LaMotte COD3 Plus Operator's Manual
Operator’s
Manual
COD3 Plus
Colorimeter
1925-MN
Version 1.0
11.07.14
V2
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CONTENTS
GENERAL INFORMATION
Packaging & Delivery ...................................................................................... 5
General Precautions ...................................................................................... 5
Safety Precautions ......................................................................................... 5
Limits of Liability ............................................................................................. 6
Warranty ......................................................................................................... 6
Register Your Meter ......................................................................................... 6
Specications ................................................................................................ 7
Statistical and Technical Denitions ............................................................... 8
Contents and Accessories ............................................................................. 9
EPA Compliance .......................................................................................... 10
CE Compliance ............................................................................................. 10
IP 67 Certication .......................................................................................... 10
CHEMICAL TESTING
Water Sampling for Chemical Analysis ........................................................... 11
Filtration ........................................................................................................... 12
An Introduction to Colorimetric Analysis ..................................................... 13
Reagent Blank ............................................................................................. 14
Colorimeter Tubes and Chamber ................................................................ 14
Meter Care .................................................................................................... 14
Selecting an Appropriate Wavelength ........................................................ 14
Calibration .................................................................................................... 15
Calibration Curves ....................................................................................... 15
Standard Additions ...................................................................................... 18
Sample Dilution & Volumetric Measurements ............................................ 19
Interferences ................................................................................................ 20
Stray Light Interference ............................................................................... 20
OPERATION OF THE COD3 PLUS COLORIMETER
Overview ...................................................................................................... 21
Components ................................................................................................ 22
GENERAL OPERATING PROCEDURES
The Keypad ................................................................................................. 23
Sample Holders ............................................................................................ 23
The Display & the Menus ............................................................................ 24
Looping Menus ............................................................................................. 26
TESTING
Testing Menu ............................................................................................... 27
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Test Sequences ........................................................................................... 28
General Testing Procedures ........................................................................ 29
Testing With LaMotte Pre-Programmed Tests ............................................. 29
Calibrating LaMotte Pre-Progammed Tests ................................................. 32
Measuring in the Absorbance Mode ............................................................ 36
EDITING MENU
Editing a Sequence ..................................................................................... 39
Adding a Test ............................................................................................... 41
Deleting a Test ............................................................................................... 43
Edit User Tests ............................................................................................. 45
Naming the Test ........................................................................................... 47
Selecting the Vial and Wavelength ............................................................. 50
Entering a Two Point Calibration ................................................................. 51
Entering a Multiple Point Calibration ............................................................. 55
Selecting the Numerical Format of the Result ............................................. 58
Selecting Units of Concentration ................................................................. 59
Setting the Clock .......................................................................................... 60
Logging Data ................................................................................................ 61
Factory Setup ............................................................................................... 62
Setting the Power Save Function ................................................................. 62
Setting the Backlight Time ............................................................................ 63
Selecting a Language ................................................................................... 64
COMPUTER CONNECTION
PC Link .......................................................................................................... 66
Output .......................................................................................................... 66
Computer Connection .................................................................................. 66
SMARTLink 3 ................................................................................................. 66
BATTERY
Battery/AC Operation .................................................................................... 66
Battery Replacement ..................................................................................... 67
MAINTENANCE
Cleaning ...................................................................................................... 68
Repairs .......................................................................................................... 68
Meter Disposal .............................................................................................. 68
TROUBLESHOOTING
Error Messages ............................................................................................ 69
Troubleshooting Guide ................................................................................. 70
COD3 Plus COLORIMETER TEST PROCEDURES
APPENDIX
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COD3 Plus Colorimeter 11.14 5
GENERAL INFORMATION
PACKAGING & DELIVERY
Experienced packaging personnel at LaMotte Company assure adequate
protection against normal hazards encountered in transportation of shipments.
After the product leaves the manufacturer, all responsibility for its safe delivery
is assured by the transportation company. Damage claims must be led
immediately with the transportation company to receive compensation for
damaged goods.
