen, G Komaromy-Hiller
1Department of Pathology, University of Utah School of Medicine, Salt Lake City 84132, USA.
Abstract:
When collecting blood for amino acid testing, leaving plasma in contact with cells at room temperature lowers the concentration of arginine and raises that of ornithine. This is presumably due to the arginase content of red blood cells. In contrast, the sum of arginine and ornithine is constant over the first hour, and defines a reference interval of 74-148 mumol/L (mean +/- 2 SD, n = 20) which is more insensitive to delayed separation. The ratio of arginine to the sum of arginine plus ornithine [arg/(arg + orn)] can be used to estimate the number of specimens not separated promptly. A ratio of 0.74-0.50 (mean +/- 2 SD, n = 20) is characteristic of specimens placed on ice and separated promptly, where delayed separation produces lower ratios. Of 91 adult specimens received for plasma amino acid analysis over five months, 35 (38 percent) showed a ratio < 0.50 suggestive of delayed processing.
Related Concept Videos
Protein Digestion
Urea Cycle
Amino acids
Mass Spectrometry of Amines
Mass Spectrometry: Amine Fragmentation
In amines, the number of nitrogen atoms affects the mass of the molecular ion, which is described by the nitrogen rule of mass spectrometry. This rule states that a compound containing a single or...
Amino Acid Biosynthetic Pathways

