DissolvedOxygen

Instruction Manual • Code 7414/5860

Water Quality Test Kit

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 inthe 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 fordetermining dissolved oxygen.

TABLE OF CONTENTS

Page

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

Test ProcedurePart 1: Collecting a Water Sample ..................................... 3Part 2: Adding the Reagents ............................................... 4Part 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

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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

KIT CONTENTS

QUANTITY CONTENTS CODE

30 mL *Manganous Sulfate Solution *4167-G30 mL *Alkaline Potassium Iodide Azide *7166-G50 g *Sulfamic Acid Powder (7414 Kit) *6286-H30 mL *Sulfuric Acid, 1:1 (5860 Kit) *6141WT-G60 mL *Sodium Thiosulfate, 0.025N *4169-H30 mL Starch Indicator Solution 4170WT-G1 Spoon, 1.0 g, plastic (7414 Kit) 06971 Direct Reading Titrator 03771 Test Tube, 5-10-12.9-15-20-25 mL,

glass, w/cap0608

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.

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TEST PROCEDURE

PART 1 - COLLECTING THE WATER SAMPLE

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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.

TEST PROCEDURE

PART 2 - ADDING THE REAGENTS

5

Be careful not tointroduce air into thesample while addingthe reagents.

At this pointthe sample has

For Kit Code 5860:Add 8 drops of*Sulfuric Acid, 1:1(6141WT).

Cap and gently invert the bottleto mix the contents until the

For Kit Code 7414:Immediately use the 1.0 gspoon (0697) to add onelevel measure of *SulfamicAcid Powder (6286).

OR

NOTE: 2.

3.

Allow the precipitateto settle below theshoulder of the bottle.

5.

6. NOTE:precipitate and the reagenthave totally dissolved. Thesolution will be clear yellowto orange if the samplecontains dissolved oxygen.

been "fixed" and contactbetween the sample and theatmosphere will not affect thetest result. Samples may beheld at this point and titratedlater.

Immediately add8 drops of*ManganousSulfate Solution(4167)Add 8 drops of*AlkalinePotassium IodideAzide (7166).

AND

Remove the capfrom the bottle.

1.

4.

Cap the bottle and mixby inverting severaltimes. A precipitate willform.

TEST PROCEDURE

PART 3 - THE TITRATION

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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 . . .

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TEST PROCEDURE

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Continuetitrating untilthe blue colordisappears andthe solutionbecomescolorless.

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

Add 8 drops ofStarch IndicatorSolution(4170WT). Thesample shouldturn blue.

8.

11.10.Cap the titrationtube. Insert the tip ofthe 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.

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Result:4.0 ppm

TEST PROCEDURE

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NOTE:If the plunger ring reaches the bottom line on the scale (10 ppm)before the endpoint color change occurs, refill the Titrator andcontinue the titration. Include the value of the original amountof reagent dispensed (10 ppm) when recording the test result.

When testing is complete, discard titratingsolution in Titrator. Rinse Titrator and titrationtube thoroughly. DO NOT remove plunger oradapter tip.

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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 andWastewater. 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.

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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 SodiumThiosulfate Solution,0.025N (4169).

Swirl to dissolve.Solution will turnyellowish brown.

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EPA COMPLIANCE

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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 theTitrator 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.

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Result:2.0 ppm

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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 somegeneral guidelines to consider when analyzing test results are:

5–6 ppm Sufficient for most species

<3 ppm Stressful to most aquatic species

<2 ppm Fatal to most speciesBecause of its importance to the fish’s survival, aquaculturists, or “fish farmers,”and aquarists use the dissolved oxygen test as a primary indicator of theirsystem’s ability to support healthy fish.