Should it be necessary to return the instrument for repair or servicing, pack
instrument carefully in a suitable container with adequate packing material.
A return authorization number must be obtained from LaMotte Company by
calling 1-800-344-3100 or emailing tech@lamotte.com. Attach a letter with the
authorization number to the shipping carton which describes the kind of trouble
experienced. This valuable information will enable the service department to
make the required repairs more efciently.
GENERAL PRECAUTIONS
Before attempting to set up or operate this instrument it is important to read the
instruction manual. Failure to do so could result in personal injury or damage to
the equipment.
The COD3 Plus Colorimeter should not be stored or used in a wet or corrosive
environment. Care should be taken to prevent water or reagent chemicals from
wet colorimeter tubes from entering the colorimeter chamber.
NEVER PUT WET TUBES IN COLORIMETER.
SAFETY PRECAUTIONS
Read the labels on all LaMotte reagent containers prior to use. Some containers
include precautionary notices and rst aid information. Certain reagents are
considered hazardous substances and are designated with a * in the instruction
manual. Material Safety Data Sheets (MSDS) can be found at www.lamotte.
com. Read the MSDS before using these reagents. Additional emergency
information for all LaMotte reagents is available 24 hours a day from the Poison
Control Center listed in the front of the phone book or by contacting the 24
hour emergency line for ChemTel 1-800-255-3924 (USA, Canada, Puerto Rico);
locations outside the North American Continent 813-248-0585 (call collect). Be
prepared to supply the name and four-digit LaMotte code number found on the
container label or at the top of the MSDS or in the contents list of the procedure.
LaMotte reagents are registered with a computerized poison control information
system available to all local poison control centers.
Keep equipment and reagent chemicals out of the reach of young children.
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6 COD3 Plus Colorimeter 11.07
LIMITS OF LIABILITY
Under no circumstances shall LaMotte Company be liable for loss of life, property,
prots, or other damages incurred through the use or misuse of its products.
WARRANTY
LaMotte Company warrants this instrument to be free of defects in parts and
workmanship for 2 years from the date of shipment. If it should become
necessary to return the instrument for service during or beyond the warranty
period, contact our Technical Service Department at 1-800-344-3100 or
tech@lamotte.com for a return authorization number or visit www.lamotte.com
for troubleshooting help. The sender is responsible for shipping charges, freight,
insurance and proper packaging to prevent damage in transit. This warranty
does not apply to defects resulting from action of the user such as misuse,
improper wiring, operation outside of specication, improper maintenance or
repair, or unauthorized modication. LaMotte Company specically disclaims any
implied warranties or merchantability or tness for a specic purpose and will not
be liable for any direct, indirect, incidental or consequential damages. LaMotte
Company’s total liability is limited to repair or replacement of the product. The
warranty set forth above is inclusive and no other warranty, whether written or
oral, is expressed or implied.
REGISTER YOUR METER
To register your meter with the LaMotte Service Department, go to
www.lamotte.com and choose SUPPORT on the top navigation bar.
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COD3 Plus Colorimeter 11.14 7
SPECIFICATIONS
INSTRUMENT TYPE: Colorimeter
Readout 160 x 100 backlit LCD, 20 x 6 line graphical display
Wavelengths 428 nm, 635 nm
Wavelength Accuracy ±2% FS
Readable Resolution Determined by reagent system
Wavelength Bandwidth 10 nm typical
Photometric Range –2 to +2 AU
Photometric Precision ± 0.001 AU at 1.0 AU
Photometric Accuracy ±0.005 AU at 1.0 AU
Sample Chamber Accepts 25 mm diameter at-bottomed test tubes, 10
mm square cuvettes, 16 mm COD test tubes
Light Sources 2 LEDs
Detectors 2 silicon photodiodes
Modes Pre-programmed tests, absorbance, %T
Pre-Programmed Tests YES, with automatic wavelength selection
User Dened Tests Up to 25 user tests can be input
Languages English, Spanish, French, Portuguese, Italian,
Chinese, Japanese
USB Port Mini B
Power Requirements USB wall adapter, USB computer connection or
lithium ion rechargeable battery
Battery Charge Life: Approximately 380 tests with backlight
on to 1000 tests with backlight off. (Signal averaging
disabled).
