Cardinal Environmental Laboratories, LLC

Standard Operating Procedure

Procedure No.: 7020 Revision Date: 17/07

Subject: (Method 351.2 )Organic Nitrogen/Total Kjeldahl Nitrogen:

Automated Analysis Preparation

Approved By:

Laboratory Director ______

John Pflugh Date

Senior Chemist ______

Roberta Pettit Date

Chemist ______

Zeblus Hawkins Date

TKN/Organic Nitrogen

Method EPA 351.2

Scope and Application

This method determines total Kjeldahl nitrogen in drinking water and surface waters; domestic and industrial wastes.

Description

Organic nitrogen, found in natural compounds such as proteins, can be determined using the following methodology. The total of both organic nitrogen and ammonia concentrations is known as Total Kjeldahl Nitrogen. This method is sensitive to

0.05 ppm.

Precautions

General Requirements

Corrosives (See procedure 0020)

Sample Preservation

Samples to be analyzed for Total Kjeldahl Nitrogen (TKN) or organic nitrogen (TON)

can be collected in either plastic or glass containers. If samples cannot be analyzed immediately, preserve by adding concentrated H2SO4 to a pH of 1.5 to 2.0 and store the sample at 4°C no longer than 28 days prior to analysis.

Apparatus

- Kjeldahl flasks

- Kjeldahl distillation rack

- 250ml beakers or 250 Erlenmyer flasks

Reagents

- Copper Sulfate solution (CuS04):

Dissolve 25.1g CuSO4 in 1L water.

- TKN Acid:

Dissolve 134g K2SO4 (Potassium Sulfate) in 650ml water. Add 200ml

conc. H2SO4 slowly, dilute to 1L.

CAUTION: solution will be hot.

- TKN Base:

Dissolve 500g NaOH and 25g Na2S2O3 5H2O (Sodium Thiosulfate) in

water and dilute to 1L.

CAUTION: solution will be hot.

- See method 3010 for additional reagents.

Procedure

1.0 Determine the appropriate sample volume by the following:

Sample DI

Type Amount H2O CuSO4 TKN Acid

Aqueous samples - 100ml --- 5 ml 15 ml

Waste sludge - 0.5g 100 ml 5 ml 15 ml

Solids - 2.0g 100 ml 5 ml 15 ml

1.1 A final volume for all samples should be 100ml.

2.0 Carefully add 15ml TKN acid and 5ml CuSO4 solution to the 100ml of sample

in the Kjeldahl flask.

2.1 Add 3-5 boiling chips.

2.2 Turn on the fume vacuum unit of the Kjeldahl distillation rack.

2.3 Place flask on lower rack, turn heating unit on to Hi to allow vigorous boiling. (Make sure boiling chips have been added.) Reduce volume to 20ml. As sample reduces, white fumes will be apparent.

2.4 Continue digestion on Hi for at least 30 additional minutes.

(As digestion proceeds the sample may turn clear or straw colored).

Digestion is completed when sample is reduced to 10 mls.

2.5 Turn heater mantle off and allow sample to cool completely. Do not turn the

fume vacuum unit off until sample is cooled completely.

2.6 Add 100ml ultra pure water. Carefully, (with neck pointed away), add 15ml TKN base. Swirl flask and place on top distillation rack.

2.7 Go to step 2.7 of SOP 3010 for distillation procedure. Go to step 2.1 of SOP 3010

for selection of appropriate collection scrubber.

Quality Control

* Each analytical batch analyzed for TKN must be accompanied by a method

blank consisting of 100ml ultra pure water taken through all digestion and

distillation steps.

* Each analytical batch analyzed must also be accompanied by two standards with concentrations of 2.0 ppm and 20.0 ppm

* All weights, volumes, comments etc. for each batch must be entered in

notebook form for data review.

* Every 10th sample of similar matrix shall be analyzed in duplicate and

% RPD calculated. Every 20th sample shall be analyzed as a duplicate spike

and % recoveries and % RPD calculated.

(See procedure 0110 for calculations).

* Required recoveries for duplicate and spike duplicates shall be determined using historical data. The current acceptable limits for these parameters are listed in procedure 0120.

* Failure to meet quality control acceptable limits requires corrective action.

(See procedure 0150).

References

Standard Methods for the Examination of Water and Wastewater

17th Edition - Method 4500 Norg B.

pp. 4-94 thru 4-96

Methods for Chemical Analysis of Water and Wastes

EPA 600/4-79-020 March 1983

Method 351.3 pp 351.3-1 thru 351.3-6

National Environmental Methods Index. April 1994. Method 351.2. 7 April 2004.

<http://www.nemi.gov>

Procedure 7020

Revised 17/07