Lamotte Dissolved Oxygen User Manual

Dissolved Oxygen Oxígeno disuelto Oxygène dissous

Water Quality Test Kit

Instruction Manual Code 5860-01

Kit de análisis de la calidad del agua

Manual de instrucciones Código 5860-01

Kit d’analyse de la qualité de l’eau

Manuel d’instructions Code 5860-01

Dissolved Oxygen | Water Quality Test Kit

Short Form Instructions ...................................................................................................................... 3

Introduction ........................................................................................................................................... 4

Dissolved Oxygen, Percent Saturation, & BOD .............................................................................. 4

General Safety Precautions ................................................................................................................ 8

Use Proper Analytical Techniques ..................................................................................................... 9

Kit Contents .......................................................................................................................................... 10

Test Procedure ..................................................................................................................................... 10

Part 1: Collecting a Water Sample .......................................................................................... 10

Part 2: Adding the Reagents ..................................................................................................... 11

Part 3: Titration ............................................................................................................................ 12

Percent Saturation ............................................................................................................................. 14

Biochemical Oxygen Demand .......................................................................................................... 15

Warning! This set contains chemicals that may be harmful if misused. Read cautions on individual containers carefully. Not to be used by children except under adult supervision.

SHORT FORM INSTRUCTIONS

Read all instructions before performing test. Use this guide as a 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. Add 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 DISTURB TITRATOR.

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

12. Continue titration until blue color just disappears and solution is colorless.

13. Read result in ppm Dissolved Oxygen.

INTRODUCTION

Aquatic animals need dissolved oxygen to live. Fish, invertebrates, plants, and aerobic bacteria all require oxygen for respiration. Oxygen dissolves readily into water from the atmosphere until the water is saturated. Once dissolved in the water, the oxygen diﬀ uses very slowly and distribution depends on the movement of the aerated water. Oxygen is also produced by aquatic plants, algae, and phytoplankton as a by-product of photosynthesis.

This test kit uses the azide modiﬁ cation of the Winkler method for determining dissolved oxygen.

DISSOLVED OXYGEN, PERCENT SATURATION & BOD

Oxygen is critical to the survival of aquatic plants and animals, and a shortage of dissolved oxygen is not only a sign of pollution, it is harmful to ﬁ sh. Some aquatic species are more sensitive to oxygen depletion than others, but some general guidelines to consider when analyzing test results are:

5–6 ppm Suﬃ cient for most species

< 3 ppm Stressful to most aquatic species < 2 ppm Fatal to most species

Because of its importance to the ﬁ sh’s survival, aquaculturists, or “ﬁ sh farmers,” and aquarists use the dissolved oxygen test as a primary indicator of their system’s ability to support healthy ﬁ sh.

WHERE DOES THE OXYGEN COME FROM?

The oxygen found in water comes from many sources, but the largest source is oxygen absorbed from the atmosphere. Wave action and splashing allows more oxygen to be absorbed into the water. A second major source of oxygen is aquatic plants, including algae; during photosynthesis plants remove carbon dioxide from the water and replace it with oxygen.

Absorption

Oxygen is continuously moving between the water and surrounding air. The direction and speed of this movement is dependent upon the amount of contact between the air and water. A tumbling mountain stream or windswept, wave-covered lake, where more of the water’s surface is exposed to the air, will absorb more oxygen from the atmosphere than a calm, smooth body of water. This is the idea behind aerators: by creating bubbles and waves the surface area is increased and more oxygen can enter the water.

Photosynthesis

In the leaves of plants, one of the most important chemical processes on Earth is constantly occurring: photosynthesis. During daylight, plants constantly take carbon dioxide from the air, and in the presence of water convert it to oxygen and carbohydrates, which are used to produce additional plant material. Since photosynthesis requires light, plants photosynthesis

Light + nCO2 + nH2O (C2HO)n + nO Light + Carbon Dioxide + Water Carbohydrate + Oxygen

do not photosynthesize at night, so no oxygen is produced. Chemically, the

reaction can be written as:

WHERE DOES THE OXYGEN GO?

