Nitrate standard dilutions
Below are methods for preparing 5 mL or 10 mL nitrate standards in three different concentration ranges. Adjust volumes as necessary for preparing larger volumes.
- Low-range: 0 - 40 ppm e.g. Hach NitraVer5, API test kit, Nitrate reductase method
- Mid-range: 0 - 80 ppm e.g. Hach NitraVer5, API test kit.
- High-range: 0 - 200 ppm e.g. API Test Kit
In each case, the first step is preparing a working stock by diluting a commercially available nitrate standard. This working stock is then diluted further resulting in a set of 8 nitrate concentrations (plus a distilled water blank).
In addition to the equipment listed on the appropriate nitrate assay page, you will also need the following equipment and reagents if you plan to collect nitrate calibration data:
- 1,000 ppm N (4,430 ppm as NO3) standard, Labchem Cat # LC18570-1
- 100 mL volumetric flask for preparing the working stock
- 5 mL or 10 mL sample tubes
- Distilled water
Low-range (0.00 - 40 ppm NO3)
- Volume: 5 mL
- 40 ppm NO3 working stock: 1.129 mL of the 4,430 ppm (1,000 ppm as N) standard in 100 mL distilled water in volumetric flask. Fill to the line with distilled water.
| Tube |
NO3 concentration (ppm) |
Volume of 40 ppm working stock (mL) |
Volume of distilled water (mL) |
|---|
| 1 |
0 |
0.000 |
5.00 |
| 2 |
5 |
0.625 |
4.375 |
| 3 |
10 |
1.250 |
3.75 |
| 4 |
15 |
1.875 |
3.125 |
| 5 |
20 |
2.500 |
2.50 |
| 6 |
25 |
3.125 |
1.875 |
| 7 |
30 |
3.750 |
1.25 |
| 8 |
35 |
4.375 |
0.625 |
| 9 |
40 |
5.000 |
0.00 |
Mid-range (0 - 80 ppm NO3)
- Volume: 10 mL
- 80 ppm NO3 working stock: 2.257 mL of the 4,430 ppm (1,000 ppm as N) standard in 100 mL distilled water in volumetric flask. Fill to the line with distilled water.
| Tube |
NO3 concentration (ppm) |
Volume of 100 ppm working stock (mL) |
Volume of distilled water (mL) |
|---|
| 1 |
0 |
0.0 |
10.0 |
| 2 |
10 |
1.0 |
9.0 |
| 3 |
20 |
2.0 |
8.0 |
| 4 |
30 |
3.0 |
7.0 |
| 5 |
40 |
4.0 |
6.0 |
| 6 |
50 |
5.0 |
5.0 |
| 7 |
60 |
6.0 |
4.0 |
| 8 |
70 |
7.0 |
3.0 |
| 9 |
80 |
8.0 |
2.0 |
High-range (0.00 - 200 ppm NO3)
- Volume: 5 mL
- 200 ppm NO3 working stock: 4.515 mL of the 4,430 ppm (1,000 ppm as N) standard in 100 mL distilled water in volumetric flask. Fill to the line with distilled water.
| Tube |
NO3 concentration (ppm) |
Volume of 200 ppm working stock (mL) |
Volume of distilled water (mL) |
|---|
| 1 |
0 |
0.000 |
5.00 |
| 2 |
25 |
0.625 |
4.375 |
| 3 |
50 |
1.250 |
3.75 |
| 4 |
75 |
1.875 |
3.125 |
| 5 |
100 |
2.500 |
2.50 |
| 6 |
125 |
3.125 |
1.875 |
| 7 |
150 |
3.750 |
1.25 |
| 8 |
175 |
4.375 |
0.625 |
| 9 |
200 |
5.000 |
0.00 |
