CHLORINE DIOXIDE (0 to 5.00 mg/l) Method 10126 DPD Method* Scope and Application: for measuring chlorine dioxide in clean water For water 530 nm 1. Enter the stored program for chlorine dioxide (ClO 2 ) powder pillows. Press: 76 READ/ENTER The display will show: DIAL nm TO 530 2. Rotate the wavelength dial until the display shows: 530 nm Note: For DR/3000s, set the wavelength to 530 nm. 3. Insert the 10-mL cell riser into the sample compartment. Note: For the DR/3000s use the appropriate 10-mL cell riser. 4. Press: READ/ENTER The display will show: mg/l ClO 2 DPD Note: See Instrument Setup to enter this method into the DR/2000. Note: For DR/3000s: Press: MANUAL PROGRAM Press: 4.357 CONC FACTOR Press: ZERO Press: 2 CONC Note: DR/2000s with software versions 3.0 and greater will display P and the program number. Note: DR/2000 with software versions 3.0 and greater will not display Dial to message if the wavelength is already set correctly. The display will show the message in step 4. Proceed with step 5. * Adapted from Standard Methods for the Examination of Water and Wastewater.
5. Fill a sample cell with 10-mL of sample. Note: Analyze samples immediately after collection; chlorine dioxide is unstable in aqueous solutions. See Sampling and Storage following these steps. Note: For best results, run a reagent blank using deionized water as the sample. Subtract the blank value from the sample reading to obtain the final result. 6. Place the sample into the cell holder. Close the light shield. Note: For the DR/2000, place the cell so that the graduation faces left. For the DR/3000, insert the cell volume mark so it faces forward. 7. Press: ZERO The display will show: then: WAIT 0.00 mg/l ClO 2 DPD Note: The DR/3000 will show 0.00. 8. Add four drops of Glycine Reagent to the sample cell. Swirl to mix. This is the prepared sample. 9. Add the contents of one DPD Free Chlorine Powder Pillow to the prepared sample. Swirl to mix. Note: A pink color will develop if chlorine dioxide is present. 10. Wait 30 seconds for undissolved powder to settle. Within one minute of reagent addition, place the prepared sample into the cell holder. Close the light shield. Note: For the DR/2000, place the cell so that the graduation faces left. For the DR/3000, insert the cell volume mark so it faces forward. 11. Press: READ/ENTER The display will show: WAIT then the results in mg/l ClO 2 will be displayed. Note: In the Constant-On mode, pressing READ/ENTER is not required. WAIT will not appear. When the display stabilizes, read the result. Note: For the DR/3000, insert the sample cell and read the result. Note: If the sample temporarily turns yellow after reagent addition, or the display flashes limit, it is due to high chlorine dioxide levels. Dilute a fresh sample with chlorine dioxidefree water and repeat the test. A slight loss of chlorine dioxide may occur during dilution. Multiply the result by the dilution factor. 2
Using AccuVac Ampuls 530 nm 1. Enter the stored program number for the DPD chlorine dioxide (ClO 2 ) AccuVac Ampul method. Press: 77 ENTER The display will show: Dial nm to 530 Note: See Instrument Setup to enter this method into the DR/2000. 2. Rotate the wavelength dial until the small display shows: 530 nm Note: For DR/3000s, set the wavelength to 530 nm. 3. Press: READ/ENTER The display will show: mg/l ClO 2 AV 4. Fill a zeroing vial (the blank) with at least 10 ml of sample. Fill a 50-mL beaker with 40 ml of sample. Using the correct sample volume is important. Note: Analyze samples immediately after collection because chlorine dioxide is unstable in liquids. See Sampling and Storage following these steps. Note: For DR/3000s: Press: MANUAL PROGRAM Press: 4.895 CONC FACTOR Press: ZERO Press: 2 CONC Note: For best results, run a reagent blank using deionized water as the sample. Subtract the blank value from the sample reading to obtain the final result. Note: DR/2000s with software versions 3.0 and greater will display P and the program number. Note: DR/2000 with software versions 3.0 and greater will not display Dial to message if the wavelength is already set correctly. The display will show the message in step 3. Proceed with step 4. 3