Once in the water, oxygen is used by the aquatic life. Fish and other aquatic animals need oxygen to breathe or respire. Oxygen is also consumed by bacteria to decay, or decompose, dead plants and animals.

Respiration

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

Decomposition

All plant and animal waste eventually decomposes, whether it is from living animals or dead plants and animals. In the decomposition process, bacteria use oxygen to oxidize, or chemically alter, the material to break it down to its component parts. Some aquatic systems may undergo extreme amounts of oxidation, leaving no oxygen the living organisms, which eventually leave or suﬀ ocate.

for

PERCENT SATURATION

The oxygen level of a water system is not only dependant on production and consumption. The potential dissolved oxygen capacity of water is limited by atmospheric pressure (altitude), salinity, and temperature. These factors determine the highest DO level possible. The percent saturation value expresses the quantity of dissolved oxygen in the sample as a percent of the theoretical potential.

When water holds all of the dissolved oxygen that it can hold at a given altitude, temperature, and salinity, it is said to be 100% saturated. If it holds a quarter as much as it could possibly hold under those conditions it is 25% saturated. It is possible to get percent saturation values over 100% when water becomes highly aerated by tumbling over rapids and dams. It can also become supersaturated on a sunny day when dense areas of plants or algae produce oxygen through photosynthesis.

Low atmospheric pressure found at higher altitudes slightly decreases the solubility of oxygen in water so the dissolved oxygen value must be corrected for altitude.

The various minerals dissolved in water lower the capacity of the water to hold oxygen. correction factor can also be applied to dissolved oxygen measurements in saline waters. In fresh water, where the salinity is very low, this eﬀ ect is insigniﬁ cant when compared to the eﬀ ect of temperature. Therefore, a correction for salinity is not incorporated into the calculation.

Cold water can hold more oxygen than warm water. That is why ﬁ sh that require higher levels of oxygen, like trout, are found in cold water and dissolved oxygen concentrations usually higher in the winter than they are in the summer at the same location. The percent saturation concentration can be corrected for water temperature.

Percent saturation levels from 80 to 120 percent are considered to be excellent. Levels between 60 and 79 percent are adequate. Above 125 percent and below 60 percent saturation, levels are poor. Fish and invertebrates that can move will leave areas with low dissolved oxygen and move to areas with higher levels. Slow moving, trapped or nonmobile aquatic animals may perish if levels become too low. Extremely high dissolved oxygen concentrations are harmful to ﬁ sh even for very short periods of time. Gas bubble disease, which is characterized by the rupturing of capillaries in the gills due to supersaturated water, is usually fatal.

are

MEASURING BIOCHEMICAL OXYGEN DEMAND

Biochemical oxygen demand is determined by measuring the dissolved oxygen concentration in a freshly collected water sample and comparing it to the dissolved oxygen level in a sample that was collected at the same time but incubated under speciﬁ c conditions for a speciﬁ c length of time. The diﬀ erence between the two oxygen levels represents the amount of oxygen required for the decomposition of organic material and the oxidation of chemicals in the water during the storage period, a measurement known as the BOD.

Unpolluted, natural waters will have a BOD of 5 ppm or less. Raw sewage may have levels of 150 to 300 ppm. Wastewater treatment plants must reduce BOD to levels speciﬁ ed in their discharge permits, usually between 8 and 150 ppm BOD.

TESTING DISSOLVED OXYGEN

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

MnSO4 + 2KOH Mn(OH)2 + K2SO

Manganous + Potassium Manganous + Potassium Sulfate Hydroxide Hydroxide Sulfate

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

4Mn(OH)2 + O2 + 2H2O 4Mn(OH)

Manganous Hydroxide + Oxygen + Water Manganic Hydroxide

After the brown precipitate is formed, Sulfuric Acid 1:1 (6141) (a strong acid), is added to the sample. The acid converts the manganic hydroxide to manganic sulfate. At this point the sample is considered into the sample is reduced.

