LaMotte DPD-FAS User Manual

DPD-FAS TITRIMETRIC OUT FIT

MODEL DT · CODE 6806

QUANTITY CONTENTS CODE

250 mL Sodium Bicarbonate, 5.5% 6813-K 120 mL *Ferrous Ammonium Sulfate *6815-J 120 mL Glycine Solution 6811-J 100 g *DPD #1 Powder *6807-J 60 g *Potassium Iodide Crystals *6809-H 60 mL *Sulfuric Acid, 5% *6520-H 60 mL *Steadifac Reagent *6383WT-H 60 mL *Sodium Arsenite Solution *4128-H 30 mL Potassium Iodide, 0.5% 6810-G 20 g *EDTA Disodium Salt *6382-F 1 Deionized Water, 250 mL 5115PS-K 1 Deionized Water, 250 mL 5115PT-K 1 Spoon, 0.25g, plastic 0695 1 Spoon, 0.5 g, plastic 0698 1 Spoon, 1.0 g, plastic 0697 2 Flasks, Erlenmeyer, 250 mL 0433 1 Buret, 10 mL, funnel top 0426 1 Graduated Cylinder, 100 mL, glass 0419 1 Graduated Cylinder, 25 mL, glass 0417 1 Pipet, 0.5 mL, plastic w/20 mm cap 0369 4 Pipets, 1.0 mL, plastic 0354 1 Chemistry & Control of

Modern Chlorination

*WARNING: Reagents marked with a * are considered to be potential health hazards. To view or print a Material Safety Data Sheet (MSDS) for these reagents see MSDS CD or www.lamotte.com. To obtain a printed copy, contact LaMotte by email, phone or fax.

To order individual reagents or test kit components, use the specified code numbers.

1597

INTRODUCTION

The DPD-FAS (Diethyl-p-phenylene Diamine-Ferrous Ammonium Sulfate) titrimetric method of A. T. Palin, as described in Standard Methods APHA, AWWA , WPCF, 18th edition, provides a simple and accurate means of differentiating free and combined chlorine fractions, and while these determinations are of primary interest, an extension of the basic methods permits the determination of chlorine dioxide, chlorite, bromine, iodine and ozone.

The Model DT Outfit with special stabilized reagents and common glassware makes the method suitable for both laboratory and field use. The instructions are divided into 6 major sections (I-VI). Use the section that describes the sample being tested.

I. DPD Method for Free & Combined Chlorine II. Simplified Procedure for Free, Combined & Total Chlorine and

Nitrogen Trichloride

III.DPD Method for Chlorine Dioxide and Chlorite IV.DPD Method for Bromine V. DPD Method for Iodine VI.DPD Method for Ozone

DILUTED FAS TITRANT PREPARATION

A diluted stock of FAS titrant should be made fresh each day and any left at the end of the day should be discarded. Use the 1.0 mL pipet (0354) to measure and transfer 1.0 mL of *Ferrous Ammonium Sulfate (6815) to the 25 mL graduated cylinder (0417). Fill the graduated cylinder to the 25 mL line with deionized water (5115PS). Invert several times to mix. When a titration is made, pour the diluted FAS into the funnel top of the buret (0426) until it is full to the top. Adjust to the “0” line.

NOTE: The quantities given are suitable for concentrations of Total Chlorine up to 5 mg/L (5 ppm). Where the Total Chlorine exceeds 5 mg/L, use a smaller amount of the sample and dilute to 100 mL with distilled water, and use the usual amounts of reagents given for a 100 mL sample.

CONCENTRATION RANGE OF DPD PROCEDURES

The quantities of reagents that have been given for all of the tests described are suitable for concentrations of total available chlorine up to 5 mg/L (ppm). Where the total chlorine exceeds this figure, use a smaller sample and dilute with distilled water to a total volume of 100 mL.

PROCEDURES I. DPD METHOD FOR FREE & COMBINED CHLORINE

A. FREE CHLORINE

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the 250 mL Erlenmeyer flask (0433).

2. Fill the 100 mL graduated cylinder (0419) to the 100 mL line with sample water. Pour into Erlenmeyer flask. Swirl until powder is dissolved. If free chlorine is present, solution will turn pink.

NOTE: In the presence of high monochloramine, add 10 drops of *Steadifac Reagent (6383WT) to prevent interference. This will give a Free Chlorine reading only. Discard and start again at Step 1A and continue to Step B5 for monochloramine, etc. Do not add *Steadifac Reagent if other forms of chlorine are to be determined.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Record buret reading as Reading A.

Reading A (mL) = (ppm) Free Chlorine

Retain sample and buret for testing Monochloramine.

B. MONOCHLORAMINE

4. Use the 1.0 g spoon (0697) to add one small *Potassium Iodide Crystal (6809) to the sample from Step 3. Swirl to mix. If monochloramine is present, solution will turn pink.