5. Place the AccuVac Vial Adapter into the cell holder of the instrument. Note: For DR/2000s, place the grip tab at the rear of the cell holder. For DR/3000s the grip holder should face left or right. 6. Place the blank into the cell holder. Close the light shield. 7. Press: ZERO The display will show: WAIT then: 0.00 mg/l ClO 2 AV 8. Add 16 drops of Glycine Reagent to the sample in the beaker. Swirl to mix. Note: The DR/3000 will show 0.00. 9. Fill a DPD Free Chlorine Reagent AccuVac Ampul with sample. Note: Keep the tip immersed while the ampul fills completely. 10. Quickly invert the ampul several times to mix. Wipe off any liquid or fingerprints. Note: A pink color will form if chlorine dioxide is present. 11. Wait 30 seconds for undissolved powder to settle. Within one minute of sample addition, place the AccuVac Ampul into the cell holder. Close the light shield. Note: Proceed immediately to Step 12. 12. Press: READ/ENTER The display will show: WAIT then the result in mg/l ClO 2 will be displayed. Note: In the Constant-On mode, pressing READ/ENTER is not required. WAIT will not appear. When the display stabilizes, read the result. For the DR/3000, insert the sample cell and read the result. Note: If the sample temporarily turns yellow after reagent addition, or the display flashes limit, it is due to high chlorine dioxide levels. Dilute a fresh sample and repeat the test. A slight loss of chlorine dioxide may occur during dilution. Multiply the result by the dilution factor. 4
INSTRUMENT SETUP Entering the Powder Pillow Method DR/2000s with Software Version 2.0 and 2.2 Enter the calibration as an update to Hach stored programs. 1. Press: I/O 2. Press: SHIFT CONFIG/METH 3. Press: 76 READ/ENTER 4. Within 3 seconds, press: SHIFT PROG/3 CONFIG/METH The display will show: ENTER nm 5. Press: 530 READ/ENTER Note: If you make an error, press SHIFT CLEAR and re-enter the number. When the number is correct, press READ/ENTER. 6. The display will show: Decimal? 00.00 The decimal is correctly positioned. Press READ/ENTER. 7. The display will show: UNITS? 8. Use the arrow keys to select the appropriate unit of measure. Press the down arrow key twice. The display will show: mg/l 9. Press READ/ENTER when the correct unit for measure is displayed. The display will show: SYMBOL? 10. Construct the correct symbol display: ClO 2 a. Select letters and regular numbers by scrolling to the correct symbol with the arrow keys. b. To make letters uppercase, press the SHIFT key. c. To enter subscript numbers, enter the digit using the numeric pad. 5
d. To enter superscript numbers, enter the digit using the numeric pad, then make it superscript by pressing SHIFT. e. The space is the character displayed after one press of the down arrow. f. Accept each symbol by pressing READ/ENTER. g. To end symbol entry, press READ/ENTER a second time after accepting the last character. 11. When the instrument is out of symbol entry mode, the display will show: TIMER? 12. Press SHIFT TIMER. The display will show: MM:SS TIME 1? 13. Enter a timer value of one minute: 0 1 0 0 14. Press READ/ENTER to accept the value. The display will show: MM:SS TIME 2? 15. Press READ/ENTER to complete timer entry. The display will show: #1 Data 16. Enter the following 12 numbers as shown. Complete each number entry by pressing the READ/ENTER key. # 1 Data 0 # 2 Data 13365 # 3 Data 13879 # 4 Data 14393 #5 Data 14906 # 6 Data 15165 # 7 Data 65535 # 8 Data 65535 # 9 Data 65535 # 10 Data 5461 # 11 Data 512 Checksum 53394 The final number is a check value which determines if the data sequence was correctly entered. If an error was made during number entry, the display will return to the prompt for # 1 data and the entire sequence must be re-entered. If all numbers are correctly entered, the display will return to the method prompt and is ready for use. 6
