Method (0.04 to 4.50 mg/l Cl 2 ) Powder Pillows

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1 Chlorine Free, Indophenol, Indophenol 1 1 Patent pending. DOC Method (0.04 to 4.50 mg/l Cl 2 ) Powder Pillows Scope and Application: For determining residual free chlorine levels in the presence of manganese, chloramines and other oxidants which interfere with DPD colorimetric, DPD titrimetric, and amperometric methods for free chlorine. For use in potable water, chlorinated drinking water, swimming pool water and treated wastewater effluent. Test preparation How to use instrument-specific information The Instrument-specific information table shows requirements that can vary between instruments. To use this table, select an instrument, then read across to find the corresponding information required to perform this test. Table 1 Instrument-specific information Instrument Sample cell Cell orientation Adapter Program DR Orientation key toward user A DR cm (flat) path aligned with arrow on adapter LZV585 (B) 66 DR cm (flat) path aligned with arrow on adapter LZV585 (B) 66 DR cm (flat) path aligned with arrow on adapter LZV585 (B) 66 DR/ cm (flat) path aligned with slots in cell holder 66 DR/ cm (flat) path aligned with light path. Refer to the user manual for more information DR/850 & DR/ Slots in the 2 clock position in cell holder 110 Pocket Colorimeter II Monochloramine Diamond mark faces keypad Chlorine Before starting the test: Put the protective cover or lid over the cell compartment during measurements. The sample and reagent from one analysis can contaminate other analyses and interfere with the test results. Be sure to rinse the cells and caps several times with deionized water or with the sample water to be tested before each test. Do not switch the sample cell caps between the Blank and Sample during the analysis. Tap sample cells lightly on a hard surface or slowly invert the cells to remove air bubbles from the cell walls. Be sure to keep the cap on the sample cells when not used to avoid ammonia contamination. Page 1 of 8

2 Collect the following items: Description Freechlor F Reagent Solution Quantity 5 drops Monochlor F Reagent Pillows 2 Sample cell (refer to Instrument-specific information) 2 See Consumables and replacement items for reorder information. Indophenol Method Stored Programs 66 Monochloramine LR Start 1. Select the test. Insert the correct adapter (refer to Instrument-specific information). 2. Fill 2 sample cells to the 10-mL line with sample. Mark one cell as the Blank. Mark the other cell as the Sample. 3. Add 5 drops of the Freechlor F Reagent to the Sample cell. 4. Cap and invert the cell to mix. Zero 5. Add the contents of one Monochlor F Reagent Powder Pillow to the Blank cell and to the Sample cell. Cap and shake both cells 20 seconds to dissolve. 6. Press TIMER>OK. A 5-minute reaction will start. If the sample temperature is less than 18 C (64 F), refer to Table 2 for the correct reaction time. 7. When the timer stops, invert the Blank cell to mix. Insert the cell into the cell holder. 8. ZERO the instrument. The display will show: 0.00 mg/l Cl 2 Page 2 of 8

3 Indophenol Method (continued) 9. Invert the Sample cell to mix. Insert the cell into the cell holder. READ the results in mg/l Cl 2. Color reaction time Use Table 2 to find the reaction time when the sample temperature is less than 18 C (64 F). The color is stable for 30 minutes after the reaction time is reached. If a temperature measurement is not available, read the sample after the color is stable. Table 2 Color development based on sample temperature Sample Temperature C F Reaction Time (minutes) greater than 25 greater than 77 2 Page 3 of 8

