1.1 ECCLS Measurement Procedure
o
o
Serum start, 37 C and 30
c
The component concentrations in the final reaction mixture
are the same as those of the IFCC GT provisional Reference
Method (l). The standard reaction conditions have been defi-
o
ned at 37 C in Table l below. The reaction system performs
o
Optimum pH (30 C) for
o
o
equally well at 37 C and 30 C (2-6).
GT in human serum lies between 7.8 and 8.0 (l). The pH of the
glycylglycine-NaOH buffer decreases about 0.2 pH units by
o
increasing the temperature from 30 C to 37
o
o
c. The same buf-
fer, adjusteä to a pH of 7.90 at 30 C may be used for measu–
o
rements at 37 C (2-6). The effect on reaction rates is neg-
ligible.
The ECCLS standard Procedure is a one-stage method in which
the reaction is starteä by addition of serum (Table l)
Table l
Concentrations are specified in the complete reaction mixture
at 37 °C, to ensure that maximal GT catalytic activity will
be supported at both 37 °C and 30 °c.
A buffer adjusted to pH 7.90 (30 °c) may well be used.
Incubation-activation with reagent A.
Volume fraction 0.909.
Example of
L-gamma-glutamyl-3-carboxy-4-
volume
(pL)
nitroanilide
6
mmol/L
Glycylglzcine-NaOH buffer, pH
7.7 (37 C)
150 mmol/L
500
pL
Add serum.
Volume fraction
0.091
so
_pL
Mix careful ly.
A
eonstant reaction rate is
achieved and rnanitared for the minimum time
and number of data points to obta i n acceptable
precision around the upper reference limit.
78
Klinisk kemi
i
Norden 2: supp/, 1990
