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Contributors: All participants
Early users of the doubly-labelled water method have tended to adopt their own variants and extensions of Lifson's initial notation. This causes unnecessary difficulty when the reader has to cross-refer to the author's particular usage, and in certain cases can lead to ambiguity. The working group therefore agreed to adopt the following notation for use in this and subsequent publications relating to human applications of doubly-labelled water. Others entering the field for the first time are strongly urged to employ the same symbols which will be referred to as 'IDECG Notation'.
Table 2.1. IDECG Notation
Variable |
Notation |
Isotopes |
|
Unspecified
isotopes of H or O |
*H or *O |
Oxygen |
O or 16O
and 18O |
Hydrogen (protium) |
H or 1H |
Deuterium |
D or 2H |
Tritium |
T or 3H |
Dosing
variables |
|
Dose administered
to subject |
A (AD
and AO) |
Dose diluted for
analysis |
a (aD
and aO) |
Amount of water
used for dilution |
W |
Pool
sizes and rate constants |
|
Pool size |
N (ND
and NO) |
Rate constant |
k (kD
and kO) |
Production rate |
r |
Uncorrected
production rate |
r' |
Fractionation
factors |
|
2H2O
vapour/liquid |
f1 |
H218O
vapour/liquid |
f2 |
C18O2/H218O |
f3 |
Mass
spectrometric variables |
|
Isotopic enrichment
(relative to a standard) |
d |
Fractional
abundance (concentration) |
C |
Atom percent excess |
APE |
Parts per million |
ppm |
Working standard |
ws |
Vienna-Standard
Mean Ocean Water |
V-SMOW or SMOW |
Standard Light
Antarctic Precipitation |
SLAP |