RAPID LIQUID TESTING. Hach Company, 1996 All rights reserved. Printed in the U.S.A dld/dp ed

Transcription

1 RAPID LIQUID TESTING Hach Company, 1996 All rights reserved. Printed in the U.S.A dld/dp ed

2 TABLE OF CONTENTS OPERATION...1 INTRODUCTION...3 Rapid Liquid Testing...3 Rapid Liquid Reagents...3 Use of Repipet Jr. Dispensers...3 Repipet Calibration...4 Changing Reagent Bottles...5 Use of the Pour-Thru Cell...6 Analytical Techniques for Low-level Analysis...7 PROCEDURES...9 Chlorine, Free...11 Chlorine, Total...25 Hardness, Total, Ultra Low Range...33 Iron...43 Nitrite, Low Range...51 Phosphorus, Reactive, Low Range...65 Phosphorus, Reactive, High Range...85 Silica, Ultra Low Range...93 GENERAL INFORMATION HOW TO ORDER REPAIR SERVICE ADDITIONAL INFORMATION iii

3 OPERATION WARNING Handling chemical samples, standards, and reagents can be dangerous. Review the necessary Material Safety Data Sheets and become familiar with all safety procedures before handling any chemicals. ADVERTÊNCIA A manipulação de amostras, padrões e reagentes químicos pode ser perigosa. Reveja as necessárias Fichas Técnicas de Segurança do Material e familiarizese com os procedimentos de segurança antes de manipular quaisquer substãncias químicas. ADVERTENCIA La manipulación de muestras químicas, patrones y reactivos puede ser peligrosa. Antes de manipular cualquier productor químico, conviene leer las Fichas Técnicas de Seguridad y familiarizarse con los procedimientos de sugeridad. ATTENTION La manipulation des échantillons chimiques, étalons et réactifs peut être dangereuse. Lire les fiches de données de sécurité des produits nécessaires et se familiariser avec toutes les procédures de sécurité avant de manipuler tout produit chimique. WARNUNG Da das Arbeiten mit chemikalischen Proben, Standards, Reagenzien und Abfällen mit Gefahren verbunden ist, empfiehlt die Hach Company dem Benutzer dieser Produkte dringend, sich vor der Arbeit mit sicheren Verfahrensweisen und dem richtigen Gebrauch der Chemikalien oder Biogefahrgut vertraut zu machen und alle entsprechenden Materialsicherheitsdatenblätter aufmerksam zu lesen. 1

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5 SECTION 1 INTRODUCTION 1.1 Rapid Liquid Testing Rapid Liquid Testing provides a fast, economical way to analyze multiple water samples. The use of liquid reagents, a convenient dispenser, and a Pour-Thru Cell allow for quick reagent addition and mixing with minimal sample handling. 1.2 Rapid Liquid Reagents Liquid reagents are used with the Rapid Liquid Testing method to allow for fast reagent addition and mixing. However, some reagents are less stable in liquid form than they are in solid (powder) form. To ensure that these less-stable reagents will perform well, Hach has packaged them in two forms powder and liquid which must be mixed together before use. Once the reagent is prepared, it must be used within the period of time noted in each procedure; typically one month. The date of preparation should always be recorded on the reagent bottle so the age of the reagent can be determined. Reagents left unused for longer than the time specified should be discarded and should not be added to freshly prepared reagent. See the corresponding Material Safety Data Sheet (MSDS) or current Federal, State, and local regulations for disposal information. If the quality of a prepared reagent is in question, an accuracy check (as specified in the procedures) can be performed using a standard that is near the upper end of the range for the analysis. The test should give a result that is within 10% of the value of the standard. Some of the reagents used in Rapid Liquid analysis may have labels suggesting they are to be used with a process analyzer. This is because many of the Rapid Liquid methods have been adapted from those of Hach process analyzers. The reagents are intended for Rapid Liquid Analysis as well as for process analyzers. 1.3 Use of Repipet Jr. Dispensers Repipet dispensers can be directly attached to Hach reagent bottles for quick addition of reagent to samples. They must be assembled before initial use. The inlet tubing must be cut to fit properly on the reagent bottle, and the dispenser must be primed before initial use to minimize air bubbles in the dispenser. See the instruction and parts list provided with the Repipet dispenser for more information. 3

6 1.3.1 Repipet Calibration Take care to avoid contamination of the reagent when placing Repipet dispensers on the bottles. Rinse the inlet tubing and inside of the dispenser cap with copious amounts of demineralized water using a wash bottle. Place the inlet tubing into a beaker of demineralized water and depress the plunger times to rinse the inside of the dispenser. (For sensitive analysis in the low µg/l range, pour a small amount of reagent into the beaker of rinse water.) Remove the dispenser from the water and depress the plunger until all of the rinse water has been expelled. Shake off any excess water on the dispenser, place the dispenser on the reagent bottle, and tighten. Calibration of Repipet Dispensers before initial use is recommended for greatest accuracy. Calibrate Repipet dispensers using demineralized water. Each 1 ml dispensation should weigh 1.00 gram. Repeated weighing of water dispensations and adjustments of the Repipet are accomplished as follows: 1. Pre-weigh a small container using a top-loading balance. 2. Place the inlet tube of an assembled Repipet dispenser in a beaker of water at room temperature and repeatedly depress the plunger until no large air bubbles remain in the plunger barrel. (Small air bubbles remaining should not affect the accuracy of the dispenser.) 3. Dispense the water repeatedly into the weighed container noting the weight of each dispensation. Each dispensation should weigh 1.00 gram. 4. If the dispensation is more or less than one gram, adjust the volume on the Repipet as follows: a) Loosen the cap of the Repipet until the metal calibration lock ring moves back and forth. b) Move the ring toward the negative (-) side to decrease the amount of water dispensed or to the positive (+) side to increase the amount. Retighten the cap. Each 10 µl adjustment should change the weight dispensed by 0.01 grams. Example: If the amount of water initially dispensed was 0.98 grams, move the metal ring to the positive (+) side to approximately 20 µl and retighten. Depress the plunger 4

