Basic Concepts in Clinical Biochemistry-A Practical Guide.7z

18.3 Principle........................................

Creatinine present in serum directly reacts with alkaline picrate resulting in the
formation of a red-colored tautomer of creatinine picrate, the intensity of which is
measured at 520 nm. The color produced by creatinine fades after acidifying with
0.25 ml of 0.1 N H 2 SO 4 but remains if produced by non-specific chromogens.

NO 2

HO

NH

HN N

O

O

O

H

H H

HC H

NH

H

OC

C

N+ N

N

N+ N

H

NH

N

O

Picric acid Creatinine

NO 2

NO 2

NO (^2) NO
2
CH 3
NO 2
CH 3
NO 2
CH 3
O
Creatinine-Picrate adduct
O
C
O
O
C
δ HC
δ
= =
Liver & pancreas
Creatine
Creatine
BLOOD
MUSCLE
Creatinine
Excretion
2g/day
Creatine
(40%) (60%)
Phosphocreatine
Food intake
Na
K
INSULIN
Na, Cl
Arginine
Glycine
Methionine
Fig. 18.1 Creatinine metabolism
76 18 To Estimate Creatinine Level in Serum and Urine by Jaffe’s Reaction