Battery Life: Approximately 500 charges.
Electrical Rating Provided on nameplate label
Data Logger 500 test results stored for download to a PC
Waterproof IP67 with USB port plug in place
Dimensions (LxWxH) 3.5 x 7.5 x 2.5 inches, 8.84 x 19.05 x 6.35 cm
Weight 13 oz, 362 g (meter only)
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8 COD3 Plus Colorimeter 11.07
STATISTICAL & TECHNICAL DEFINITIONS RELATED TO PRODUCT
SPECIFICATIONS
Method Detection Limit (MDL): “The method detection limit (MDL) is dened
as the minimum concentration of a substance that can be measured and
reported with 99% condence that the analyte concentration is greater than zero
and is determined from analysis of a sample in a given matrix containing the
analyte.”1 Note that, “As Dr. William Horwitz once stated, ‘In almost all cases when
dealing with a limit of detection or limit of determination, the primary purpose of
determining that limit is to stay away from it.’”
2
Accuracy: Accuracy is the nearness of a measurement to the accepted or true
value.3 The accuracy can be expressed as a range, about the true value, in
which a measurement occurs (i.e. ±0.5 ppm). It can also be expressed as the
% recovery of a known amount of analyte in a determination of the analyte (i.e.
103.5 %).
Resolution: Resolution is the smallest discernible difference between any
two measurements that can be made.4 For meters this is usually how many
decimal places are displayed. (i.e. 0.01). Note that the resolution many change
with concentration or range. In some cases the resolution may be less than the
smallest interval, if it is possible to make a reading that falls between calibration
marks. A word of caution, that resolution has very little relationship to accuracy or
precision. The resolution will always be less than the accuracy or precision but it
is not a statistical measure of how well a method of analysis works. The resolution
can be very, very good and the accuracy and precision can be very bad! This is
not a useful measure of the performance of a test method.
Repeatability: Repeatability is the within-run precision.5 A run is a single data
set, from set up to clean up. Generally, one run occurs on one day. However, for
meter calibrations, a single calibration is considered a single run or data set, even
though it may take 2 or 3 days.
Reproducibility: Reproducibility is the between-run precision.
6
Detection Limit (DL): The detection limit (DL) for the 2020we/wi
is dened as the minimum value or concentration that can be determined by the
meter, which is greater than zero, independent of matrix, glassware, and other
sample handling sources of error. It is the detection limit for the optical system of
the meter.
1
CFR 40, part 136, appendix B
2
Statistics in Analytical Chemistry: Part 7 – A Review, D. Coleman and L Vanatta,
American Laboratory, Sept 2003, P. 31.
3
Skoog, D.A., West, D. M., Fundamental of Analytical Chemistry, 2nd ed., Holt
Rinehart and Winston, Inc, 1969, p. 26.
4
Statistics in Analytical Chemistry: Part 7 – A Review, D. Coleman and L Vanatta,
American Laboratory, Sept 2003, P. 34.
5
Jeffery G. H., Basset J., Mendham J., Denney R. C., Vogel’s Textbook of
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COD3 Plus Colorimeter 11.14 9
Quantitative Chemical Analysis, 5th ed., Longman Scientic & Technical, 1989, p.
130.
6
Jeffery G. H., Basset J., Mendham J., Denney R. C., Vogel’s Textbook of
Quantitative Chemical Analysis, 5th ed., Longman Scientic & Technical, 1989, p.