7 repeatedly until several dispensations weigh 1.00 gram each. Repeat the adjustment if the weight is not 1.00 gram. Note: Adjust the above procedure accordingly for dispenser volumes other than 1 ml. Remove the cap from the reagent bottle. Screw the Repipet dispenser on the reagent bottle until tight, making sure the screw cap adapter inside the dispenser cap fits the reagent bottle. Depress the plunger until large air bubbles are purged from the tubing (at least 4-5 times). Record the weight of one dispensation of reagent as in the calibration procedure above; use this weight to periodically check the calibration of the Repipet. Over time the dispenser may give inconsistent or inaccurate results. This may indicate that inlet or outlet valves need to be replaced. See the instructions and the parts list provided with the Repipet dispenser for further information. Place the outlet tip closure provided with the dispenser over the outlet tip of the Repipet when not in use. If the Repipet dispenser has been allowed to sit for several hours without use, depress the plunger 3 to 4 times to purge any large air bubbles. Use of a TenSette pipet is appropriate for reagent addition with some Hach procedures but is not recommended for Rapid Liquid Testing due to potential contamination of reagent bottles. See section 1.6 Analytical Techniques for Low-level Analysis on page 7 for more information. 1.4 Changing Reagent Bottles When the reagent is depleted, remove the dispenser from the reagent bottle. Rinse the dispenser by placing the inlet tube in a beaker of demineralized water and depressing the plunger 4-5 times. Rinse the outside of the inlet tubing with demineralized water. Empty the dispenser by repeatedly depressing the plunger. Place the dispenser on a fresh reagent bottle and tighten. Depress the plunger repeatedly until no large air bubbles remain in the plunger barrel. Discard any unused reagent from the previous bottle. Do not transfer leftover reagent from a used bottle to a fresh one. 5

8 Over time the dispenser may give inconsistent or inaccurate results. This may indicate that inlet or outlet valves need to be replaced. See the instructions and the parts list provided with the Repipet dispenser for further information. Place the outlet tip closure provided with the dispenser over the outlet tip of the Repipet when not in use. If the Repipet dispenser has been allowed to sit for several hours without use, depress the plunger 3 to 4 times to purge any large air bubbles. Use of a TenSette pipet is appropriate for reagent addition with some Hach procedures but is not recommended for Rapid Liquid Testing due to potential contamination of reagent bottles. 1.5 Use of the Pour-Thru Cell Samples for any one analysis method can typically be poured into the Pour-Thru Cell in succession without rinsing the cell. However, it is advisable to rinse the Pour-Thru Cell when going from a concentrated to a dilute sample and when the next sample is not yet ready for analysis. When switching from one analysis method to another, it is important to prevent contamination in the next analysis. For example, if a Total Chlorine analysis is followed by a Free Chlorine analysis, any remaining reagent left in the Pour-Thru Cell from the Total Chlorine analysis can interfere with the Free Chlorine analysis. To prevent contamination when changing from one analysis to another, rinse the Pour-Thru Cell thoroughly. First rinse the funnel of the Pour-Thru Cell with demineralized water using a wash bottle, then pour at least 50 ml of demineralized water into the funnel. A reagent rinse of the Pour-Thru Cell with a dilute solution of the reagent to be used in the next analysis will further reduce the possibility of contamination. If reagents have been allowed to sit in the Pour-Thru Cell for long periods of time, a build-up of colored products may develop. This build-up can be removed by rinsing with either acid or base; most procedures specify which to use. When not in use, place a small beaker over the glass funnel of the Pour-Thru Cell. For additional information on using the Pour-Thru Cell, refer to 6

9 the DR/2000 or DR/3000 instrument manual. 1.6 Analytical Techniques for Low-level Analysis Many of the analyses available with Rapid Liquid Testing allow for the detection of very low levels of analytes. When measuring low analyte concentrations, it is very important to control contamination throughout the analysis. Keeping containers such as screw-cap flasks closed when not in use, covering the Pour- Thru Cell when not in use, and rinsing and inverting graduate cylinders immediately after use will minimize contamination from outside sources. Keeping labware clean is extremely important in low-level analysis. Initial cleaning of labware should include a reagent rinse, where a dilute solution of the reagent to be used is added to the labware to react with any analyte not removed by normal cleaning. If the labware is not used for other analyses, only occasional reagent rinses are necessary. Dedicating labware for use on only one test method reduces the possibility that reagents from one analysis will contaminate another. For instance, the reagents used in the Total Chlorine test will interfere with the Free Chlorine test. All measurements in low-level analysis should be made with care. This is especially true when preparing standards for accuracy checks. Use only Class A labware and high quality demineralized water. To control reagent contamination, avoid placing anything (such as a pipet) into a reagent bottle. (Repipet dispensers will not contaminate reagent bottles if they are thoroughly cleaned before being attached to the bottles. See the section titled Use of the Repipet Jr. Dispenser for cleaning instructions.) If reagent must be taken from a bottle without using the Repipet dispenser, pour a small amount into another container and pipet from that container. Do not return any solution to the original reagent bottle. 7

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11 PROCEDURES Handling chemical samples, standards, and reagents can be dangerous. Review the necessary Material Safety Data Sheets and become familiar with all safety procedures before handling any chemicals. 9

