3. REACTION BLANK RATES
3.1 Reagent Blank Rates
Autohydrolysis of L-gamma-glutamyl-3-carboxy-4-nitroanilide
eauses an apparent blank rate corresponding to an increase in
410 nm absorbance
<
0.0005 per 60s (1,4,5). For routine use
correction for reagent blank rate may be omitted (2-7).
4. CALCULATION OF CATALYTIC ACTIVITY CONCENTRATION
For routine determination of the catalytic activity concent–
ration of GT in serum corrections for reagent blank and samp–
le blank rates may be omitted.
4.1 Molar Absorption Coefficient of the Monitored
Product
The apparent molar absorbance will vary markedly from one
routine spectrometer to another, because the product has to
be monitored under unfavourable photometric conditions. This
is discussed in the original IFCC document (l) in which a
procedure for the measurement of the absorption coefficient
is also given.
Before calcu1ation of the catalytic activity concentration is
carried out the apparent molar absorption coefficient of the
monitored product for the used type of spectrometer must be
established (Cf. 4, above).
~~exception
may be instruments
using the Hg 405 nm emission line and one and the same,
well-defined pathlength.
Under strictly defined conditions values in glycylglycine
o
buffer, 150
~~ol/L
pH 7.90 (30 C) at 410 nm of 790.8 and 796
2
-l
m x mol
have been found (1,11). In the example below a
value of 790.8 has been used. At 405 nm values between 944.8
2
-l
and 949.0 m x mol
have been found (8,12)
84
Klinisk kemi i Norden 2: supp/, 1990