“ﬁ xed” and concern for additional oxygen being introduced

Chemically, this reaction can be written as:

2Mn(OH)3 + 3H2SO4 Mn2(SO4)3 + 6H2O Manganic Hydroxide + Sulfuric Acid Manganic Sulfate + Water

Simultaneously, iodine from the potassium iodide in the Alkaline Potassium Iodide Azide Solution is oxidized by manganic sulfate, releasing free iodine into the water. Since the manganic sulfate for this reaction comes from the reaction between the manganous hydroxide and oxygen, the amount of iodine released is directly proportional amount

of oxygen present in the original sample. The release of free iodine is indicated

to the

by the sample turning a yellow-brown color. Chemically, this reaction can be written as:

Mn2(SO4)3 + 2KI 2MnSO4 + K2SO4 + I

Manganic + Potassium Manganous + Potassium + Iodine Sulfate Iodide Sulfate Sulfate

The ﬁ nal 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 from yellow-brown to colorless. Often a starch indicator is added to enhance the ﬁ nal endpoint. Chemically, this reaction can be written as:

2Na2S2O3 + I2 Na2S4O6 + 2NaI Sodium Thiosulfate + Iodine Sodium Tetrathionate + Sodium Iodide

GENERAL SAFETY PRECAUTIONS

Store the test kit in a cool dry area.

Read all instructions and note precautions before performing the test procedure.

Instruction

Manual

Safety

Data

Read the labels on

Sheet

all reagent bottles. Note warnings and ﬁ rst aid information. Read all Safety Data Sheets.

Avoid contact between reagent chemicals and skin, eyes, nose, and mouth.

*WARNING: Reagents marked with an * are considered to be potential health hazards. for these reagents go to www.lamotte.com. Search for the four digit reagent code number listed on the reagent label, in the contents list or in the test procedures. Omit any letter that follows or precedes the four digit code number. For example, if the code is 4450WT-H, search 4450. To obtain a printed copy, contact LaMotte by email, phone or fax.

Emergency information for all LaMotte reagents is available from Chem-Tel: US, 1-800-255-3924 International, call collect, 813-248-0585

Keep all equipment and reagent chemicals out of the reach of young children.

Wear safety glasses when performing test procedures.

To view or print a Safety Data Sheet (SDS)

USE PROPER ANALYTICAL TECHNIQUES

Use test tube caps or stoppers, not your ﬁ ngers, to cover tubes during shaking or mixing.

Wipe up any reagent chemical spills immediately.

Tightly close all containers immediately after use.

Do not interchange caps from containers.

Hold dropper bottles vertically upside-down, and not at an angle, when dispensing a reagent. Squeeze the bottle gently to dispense the reagent one drop at a time.

Thoroughly rinse test tubes before and after each test.

Avoid prolonged exposure of equipment and reagents to direct sunlight. Protect reagents from extremes of temperature.

DISSOLVED OXYGEN CODE 5860-01

QUANTITY CONTENTS CODE

30 mL *Manganous Sulfate Solution *4167-G 30 mL *Alkaline Potassium Iodide Azide *7166-G 30 mL *Sulfuric Acid, 1:1 *6141WT-G 60 mL Sodium Thiosulfate, 0.025N 4169-H 30 mL Starch Indicator Solution 4170WT-G 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 an * are considered to be potential health hazards. See page XX for further safety information.

To order individual reagents or test kit components, use the speciﬁ ed code number.

TEST PROCEDURE

Part 1 - Collecting the Water Sample

1. 2.

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

Tightly cap the bottle, and submerge it to the desired depth.

3. 4.

Remove the cap and allow the bottle to ﬁ ll.

6.5.