130
CONTENTS AND ACCESSORIES
CONTENTS
COD3 Plus Colorimeter
Test Tubes, with Caps
COD/UDV Adapter
USB Wall Adapter
USB Cable
COD3 Plus Colorimeter Quick Start Guide
COD3 Plus Colorimeter Manual
ACCESSORIES
Test Tubes, with Caps Code 0290-6
Replacement Chamber Code 3-0038
USB Cable Code 1720
USB Wall Adapter Code 1721
COD/UDV Adapter Code 1724
Car Charger Code 5-0132
SMARTLink3 Program (CD) Code 1901-CD
Small Field Carrying Case
(37.5 27.5 x 13.75 cm)
Code 1910-GCS150
Large Field Carrying Case
(45 x 32.5 x 20 cm)
Code 1910-GCS440
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10 COD3 Plus Colorimeter 11.07
EPA COMPLIANCE
The COD3 Plus Colorimeter is an EPA-Accepted instrument. EPA-Accepted
means that the instrument meets the requirements for instrumentation as found
in test procedures that are approved for the National Primary Drinking Water
Regulations (NPDWR) or National Pollutant Discharge Elimination System
(NPDES) compliance monitoring programs. EPA-Accepted instruments may be
used with approved test procedures without additional approval.
CE COMPLIANCE
The COD3 Plus Colorimeter has earned the European CE Mark of Compliance for
electromagnetic compatibility and safety. The Declaration of Conformity for the
COD3 Plus Colorimeter is available at www.lamotte.com.
IP67 CERTIFICATION
The COD3 Plus meets IP67 standards for protection against dust and immersion
only when the USB port plug is in place. Documentation is available at www.
lamotte.com.
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COD3 Plus Colorimeter 11.14 11
CHEMICAL TESTING
WATER SAMPLING FOR CHEMICAL ANALYSIS
Taking Representative Samples
The underlying factor to be considered for any type of water sampling is whether
or not the sample is truly representative of the source. To properly collect a
representative sample:
• Sample as frequently as possible.
• Collect a large sample or at least enough to conduct whatever tests are
necessary.
• Make a composite sample for the same sampling area.
• Handle the sample in such a way as to prevent deterioration or
contamination before the analysis is performed.
• Perform analysis for dissolved gases such as dissolved oxygen, carbon
dioxide, and hydrogen sulde immediately at the site of sampling. Samples
for testing these factors, as well as samples for pH, cannot be stored for later
examination.
• Make a list of conditions or observations which may affect the sample. Other
considerations for taking representative samples are dependent upon the
source of the sample. Taking samples from surface waters involves different
considerations than taking samples from impounded and sub-surface
waters.
Sampling of Open Water Systems
Surface waters, such as those found in streams and rivers, are usually well mixed.
The sample should be taken downstream from any tributary, industrial or sewage
pollution source. For comparison purposes samples may be taken upstream and
at the source of the pollution before mixing.
In ponds, lakes, and reservoirs with restricted ow, it is necessary to collect a
number of samples in a cross section of the body of water, and where possible
composite samples should be made to ensure representative samples.
To collect samples from surface waters, select a suitable plastic container with
a tight tting screw cap. Rinse the container several times with the sample to be
tested, then immerse the container below the surface until it is lled to overowing
and replace the cap. If the sample is not to be tested immediately, pour a small
part of the sample out and reseal. This will allow for any expansion. Any condition
which might affect the sample should be listed.
Sub-surface sampling is required to obtain a vertical prole of streams, lakes,
ponds, and reservoirs at specic depths. This type of sampling requires more
sophisticated sampling equipment.
For dissolved oxygen studies, or for tests requiring small sample sizes, a Water
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12 COD3 Plus Colorimeter 11.07
Sampler (LaMotte Code 1060) will serve as a subsurface or in-depth sampler.
This weighted device is lowered to the sampling depth and allowed to rest at
this depth for a few minutes. The water percolates into the sample chamber
displacing the air which bubbles to the surface. When the bubbles cease to rise,
the device has ushed itself approximately ve times and it may be raised to
the surface for examination. The inner chamber of the sampling device is lifted
out and portions of the water sample are carefully dispensed for subsequent
chemical analysis.
A Snap-Plunger Water Sampler (LaMotte Code 1077) is another “in-depth”
sampling device which is designed to collect large samples which can be used
for a multitude of tests. Basically, this collection apparatus is a hollow cylinder
with a spring loaded plunger attached to each end. The device is cocked
above the surface of the water and lowered to the desired depth. A weighted
messenger is sent down the calibrated line to trip the closing mechanism and the
plungers seal the sample from mixing with intermediate layers as it is brought to
the surface. A special drain outlet is provided to draw off samples for chemical
analysis.
