CHLORAMINE, MONO, High Range ( mg/l Cl 2 ) Method 10172

Transcription

1 CHLORAMINE, MONO, High Range ( mg/l Cl 2 ) Method Indophenol Method * For chlorinated drinking water and chlorinated wastewater 1. Enter the user program number for Chloramine, HR. Press: PRGM The display will show: PRGM? Note: For most accurate results, perform a Reagent Blank Correction (Section 1 of the DR/800 Instrument Manual). 2. Press: 111 ENTER The display will show: mg/l Cl 2 and then Zero Note: For alternate forms, press the CONC key. 3. Insert the COD/TNT Vial Adapter into the cell holder by rotating the adapter until it drops in place. Push down to fully insert it. Note: For better performance, adiffuser band covers the light path holes on the adapter. Do not remove the band. 4. Remove the cap from one HR Monochloramine Diluent vial. Use a glass pipet to add 2.0 ml of sample to the vial. Re-cap and invert several times to mix. 5. Wipe the outside of the vial clean. Place the vial into the adapter. Cover the sample vial tightly with the instrument cap. 6. Press: ZERO The cursor will move to the right and the display will show: 0.0 mg/l Cl Remove the vial from the cell holder, uncap, and add the contents of one Monochlor F pillow to the sample. Cap and shake the vial about 20 seconds to dissolve. 8. Press: TIMER ENTER A five-minute reaction period will begin. Note: Use the microfunnel as an aid in adding reagent powder to the vial. * U.S. Patent 6,315,950 99

2 9. After the timer beeps, wipe the prepared vial and place it into the instrument. Cover the sample vial tightly with the instrument cap. Sampling and Storage 10. Press: READ. The cursor will move to the right, then the results in mg/l monochloramine (as Cl 2 ) will be displayed. Analyze samples for monochloramine immediately after collection. Rinse the sample container several times with the sample water allowing it to overflow each time. If sampling from a tap, let the water flow for at least 5 minutes. Cap the container so that there is no head space (air) above the sample. Accuracy Check Prepare the following monochloramine standard fresh before use: 1. Using a clean 100-mL Class A volumetric flask, add the contents of one Buffer Powder Pillow, ph 8.3, to approximately 50 ml of organic-free water. Swirl to dissolve the powder. 2. Use a Class A volumetric pipet to transfer 2.00 ml of Nitrogen Ammonia Standard Solution, 100-mg/L as NH 3 N, into a flask. 3. Dilute to volume with organic-free water. Cap and mix thoroughly. This is the 2.00-mg/L buffered ammonia standard. 4. Pipet ml of the buffered ammonia standard into a clean 100-mL beaker. Add a magnetic stir bar and place the beaker on a stir plate. 5. Note the free chlorine concentration for the Chlorine Solution Ampules, mg/l. Use ampules from a recent lot. 100

3 Method Performance 6. Calculate the amount of Chlorine Solution to be added to the ammonia standard using the following equation: ml chlorine solution required 455 = free chlorine concentration 7. Turn the stir plate on to medium speed. 8. Open an ampule. Use a glass Mohr pipet to add the calculated amount of Chlorine Solution slowly to the ammonia standard while it is mixing. 9. Allow the monochloramine solution to mix for 1 minute after all the Chlorine Solution is added. 10. Quantitatively transfer the monochloramine solution to a clean 100-mL Class A volumetric flask. Dilute to the mark with organic-free water. Cap and mix thoroughly. This is a nominal 4.5-mg/L (as Cl 2 ) monochloramine standard. Use this solution within 1 hour of preparation. Precision In a single laboratory, using a standard solution of 3.5 mg/l monochloramine as chlorine and two representative lots of reagent, a single operator obtained a standard deviation of ±0.2mg/L Cl 2. Estimated Detection Limit The estimated detection limit (EDL) for Method is 0.2 mg/ L Cl 2. For more information on the EDL, see Section 1 of the DR/ 800 Procedure Manual. Interferences The following have been tested for interference and found not to interfere up to the indicated levels: Table 11 Non-interfering Substances Substance Maximum Level Tested Alanine 1 mg/l N Aluminum Bromide 100 mg/l Br - Bromine 15 mg/l Br 2 Calcium 1000 mg/l as CaCO 3 101

4 Table 11 Non-interfering Substances (Continued) Substance Chloride Maximum Level Tested 18,000 mg/l Chlorine Dioxide 5 mg/l ClO 2 Chromium (III) 5 mg/l Copper Cyanide CN Free Chlorine Cl 2 Glycine Iron (II) Iron (III) 1 mg/l N Magnesium 1000 mg/l as CaCO 3 Manganese (VII) Lead Nitrate Nitrite 100 mg/l N 50 mg/l N Phosphate 100 mg/l PO 4 Silica 100 mg/l SiO 2 Silver Sulfate 2600 mg/l Sulfite 2 50 mg/l SO 3 Tyrosine 1 mg/l as N Urea as N Zinc 5 mg/l Table 12 Interfering Substances Interfering Substance and its effect Interference Level Recommended Treatment Ozone Above 1 mg/l Usually doesn t coexist with monochloramine Sulfide + Turns a rust color if present. Thiocyanate Above 0.5 mg/l Usually doesn t coexist with monochloramine 102

5 Summary of Method Safety Instrument Setup The sample is first diluted in a Test N Tube. In the presence of a cyanoferrate catalyst, monochloramine (NH 2 Cl) in the sample reacts with a substituted phenol to form an intermediate monoimine compound. The intermediate compound couples with excess substituted phenol to form a green indophenol. Color intensity is proportional to the amount of monochloramine present in the sample. Good safety habits and laboratory techniques should be used throughout the procedure. Consult the Material Safety Data Sheet (MSDS) for information specific to the reagent used. This procedure will add the current method as a new Hach program to your DR/850 or DR/890 instrument. 1. Turn the instrument on by pressing the ON key. 2. Press the SETUP key. 3. Press the down arrow key until the prompt line shows USER. 4. Press the ENTER key. 5. Key in 8138, then press ENTER. 6. Key the number in the Enter column corresponding to line number 1 on the display. Press ENTER. Repeat for lines 2 56 on the display. Table 13 Line number on display Enter Line number on display Enter

6 Table 13 (Continued)

7 REQUIRED REAGENTS Quantity Required Description Per Test Unit Cat. No. HR Monochloramine Test N Tubes, 50 tests Includes: HR Monochloramine Diluent Vials * Funnel, micro each Monochlor F Reagent Pillows /pkg REQUIRED APPARATUS COD/TNT Vial Adapter, DR/ each Pipet, Mohr, glass, 2.00-mL each Test Tube Rack each OPTIONAL REAGENTS Organic-free Water mL Buffer Powder Pillows, ph /pkg Nitrogen, Ammonia Standard Solution, 100-mg/L as NH 3 N mL Chlorine Solution Voluette Ampule, mg/l, 10-mL...16/pkg OPTIONAL APPARATUS Beaker, 100-mL...each H Clippers (medium powder pillows)...each Clippers (shears)...each Flask, Volumetric, Class A, 100-mL...each Pipet, Mohr, Glass, 10-mL...each Pipet, Volumetric, Class A, 2.00-mL...each Pipet, Volumetric, Class A, mL...each Stir Bar, Octagonal...each Stirrer, Magnetic, 110 V, 4 x 4...each * Not sold separately. 105