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13 CHLORINE, FREE (0 to 2.00 mg/l) DPD Rapid Liquid Method* For DR/2000 and DR/3000 Instruments Method For treated water 530 nm 1. Enter the stored program number for free and total chlorine (Cl 2 ). Press: 8 2 READ/ENTER The display will show: DIAL nm to 530 Note: DR/2000s with software versions 3.0 and greater will display P and the program number. Note: Instruments with software versions 3.0 and greater will not display the DIAL nm to message if the wavelength is already set correctly. The display will show the message in Step 3. Proceed with Step 4. Note: Samples must be analyzed immediately and cannot be preserved for later analysis. Note: For instruments that do not have this stored program, refer to Instrument Setup following these steps. Note: For DR/3000s: Press: Manual Program Press Conc Factor 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 Cl 2 RL Note: For DR/3000s: Press: 10 Signal Average Press: Zero Press: 2 Conc 4. Install the Pour-Thru Cell and flush with 50 ml of demineralized water. Note: Clean the Pour-Thru Cell and all labware as specified under Analysis Labware. Note: The windows of the Pour-Thru Cell should face side-to-side in the DR/2000 and front-to-back in the DR/3000. * Adapted from Standard Methods for the Examination of Water and Wastewater 11

14 CHLORINE, FREE, continued 5. Pour approximately 50 ml of sample into the Pour-Thru Cell. 6. When the flow has stopped, press: ZERO The display will show: WAIT then: 0.00 mg/l Cl 2 RL Note: For the DR/3000: Press: Zero Conc 7. Add 1.0 ml of Free Chlorine Buffer Solution to a clean, dry 100-mL glass mixing cylinder using the Repipet dispenser. 8. Add 1.0 ml of prepared Free Chlorine Indicator Solution to the same mixing cylinder. Swirl to mix the reagents. Proceed to step 9 immediately. Note: See Reagent Preparation for instructions on preparing the indicator solution. 12

15 CHLORINE, FREE, continued 9. Carefully fill the mixing cylinder to the 80- ml mark with sample. Stopper the cylinder and gently invert it twice to mix. Proceed to step 10 immediately. 10. Fill the funnel of the Pour-Thru Cell with the reacted sample from the mixing cylinder. Note: It is not necessary to pour the entire sample into the Pour-Thru Cell; approximately half of the sample may be discarded. 11.After the flow has stopped, press: READ/ENTER The display will show: WAIT then the result in mg/l chlorine (Cl 2 ) will be displayed. Note: If the display flashes 2.20, dilute a fresh sample and repeat the test. A slight loss of chlorine may occur during the dilution. Multiply the result by the appropriate dilution factor; see Sample Dilution Techniques in Section I of the DR/2000 or DR/3000 Procedures manual. Note: In the constant-on mode, pressing READ/ ENTER is not required. WAIT will not appear. When the display stabilizes, read the result. 12.Flush the Pour-Thru Cell with at least 50 ml of demineralized water immediately after use. Note: Protect the Pour-Thru Cell from contamination by inverting a small beaker over the top of the glass funnel when not in use. Sampling and Storage Samples must be analyzed immediately and cannot be preserved for later analysis. A common testing error is introduced if the analyst does not obtain a representative sample. If sampling from a tap, let the water flow for at least five 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. Perform the chlorine analysis immediately. 13

16 CHLORINE, FREE, continued Avoid plastic containers since these may have a chlorine demand. Pre-treat glass sample containers to remove any chlorine demand by soaking in a dilute bleach solution (1 ml commercial bleach to l liter of demineralized water) for at least 1 hour. Rinse thoroughly with demineralized water. If sample containers are rinsed thoroughly with demineralized water after use, only occasional pretreatment is necessary. A pretreated BOD bottle with a ground-glass stopper makes an ideal sample container for chlorine analysis. Analysis Labware Glassware used in this test must be chlorine demand-free. Fill the 100 ml mixing cylinder and sample container with a dilute solution of chlorine bleach prepared by adding 1 ml of commercial bleach to 1 liter of water. Soak in this solution at least one hour. After soaking, rinse with copious amounts of demineralized water and allow to dry before use. If the mixing cylinder is thoroughly rinsed with demineralized water and allowed to dry after each use, only occasional pretreatment is necessary. Do not use the same mixing cylinder for Free and Total Chlorine analysis. Treat the Pour-Thru Cell similarly with dilute bleach and let stand for several minutes. Rinse several times with demineralized water. Cleaning the Pour-thru Cell The Pour-Thru Cell may accumulate a buildup of colored reaction products, especially if the reacted solutions are allowed to remain in the cell for long periods after measurement. Remove the buildup by rinsing the cell with 5.25 N Sulfuric Acid followed by several rinsings with demineralized water. Reagent Preparation The Free Chlorine Indicator Solution must be prepared before use. Using a powder funnel, add the contents of one 24 g bottle of DPD Powder (Cat. No ) to one 473-mL bottle of Free Chlorine Indicator Solution (Cat. No ). Invert several times and swirl until the powder is completely dissolved. A pink color may develop, but should not affect results. This solution will give accurate results for at least one month after mixing when stored at C (68-77 C). Write the date of preparation on the Indicator Solution Bottle. Discard any remaining 14

17 CHLORINE, FREE, continued solution after one month. Use of this reagent after one month may result in high reagent blanks and low values at high concentration. Do not combine fresh reagent with previously mixed reagent. Accuracy Check Standard Additions Method a) Snap the top off a Chlorine Voluette Ampule Standard Solution, 50 to 75 mg/l Cl 2. b) Use the TenSette Pipet to add 0.3, 0.6 and 0.9 ml of standard to three 80-mL samples, respectively. Swirl gently to mix. c) Analyze each sample as described above. Each 0.3 ml of standard will cause an incremental increase in chlorine, the exact value of which depends on the concentration in the ampule. Check the certificate enclosed with the ampules for this value. d) Calculate the concentration of chlorine added to each sample as follows: ml of standard addition ml of standard addition + ml of sample chlorine concentration in ampule = concentration of chlorine added to the sample Example: ml 72.3 mg/l= 0.27 mg/l chlorine added to the sample 80.3 ml e) If the concentration of each sample does not increase by the calculated amount, refer to Standard Additions in Section I of the DR/2000 or DR/3000 Procedures Manual for more information. Precision DR/2000: In a single laboratory using 8 concentrations of chlorine standards and two lots of reagents with a DR/2000, a single operator obtained a calibration curve that showed a 99% confidence interval at 1.00 mg/l of ±0.004 mg/l chlorine. DR/3000: In a single laboratory using 8 concentrations of chlorine standards and two lots of reagents with a DR/3000, a single operator obtained a calibration curve that showed a 99% confidence interval at 1.00 mg/l of ±0.004 mg/l chlorine. 15

