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Nitrogen, Total Kjeldahl
AQUEOUS SAMPLES (Solutions of suspensions in water—less than 1% solids)
Expected Nitrogen Concentration (mg/L)
425–22500
Expected Nitrogen Concentration (mg/L)
106–5600
350–18,000
1000–56,000
4200–220,000
Expected Nitrogen Concentration (mg/L)
210–11,000
2100–110,000
Sample Collection, Storage, and Preservation
Accuracy Check
Nitrogen, Total Kjeldahl
Page 4 of 6
0.5–28
2–112
11–560
45–2250
42–2200
85–4500
Collect samples in clean glass or plastic containers. Adjust the pH to 2 or less
with Sulfuric Acid (Cat. No. 979-49) (about 2 mL per liter) and cool to 4 °C
(39 °F). Preserved samples can be stored up to 28 days.
Kjeldahl Nitrogen Standard Method
This procedure checks digestion efficiency and indicates that amount of bound
nitrogen that is freed during digestion. The methods and standards available to
check digestion technique are found in the Accuracy Check section following the
procedure in the Digesdahl
digested Kjeldahl standard, perform the above TKN analysis on the colorimeter.
The TKN value should come within ±3% of the value of the prepared
Kjeldahl standard.
Standard Solution Method (to check calibration accuracy only)
1. Add one drop of TKN Indicator to each 25-mL graduated mixing cylinder.
2. Fill one cylinder to the 20-mL mark with deionized water. Fill the other
cylinder to the 20-mL mark with a 1.0-mg/L NH
3. Add 3 drops of Mineral Stabilizer to each cylinder. Invert several times
to mix.
4. Add 3 drops of Polyvinyl Alcohol Dispersing agent to each cylinder.
5. Perform the TKN procedure as described in step 10 to step 16. The display
should show 26–27 mg/L TKN.
Table 1
DRY SAMPLES
OILS AND FATS
®
Digestion Apparatus Instruction Manual. Using the
Analysis Volume (mL)
10.0
5.0
2.00
1.00
0.500
Analysis Volume (mL)
10.0
5.00
2.00
1.00
0.50
Analysis Volume (mL)
10.0
5.00
1.00
–N solution.
3
NitrogenTK_None_Other_NES_Eng_Ody.fm
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