Retrieve the bottle and make sure that no air bubbles are

trapped inside. Replace the cap while the bottle is still submerged.

Tap the sides of the bottle to dislodge any air bubbles.

Part 2 - Adding the Reagents

NOTE: Be careful not to introduce air into the sample while adding the reagents.

1. 2.

Immediately add 8 drops of *Manganous

Sulfate Solution (4167Remove the cap from the bottle.

3. 4.

Cap the bottle and mix by inverting several times. A precipitate will form.

CN) and Add 8 drops of

*Alkaline Potassium

Iodide Azide (7166-

CN).

Allow the precipitate to settle below the shoulder of the bottle.

Cap and gently invert the bottle

6.5.

to mix the contents until the precipitate and the reagent have

Add 8 drops of *Sulfuric Acid, 1:1 (6141WT-CN).

NOTE: At this point the sample has been “ﬁ xed” and contact between the sample and the atmosphere will not aﬀ ect the test result. Samples may be held at this point and titrated later.

totally dissolved. The solution will be clear yellow to orange if the sample contains dissolved oxygen.

Part 3 - The Titration

1. 2.

0.1

Fill the titration tube (0608) to the 20 mL line with the ﬁ xed sample. Cap the tube.

3. 4.

Insert the Titrator into the plug in the top of the Sodium Thiosulfate,

0.025N (4169-CN) titrating solution.

Invert the bottle and slowly withdraw the plunger until the large ring on the plunger is opposite the zero (0) line on the scale.

0.1

0.2

Depress plunger of

0.3

0.4

the Titrator (0377).

0.5

0.6

0.7

0.8

0.9

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

NOTE: If small air bubbles appear in the titrator barrel, expel them by partially ﬁ lling the barrel and pumping the titration solution back into the reagent container. Repeat until bubble disappears.

Turn the bottle upright and remove the Titrator.

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NOTE: If the sample is a very pale yellow, go to Step 9.

6. 7.

Insert the tip of the Titraror into the opening of the titration tube cap.

8. 9.

Slowly depress the plunger to dispense the titrating solution until the yellow-brown color changes to a very pale yellow. Gently swirl the tube during the titration to mix the contents.

Carefully remove the Titrator and cap. Do not disturb the Titrator plunger.

Cap the titration tube. Insert the tip of the Titrator into the opening of the titration tube cap.

12.

Read the test result directly from the scale where the large ring on the Titrator meets the Titrator barrel. Record as ppm Dissolved Oxygen. Each minor division on the Titrator scale equals 0.2 ppm.

Add 8 drops of Starch Indicator Solution (4170WT-CN). The sample should turn blue.

1110

11.10.

Continue titrating until the blue color disappears and the solution becomes colorless.

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

the value

amount of

(10 ppm)

NOTE: When testing is complete, discard the titrating solution in the Titrator. Rinse Titrator and titration tube thoroughly. DO NOT remove plunger or adapter tip.

PERCENT SATURATION

Use the atmospheric pressure reading from a barometer or the local altitude to determine the correction factor from the chart below. Multiply the dissolved oxygen test result (ppm) by the correction factor to obtain the corrected dissolved oxygen value.

Atmospheric Pressure (mmHg)

775 540 1.02 760 0 1.00 745 542 0.98 730 1094 0.96 714 1688 0.94 699 2274 0.92 684 2864 0.90 669 3466 0.88 654 4082 0.86 638 4756 0.84 623 5403 0.82 608 6065 0.80 593 6744 0.78 578 7440 0.76 562 8204 0.74 547 8939 0.72 532 9694 0.70 517 10,472 0.68

Equivalent Altitude (ft) Correction Factor

To determine the percent saturation, locate the temperature (°C) of the water sample on the top scale. Locate the corrected dissolved oxygen concentration (ppm) on the bottom scale. Draw a straight line between the two points. Read the % saturation where the line crosses the % saturation scale.

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