157 / 172
Table-6
AOAC 959.03 (Urease Method) vs. AOAC 2003.14 (HPLC) Results for Analyses of Unreacted Urea in
Urea-Triazone Liquid Fertilizers
Urease HPLC Urease HPLC Urease vs
HPLC
1
A
0.20
0.34
20.2
33.7
60
20ml 1% Solution
B
0.11
0.16
10.9
16.1
68
C
0.24
0.32
23.5
32.1
73
D
0.27
0.35
27.3
35.1
78
2
A
0.17
0.34
16.9
33.7
50
10ml Glycerol Ext.
B
0.08
0.16
7.5
16.1
47
C
0.14
0.32
14.2
32.1
44
D
0.25
0.35
25.4
35.1
72
2
A
0.34
0.34
34.3
33.7
102
20ml Glycerol Ext.
B
0.17
0.16
17.0
16.1
106
C
0.32
0.32
32.4
32.1
101
D
0.33
0.35
33.4
35.1
95
3
A
0.15
0.34
15.0
33.7
45
20ml 1% Solution
B
0.10
0.16
9.5
16.1
59
C
0.18
0.32
17.8
32.1
55
D
0.32
0.35
32.4
35.1
92
4
A
0.18
0.34
18.1
33.7
54
20ml 1% Solution
B
0.11
0.16
11.0
16.1
68
C
0.18
0.32
18.4
32.1
57
D
0.24
0.35
23.5
35.1
67
5
A
0.17
0.16
6.9
16.1
43
Two Tablets
B
0.13
0.32
13.0
32.1
40
6
B
0.17
0.16
16.9
16.1
105
10ml Glycerol Ext.
C
0.33
0.32
33.1
32.1
103
6
B
0.17
0.16
17.1
16.1
106
20ml Glycerol Ext.
C
0.33
0.32
33.2
32.1
103
7
A
0.34
0.34
34.0
33.7
101
20ml 1% Solution
B
0.16
0.16
16.2
16.1
101
C
0.32
0.32
32.3
32.1
101
D
0.33
0.35
33.0
35.1
94
Sample
amount used
In quantitative terms, hydrolyses of urea in these four fertilizer samples by these urease sources tended
to be in the range of 40-80%. Each of the urease sources should have hydrolyzed all the urea in these
type of fertilizers based on the tests done using the pure urea (Table 4), within the scope of the Urease
Method. Fertilizer “B” contains only about half of the urea of the other three fertilizer samples (A, C, and