DR/2000s With Software Version 3.0 1. Turn the instrument on. After the self test, press SHIFT METHOD to enter the configuration mode. The display will show: MOMENTARY or CONSTANT ON 2. Press the up arrow key twice to select HACH UPDATE. Press READ/ENTER. The display will show: ENTER #: 3. Press: 76 READ/ENTER. The display will show: P 76 ENTER nm Note: If you make an error, press SHIFT CLEAR and re-enter the number. When the number is correct, press READ/ENTER. 4. Press: 530 READ/ENTER. The display will show: P 76 Decimal? 00.00 5. The decimal point is correctly positioned. Press READ/ENTER. The display will show: P 76 UNITS? 6. Use the arrow keys to select the appropriate unit of measure. Press the down arrow key twice. The display will show: P 76 mg/l 7. Press READ/ENTER when the correct unit of measure is displayed. This display will show: P 76 mg/l _ 8. Construct the display to read the correct symbol. The symbol must be entered exactly as shown: ClO 2 To enter the display symbol, press the following key sequence, pressing the enter key twice after entering each number: To enter C, press 67 ENTER ENTER To enter l, press 108 ENTER ENTER To enter O, press 79 ENTER ENTER To enter 2, press 18 ENTER ENTER ENTER Alternately, scroll to each of the character using the arrow keys as follows: a. Select letters and numbers by scrolling to the correct character with the arrow keys. b. To make a letter uppercase, press the SHIFT key. c. To make the number 2 subscript, scroll to 2, then press SHIFT until the display is correct. 7
d. The space is the character displayed after one press of the down arrow key. e. Make sure to enter the display line EXACTLY as shown, including the spaces. Do not enter trailing spaces. f. Accept each symbol by pressing READ/ENTER. g. To end symbol entry, press READ/ENTER twice after accepting the last character (press READ/ENTER a total of three times). 9. When the instrument is out of symbol entry mode, the display will read: P 76 TIMER? 10. This method has one timed step, so press SHIFT TIMER. The display will show: MM:SS TIME 1? 11. Enter a timer value of 1 minute. Press 0100 READ/ENTER. The display will show: MM:SS TIME 2? 12. Press READ/ENTER to complete the timer entry. The display will show: #0 STANDARD 13. Press READ/ENTER to display the zero data pair. The display will show: 0.000 Abs 00.00 mg/l 14. Press READ/ENTER. The display will show: #1 STANDARD 15. Press READ/ENTER. The display will prompt for entry of the first concentration point: #1 00.00 mg/l 16. Enter concentration point #1 from the table below by pressing 0025 so that the display shows: # 1 00.25 mg/l 17. Press READ/ENTER. The display will prompt for entry of the first absorbance point: # 1 0.000 Abs 18. Enter absorbance point #1 from the table below by pressing 0060. The display will show: # 1 0.60 Abs 19. Press READ/ENTER. The display will show the first data pair: 0.60 Abs 00.25 mg/l 20. Press READ/ENTER to accept the first data pair. The display will show: #2 STANDARD 8
21. Following steps 15-20 above, enter the remaining data pair values from the table below:. 22. When the last data point is entered, the display will show: #13 STANDARD 23. Press SHIFT READ/ENTER to complete data point entry. The display will show: #: 24. Enter the validation number 11846. The display will show: #: 11846 25. Press READ/ENTER. The display will show: COMPLETED then: P 76 mg/l ClO 2 Standard Concentration (mg/l) Absorbance (Abs) #0 0 0.000 #1 0.25 0.060 #2 0.50 0.120 #3 1.00 0.238 #4 1.50 0.354 #5 2.00 0.468 #6 2.50 0.581 #7 3.00 0.692 #8 3.50 0.801 #9 4.00 0.908 #10 4.50 1.015 #11 5.00 1.120 #12 5.50 1.223 If the display shows INCORRECT #, then prompts for the validation number, a mistake may have been made during data entry. Make sure the validation number is correct. If so, the error occurred during some other portion of the method entry. Press METH and respond to the ABORT? message by pressing READ/ENTER, then re-enter the method. The instrument is now ready for use with method 76. 9
