Nitrogen, Simplified TKN (s-tkn ) DOC

Transcription

1 Nitrogen, Simplified Total Kjeldahl, TNTplus 880, DOC s-tkn Method Method to 16 mg/l TKN TNTplus 880 Scope and Application: For water and wastewater. Digestion is required. Test preparation Before starting the test: DR 2800 only: Install the light shield in Cell Compartment #2 before performing this test. Read the Safety Advice and Expiration Date on the package. The recommended sample and reagent temperature is C (59 77 F). If test is not performed at the recommended temperature an incorrect result may be obtained. Samples must be preserved with acid as specified in Sample collection, preservation and storage. Be sure to neutralize the samples and adjust to room temperature before the test. Correct for volume additions. After the addition of reagents A, B and C, the reagent bottles must be capped immediately. The reaction tubes should not be used more than13 times. After use, clean thoroughly with a brush and water, then rinse well with nitrogen-free distilled water and dry. Slight turbidity does not interfere; high turbidity after the addition of the MicroCap C should be allowed to settle or filtered. The nitrite concentration can be determined with TNTplus 839/840 reagents on samples that have not been preserved. The nitrite concentration must then be subtracted from the s-tkn result. The Total Nitrogen concentration must be between 1 and 16 mg/l N. Dilute the sample if necessary. The combined nitrate/nitrite concentration must be between 0.23 and 13.5 mg/l N. Dilute the sample if necessary. The recommended reagent storage temperature is C (59 77 F). TNTplus methods are activated from the Main Menu when the sample vial is inserted into the sample cell holder. Collect the following items: Description Quantity s-tkn TNTplus reagent set 1 Light Shield (DR 2800 only) 1 Pipet for 1.3 ml sample 1 Pipet for 1.0 ml sample 1 Pipet for 0.5 ml sample 1 Pipet for 0.2 ml sample 1 Pipet tips varies DRB 200 Reactor, with 20 mm vial wells 1 See Consumables and replacement items for reorder information.

2 s-tkn TNTplus method 1. Turn on the DRB 200 Reactor and heat to 100 C. 2. Add 1.3 ml of sample, 1.3 ml of Solution A and 1 Reagent B tablet in quick succession to a dry 20-mm reaction tube. Close the reaction tube immediately. Do not invert. 3. Insert the reaction tube in the reactor and close the lid. 4. Heat for one hour. 5. Remove the hot reaction tube from the reactor. Cool the reaction tube to room temperature (15 20 C). 6. After the reaction tube has cooled, remove the cap and add 1 Micro Cap C to the tube. 7. Cap and invert the reaction tube 2 3 times until no more streaks can be seen in the reaction tube solution. 8. Pipet 0.5 ml (500 μl) of the digested sample from the reaction tube into a Test Vial 1 (red label). 9. Pipet 0.2 ml (200 μl) of Solution D into the test vial. 10. Quickly cap and invert the test vial 2 3 times until no more streaks can be seen in the vial solution. Proceed immediately to step Pipet 1.0 ml (1000 μl) of undigested sample into a Test Vial 2 (green label). 12. Pipet 0.2 ml (200 μl) of Solution D into the test vial.

3 s-tkn TNTplus method (continued) 13. Quickly cap and invert the test vial 2 3 times until no more streaks can be seen in the vial solution. 14. Wait 15 minutes. 15. After the timer expires wipe the Test Vial 1 (red label) and insert the prepared vial into the cell holder. The instrument reads the barcode and displays E1. Proceed immediately to step Wipe the Test Vial 2 (green label) and insert the prepared vial into the cell holder. The instrument reads the barcode. Results are in mg/l Total N, mg/l NO 3 N + NO 2 N, and mg/l TKN. Interferences High levels of oxidizable organic substances (COD) affect the reagent color and give high results. This test can only be used for wastewater when the COD level is less than 500 mg/l COD. The substances listed in the Non-interfering substances table have been individually tested up to the given concentrations and do not cause interference. The cumulative effects and influence of other substances have not been determined. Table 1 Non-interfering substances Substance Cadmium, Cd 2+ Calcium, Ca 2+ Chloride, Cl Chromium, Cr 6+ Cobalt, Co 2+ Copper, Cu 2+ Iron, Fe 2+ Iron, Fe 3+ Lead, Pb 2+ Nickel, Ni 2+ Nitrite, NO 2 Potassium, K + Silver, Ag + Sodium, Na + Tin, Sn 2+ Highest level tested 500 mg/l 5 mg/l 10 mg/l 10 mg/l 2 mg/l 500 mg/l 100 mg/l 500 mg/l