18 CHLORINE, FREE, continued Interferences Samples containing more than 400 mg/l alkalinity may not develop the full amount of color, or it may instantly fade. Neutralize these samples to a ph of 6 to 7 with 1 N Sulfuric Acid. Determine the amount required on a separate 80-mL sample, then add the same amount to the sample to be tested. Samples containing monochloramine will cause a gradual drift to higher chlorine readings. When read within one minute of reagent addition, 3.0 mg/l monochloramine will cause an increase of less than 0.1 mg/l in the free chlorine reading. Note: If sodium arsenite is used, collect the spent sample for proper disposal according to the hazardous waste regulations for arsenic. Refer to the DR/2000 or DR/3000 Instrument Manual for information on modifying the Pour-Thru Cell for collecting the sample after analysis. Bromine, iodine, ozone and oxidized forms of manganese also may react and show as chlorine. Hexavalent chromium at levels >1 mg/l will cause a positive interference. To compensate for the effects of manganese (Mn 4+ ) or chromium (Cr 6+ ), adjust ph to 6 to 7 as described above, then add 9 drops of potassium iodide, 30 g/l, to 80 ml of sample, mix and wait 1 minute. Add 9 drops of sodium arsenite, 5 g/l, and mix. Analyze this sample as described above. (If chromium is present, allow exactly the same reaction period with the DPD for both analyses.) Subtract the result of this test from the original analysis to obtain the accurate chlorine result. Hardness at levels below 1000 mg/l as CaCO 3 will not interfere. Summary of Method Chlorine in the sample as hypochlorous acid or hypochlorite ion (free chlorine or free available chlorine) immediately reacts with DPD (N,N-diethyl-p-phenylenediamine) indicator to form a red color which is proportional to the chlorine concentration. 16

19 CHLORINE, FREE, continued REQUIRED REAGENTS Description Cat. No. DPD Indicator Powder, 24 g Free Chlorine Indicator Solution, 473 ml Free Chlorine Buffer Solution, 473 ml REQUIRED APPARATUS Cylinder, mixing, glass, 100 ml, each Dispenser, fixed volume, 1.0 ml Repipet Jr., each (two required) Pour-Thru Cell Assembly Kit, DR/2000, each Pour-Thru Cell Assembly Kit, DR/3000, each OPTIONAL REAGENTS Chlorine Standard Solution, Voluette Ampule, mg/l, 10 ml, 16/pkg Chlorine Standard Solution, Voluette Ampule, mg/l, 2 ml, 20/pkg Potassium Iodide Solution, 30 g/l, 100 ml* MDB Sodium Arsenite, 5 g/l, 100 ml* MDB Sodium Hydroxide Standard Solution, N, 100 ml* MDB Sulfuric Acid Standard Solution, N, 100 ml* MDB Sulfuric Acid Standard Solution, 5.25 N, 1 L Water, demineralized, 4 L OPTIONAL APPARATUS Ampule Breaker Kit, each Beaker, poly, 50 ml Bottle, wash, 125 ml, each Bottle, BOD, w/stopper, 300 ml Funnel, powder, each ph Meter, EC10, portable, each Pipet, TenSette, 0.1 to 1.0 ml, each Pipet Tips, for TenSette Pipet, 50/pkg * Contact Hach for larger sizes. 17

20 CHLORINE, FREE, continued INSTRUMENT SETUP When this instrument setup has been entered into the instrument, the user may perform either the Free or Total Chlorine procedure. The timed step is entered for the total chlorine procedure and does not affect the function of the free chlorine procedure. DR/2000 with and 1.27 software Enter the calibration as an operator-programmed calibration. Follow the steps in the Operation section of the DR/2000 Instrument Manual. Store the method as follows: nm = 530 Decimal = Units = mg/l Symbol = Cl 2 RL Timer 1 = 1:00 Enter the calibration with absorbance values for zero and #1 standard. With the sample cell compartment empty, begin by storing standards 0 and 1 as the concentrations shown in the table below. Accept Abs as the absorbance value for all standards. Store the calibration values by pressing SHIFT READ/ENTER. Next, edit the absorbance values for the standards to the values given below. Follow the steps given in the Operations section of the DR/2000 Instrument Manual. The method is now stored as an operator-programmed method number between 950 and 999. Record the method number for future reference. DR/2000 with Software Versions 2.0 and 2.2 Enter the calibration as an update to Hach stored programs. 1. Press: Std. Conc Abs # #

21 CHLORINE, FREE, continued 2. Press: 3. Press: 4. Within 3 seconds, press: The display will show: ENTER nm 5. Press: Press READ/ENTER. If you make an error, press SHIFT CLEAR and re-enter the number. When the number is correct, press READ/ENTER. The display will show: DECIMAL? The decimal point 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 of measure is displayed. The display will show: SYMBOL? 19