WHERE DOES THE OXYGEN COME FROM?The oxygen found in water comes from many sources, but the largest source isoxygen absorbed from the atmosphere. Wave action and splashing allows moreoxygen to be absorbed into the water. A second major source of oxygen isaquatic plants, including algae; during photosynthesis plants remove carbondioxide from the water and replace it with oxygen.AbsorptionOxygen is continuously moving between the water and surrounding air. Thedirection and speed of this movement is dependent upon the amount ofcontact between the air and water. A tumbling mountain stream orwindswept, wave-covered lake, where more of the water’s surface is exposed tothe air, will absorb more oxygen from the atmosphere than a calm, smoothbody of water. This is the idea behind aerators: by creating bubbles and wavesthe surface area is increased and more oxygen can enter the water.PhotosynthesisIn the leaves of plants, one of the most important chemical processes on Earthis constantly occurring: photosynthesis. During daylight, plants constantlytake carbon dioxide from the air, and in the presence of water convert it tooxygen and carbohydrates, which are used to produce additional plantmaterial. Since photosynthesis requires light, plants do not photosynthesize atnight, so no oxygen is produced. Chemically, the photosynthesis reaction canbe written as:

Light + nCO2 + nH2O � �� (C2HO)n + nO2

Light + CarbonDioxide

+ Water � �� Carbohydrate + Oxygen

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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.RespirationAll 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 itscomponent 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 salt

water.• Temperature - Cold water can hold more oxygen than warm water.• Atmospheric pressure (Altitude) - The greater the atmospheric

pressure the more oxygen the water will hold.

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

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Immediately upon formation of the precipitate, the oxygen in the wateroxidizes an equivalent amount of the manganous hydroxide to brown-coloredmanganic hydroxide. For every molecule of oxygen in the water, fourmolecules of manganous hydroxide are converted to manganic hydroxide.Chemically, this reaction can be written as:

4Mn(OH)2 + O2 + 2H2O � �� 4Mn(OH)3

ManganousHydroxide

+ Oxygen + Water � �� ManganicHydroxide

After the brown precipitate is formed, a strong acid, such as Sulfamic AcidPowder (6286) or Sulfuric Acid, 1:1 (6141) is added to the sample. The acidconverts the manganic hydroxide to manganic sulfate. At this point thesample is considered “fixed” and concern for additional oxygen beingintroduced into the sample is reduced. Chemically, this reaction can bewritten as:

2Mn(OH)3 + 3H2SO4 � �� Mn2(SO4)3 + 6H2O

ManganicHydroxide

+ SulfuricAcid

� �� ManganicSulfate

+ Water

Simultaneously, iodine from the potassium iodide in the Alkaline PotassiumIodide Azide Solution is oxidized by manganic sulfate, releasing free iodineinto the water. Since the manganic sulfate for this reaction comes from thereaction between the manganous hydroxide and oxygen, the amount of iodinereleased is directly proportional to the amount of oxygen present in theoriginal sample. The release of free iodine is indicated by the sample turning ayellow-brown color. Chemically, this reaction can be written as:

Mn2(SO4)3 + 2KI � �� 2MnSO4 + K2SO4 + I2

ManganicSulfate

+ PotassiumIodide

� �� ManganousSulfate

+ PotassiumSulfate

+ Iodine

The final stage in the Winkler titration is the addition of sodium thiosulfate.The sodium thiosulfate reacts with the free iodine to produce sodium iodide.When all of the iodine has been converted the sample changes fromyellow-brown to colorless. Often a starch indicator is added to enhance thefinal endpoint. Chemically, this reaction can be written as:

2Na2S2O3 + I2 � �� Na2S4O6 + 2NaI

SodiumThiosulfate

+ Iodine � �� SodiumTetrathionate

+ SodiumIodide

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GENERAL SAFETY PRECAUTIONS

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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-Tel’s 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 andnote precautionsbefore performingthe testprocedure.

Instruction

Manual

2.

Keep allequipmentand reagentchemicals outof the reach ofyoungchildren.

Material

Safety

Data

SheetRead the labels onall reagent bottles.Note warnings andfirst aid information.Read all MaterialSafety Data Sheets.

3. 4.

5. 6.

USE PROPER ANALYTICAL TECHNIQUES

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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.Protectreagents fromextremes oftemperature.

2.

Wipe up any reagentchemical spills immediately.3. 4.

5. 6.

Hold dropper bottles verticallyupside-down, and not at anangle, when dispensing areagent. Squeezethe bottle gently todispense thereagent one dropat a time.

Thoroughly rinse test tubesbefore and after each test.

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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

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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

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