Entering the AccuVac Ampul Method DR/2000s with Software Version 2.0 and 2.2 Enter the calibration as an update to Hach stored programs. 1. Press: I/O 2. Press: SHIFT CONFIG/METH 3. Press: 77 READ/ENTER 4. Within 3 seconds, press: SHIFT PROG/3 CONFIG/METH. The display will show: ENTER nm 5. Press: 530 READ/ENTER. The display will show: Decimal? 00.00 Note: If you make an error, press SHIFT CLEAR and re-enter the number. When the number is correct, press READ/ENTER. 6. The decimal is correctly positioned. Press READ/ENTER. 7. The display will show: UNITS? 8. Use the arrow keys to select the appropriate unit of measure. Press the down arrow key twice. The display will show: mg/l 9. Press READ/ENTER when the correct unit for measure is displayed. The display will show: SYMBOL? 10. Construct the correct symbol display: ClO 2 AV a. Select letters and regular numbers by scrolling to the correct symbol with the arrow keys. b. To make letters uppercase, press the SHIFT key. c. To enter subscript numbers, enter the digit using the numeric pad. d. To enter superscript numbers, enter the digit using the numeric pad, then make it superscript by pressing SHIFT. e. The space is the character displayed after one press of the down arrow. f. Accept each symbol by pressing READ/ENTER. g. To end symbol entry, press READ/ENTER a second time after accepting the last character. 11. When the instrument is out of symbol entry mode, the display will show: TIMER? 10
12. Press SHIFT TIMER. The display will show: MM:SS TIME 1? 13. Enter a timer value of one minute. PRESS 0 1 0 0. 14. Press READ/ENTER to accept the value. The display will show: MM:SS TIME 2? 15. Press READ/ENTER to complete timer entry. The display will show: #1 DATA 16. Enter the following 12 numbers as shown. Complete each number entry by pressing the READ/ENTER key. The final number is a check value which determines if the data sequence was correctly entered. If an error was made during number entry, the display will return to the prompt for # 1 data and the entire sequence must be re-entered. If all numbers are correctly entered, the display will return to the method prompt and is ready for use. DR/2000s With Software Version 3.0 1. Turn the instrument on. After the self test, press SHIFT METHOD to enter the configuration mode. The display will show: MOMENTARY or CONSTANT ON 2. Press the up arrow key twice to select HACH UPDATE. Press READ/ENTER. The display will show: ENTER #: 3. Press: 77. The display will show: P 77 ENTER nm # 1 Data 0 # 2 Data 14908 # 3 Data 15678 # 4 Data 16450 #5 Data 16964 # 6 Data 17919 # 7 Data 65535 # 8 Data 65535 # 9 Data 65535 # 10 Data 5461 # 11 Data 512 Checksum 43183 Note: If you make an error, press SHIFT CLEAR and re-enter the number. When the number is correct, press READ/ENTER. 4. Press: 530 READ/ENTER. The display will show: P 76 Decimal? 00.00 11
5. The decimal point is correctly positioned. Press READ/ENTER. The display will show: P 77 UNITS? 6. Use the arrow keys to select the appropriate unit of measure. Press the down arrow key twice. The display will show: P 77 mg/l 7. Press READ/ENTER when the correct unit of measure is displayed. This display will show: P 77 mg/l _ 8. Construct the display to read the correct symbol. The symbol must be entered exactly as shown including single spaces preceding AV: ClO 2 AV To enter the display symbol, press the following key sequence, pressing the enter key twice after entering each number: To enter C, press 67 ENTER ENTER To enter l, press 108 ENTER ENTER To enter O, press 79 ENTER ENTER To enter 2, press 18 ENTER ENTER To enter a space, press 32 ENTER ENTER To enter A, press 65 ENTER ENTER To enter V, press 86 ENTER ENTER ENTER Alternately, scroll to each of the character using the arrow keys