22 CHLORINE, FREE, continued 10. Construct the correct symbol display: Cl 2 RL a) Select letters and regular numbers by scrolling to the correct symbol with the ARROW keys. b) To make a letter uppercase, press the SHIFT key. c) To enter subscript numbers, enter the digit on the numeric keypad. d) To enter superscript numbers, enter the digit on the numeric keypad number then make it a 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. The method for Total Chlorine has one timed step, so press SHIFT TIMER. The display will show: MM:SS TIME 1? 13. Enter a timer value of 1 minute. Press: 14. Press READ/ENTER to accept the timer value. The display will show: MM:SS TIME 2? 15. Press READ/ENTER to complete the timer entry. The display will show: #1 Data 20

23 CHLORINE, FREE, continued 16. Enter the following 12 numbers as shown. Complete each number entry by pressing the READ/ENTER key. # 1 Data 0 # 2 Data 6167 # 3 Data 6167 # 4 Data 6168 # 5 Data 5912 # 6 Data 5912 # 7 Data # 8 Data # 9 Data #10 Data #11 Data 512 Checksum 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 data # 1 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/2000 with Software Version 3.0 and Above 1. Turn the instrument on. Press SHIFT METHOD to enter 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: The display will show: P 82 ENTER nm 4. Press: The display will show: P 82 DECIMAL?

24 CHLORINE, FREE, continued Note: If you make an error, press SHIFT CLEAR and re-enter the number. When the number is correct, press READ/ENTER. 5. The decimal point is correctly positioned. Press READ/ENTER. The display will show: P 82 UNITS? 6. Use the ARROW keys to select the appropriate unit of measure. Press the DOWN ARROW key twice. The display will show: P 82 mg/l 7. Press READ/ENTER when the correct unit of measure is displayed. The display will show: P 82 mg/l _ 8. Construct the display to read the correct symbol. The symbol must be entered exactly as shown including dashes and spaces between characters: Cl 2 RL 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) Make a number or sign superscript, subscript or regular by pressing SHIFT until the symbol is correct. The 2 in the symbol must be shifted to subscript. d) The space is the character displayed after one press of the down arrow. e) Make sure to enter the display line EXACTLY as shown, including all spaces. Do not enter trailing spaces. f) Accept each symbol by pressing READ/ENTER. g) When the last character of the symbol is accepted with the READ/ENTER key, press READ/ENTER a second time to end display entry mode. 9. When the instrument is out of symbol entry mode, the display will show: P82 TIMER 10. This method has one timed step, so press SHIFT TIMER. The display will show: MM:SS TIME 1? 22

25 CHLORINE, FREE, continued 11. Enter a timer value of 1 minute. Press: 12. Press READ/ENTER to accept the timer value. The display will show: MM:SS TIME 2? 13. Press READ/ENTER to complete the timer entry. The display will show: #0 STANDARD 14. Press READ/ENTER to display the zero data pair. The display will show: Abs mg/l Press READ/ENTER. The display will show: # 1 STANDARD 15. Press READ/ENTER. The display will prompt for entry of the first concentration point: # mg/l 16. Enter concentration point #1 from the table below by pressing so that the display shows: # mg/l 17. Press READ/ENTER. The display will prompt for entry of the first absorbance point: # Abs 18. Enter absorbance point #1 from the table below by pressing so that the display shows: # Abs 19. Press READ/ENTER. The display will show the first data pair: Abs mg/l 20. Press READ/ENTER to accept the first data pair. The display will show: # 2 STANDARD 23

26 CHLORINE, FREE, continued 21. The data pair values from the table below are now entered. Standard Concentration Absorbance # 0 [ 0.00] mg/l [0.000] Abs # 1 [ 2.20] mg/l [1.166] Abs 22. When the last point pair is entered, the display will show: # 2 STANDARD 23. Press SHIFT READ/ENTER to complete data point entry The display will show: #: 24. Enter the validation number: so that the display shows: #: Press READ/ENTER. The display will show: COMPLETED then: P82 mg/l Cl 2 RL If the display shows: INCORRECT # then prompts again for the validation number, you may have made an error during data entry. Make sure that the validation number is correct. If so then the error occurred during some other portion of the method entry. You must 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

27 CHLORINE, TOTAL (0 to 2.00 mg/l) DPD Rapid Liquid Method * For DR/2000 and DR/3000 Instruments Method For treated water 530 nm 1. Enter the stored program number for free and total chlorine (Cl 2 ). Press: 8 2 READ/ENTER The display will show: DIAL nm TO 530 Note: DR/2000s with software versions 3.0 and greater will display P and the program number. Note: Instruments with software versions 3.0 and greater will not display DIAL nm TO message if the wavelength is already set correctly. The display will show the message in Step 3. Proceed with Step 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 Cl 2 RL Note: For DR/3000s: Press: 10 Signal Average Press: Zero Press: 2 Conc 4. Install the Pour-Thru Cell and flush with 50 ml of demineralized water. Note: Clean the Pour-Thru Cell and all labware as specified under Analysis Labware. Note: The windows of the Pour-Thru Cell should face side-to-side in the DR/2000 and front-to-back in the DR/3000. Note: Samples must be analyzed immediately and cannot be preserved for later analysis. Note: For instruments that do not have this stored program, refer to the Free Chlorine Instrument Setup on page 18. Note: For DR/3000s: Press: Manual Program Press Conc Factor * Adapted from Standard Methods for the Examination of Water and Wastewater 25

28 CHLORINE, TOTAL, continued 5. Pour approximately 50 ml of sample into the Pour-Thru Cell. 6. When the flow has stopped, press: ZERO The display will show: WAIT then: 0.00 mg/l Cl 2 RL Note: For the DR/3000: Press: Zero Conc 7. Add 1.0 ml of Total Chlorine Buffer Solution to a clean, dry glass 100- ml mixing cylinder using the Repipet dispenser. 8. Add 1.0 ml of prepared Total Chlorine Indicator Solution to the same mixing cylinder. Swirl to mix the reagents. Proceed to step 9 immediately. Note: See Reagent Preparation for instructions on preparing the indicator solution. 26