4 Interferences Interfering substance The substances listed in Table 3 have been tested for interference and do not interfere at or below the indicated levels. Refer to Table 4 for substances that do interfere with the test. Table 3 Non-interfering substances Interference level Alanine 1 mg/l N Aluminum 10 mg/l Al 3+ Bromide 100 mg/l Br - Bromine 15 mg/l Br 2 Calcium 1000 mg/l as CaCO 3 Chloride 18,000 mg/l Cl - Chlorine Dioxide 5 mg/l ClO 2 Chromium (III) 5 mg/l Cr 3+ Copper 10 mg/l Cu Cyanide 10 mg/l CN - Dichloramine 10 mg/l as Cl 2 Fluoride 5 mg/l F - Glycine 1 mg/l N Iodine 4 mg/l I 2 Iron (II) 10 mg/l Fe 2+ Iron (III) 10 mg/l Fe 3+ Lead 10 mg/l Pb Manganese (7+) 3 mg/l MnO 4 Nitrate 100 mg/l NO 3 N Nitrite 50 mg/l NO 2 N Oxone 1 (potassium peroxomonopersulfate) 30 mg/l Phosphate 100 mg/l PO 3-4 Silica 100 mg/l SiO 2 Sulfate 2600 ppm SO 2-4 Tyrosine 1 mg/l N Urea 10 mg/l N Zinc 5 mg/l Zn 2+ 1 Oxone is a registered trademark of E.I. du Pont de Nemours & Co., Inc. Table 4 Interfering substances Interfering substance Interference level Ozone 1 > 1 mg/l O 3 Sulfide 1 > 0.5 mg/l S 2-1 This compound does not usually exist with free chlorine. Page 4 of 8

5 Sample collection, preservation and storage Testing applications Analyze samples for chlorine immediately after collection. Free chlorine is a strong oxidizing agent and it is unstable in natural waters. It reacts rapidly with various inorganic compounds and more slowly oxidizes organic compounds. Many factors, including reactant concentrations, sunlight, ph, temperature and salinity influence the decomposition of free chlorine in water. Avoid plastic containers because they can have a large chlorine demand. Pretreat glass sample containers to remove any chlorine 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 or distilled water. If sample containers are rinsed thoroughly with deionized or distilled water after use, only occasional pre-treatment is necessary. A common error in testing for chlorine is not 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 containers 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. Perform the chlorine analysis immediately. Finished chlorinated drinking waters and distributions systems Finished waters contain free chlorine and various levels of organic chloramines and inorganic contaminants. It is generally assumed that the free chlorine has reacted with all easily oxidizable species present and the remaining free chlorine is likely present in a steady-state equilibrium. Replicate analyses for free chlorine on this type of water should give equivalent results. It is especially important when testing water where free chlorine residual levels are low to observe all precautions that refer to sample cell cleanliness, water temperature and sampling techniques. At breakpoint These waters may contain a mixture of free chlorine, chloramines and nuisance residuals depending on water temperature, mixing efficiencies, sampling location and distance beyond the theoretical breakpoint. It is important to note that the water can be in a state of "dynamic equilibrium" and the chemical speciation can change rapidly, especially if one is at or near breakpoint. The chemical speciation can change dynamically in both the Blank cell and the Sample cell. The test must be conducted immediately on these types of samples. Test results may be difficult to replicate on duplicate samples depending on the dynamics of the water. Test results are best used to identify free chlorine trends and to monitor changes due to different mixing efficiencies, sampling locations, temperature changes, increased chlorine feed rates, etc. In chloramination kinetic studies These waters will contain a mixture of free chlorine and chloramines depending on water temperature, mixing efficiencies, sampling locations, feed rates for chlorine and ammonia and contact time. It is important to note that the water is in a state of "dynamic equilibrium" and the chemical speciation can change rapidly depending on water conditions. The chemical speciation can change dynamically in both the Blank cell and the Sample cell. The test must be conducted immediately on these types of samples. Test results may be difficult to replicate on duplicate samples depending on the dynamics of the water. Test results are best used to identify free chlorine trends and to monitor changes based on changes in mixing efficiencies, sampling locations, water temperature changes, increased chlorine feed rates, etc. With other oxidants such as Oxone, permanganate, chlorine dioxide, bromine and iodine It is assumed that the free chlorine residual has stabilized in the presence of the other oxidants. Replicate analyses for free chlorine on this type of water should give equivalent results. The levels of alternate oxidants that can be present without interference have been tested only in laboratory bench studies (refer to Table 3). Field data for free chlorine in the presence of these oxidants is not available. Page 5 of 8

