DO Test Procedure

7/27/2019 DO Test Procedure

1/21

DissolvedOxygen

Instruction Manual Code 7414/5860Water Quality Test Kit


2/21


3/21

INTRODUCTION

Aquatic animals need dissolved oxygen to live. Fish, invertebrates, plants, andaerobic bacteria all require oxygen for respiration. Oxygen dissolves readilyinto water from the atmosphere until the water is saturated. Once dissolved in

the water, the oxygen diffuses very slowly and distribution depends on themovement of the aerated water. Oxygen is also produced by aquatic plants,algae, and phytoplankton as a by-product of photosynthesis.

The amount of oxygen required varies according to species and stage of life.Dissolved Oxygen levels below 3 ppm are stressful to most aquatic organisms.Dissolved Oxygen levels below 2 or 1 ppm will not support fish. Levels of 5 to6 ppm are usually required for growth and activity.

This test kit uses the azide modification of the Winkler method for

determining dissolved oxygen.

TABLE OF CONTENTS

Page

Kit Contents....................................................................... 2

Test Procedure

Part 1: Collecting a Water Sample ..................................... 3

Part 2: Adding the Reagents ............................................... 4

Part 3: Titration................................................................... 5

EPA Compliance................................................................. 8

Dissolved Oxygen Fact Sheet............................................. 10

General Safety Precautions................................................ 13

Use Proper Analytical Techniques..................................... 14

Material Safety Data Sheets ............................................. 15

Kit Diagrams..................................................................... 21

Short Form Instructions ...................................... Back Cover

2

WARNING! This set contains chemicalsthat may be harmful if misused. Read

cautions on individual containerscarefully. Not to be used by children

except under adult supervision


4/21

KIT CONTENTS

QUANTITY CONTENTS CODE

30 mL *Manganous Sulfate Solution *4167-G

30 mL *Alkaline Potassium Iodide Azide *7166-G

50 g *Sulfamic Acid Powder (7414 Kit) *6286-H

30 mL *Sulfuric Acid, 1:1 (5860 Kit) *6141WT-G

60 mL *Sodium Thiosulfate, 0.025N *4169-H

30 mL Starch Indicator Solution 4170WT-G

1 Spoon, 1.0 g, plastic (7414 Kit) 0697

1 Direct Reading Titrator 0377

1 Test Tube, 5-10-12.9-15-20-25 mL,glass, w/cap

0608

1 Water Sampling Bottle, 60 mL, glass 0688-DO

*WARNING: Reagents marked with a * are considered to be potential healthhazards. To view or print a Material Safety Data Sheet (MSDS) for thesereagents 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 codenumbers.

3


5/21

TEST PROCEDURE

PART 1 - COLLECTING THE WATER SAMPLE

4

6.

Rinse the Water Sampling Bottle(0688-DO) with the sample water.

1.

Remove the cap and allow thebottle to fill.

3.

Tap the sides of the bottle todislodge any air bubbles.

4.

Tightly cap the bottle, andsubmerge it to the desired depth.

2.

Replace the cap while thebottle is still submerged.

5.

Retrieve the bottle and makesure that no air bubbles aretrapped inside.


6/21


7/21

TEST PROCEDURE

PART 3 - THE TITRATION

6

Fill the titrationtube (0608) to the20 mL line with thefixed sample. Capthe tube.

If small air bubbles appear inthe Titrator barrel, expel themby partially filling the barreland pumping the titrationsolution back into the reagentcontainer. Repeat until bubbledisappears.

NOTE:

2.Depress plungerof the Titrator(0377).

Insert the Titratorinto the plug in thetop of the *SodiumThiosulfate, 0.025N(4169) titratingsolution.

3.

5. Turn the bottleupright and removethe Titrator. NOTE:If the sample is a verypale yellow, go to Step 9.

4. Invert the bottle andslowly withdraw theplunger until thelarge ring on theplunger is oppositethe zero (0) line onthe scale.

continued . . .

1.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


8/21

TEST PROCEDURE

7

9.

6.

Continuetitrating untilthe blue colordisappears and

the solutionbecomescolorless.

Carefully remove theTitrator and cap. Donot to disturb theTitrator plunger.

