HACH DR6000 Nitrogen Total TNTplus Test User Manual

Persulfate Digestion Method
100 to 250 mg/L N (UHR+)
DOC316.53.01548
Method 10208
® TNTplus 818

Scope and application: For water and wastewater.
Test preparation

Instrument-specific information

Table 1 shows all of the instruments that have the program for this test. The table also shows the adapter and light shield requirements for the applicable instruments that can use TNTplus vials.
To use the table, select an instrument, then read across to find the applicable information for this test.
Table 1 Instrument-specific information for TNTplus vials

Before starting

DR3900, DR3800, DR2800: Install the light shield in Cell Compartment #2 before this test is started.

Review the safety information and the expiration date on the package.
The recommended sample pH is 3–12.
The sample temperature must be 15–25 °C (59–77 °F) for accurate results.
The recommended temperature for reagent storage is 15–25 °C (59–77 °F).
Important: Make sure to close each reagent bottle immediately after each use.
The 20-mm reaction tube can be used for 7 tests. After each use, clean the tube thoroughly with a brush and water, then rinse well with high-quality distilled water and let dry.
Use only high-quality deionized water or organic-free water for standards preparation, sample dilutions or reagent blanks.
DR1900: Go to All Programs>LCK or TNTplus Methods>Options to select the TNTplus number for the test. Other instruments automatically select the method from the barcode on the vial.
Review the Safety Data Sheets (MSDS/SDS) for the chemicals that are used. Use the recommended personal protective equipment.
Dispose of reacted solutions according to local, state and federal regulations. Refer to the Safety Data Sheets for disposal information for unused reagents. Refer to the environmental, health and safety staff for your facility and/or local regulatory agencies for further disposal information.

Items to collect

Items to collect (continued)

Refer to Consumables and replacement items on page 4 for order information.
Sample collection and storage

• Collect samples in clean glass or plastic bottles.
• Analyze the samples as soon as possible for best results.
• To preserve samples for later analysis, adjust the sample pH to less than 2 with concentrated sulfuric acid (approximately 2 mL per liter). No acid addition is necessary if the sample is tested immediately.
• Keep the preserved samples at or below 6 °C (43 °F) for a maximum of 28 days.
• Let the sample temperature increase to room temperature before analysis.
• Before analysis, adjust the pH to 7 with 5 N sodium hydroxide solution.
• Correct the test result for the dilution caused by the volume additions.

Test procedure

1. Set the DRB200 reactor power to on. Set the temperature to 120 °C.

2. Add 0.1 mL of sample, 2.3 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 preheated DRB200 reactor. Close the lid.

4. Keep the reaction tubes  in the reactor for30 minutes

5. When the timer expires, carefully remove the reaction tube from the reactor. Let the temperature of the reaction tube decrease to room temperature.

6. Invert the reaction tube 2–3 times.

7. Use a pipet to slowly add 0.5 mL of the digested sample from the 20‑mm reaction tube into a test vial.

8. Use a pipet to slowly add 0.2 mL of Solution D to the test vial.

9. Quickly tighten the cap on the vial and invert until completely mixed.

10. Start the reaction time of 15 minutes.

11. When the timer expires, clean the vial.

12. DR1900 only: Select program 818. Refer to Before starting on page 1.

13. Insert the vial into the cell holder. DR1900 only: Push READ.
    Results show in mg/L N.

Reagent blank correction

For the best results, measure the reagent blank value for each new lot of reagent.
Replace the sample with deionized water in the test procedure to determine the reagent blank value. Subtract the reagent blank value from the sample results automatically with the reagent blank adjust option. Measure the reagent blank value when a new lot of
reagent is used.

1. Use deionized water as the sample in the test procedure to measure the reagent blank value.
2. Set the reagent blank function to on. The measured reagent blank value is shown.
3. Accept the blank value. The reagent blank value is then subtracted from all results until the reagent blank function is set to off or a different method is selected.
   Note: As an alternative, record or enter the reagent blank value at a different time. Push the highlighted reagent blank box and use the keypad to enter the value.

Interferences

A light pink color may develop during the reaction. This color does not interfere with the analysis. Table 2 shows that the ions were individually examined to the given concentrations and do not cause interference. No cumulative effects or influences of other ions were found.

Table 2 Interfering substances

Accuracy check

Standard solution method

Use the standard solution method to validate the test procedure, the reagents and the instrument.
Items to collect:

• Nitrogen, Ammonia Standard Solution, 150-mg/L NH3–N
  1. Use the test procedure to measure the concentration of the standard solution.
  2. Compare the expected result to the actual result.

Summary of Method

Inorganic and organic nitrogen compounds are digested with peroxodisulfate and oxidized to nitrate. The nitrate ions react with 2,6-dimethylphenol in a solution of sulfuric and phosphoric acid to form a nitrophenol. The measurement wavelength is 345 nm.

Consumables and replacement items
Required reagents

Required apparatus

DRB200-01
DRB200 Reactor, 230 VAC option, 9 x 13 mm + 2 x 20 mm, 1 block| 1| each| DRB200-05
Pipet, adjustable volume, 1.0–5.0 mL| 1| each| BBP065
Pipet tips, for 1.0–5.0 mL pipet| 1| 75/pkg| BBP068
Pipet, adjustable volume, 0.1–1.0 mL| 1| each| BBP078
Pipet tips, for 0.1–1.0 mL pipet| 2| 100/pkg| BBP079
Test tube rack for 20-mm vials, 20 holes| 1| each| 2497912
Test tube rack for 20-mm vials, 40 holes| 1| each| 2497902
Light shield, DR3800, DR2800, DR2700| 1| each| LZV646
Light shield, DR3900| 1| each| LZV849

Recommended standards

1479110

Optional reagents and apparatus

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