NOTE: If dichloramine concentration is expected to be high, substitute 2 drops Potassium Iodide, 0.5% (6810) for one *Potassium Iodide Crystal (6809) in Step 4.

5. Continue titrating with the diluted Ferrous Ammonium Sulfate Solution until the pink color disappears. Record buret reading as Reading B.

(Reading B – Reading A), mL = (ppm) Monochloramine

Retain sample and buret for testing Dichloramine.

C. DICHLORAMINE

6. Use the 1.0 g spoon (0697) to add 1.0 g of *Potassium Iodide Crystals (6809) to the sample from Step 5. Swirl until crystals are dissolved. Wait 2 minutes. If Dichloramine is present, solution will turn pink.

7. Continue titrating with the diluted Ferrous Ammonium Sulfate Solution until the pink color disappears. Record buret reading as Reading C.

Reading C (mL) = (ppm) Total Chlorine

(Reading C – Reading B), mL = (ppm) Dichloramine3

II. SIMPLIFIED PROCEDURE FOR FREE, COMBINED &

TOTAL CHLORINE AND NITROGEN TRICHLORIDE

A. FREE CHLORINE

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the 250 mL Erlenmeyer flask (0433).

2. Fill the 100 mL graduated cylinder (0419) to the 100 mL line with sample water. Pour into Erlenmeyer flask. Swirl until powder is dissolved. If Free Available Chlorine is present, solution will turn pink.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Record buret reading as Reading A.

Reading A (mL) = (ppm) Free Chlorine

Retain sample and buret for testing Monochloramine.

B. TOTAL CHLORINE

4. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to a clean 250 mL Erlenmeyer flask (0433).

5. Use the 1.0 g spoon (0697) to add 1.0 g of *Potassium Iodide Crystals (6809) to the flask (0433).

6. Use the 100 mL graduated cylinder (0419) to add 100 mL of sample water to the flask (0433). Swirl until reagents are dissolved. Wait 2 minutes. If Total Chlorine is present, solution will turn pink.

7. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Record buret reading as Reading B.

Reading B (mL) = (ppm) Total Chlorine

C. COMBINED CHLORINE

Reading B – Reading A = (ppm) Combined Chlorine

D. NITROGEN TRICHLORIDE

The absence of color in Step A indicates the absence of nitrogen trichloride, since this compound exists in water only in the presence of free-chlorine. Nitrogen trichloride, readily identified by its distinctive odor, is estimated by the following procedure.

1. Use the 1.0 g spoon (0697) to add one small *Potassium Iodide Crystal (6809) to a clean 250 mL Erlenmeyer flask (0433).

2. Use the 100 mL graduated cylinder ((0419) to add 100 mL of sample water to the flask (0433). Swirl until crystals are dissolved.

3. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the flask (0433). Swirl until powder is dissolved. If Nitrogen Trichloride is present, solution will turn pink.

4. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Record buret reading as Reading D.

5. Obtain a new sample. Run the test for Free Chlorine (Part A). Record result as Reading A.

NOTE: If Free Chlorine has already been determined, use the result (Reading A) in the equation below.

2 x (Reading D – Reading A), mL = (ppm) Nitrogen Trichloride

CALCULATIONS: (Sections I and II)

For a 100 mL sample, 1.00 mL diluted FAS solution equals 1.00 mg per

1.0 (ppm) Chlorine.

Reading NCl3 Absent NCl3 Present

A Free Cl Free Cl

B – A NH2 Cl NH2Cl

C– B NH2Cl +

D Free Cl +

2(D – A) NCl

C – D NHCl

NCl NCl

Should monochloramine be present with nitrogen trichloride, which is unlikely, it will be included in Reading D, in which case NCl3 is obtained from 2(D – B). Chlorine dioxide if present, is included in Reading A to the extent of one-fifth of its total chlorine content. For the determination of chlorine dioxide and of mixtures of free chlorine, chlorine dioxide, chlorite and chloramines, see Chlorine Dioxide and Chlorite-DPD Method which follows.

E. INTERFERENCE

The only interference in chlorine testing is the possibility of oxidized manganese in the water. This can be tested as follows:

1. Use the 1.0 g spoon (0697) to add two *Potassium Iodide Crystals (6810) to a clean 250 mL Erlenmeyer flask (0433).

2. Use the 100 mL graduated cylinder (0419) to add 100 mL of sample water to the flask (0433). Swirl to mix.

3. Use the 0.5 mL pipet (0369) to add 0.5 mL of *Sodium Arsenite Solution (4128).

4. Use the 0.5 g spoon to add 0.5 g of *DPD #1 (6807) Powder. Swirl until reagents are dissolved. If oxidized manganese is present, solution will turn pink.

5. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Record buret reading. Subtract this reading from the previous test readings.

III.DPD METHOD FOR CHLORINE DIOXIDE AND CHLORITE

This method is an extension of the standard DPD method for determining free chlorine and chloramines in water.

NOTE: Titration should be carried out as rapidly as possible ignoring any color driftback at endpoints.

A. CHLORINE DIOXIDE USING *STEADIFAC REAGENT

1. Use the 1.0 mL pipet (0354) to add 2 mL of Glycine Solution (6811) to a 100 mL sample. Mix.

2. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the sample.

3. Use the 0.25 g spoon (0695) to add 0.25 g of *EDTA Disodium Salt (6382). Mix.

4. Add 10 drops of *Steadifac Reagent (6383WT). Mix.

5. Titrate rapidly with the diluted Ferrous Ammonium Sulfate

Solution. This is Reading G1. NOTE: To obtain chlorine dioxide in terms of mg/L ClO2, multiply

the G1 reading by 1.9 instead of 5.

B. CHLORINE DIOXIDE WITHOUT *STEADIFAC REAGENT

1. Use a second 100 mL sample to follow procedures of Steps 1 through 3 above.

2. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution. This is Reading G2.

C. FREE CHLORINE

1. Use the 0.5 g spoon to add 0.5 g of *DPD #1 Powder (6807) to a third 100 mL sample. Mix.

2. Use the 0.5 g spoon to add 0.25 g of *EDTA Disodium Salt (6382). Mix.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution. This is Reading A. DO NOT DISCARD SOLUTION. Solution will be used for Combined Chlorine test.

D. MONOCHLORAMINE

4. Use the 1.0 g spoon (0697) to add one small *Potassium Iodide Crystal (6809) to the sample from Step 3. Swirl to mix. If monochloramine is present, solution will turn pink.

NOTE: If dichloramine concentration is expected to be high, substitute 2 drops Potassium Iodide, 0.5% (6810) for one *Potassium Iodide Crystal in Step 4.

5. Continue titrating with the diluted Ferrous Ammonium Sulfate Solution until the pink color disappears. Record buret reading as Reading B.

(Reading B – Reading A), mL = (ppm) Monochloramine

Retain sample and buret for testing Dichloramine.

E. COMBINED CHLORINE

6. Use the 1.0 g spoon (0697) to add 1 g of *Potassium Iodide Crystals (6809) to the solution from the Free Chlorine test above. Mix to dissolve crystals. Wait 2 minutes.

7. Add 10 drops of *Steadifac Reagent (6383WT). Mix.

8. Titrate rapidly with the diluted Ferrous Ammonium Sulfate

Solution. This is Reading C. DO NOT DISCARD SOLUTION. Solution will be used for Total Chlorine Including Chlorite test.

F. TOTAL CHLORINE INCLUDING CHLORITE

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to a clean 250 mL Erlenmeyer flask (0433).

2. Use the 1.0 g spoon (0697) to add 1.0 g of *Potassium Iodide Crystals (6809) to the flask (0433).

3. Use the 100 mL graduated cylinder ((0419) to add 100 mL of sample water to the flask (0433). Swirl until reagents are dissolved. Wait 2 minutes. If Total Chlorine is present, solution will turn pink.

4. Use the 1.0 mL pipet (0354) to add 1 mL of *Sulfuric Acid, 5% (6520) to the solution from the Combined Chlorine test. Mix. Wait 2 minutes.

5. Use the 1.0 mL pipet (0354) to add 5 mL of *Sodium Bicarbonate,

5.5% (6813). Mix.

6. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution. This is Reading D.

CALCULATIONS: For a 100 mL sample, 1 mL of diluted Ferrous Ammonium Sulfate equals 1 mg/L Chlorine, ppm Chlorine.

With Calculations as Follows:

In the Case of

Chlorine Dioxide:

Chlorine Dioxide = 5G1 Free Chlorine = A – G2 Combined Chlorine = C – A Chlorite = D – C – 5G1 + G2

Tot a l ClO2 Chlorine =

D – C + G2

(this figure should equal

5G1)

Total Chlorine = D

RESULTS WITH MODIFIED TITRIMETRIC PROCEDURE

The following results were obtained by Dr. A. T. Palin using solutions of chlorine dioxide in distilled water.