29 CHLORINE, TOTAL, continued 9. Carefully fill the mixing cylinder to the 80-mL mark with sample. Stopper the cylinder and gently invert it twice to mix. 10.Press: SHIFT TIMER A one-minute reaction time will begin. Note: For the DR/3000, press: 1 Timer 11.When the timer beeps, fill the funnel of the Pour-Thru Cell with the reacted sample from the mixing cylinder. Note: It is not necessary to pour the entire sample into the Pour-Thru Cell; approximately half of the sample can be discarded. 12.After the flow has stopped, press: READ/ENTER The display will show: WAIT then the result in mg/l chlorine (Cl 2 ) will be displayed. Note: For the DR/3000: Press: Conc Note: Complete this step within two minutes after the timer beeps. Note: If the display flashes 2.20, or shows OVER- RANGE, dilute a fresh sample and repeat the test. A slight loss of chlorine may occur during the dilution. Multiply the result by the appropriate dilution factor; see Sample Dilution Techniques in Section I of the DR/2000 or DR/3000 Procedures Manual. Note: In the constant-on mode, pressing READ/ ENTER is not required. WAIT will not appear. When the display stabilizes, read the result. 27

30 CHLORINE, TOTAL, continued 13.Flush the Pour-Thru Cell with at least 50 ml of demineralized water immediately after use. Note: Protect the Pour- Thru Cell from contamination by inverting a small beaker over the top of the glass funnel when not in use. Sampling and Storage Samples must be analyzed immediately and cannot be preserved for later analysis. A common testing error is introduced if the analyst does not obtain a representative sample. If sampling from a tap, let the water flow for at least five 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. Perform the chlorine analysis immediately. Avoid plastic containers since these may have a chlorine demand. Pre-treat glass sample containers to remove any chlorine demand by soaking in a dilute bleach solution (1 ml commercial bleach to l liter of demineralized water) for at least 1 hour. Rinse thoroughly with demineralized water. If sample containers are rinsed thoroughly with demineralized water after use, only occasional pretreatment is necessary. A pre-treated BOD bottle with a ground-glass stopper makes an ideal sample container for chlorine analysis. 28

31 CHLORINE, TOTAL, continued Analysis Labware Glassware used in this test must be chlorine demand-free. Fill the 100 ml mixing cylinder and sample container with a dilute solution of chlorine bleach prepared by adding 1 ml of commercial bleach to 1 liter of water. Soak in this solution at least one hour. After soaking, rinse with copious amounts of demineralized water and allow to dry before use. If the mixing cylinder is rinsed thoroughly with demineralized water and allowed to dry after use, only occasional pretreatment is necessary. Do not use the same mixing cylinder for Free and Total Chlorine analysis. Treat the Pour-Thru Cell similarly with dilute bleach and let stand for several minutes. Rinse several times with demineralized water. Cleaning the Pour-thru Cell The Pour-Thru Cell may accumulate a buildup of colored reaction products, especially if the reacted solutions are allowed to remain in the cell for long periods after measurement. Remove the buildup by rinsing the cell with 5.25 N sulfuric acid followed by several rinsings with demineralized water. Reagent Preparation The Total Chlorine Indicator Solution must be prepared before use. Using a powder funnel, add the contents of one 24 g bottle of DPD Powder (Cat. No ) to one 473-mL bottle of Total Chlorine Indicator Solution (Cat. No ). Invert several times and swirl until the powder is completely dissolved. A pink color may develop, but should not affect results. This solution will give accurate results for at least one month after mixing when stored at C (68-77 C). Write the date of preparation on the Indicator Solution Bottle. Discard any remaining solution after one month. Use of this reagent after one month may result in high reagent blanks and low values at high concentration. Do not combine fresh reagent with previously mixed reagent. 29

32 CHLORINE, TOTAL, continued Accuracy Check Standard Additions Method a) Snap the top off a Chlorine Voluette Ampule Standard Solution, mg/l Cl 2. b) Use the TenSette Pipet to add 0.3, 0.6 and 0.9 ml of standard to three 80-mL samples, respectively. Swirl gently to mix. c) Analyze each sample as described above. Each 0.3 ml of standard will cause an incremental increase in chlorine, the exact value of which depends on the concentration in the ampule. Check the certificate enclosed with the ampules for this value. d) Calculate the concentration of chlorine added to each sample as follows: ml of standard addition ml of standard addition + ml of sample chlorine concentration in ampule = concentration of chlorine added to the sample Example: 0.3 ml mg/l= 0.27 mg/l chlorine added to the sample 80.3 ml e) If the concentration of each sample does not increase by the calculated amount, refer to Standard Additions in Section I of the DR/2000 or DR/3000 Procedures Manual for more information. Precision DR/2000: In a single laboratory using 9 concentrations of chlorine standards and two lots of reagents with a DR/2000, a single operator obtained a calibration curve that showed a 99% confidence interval at 1.00 mg/l of ±0.005 mg/l chlorine. DR/3000: In a single laboratory using 9 concentrations of chlorine standards and two lots of reagents with a DR/3000, a single operator obtained a calibration curve that showed a 99% confidence interval at 1.00 mg/l of ±0.005 mg/l chlorine. 30