6 Accuracy check Important Note: This procedure is only valid for stabilized or equilibrated free chlorine samples. Standard additions method (sample spike) Required for accuracy check: Chlorine Standard Solution, 2-mL PourRite Ampule, mg/l PourRite Ampule Breaker Pipet, TenSette, ml Pipet tips Method performance 1. After reading test results, leave the sample cell (unspiked sample) in the instrument. 2. Select standard additions from the instrument menu (if available). Refer to the instrument user manual for specific instructions. Refer to step 9 if a standard additions menu is not available. 3. Enter the average chlorine concentration from the label or certificate that is enclosed with the standard solution ampules. 4. A summary of the standard additions procedure will be displayed. Press OK to accept the default values for standard concentration, sample volume and spike volumes. After the values are accepted, the unspiked sample reading will appear in the top row. 5. Open one standard solution ampule. 6. Use the TenSette Pipet to prepare 3 spiked samples: add 0.1 ml, 0.2 ml, and 0.3 ml of standard to three 10-mL portions of fresh sample. 7. Follow the Indophenol Method test procedure for each of the spiked samples, starting with the 0.1 ml sample spike. Measure each of the spiked samples in the instrument. 8. Select GRAPH to view the results. Select IDEAL LINE (or best-fit) to compare the standard addition results to the theoretical 100% recovery. 9. If a standard additions menu is not available, calculate the percent recovery: a. Put the spiked sample in the cell holder and press READ. b. Calculate the concentration of chlorine that was added to the sample: 0.1 ml concentration of chlorine standard (mg/l Cl 2 ) mg/l chlorine added = ml c. Find the expected result of the spiked sample from the sum of the unspiked sample result plus the concentration of chlorine that was added (step b). d. Calculate the percent recovery from the actual (step a) and the expected (step c) results. Note: If results are not within acceptable limits (± 10%), be sure that the sample volumes and sample spikes are measured accurately. The sample volumes and sample spikes that are used should agree with the selections in the standard additions menu. If all procedures are followed correctly but the standard additions results are not within acceptable limits, the sample may contain an interference. In a single laboratory with a standard solution of 3.51 mg/l chlorine (as Cl 2 ) and a single lot of reagent with a single instrument (DR 5000), a single operator obtained a standard deviation of ± 0.04 mg/l Cl 2. Page 6 of 8

7 Summary of method An ammonia solution at a ph of 8.3 is added to a sample containing free chlorine. The free chlorine is immediately converted into monochloramine (NH 2 Cl). The monochloramine is then determined by the indophenol method using Monochlor F Reagent. In this method, the monochloramine reacts with a substituted phenol in the presence of a cyanoferrate catalyst to form an intermediate monoimine compound. The intermediate compound couples with excess substituted phenol to form a green-colored indophenol compound, which is proportional to the amount of free chlorine present in the sample. A sample blank containing Monochlor F Reagent compensates for background color from the reagent and sample. Test results are measured with a spectrophotometer at 655 nm or with a colorimeter at 610 nm. Consumables and replacement items Required reagents Description Quantity/Test Unit Catalog number Freechlor F Reagent Solution 5 drops 50-mL SCDB Monochlor F Reagent Pillows 2 100/pkg Recommended standards Description Unit Catalog number Chlorine Standard Solution, 2-mL PourRite Ampule, mg/l 20/pkg Chlorine Standard Solution, 2-mL PourRite Ampule, mg/l 20/pkg Chlorine Standard Solution, 10-mL Voluette Ampule, mg/l 16/pkg Optional reagents and apparatus Description Unit Catalog number Ampule Breaker, 2-mL PourRite Ampules each Ampule Breaker Kit, 10-mL Volulette Ampules each Pipet, TenSette, 0.1 to 1.0 ml each Pipet Tips, for TenSette Pipet /pkg Pipet Tips, for TenSette Pipet /pkg Clippers (shears) each Thermometer, non-mercury, 10 to 225 C each Wipers, disposable, 28 x 37 cm 188/pkg Page 7 of 8

8 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 July 2009, Edition 1