as follows: a. Select letters and numbers by scrolling to the correct character with the arrow keys. b. To make a letter uppercase, press the SHIFT key. c. To make the number 2 subscript, scroll to 2, then press SHIFT until the display is correct. d. The space is the character displayed after one press of the down arrow key. e. Make sure to enter the display line EXACTLY as shown, including the spaces. Do not enter trailing spaces. f. Accept each symbol by pressing READ/ENTER. g. To end symbol entry, press READ/ENTER twice after accepting the last character (press READ/ENTER a total of three times). 9. When the instrument is out of symbol entry mode, the display will read: P 77 TIMER? 10. This method has one timed step, so press SHIFT TIMER. The display will show: MM:SS TIME 1? 12
11. Enter a timer value of 1 minute. Press 0100 READ/ENTER. The display will show: MM:SS TIME 2? 12. Press READ/ENTER to complete the timer entry. The display will show: #0 STANDARD 13. Press READ/ENTER to display the zero data pair. The display will show: 0.000 Abs 00.00 mg/l 14. Press READ/ENTER. The display will show: #1 STANDARD 15. Press READ/ENTER. The display will prompt for entry of the first concentration point: #1 00.00 mg/l 16. Enter concentration point #1 from the table below by pressing 0025 so that the display shows: # 1 00.25 mg/l 17. Press READ/ENTER. The display will prompt for entry of the first absorbance point: # 1 0.000 Abs 18. Enter absorbance point #1 from the table below by pressing 0054. The display will show: # 1 0.054 Abs 19. Press READ/ENTER. The display will show the first data pair: 0.054 Abs 00.25 mg/l 20. Press READ/ENTER to accept the first data pair. The display will show: #2 STANDARD 13
21. Following steps 15-20 above, enter the remaining data pair values from the table below:. 22. When the last data point is entered, the display will show: #13 STANDARD 23. Press SHIFT READ/ENTER to complete data point entry. The display will show: #: 24. Enter the validation number 11178. The display will show: #: 11178 25. Press READ/ENTER. The display will show: COMPLETED then: P 77 mg/l ClO 2 AV Standard Concentration (mg/l) Absorbance (Abs) #0 0 0.000 #1 0.25 0.054 #2 0.50 0.107 #3 1.00 0.213 #4 1.50 0.316 #5 2.00 0.417 #6 2.50 0.517 #7 3.00 0.615 #8 3.50 0.711 #9 4.00 0.806 #10 4.50 0.899 #11 5.00 0.991 #12 5.50 1.082 If the display shows INCORRECT #, then prompts for the validation number, a mistake may have been made during data entry. Make sure the validation number is correct. If so, the error occurred during some other portion of the method entry. Press METH and respond to the ABORT? message by pressing READ/ENTER, then re-enter the method. The instrument is now ready for use with method 77. 14
SAMPLING AND STORAGE Analyze samples for chlorine dioxide immediately after collection. Chlorine dioxide is strong oxidizing agent and is unstable in natural waters. It reacts quickly with various compounds and oxidizes organic compounds more slowly. Many factors, including sunlight, ph, temperature, ClO 2 concentration, and salinity, will influence decomposition of chlorine dioxide in water. Avoid plastic containers since these may have a large chlorine dioxide demand. Pretreat glass sample containers to remove any chlorine dioxide demand by soaking in a dilute bleach solution (1 ml commercial bleach to 1 liter of deionized water) for at least 1 hour. Rinse thoroughly with deionized water. With thorough rinsing, only occasional pretreatment is necessary. A common error in testing for chlorine dioxide is obtaining a representative sample. If sampling from a tap, let the water flow for at least 5 minutes to ensure a representative sample. Let the container overflow with the sample several times, then cap the sample container so there is no headspace (air) above the sample. If sampling with a sample cell, rinse the cell several times with the sample, then carefully fill to the 10-mL mark. Proceed with the chlorine dioxide test immediately. 15