33 CHLORINE, TOTAL, continued Interferences Note: If sodium arsenite is used, collect the spent sample for proper disposal according to the hazardous waste regulations for arsenic. Refer to the DR/2000 Instrument Manual for information on modifying the Pour-Thru Cell for collecting samples after analysis. Samples containing more than 700 mg/l alkalinity may not develop the full amount of color, or it may instantly fade. Neutralize these samples to a ph of 6 to 7 with 1 N sulfuric acid. Determine the amount required on a separate 80-mL sample; then add the same amount to the sample to be tested. Bromine, iodine, ozone and oxidized forms of manganese also may react and show as chlorine. Hexavalent chromium a levels >1 mg/l will cause a positive interference. To compensate for the effects of manganese (Mn 4+ ) or chromium (Cr 6+ ), adjust ph to 6 to 7 as described above, then add 9 drops of potassium iodide, 30 g/l, to 80 ml of sample, mix and wait 1 minute. Add 9 drops of sodium arsenite, 5 g/l, and mix. Analyze this sample as described above. (If chromium is present, allow exactly the same reaction period with the DPD for both analyses.) Subtract the result of this test from the original analysis to obtain the accurate chlorine result. Hardness at levels below 1000 mg/l as CaCO 3 will not interfere. Summary of Method Chlorine can be present in water as free available chlorine and as combined available chlorine. Both forms can exist in the same water and can be determined together as the total available chlorine. Free chlorine is available as hypochlorous acid or hypochlorite ion. Combined chlorine exists as monochloramine, dichloramine, nitrogen trichloride and other chloro derivatives. The combined chlorine oxidizes iodide in the reagent to iodine. The iodine reacts with DPD (N,N-diethyl-p-phenylenediamine) indicator along with free chlorine present in the sample to form a red color which is proportional to the total chlorine concentration. To determine the concentration of combined chlorine, run a free chlorine test. Subtract the results from the results of the total chlorine test to obtain combined chlorine. 31

34 CHLORINE, TOTAL, continued REQUIRED REAGENTS Description Cat. No. DPD Indicator Powder, 24 g Total Chlorine Indicator Solution, 473 ml Total Chlorine Buffer Solution, 473 ml REQUIRED APPARATUS Cylinder, mixing, glass, 100 ml, each Dispenser, fixed volume, 1.0 ml RePipet Jr., each (two required) Pour-Thru Cell Assembly Kit, DR/2000, each Pour-Thru Cell Assembly Kit, DR/3000, each OPTIONAL REAGENTS Chlorine Standard Solution, Voluette Ampule, mg/l, 10 ml, 16/pkg Chlorine Standard Solution, Voluette Ampule, mg/l, 10 ml, 20/pkg Potassium Iodide Solution, 30 g/l, 100 ml * MDB Sodium Arsenite, 5 g/l, 100 ml* MDB Sodium Hydroxide Standard Solution, N, 100 ml* MDB Sulfuric Acid Standard Solution, N, 100 ml* MDB Sulfuric Acid Standard Solution, 5.25 N, 1 L Water, demineralized, 4 L OPTIONAL APPARATUS Ampule Breaker Kit, each Beaker, poly, 50 ml Bottle, Wash, 125 ml each Bottle, BOD, w/stopper, 300 ml Funnel, powder, each ph Meter, EC10, portable, each Pipet, TenSette, 0.1 to 1.0 ml, each Pipet Tips, for TenSette Pipet, 50/pkg INSTRUMENT SETUP The instrument setup for this procedure is identical to the setup for the Free Chlorine procedure. If you need to enter the setup into your instrument s memory, please refer to that setup on page 18. If you have already entered the setup for the Free Chlorine procedure, it is not necessary to enter it again. * Contact Hach for larger sizes. 32

35 Method 8374 HARDNESS, TOTAL, ULTRA LOW RANGE (0 to 1,000 µg/l Ca & Mg as CaCO 3 ) Calcium and Magnesium; Chlorophosphonazo Rapid Liquid Method For DR/2000 and DR/3000 Instruments For boiler, cooling, and ultra-pure waters 699 nm 1. Enter the stored program number for ultra low range hardness. Press: READ/ENTER The display will show: DIAL nm to 669 Note: For DR/2000s without this stored program, see Instrument Setup following these steps. Note: for DR/3000s, Press: Manual Program Press: Conc Factor 2. Rotate the wavelength dial until the small display shows: 669 nm Note: For DR/3000s, set the wavelength to nm. 3. Press: READ/ENTER The display will show: µg/l as CaCO 3 Note: For DR/3000s, Press: 10 Signal Average Press: Zero Press: 0 Conc 4. Install the Pour-Thru Cell and flush with 50 ml of ultra-pure water. Note: Pre-clean the Pour- Thru Cell and all labware as specified in the Analysis Labware section of this procedure. Note: Make sure the windows of the Pour-Thru Cell face side-to-side in the DR/2000 and front-to-back in the DR/ Rinse a clean 125-mL plastic Erlenmeyer flask three times with the sample. 6. Rinse a clean 50-mL plastic graduated cylinder three times with the sample. 7. Fill this rinsed cylinder to the 50-mL mark with sample. 8. Pour the contents of the 50-mL cylinder into the flask. 33

36 HARDNESS, TOTAL, ULTRA LOW RANGE, continued 9. Add 2.0 ml of Chlorophosphonazo Reagent to the sample using the Repipet Dispenser. Swirl to mix. 10.Pour approximately half (25 ml) of the sample into the Pour- Thru Cell. Note: A clean, dry, plastic 25-mL graduated cylinder may be used for measuring half of the sample. 11.After the flow has stopped, press: ZERO The display will show: WAIT then 12.Add one drop of CDTA Reagent for Ultra Low Range Hardness to the remaining sample in the flask. Swirl to mix. Note: Complete steps within 1-2 minutes. 0 µg/l as CaCO 3 Note: For DR/3000s, Press: Zero Conc 34