Titrimetric Readings using Modified Procedure

G1 G2 A C D

(mg/L as Available Cl2)

0.16 0.16 0.19 0.20 0.82

0.33 0.33 0.46 0.55 1.83

0.54 0.57 0.78 0.86 3.06

0.80 0.97 1.28 1.49 4.69

0.84 0.95 1.30 1.50 4.81

1.22 1.45 1.83 2.02 6.73

The difference between G2 and G1 represents the extent of the errors in titrations caused by slow color drift-back at end points due to the slight activation of chlorite in neutral solution. The G readings are now to be interpreted thus:

ClO

G1 =

G2 =

ClO

5 + K*

*where K = the “breakthrough” error

IV. DPD METHOD FOR BROMINE

Bromine may consist of free bromine or bromamines or a mixture of these. The term “Bromine” refers to the total of free bromine and bromamines.

A. BROMINE (IN THE ABSENCE OF CHLORINE)

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the 250 mL Erlenmeyer flask (0433).

2. Fill the 100 mL graduated cylinder (0419) to the 100 mL line with sample water. Pour into Erlenmeyer flask. Swirl until powder is dissolved. If Bromine is present, solution will turn pink.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears.

NOTE: Results obtained in mg/L (ppm) Free Chlorine. Multiply by

2.25 to convert to Bromine.

B. BROMINE (IN THE PRESENCE OF CHLORINE)

1. Use the 1.0 mL pipet to add 2 mL of Glycine Solution (6811) to a 100 mL sample. Mix.

2. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807). Mix.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution. This is Reading BR.

C. FREE CHLORINE

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the 250 mL Erlenmeyer flask (0433).

2. Fill the 100 mL graduated cylinder (0419) to the 100 mL line with sample water. Pour into Erlenmeyer flask. Swirl until powder is dissolved. If free chlorine is present, solution will turn pink.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Record buret reading as Reading A.

Reading A – BR (mL) = (ppm) Free Chlorine

Retain sample and buret for testing Monochloramine.

D. MONOCHLORAMINE

4. Use the 1.0 g spoon (0697) to add one small *Potassium Iodide Crystal (6809) to the sample from Step 3. Swirl to mix. If monochloramine is present, solution will turn pink.

5. Continue titrating with the diluted Ferrous Ammonium Sulfate Solution until the pink color disappears. Record buret reading as Reading B.

(Reading B – Reading A), mL = (ppm) Monochloramine

Retain sample and buret for testing Dichloramine.

E. DICHLORAMINE

7. Continue titrating with the diluted Ferrous Ammonium Sulfate Solution until the pink color disappears. Record buret reading as Reading C.

NOTE: For 100 mL sample, 1 mL FAS solution equals 1 mg/L (ppm) Chlorine.

Calculations

Bromine = BR Free Chlorine = A – BR Monochloramine = B – A Dichloramine = C – B Combined Chlorine = C – A

V. DPD METHOD FOR IODINE

Iodine reacts with DPD in the same manner as Free Chlorine so that it is necessary only to perform the procedure for Free Chlorine. DPD methods for differentiating free iodine from free chlorine and chloramines have not been developed. For a 100 mL sample, 1 mL FAS solution equals 1 mg/L (ppm) available chlorine. If it is desired to report in terms of iodine, multiply the result by 3.6.

A. IODINE

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the 250 mL Erlenmeyer flask (0433).

2. Fill the 100 mL graduated cylinder (0419) to the 100 mL line with sample water. Pour into Erlenmeyer flask. Swirl until powder is dissolved. If Iodine is present, solution will turn pink.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears.

4. Multiply result by 3.6 to obtain mg/L (ppm) Iodine.

VI.DPD METHOD FOR OZONE

A. OZONE (IN THE ABSENCE OF CHLORINE COMPOUNDS)

1. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807) to the 250 mL Erlenmeyer flask (0433).

2. Fill the 100 mL graduated cylinder (0419) to the 100 mL line with sample water. Pour into Erlenmeyer flask. Swirl until powder is dissolved. If ozone is present, solution will turn pink.

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears.

4. Multiply result by 0.676 to obtain (ppm) Ozone.

B. OZONE (IN THE PRESENCE OF CHLORINE COMPOUNDS)

1. Use the 1.0 mL pipet (0354) to add 2 mL of Glycine Solution (6811) to a 100 mL sample. Mix.

2. Use the 0.5 g spoon (0698) to add 0.5 g of *Potassium Iodide Crystals (6809).

3. Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807). Mix.

4. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution in the buret until the pink color disappears. Result is Total Chlorine only.

Result Ozone – Result Total Chlorine = Ozone

NOTE: A procedure to determine the amounts of free and combined

chlorine would require a further test in which *DPD #1 Powder is added to a 100 mL sample and titrated to give free chlorine plus a proportion of ozone. After adding approximately 0.5 g of Potassium Iodide Crystals and titrating again, the result would give total chlorine plus the same proportion of ozone. Titrate the developed colors immediately at each stage. The difference between these readings give combined chlorine. This result enables the total chlorine figure as previously obtained to be subdivided into Free and Combined Chlorine.

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