Hach DR2400 - Page 525

Nitrogen, Total Kjeldahl
Nitrogen, Total Kjeldahl
NitrogenTK_None_Other_NES_Eng_Ody.fm Page 5 of 6
Method Performance
Precision
Standard: 120 mg/L NH
3
–N
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
The term Total Kjeldahl Nitrogen refers to the combination of ammonia and
organic nitrogen. However, only the organic nitrogen compounds appearing as
organically bound nitrogen in the trinegative state are determined in this test.
Nitrogen in this form is converted into ammonium salts by the action of sulfuric
acid and hydrogen peroxide. The ammonia is then analyzed by a modified
Nessler method test. Test results are measured at 460 nm.
Required Reagents
Quantity Required
Description Per Test Unit Cat. No.
Nitrogen Reagent Set, 0–150 mg/L, Nesslers Method.................................................. 250 tests ...........24953-00
Includes:
Hydrogen Peroxide, 50% ..................................................................20 mL .............. 490 mL...............21196-49
Mineral Stabilizer...............................................................................6 drops............ 50 mL SCDB .....23766-26
Nesslers Reagent ................................................................................2 mL ................ 500 mL...............21194-49
Polyvinyl Alcohol Dispersing Agent ..............................................6 drops............ 50 mL SCDB .....23765-26
Potassium Hydroxide Standard Solution, 1.0 N ...........................varies .............. 50 mL SCDB .....23144-26
Potassium Hydroxide Standard Solution, 8.0 N ...........................varies .............. 100 mL MDB.........282-32
Sulfuric Acid, ACS, concentrated ....................................................6 mL ................ 500 mL...................979-49
TKN Indicator Solution.....................................................................2 drops............ 50 mL SCDB .....22519-26
Required Apparatus
Boiling Chips, silicon carbide .................................................................2–3................... 500 g...................20557-34
Cots, finger ................................................................................................2 ....................... 2/pkg.................14647-02
Cylinder, graduated mixing, 25-mL.......................................................2 ....................... each....................26362-40
Select one based on available voltage:
Digesdahl
®
Digestion Apparatus, 115 VAC...................................1 ....................... each....................23130-20
Digesdahl
®
Digestion Apparatus, 220 VAC...................................1 ....................... each....................23130-21
Pipet, TenSette
®
, 0.1–1.0 mL....................................................................1 ....................... each....................19700-01
Pipet Tips, for 19700-01 TenSette
®
Pipet ...............................................2 ....................... 50/pkg...............21856-96
Safety Shield ..............................................................................................1....................... each....................50030-00
Sample Cells, 10-mL, w/cap...................................................................2 ....................... 6/pkg.................24276-06
Required Standards
Nitrogen Standard Solution, 1-mg/L NH
3
–N................................................................ 500 mL.................1891-49
Nitrogen Standard Solution, Voluette
®
Ampule, 10-mL .............................................. 16/pkg...............21284-10
Program 95% Confidence Limits of Distribution
399 107–133 mg/L NH
3
–N
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 1 mg/L NH
3
–N