37 HARDNESS, TOTAL, ULTRA LOW RANGE, continued 13.Pour the remaining sample into the Pour- Thru Cell. 14.After the flow has stopped, press: READ/ENTER The display will show: WAIT then the result in µg/l as CaCO 3 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: If the sample concentration is greater than 750 µg/l, a 1:1 dilution of the sample is recommended for greatest accuracy. Use ultrapure (aldehyde-free) water for the dilution. Repeat the analysis on the diluted sample and multiply the resulting concentration by Rinse the Pour-Thru cell with ultra-pure water using a wash bottle immediately after use. 16.Flush the Pour-Thru cell with an additional 50 ml of ultra-pure water. Note: Protect the Pour-Thru cell from contamination by inverting a small beaker over the top of the glass funnel when not in use. Analysis Labware Clean all containers used in this test thoroughly to remove any traces of calcium or magnesium. If possible, use plastic containers for all analysis and storage. Clean containers by normal means, then rinse with ultra-pure (aldehyde-free) water. Fill and soak for 10 minutes with a 1:25 dilution of Chlorophosphonazo Reagent in ultra-pure water. Rinse well with ultra-pure water. Keep containers tightly closed and dedicate them for ULR Hardness only. If containers are rinsed and capped after each use, only occasional soaking is necessary. Fill the Pour-Thru Cell with this same mixture of chlorophosphonazo and water and let stand for several minutes. Rinse with ultra-pure water. 35

38 HARDNESS, TOTAL, ULTRA LOW RANGE, continued Avoid contamination of the Chlorophosphonazo Reagent bottle when placing the Repipet dispenser on the bottle. Rinse the inlet tubing and inside of the dispenser cap with copious amounts of ultra-pure water using a wash bottle. Place the inlet tubing into a beaker of ultra-pure water and depress the plunger times to rinse the inside of the dispenser. (For best results, pour a small amount of reagent into the beaker of rinse water.) Remove the dispenser from the water and depress the plunger until all of the water has been expelled. Shake off any excess water on the dispenser, place the dispenser on the bottle, and tighten. Sampling and Storage Do not use glass containers. Collect samples in clean plastic containers, preferably with screw-type closures. Rinse containers several times with the water to be analyzed before capturing the final sample. Seal to avoid contamination during transport. Analyze as soon as possible. Accuracy Check Standard Additions Method a) Use a TenSette Pipet to add 0.2 ml, 0.4 ml, and 0.6 ml, of a 20 mg/l (as CaCO 3 ) Calcium Chloride standard to three 50-mL samples, respectively. b) Perform the hardness test on each sample as described above. c) Each 0.2 ml addition of standard should cause an increase of 80 µg/l hardness as CaCO 3. d) If these increases do not occur, see Standard Additions in Section I of the DR/2000 or DR/3000 Procedures Manual for more information. Standard Solution Method Use the 0.50 mg/l (as CaCO 3 ) Calcium Chloride Standard Solution listed under Optional Reagents. Analyze this solution according to the above procedure. The strength of this standard solution is 0.50 mg/l as CaCO 3 (or 500 µg/l); the analytical result should be between 460 µg/l as CaCO 3 and 540 µg/l as CaCO 3. 36

39 HARDNESS, TOTAL, ULTRA LOW RANGE, continued Precision DR/2000: In a single laboratory using a standard solution of 600 µg/l as CaCO 3 and two representative lots of reagents with a DR/2000, a single operator obtained a standard deviation of 3 µg/l. DR/3000: In a single laboratory using a standard solution 520 µg/l as CaCO 3 and two representative lots of reagents with a DR/3000, a single operator obtained a standard deviation of 4 µg/l. Interferences Interference studies were conducted at various hardness levels between 0 and 500 µg/l as CaCO 3. Various cations and anions were evaluated at levels in the range appropriate to ultra pure water applications. An ion is said to interfere when the resulting concentration is changed by ±10%. : Table 1 Negative Interference Ion Level above which ion interferes (µg/l) Aluminum 150 Sodium 79,000 : Table 2 Positive Interference Ion Level above which ion interferes (µg/l) Copper 250 Silicon 1,000 Table 3 No Interference Ion Highest Concentration Tested (µg/l) Potassium 1,000 Ammonium 1,000 Formaldehyde 47,000 Summary of Method Calcium and magnesium combine equivalently with the Chlorophosphonazo Indicator to form a complex which absorbs light very strongly at 669 nm. One drop of the CDTA reagent breaks up this complex, and the resultant decrease in absorbance is linearly related to the amount of calcium and magnesium (as CaCO 3 ) in the sample. 37

40 HARDNESS, TOTAL, ULTRA LOW RANGE, continued REQUIRED REAGENTS Description Cat. No. Chlorophosphonazo Indicator Solution, 500 ml CDTA Reagent for Ultra Low Range Hardness, 10 ml REQUIRED APPARATUS Cylinder, graduated, 50 ml, poly, each, Dispenser, Fixed-volume, 2.0 ml, Repipet Jr., each Flask, Erlenmeyer, PMP w/cap, 125 ml, each Pour-Thru Cell Assembly, DR/2000, Kit, each Pour-Thru Cell Assembly, DR/3000, Kit, each OPTIONAL REAGENTS Calcium Standard Solution, 20 mg/l as CaCO 3, 946 ml Calcium Standard Solution, 0.50 mg/l as CaCO 3, 946 ml Water, Ultra-pure (aldehyde-free), 500 ml OPTIONAL APPARATUS Beaker, poly, 50 ml Bottle, wash, 125 ml, each Cylinder, graduated, 25 ml, poly, each Flask, Erlenmeyer, PMP w/cap, 125 ml, 6/pkg Pipet, TenSette, 0.1 to 1.0 ml, each Pipet Tips, for TenSette Pipet, 50/pkg Instrument Setup For DR/2000s with software versions less than 3.0 The calibration program for this method cannot be installed in DR/2000s with software versions before 3.0. The following modifications to the procedure are necessary for these earlier software versions. a) In place of Step 1, press 0 at the METHOD #? prompt, then press READ/ENTER to place the instrument in the absorbance mode. The display will show: Abs b) Follow the instructions of Step 2. c) Follow the instructions of Step 3. The display will instead show: ZERO SAMPLE d) Follow the instructions of Steps 4 through 8. 38