Carbon isotopes in exhaled breath track metabolic substrates in brown bears (Ursus arctos)

Stable isotopes in mammalian research: a beginner's guide

“…Also presented are the average difference (for deviant samples only) and the maximal difference. Samples were processed following standard operating procedures of best practices (see Ben-David et al [2012], Pauli et al [2012], and Whiteman et al [2012] for details) by over 50 technicians, students, and investigators in 3 different laboratories. Samples were analyzed at 5 different stable isotope facilities in the United States.…”

Variability in the routing of dietary proteins and lipids to consumer tissues influences tissue‐specific isotopic discrimination

“…Fewer studies have addressed the effects of varying dietary protein and lipid contents. For example, in carnivores that consume very low (if any) levels of carbohydrates, proteins and lipids are both used as fuels for oxidative respiration and tissue synthesis . Two studies have addressed the effects of limiting dietary inputs of protein or lipids on metabolic routing in carnivores .…”

Sample matrix effects on measured carbon and oxygen isotope ratios during continuous‐flow isotope‐ratio mass spectrometry

“…Gonfiantini et al [24] performed a series of isotopologue ion intensity measurements designed to assess atomic scrambling during mass spectrometric analysis. Prior to the introduction of CO 2 into the mass spectrometer, the workers mixed it with an isotope composition of natural abundance with CO 2 enriched in 13 C, 17 O, and 18 O so that the distribution of isotopes among the mixture of molecules was not at equilibrium. During analysis, the workers observed CO 2 isotopologue ion intensity patterns that indicated significant redistribution of isotopes toward equilibrium or random assemblage.…”

“…Most commonly, the alternative analyte matrix is a medium similar in composition to air. Studies requiring analyses of this nature include samples of human and animal breath, soil pore space sampling, and atmospheric sampling for Keeling plots as well as ecological investigations …”

“…Studies requiring analyses of this nature include samples of human and animal breath, soil pore space sampling, and atmospheric sampling for Keeling plots as well as ecological investigations. [9][10][11][12][13][14][15][16][17][18] Early developers of CF-IRMS documented the need to separate analyte CO 2 from gases such as H 2 O, N 2 , O 2 , and N 2 O prior to introduction into the mass spectrometer source. [10,19,20] Schoeller and Luke [20] performed a series of experiments in which they added N 2 or O 2 to CO 2 before IRMS analysis.…”