Add 8 drops ofStarch IndicatorSolution(4170WT). Thesample should

turn blue.

8.

11.10.Cap the titrationtube. Insert the tip of

the Titrator into theopening of thetitration tube cap.

Insert the tip of theTitrator into theopening of thetitration tube cap.

Slowly depress theplunger to dispense thetitrating solution untilthe yellow-browncolor changes to a verypale yellow. Gentlyswirl the tube duringthe tiration to mix thecontents.

7.

12.Read the test result directlyfrom the scale where the largering on the Titrator meets theTitrator barrel. Record as ppmDissolved Oxygen. Eachminor division on the Titratorscale equals 0.2 ppm.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

4.0

5.0

Result:4.0 ppm


9/21


10/21

EPA COMPLIANCE

To qualify as an EPA accepted test, and to achieve the greatest accuracy, theSodium Thiosulfate Solution, 0.025N (4169) must be standardized daily. Thisprocedure follows Standard Methods for the Examination of Water and

Wastewater. Numbers in ( ) are for LaMotte products. These products are notincluded in this kit but can be ordered from LaMotte Company by using thespecified code number.

9

4.

5.

2.

3.

1.

6.

Add 2 dropsof SulfuricAcid, 5N(8517WT).

Use a 10 mL graduatedcylinder (0416) to add15 mL of DeionizedWater (5115) to thetitration tube (0608).

Use a DirectReading Titrator,0-1 Range (1.0mL capacity)(0376) to add 2mL of PotassiumBi-iodate (7346).

Use the 0.1 gspoon (0699) toadd 0.2 gPotassium IodideCrystals (6809).

Fill another DirectReading Titrator(0376) with Sodium

Thiosulfate Solution,0.025N (4169).

Swirl to dissolve.Solution will turnyellowish brown.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


11/21

EPA COMPLIANCE

10

9.Continue adding SodiumThiosulfate, 0.025N untilthe blue color disappearsand the solution iscolorless.

10.Read the test result directly from the scalewhere the large ring on the Titrator meets the

Titrator barrel. Include the value of the originalamount dispensed (1 mL). If the reading is 2.0+/-0.1 mL, the Sodium Thiosulfate, 0.025N(4169) is satisfactory. If not, discard andreplace with new reagent.

While gently swirling thetube, add SodiumThiosulfate, 0.025N untilthe color fades to paleyellow. It will benecessary to refill theDirect Reading Titrator.

7. 8.Add 3 drops ofStarchIndicatorSolution(4170WT).The solutionwill turn blue.

2.0

3.0

Result:2.0 ppm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


12/21

DISSOLVED OXYGEN FACT SHEET

Oxygen is critical to the survival of aquatic plants and animals, and a shortageof dissolved oxygen is not only a sign of pollution, it is harmful to fish. Someaquatic species are more sensitive to oxygen depletion than others, but some

general guidelines to consider when analyzing test results are:

56 ppm Sufficient for most species


13/21

WHERE DOES THE OXYGEN GO?Once in the water, oxygen is used by the aquatic life. Fish and other aquaticanimals need oxygen to breathe or respire. Oxygen is also consumed bybacteria to decay, or decompose, dead plants and animals.

Respiration

All animals, whether on land or underwater, need oxygen to respire, grow andsurvive. Plants and animals respire throughout the night and day, consumingoxygen and producing carbon dioxide, which is then used by plants duringphotosynthesis.

DecompositionAll plant and animal waste eventually decomposes, whether it is from livinganimals or dead plants and animals. In the decomposition process, bacteria useoxygen to oxidize, or chemically alter, the material to break it down to its

component parts. Some aquatic systems may undergo extreme amounts ofoxidation, leaving no oxygen for the living organisms, which eventually leaveor suffocate.

OTHER FACTORSThe oxygen level of a water system is not only dependent on production andconsumption. Many other factors work together to determine the potentialoxygen level, including:

Salt vs. fresh water - Fresh water can hold more oxygen than saltwater.

Temperature - Cold water can hold more oxygen than warm water.

Atmospheric pressure (Altitude) - The greater the atmosphericpressure the more oxygen the water will hold.

