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
2
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.
3
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.
4
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:
2
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.
5
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.
A
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.
6
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
4
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)
3
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
2
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
7
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)
8
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.
9
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.
10
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.
12
1. 2.
Immediately add 8
drops of *Manganous
Sulfate Solution (4167Remove the
cap from the
bottle.
3. 4.
34
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.
65
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.
11
totally dissolved. The solution
will be clear
yellow to
orange if the
sample contains
dissolved oxygen.
Part 3 - The Titration
12
1. 2.
0
0
0.1
Fill the titration tube
(0608) to the 20 mL line
with the fi xed sample.
Cap the tube.
34
3. 4.
Insert the Titrator into
the plug in the top of
the Sodium Thiosulfate,
0.025N (4169-CN)
titrating solution.
0
.
0
1
0
.
2
.
3
0
0
.
4
0
5
.
0
.
6
.
7
0
0
8
.
.
0
9
1
0
.
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
0.2
Depress plunger of
0.3
0.3
0.4
0.4
the Titrator (0377).
0.5
0.5
0.6
0.6
0.7
0.7
0.8
0.8
0.9
0.9
1.0
1.0
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
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.
5.
5
Turn the bottle
upright and remove
the Titrator.
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
NOTE: If the sample
is a very pale yellow,
go to Step 9.
67
6. 7.
Insert the tip of the
Titraror into the opening
of the titration tube cap.
89
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.
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.
13
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.
a
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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