INTERFERENCES A substance interferes if it changes the final reading by 0.1 mg/l or more. Interfering Substance Acidity Alkalinity Bromine, Br 2 Chlorine, Cl 2 Chloramines, organic Flocculating agents Interference Levels and Treatments Greater than 150 mg/l CaCO 3. May not develop full color or color may fade instantly. Neutralize to ph 6 7 with 1 N sodium hydroxide. Determine amount to be added on separate sample aliquot, then add the same amount to the sample being tested. Correct for volume addition (see Section 1, Correction For Volume Additions, in the DR/2000 or DR/3000 Procedures Manual). Greater than 250 mg/l CaCO 3. May not develop full color or color may fade instantly. Neutralize to ph 6 7 with 1 N sulfuric acid. Determine amount to be added on separate sample aliquot, then add the same amount to the sample being tested. Correct for volume addition (see Section 1, Correction For Volume Additions, in the DR/2000 or DR/3000 Procedures Manual). Interferes at all levels. May interfere at levels greater than 6 mg/l. Additional glycine may be able to compensate for this interference. May interfere. High levels of most flocculating agents can be tolerated. This tolerance is decreased if chlorine is present. See the information about metals in this table. In the presence of 0.6 mg/l Cl 2, Al(SO 4 ) 3 (< 500 mg/l) and FeCl 2 (<200 mg/l) may be tolerated. Hardness No effect at less than 1,000 mg/l as CaCO 3. Iodine, I 2 Manganese, oxidized (Mn 4+, Mn 7+ ) or Chromium, oxidized (Cr 6+ ) Metals Monochloramine Ozone Peroxides Extreme sample ph Highly buffered samples Interferes at all levels. Oxidized manganese interferes at all levels. Oxidized chromium interferes at levels greater than 2 mg/l. To remove the interferences: 1. Adjust sample ph to 6 7. 2. Add 3 drops potassium iodide (30 g/l) to a 25-mL sample. 3. Mix and wait one minute. 4. Add 3 drops sodium arsenite (5 g/l) and mix. 5. Analyze 10 ml of the treated sample as described in the procedure. 6. Subtract the result of this test from the original analysis to obtain the correct chlorine dioxide concentration. Various metals may interfere by combining with the glycine needed to remove the chlorine interference. Metal interference is limited except when chlorine is present. In the presence of 0.6 mg/l Cl 2, both copper (>10 mg/l) and nickel (>50 mg/l) interfere. Other metals may also interfere, depending on their ability to prevent glycine from reacting with any Cl 2 in the sample. It may be necessary to add more glycine to overcome this interference. Causes a gradual drift to higher readings. When read within 1 minute after reagent addition, 3 mg/l monochloramine causes less than a 0.1 mg/l ClO 2 increase in the reading. Interferes at levels greater than 1.5 mg/l. May interfere. Adjust to ph 6 7. See Section 1, ph Interference, in the DR/2000 or DR/3000 Procedures Manual. Adjust to ph 6 7. See Section 1, ph Interference, Section 1, in the DR/2000 or DR/3000 Procedures Manual. 16
METHOD PERFORMANCE Precision DR/2000 Program Standard 95% Confidence Limits 76 0.24 mg/l 0.22 0.26 mg/l ClO 2 76 4.79 mg/l 4.74 4.84 mg/l ClO 2 77 0.26 mg/l 0.24 0.28 mg/l ClO 2 77 4.83 mg/l 4.77 4.89 mg/l ClO 2 Program Standard DR/3000 95 % Confidence Level 10 ml 0.24 mg/l 0.23 0.27 mg/l ClO 2 10 ml 4.79 mg/l 4.74 4.82 mg/l ClO 2 AccuVac 0.26 mg/l 0.25 0.29 mg/l ClO 2 AccuVac 4.83 mg/l 4.77 4.89 mg/l ClO 2 Estimated Detection Limit Program DR/2000 EDL DR/3000 EDL 76 0.04 mg/l ClO 2 0.04 mg/l ClO 2 77 0.04 mg/l ClO 2 0.04 mg/l ClO 2 Sensitivity For DR/2000 Program Number: 76 Portion of Curve Abs Concentration At 0.40 mg/l Cl 2 0.010 0.042 mg/l At 2.50 mg/l Cl 2 0.010 0.045 mg/l At 4.00 mg/l Cl 2 0.010 0.047 mg/l Program Number: 77 Portion of Curve Abs Concentration At 0.40 mg/l Cl 2 0.010 0.047 mg/l At 2.50 mg/l Cl 2 0.010 0.051 mg/l At 4.00 mg/l Cl 2 0.010 0.053 mg/l For DR/3000 Powder Pillow AccuVac Ampul Portion of Curve Abs Concentration Concentration Entire Range 0.010 0.044 mg/l 0.049 mg/l 17
