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How to test for Nitrogen

North Carolina allows for a maximun nitrate concentraion in water of 10.0 mg/l (ppm).

Total Nitrogen Methods

This method is free from hazardous material and since all the components are all in pre-measured single dose components; the method is easy to use. You can obtain a total nitrogen testing kit from most biological suppliers, such as HACH.

• open two digestion vials containing pre-measured sodium hydroxide solution
• add the contents of one pre-measured package of potassium persulfate to each vial
• add 2 mL of sample to one vial and 2 mL of organic and nitrogen free water to the second vial (the blank reagent)
• cap the vials and shake for 30 seconds
• the powder does not need to completely dissolve
• place the two vials in a block heater reactor preheated to 103 to 106 degrees Celsius
• heat for 30 min
• immediately remove the vials from the reactor and cool to room temperature

Colorimetric finish
• open the cooled vials and add one Permachem Reagent package of sodium metabiosulfite to each vial
• cap the vials and shake for 15 seconds
• wait three min for complete reaction
• open both vials and add one Permachem Reagent package of chromo tropic acid reagent to each vial
• cap and shake for 15 seconds
• the reagent will not completely dissolve
• wait two minutes for complete reaction
• open two of the acid solution vials
• pipette 2 mL of digested treated sample into one vial
• add 2mLof digested treated blank into the other vial
• cap the vials and slowly invert 10 times
• use slow precise inversions over a 30 sec time period
• wait five minutes for full color development
• do not invert the vials again
• if nitrate is present a yellow color will develop that can be measured directly on a spectrophotometer using the absorbance maximum of 410 nm

Items needed to complete the experiment. All are from the HACH Company. The name of what is needed is listed followed by the catalog number for the item.

Description (Catalog Number)

Test ’N Tube™ HR Total Nitrogen Reagent Set (27141-00)

Required Items
• DRB 200 Reactor, 110 V, 15 x 16 mm (LTV082.53.40001)
• Or DRB 200 Reactor, 220 V, 15 x 16 mm (LTV082.52.40001)
• Funnel, micro (25843-35)
• Pipet, TenSette®, 0.1 to 1.0 mL (19700-01)
• Pipet Tips, for 19700-01 TenSette® Pipet (21856-96)
• Test Tube Cooling Rack (18641-00)

Required Standards
• Ammonia Nitrogen Standard Sol., 1000-mg/L NH3–N (23541-53)
• Primary Standard Set, for Kjeldahl Nitrogen (22778-00)
• Ammonia Nitrogen Standard Solution, 100-mg/L NH3–N. (24065-49 )
• Water, deionized (272-49)
• or Water, organic-free (26415-49)