4 Table 1 Non-interfering substances (continued) Substance Zinc, Zn 2+ Highest level tested Sample collection, preservation and storage Accuracy check Summary of method Collect samples in clean plastic or glass bottles. Preserve samples by adding concentrated Sulfuric Acid (at least 2 ml acid/l sample) until the ph is 2 or less. Store at 4 C (39 F) or less. Preserved samples may be stored up to 28 days. Before analysis, neutralize preserved samples with 5 N Sodium Hydroxide and warm to room temperature: C (59 77 F). Correct the test result for volume additions. Standard solution method Required for accuracy check: Wastewater Effluent Inorganics Quality Control Standard Solution 1. Follow the s-tkn TNTplus method test procedure using the Quality Control Standard Solution in place of the sample in steps 2 and The expected results are: 6 mg/l Total N 4 mg/l NO 3 N + NO 2 N 2 mg/l TKN Total Kjeldahl Nitrogen (TKN) is defined as the sum of organic nitrogen and ammonia. In the simplified TKN method, inorganic and organic nitrogen are oxidized to nitrate by digestion with peroxodisulfate. The nitrate ions react with 2,6-dimethylphenol in a solution of sulfuric and phosphoric acid to form a nitrophenol. Oxidized forms of nitrogen in the original sample (nitrite + nitrate due to sample preservation) are determined in the second test vial and then subtracted, resulting in TKN.

5 Consumables and replacement items Required reagents Description Quantity/Test Unit Catalog number Simplified TKN (s-tkn TM ) TNT880 reagent set 1 25/pkg TNT880 Sulfuric Acid, ACS 2 ml 500 ml Sodium Hydroxide, 5 N varies 1 L Required apparatus Description Quantity/Test Unit Catalog number Bottle, sample, low density poly, with cap, 500 ml 1 12/pkg DRB 200 Reactor V, nine 16-mm vial wells, two 20-mm vial wells 1 each LTV Light Shield (DR 2800 only) 1 each LZV646 Pipet, variable volume, 1 to 5 ml 1 each BBP065 Pipet tips, for BBP065 pipet varies 75/pkg BBP068 Pipet, variable volume, 0.2 to 1.0 ml 1 each BBP078 Pipet tips, for BBP078 pipet varies 100/pkg BBP079 1 Refer to the web site or catalog for other configurations. The DRB 200 is necessary for use with the 20-mm vials. Recommended standards Description Unit Catalog number Wastewater Effluent Inorganics Quality Control Standard Solution, mixed parameter 500 ml Filter, membrane, pore size 0.45?m, 25-mm diameter 100/pkg Filter Holder, 25-mm, for Luer-type syringe each Syringe, Luer-lock tip, 10 cc each Optional reagents and apparatus Description Unit Catalog number Nitrite, LR TNT839 reagent set 25/pkg TNT839 Nitrite, HR TNT840 reagent set 25/pkg TNT840

6 FOR TECHNICAL ASSISTANCE, PRICE INFORMATION AND ORDERING: In the U.S.A. Call toll-free Outside the U.S.A. Contact the HACH office or distributor serving you. On the Worldwide Web HACH COMPANY WORLD HEADQUARTERS Telephone: (970) FAX: (970) Hach Company, All rights reserved. Printed in the U.S.A. Updated August 2009, Edition 1