ACCURACY CHECK Because chlorine dioxide is difficult and hazardous to produce, check the DPD and glycine reagents by using chlorine standards. Proceed as follows: 1. Prepare a 1-mg/L free chlorine standard. Method 1 a. Obtain Free Chlorine Standards, (Cat. No. 14268-10). b. Determine the concentration of the standard from the certificate of analysis shipped with the standard (50-75 mg/l). Calculate the volume of standard needed as follows: ml standard needed = 100 standard concentration c. Pipet the volume of standard needed into a 100-mL volumetric flask. Dilute to the line with chlorine demand-free deionized water. Invert to mix. Method 2 Dilute 1 drop of 5% chlorine bleach in 1 liter of chlorine-demand-free deionized water. Use this as the standard. 2. Verify the standard s concentration using the Hach Free Chlorine Method, #8021. 3. Perform the chlorine dioxide test on the standard without adding glycine (step 8). 4. The chlorine dioxide reading should be about 2.3 times greater than the chlorine result. If so, this verifies the DPD and the instrument are functioning properly. Repeat the chlorine dioxide test on the chlorine standard, including the glycine addition (step 8). The reading should be less than 0.10 mg/l. This verifies that the glycine is eliminating free chlorine interference. SUMMARY OF METHOD Chlorine dioxide reacts with DPD (N, N-diethyl-p-phenylenediamine) Indicator Reagent (to the extent of one-fifth of its total available chlorine content corresponding to reduction of chlorine dioxide to chlorite) to form a pink color. The color intensity is proportional to the ClO 2 in the sample. Chlorine interference is eliminated by adding glycine, which converts free chlorine to chloroaminoacetic acid, but has no effect on chlorine dioxide at the test ph. 18
REQUIRED REAGENTS AND STANDARDS (Using Powder Pillows) Chlorine Dioxide DPD/Glycine Reagent Set (100 tests)...27709-00 Includes: (1) 21055-69, (1) 27621-33 Quantity Required Description per test Unit Cat. No. DPD Free Chlorine Reagent Powder Pillows, 10 ml... 1 pillow... 100/pkg...21055-69 Glycine Reagent...4 drops...29 ml...27621-33 REQUIRED REAGENTS AND STANDARDS (Using AccuVac Ampuls) Chlorine Dioxide DPD/Glycine AccuVac Ampul Reagent Set (25 tests)...27710-00 Includes: (1) 25020-25, (1) 27621-33 DPD Free Chlorine Reagent AccuVac Ampuls... 1 ampul... 25/pkg...25020-25 Glycine Reagent...16 drops...29 ml...27621-33 REQUIRED EQUIPMENT AND SUPPLIES (Using Powder Pillows) Cells, sample, 10 ml, matched pair...1... 2...24954-02 Cell Riser, 10 ml sample cell, DR/2000...1... each...45282-00 Cell Riser, 10 ml sample cell, DR/3000...1... each...48403-00 Stopper, hollow...2... 6/pkg...14480-00 REQUIRED EQUIPMENT AND SUPPLIES (Using AccuVac Ampuls) Beaker, 50 ml...1... each...500-41 DR/2000/3000 AccuVac Ampul Adapter...1... each...43784-00 Sample Cell, 10-mL with cap (zeroing vial)...1... each...21228-00 OPTIONAL REAGENTS AND STANDARDS Chlorine Standard Solution, 10-mL Voluette Ampule, 50 75 mg/l... 16/pkg...14268-10 DPD Free Chlorine Reagent, with dispensing caps... 250 tests...21055-29 Potassium Iodide Solution, 30 g/l...100 ml* MDB...343-32 Sodium Arsenite Solution, 5 g/l...100 ml* MDB...1047-32 Sodium Hydroxide Standard Solution, 1.00 N...100 ml* MDB...1045-32 Sulfuric Acid Standard Solution, 1.000 N...100 ml* MDB...1270-32 Water, deionized...4 liters...272-56 Water, sterile, chlorine dioxide demand-free...500 ml...26415-49 OPTIONAL EQUIPMENT AND SUPPLIES AccuVac Ampule snapper Kit... each...24052-00 Cylinder, graduated, 25 ml... each...508-40 ph meter, sension 1, portable... 1...51700-10 ph Paper, 1 to 11 ph units... 5 rolls/pkg...391-33 Pipet, TenSette, 0.1 to 1.0 ml... each...19700-01 Pipet Tips, for 19700-01 TenSette Pipet... 50/pkg...21856-96 * Contact Hach for larger sizes. 19
Hach Company, 1999. All rights reserved. Printed in the U.S.A. 8225 hm/dh 5/99 1 ed ap/dh 8/99 rev1