TESTING DISSOLVED OXYGENDissolved oxygen is often tested using the Azide modification of the Winkler

method. When testing dissolved oxygen it is critical not to introduceadditional oxygen into the sample. Many people avoid this problem by fillingthe sample bottle all the way and allowing the water to overflow for oneminute before capping.

The first step in a DO titration is the addition of Manganous Sulfate Solution(4167) and Alkaline Potassium Iodide Azide Solution (7166). These reagentsreact to form a white precipitate, or floc, of manganous hydroxide, Mn(OH)2.Chemically, this reaction can be written as:

MnSO4 + 2KOH Mn(OH)2 + K2SO4

ManganousSulfate

+ PotassiumHydroxide

ManganousHydroxide

+ PotassiumSulfate

12


14/21


15/21

GENERAL SAFETY PRECAUTIONS

14

Avoid contact betweenreagent chemicals and skin,eyes, nose, and mouth.

In the event of an accident or suspected poisoning, immediatelycall the Poison Center phone number in the front of your localtelephone directory or call a physician. Additional informationfor all LaMotte reagents is available in the United States,Canada, Puerto Rico, and the US Virgin Islands from Chem-Telby calling 1-800-255-3924. For other areas, call 813-248-0585collect to contact Chem-Tels International access number. Eachreagent can be identified by the four digit number listed on theupper left corner of the reagent label, in the contents list and inthe test procedures.

7.

1.

Store the test kitin a cool, dryarea.

Wear safety glasses whenperforming test procedures.

Read allinstructions and

note precautionsbefore performingthe testprocedure.

Instruction

Manual

2.

Keep allequipmentand reagentchemicals outof the reach ofyoungchildren.

MaterialSafety

Data

SheetRead the labels onall reagent bottles.

Note warnings andfirst aid information.Read all MaterialSafety Data Sheets.

3. 4.

5. 6.


16/21

USE PROPER ANALYTICAL TECHNIQUES

15

Use test tube caps orstoppers, not yourfingers, to covertubes duringshaking or mixing.

Tightly close allcontainers immediatelyafter use. Do notinterchange caps fromcontainers.

1.

Avoidprolongedexposure ofequipment andreagents todirect sunlight.Protect

reagents fromextremes oftemperature.

2.

Wipe up any reagentchemical spills immediately.3. 4.

5. 6.

Hold dropper bottles verticallyupside-down, and not at an

angle, when dispensing areagent. Squeezethe bottle gently todispense thereagent one dropat a time.

Thoroughly rinse test tubesbefore and after each test.


17/21

16

DISSOLVED OXYGEN KIT CODE 7414

DISSOLVED OXYGEN KIT CODE 5860

Instructions

4169-H

0688-DO

6286-H

4167-G

4170WT-G

0608Tube

7166-G

Instructions

4169-H

0688-DO

6141WT-G

4167-G

4170WT-G

0608Tube

7166-G

0377

0377

0697


18/21


19/21


20/21

SHORT FORM INSTRUCTIONS

Read all instructions before performing test. Use this guide asa quick reference.

1. Fill Water Sampling Bottle (0688-DO).

2. Add 8 drops of *Manganous Sulfate Solution (4167).

3. Add 8 drops of *Alkaline Potassium Iodide Azide (7166).

4. Cap and mix.

5. Allow precipitate to settle.

6. Use the 1.0 g spoon to add *Sulfamic Acid Powder (6286) oradd 8 drops of Sulfuric Acid, 1:1 (6141WT).

7. Cap and mix until reagent and precipitate dissolve.

8. Fill test tube (0608) to the 20 mL line.

9. Fill Titrator with *Sodium Thiosulfate, 0.025N (4169).

10. Titrate until sample color is pale yellow. DO NOT DISTURBTITRATOR.

11. Add 8 drops of Starch Indicator (4170WT).

12. Continue titration until blue color just disappears and solutionis colorless.

13. Read result in ppm Dissolved Oxygen.

LaMOTTE COMPANYHelping People Solve Analytical Challenges

PO Box 329 Chestertown Maryland 21620 USA800-344-3100 410-778-3100 (Outside U.S.A.) Fax 410-778-6394

Visit us on the web at www.lamotte.com

67414-MN 4/07


21/21

Documents

DO Test Procedure