Sampling of Closed System
To obtain representative samples from conned water systems, such as
pipe lines, tanks, vats, lters, water softeners, evaporators and condensers,
different considerations are required because of chemical changes which occur
between the inlet and outlet water. One must have a basic understanding of the
type of chemical changes which occur for the type of equipment used. Also,
consideration should be given to the rate of passage and retaining time for the
process water.
Temperature changes play an important part in deciding exactly what test should
be performed. Process water should be allowed to come to room temperature,
20–25°C, before conducting any tests.
When drawing off samples from an outlet pipe such as a tap, allow sample to
run for several minutes, rinsing the container several times before taking the nal
sample. Avoid splashing and introduction of any contaminating material.
FILTRATION
When testing natural waters that contain signicant turbidity due to suspended
solids and algae, ltration is an option. Reagent systems, whether EPA, Standard
Methods, LaMotte or any others, will generally only determine dissolved
constituents. Both EPA and Standard Methods suggest ltration through a 0.45
micron lter membrane, to remove turbidity, for the determination of dissolved
constituents.** To test for total constituents, organically bound and suspended or
colloidal materials, a rigorous high temperature acid digestion is necessary.
**LaMotte offers a ltering apparatus: syringe assembly (Code 1050) and
membrane lters, 0.45 micron, (Code 1103).
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COD3 Plus Colorimeter 11.14 13
AN INTRODUCTION TO COLORIMETRIC ANALYSIS
Most test substances in water are colorless and undetectable to the human eye.
To test for their presence we must nd a way to “see” them. The COD3 Plus
Colorimeter can be used to measure any test substance that is itself colored or
can be reacted to produce a color. In fact a simple denition of colorimetry is
“the measurement of color” and a colorimetric method is “any technique used
to evaluate an unknown color in reference to known colors”. In a colorimetric
chemical test the intensity of the color from the reaction must be proportional to
the concentration of the substance being tested. Some reactions have limitations
or variances inherent to them that may give misleading results. Many such
interferences are discussed with each particular test instruction. In the most basic
colorimetric method the reacted test sample is visually compared to a known
color standard. However, accurate and reproducible results are limited by the
eyesight of the analyst, inconsistencies in the light sources, and the fading of
color standards.
To avoid these sources of error, a colorimeter can be used to photoelectrically
measure the amount of colored light absorbed by a colored sample in reference
to a colorless sample (blank).
White light is made up of many different colors or wavelengths of light. A colored
sample typically absorbs only one color or one band of wavelengths from the
white light. Only a small difference would be measured between white light before
it passes through a colored sample versus after it passes through a colored
sample. The reason for this is that the one color absorbed by the sample is only
a small portion of the total amount of light passing through the sample. However,
if we could select only that one color or band of wavelengths of light to which the
test sample is most sensitive, we would see a large difference between the light
before it passes through the sample and after it passes through the sample.
The COD3 Plus Colorimeter passes one of four colored light beams through
one of four optical lters which transmits only one particular color or band of
wavelengths of light to the photodectector where it is measured. The difference
in the amount of colored light transmitted by a colored sample is a measurement
of the amount of colored light absorbed by the sample. In most colorimetric tests
the amount of colored light absorbed is directly proportional to the concentration
of the test factor producing the color and the path length through the sample.
However, for some tests the amount of colored light absorbed is inversely
proportional to the concentration.
The choice of the correct wavelength for testing is important. It is interesting to
note that the wavelength that gives the most sensitivity (lower detection limit)
for a test factor is the complementary color of the test sample. For example the
Nitrate-Nitrogen test produces a pink color proportional to the nitrate-nitrogen
concentration in the sample (the greater the nitrate-nitrogen concentration, the
darker the pink color). A wavelength in the green region should be selected to
analyze this sample since a pinkish-red solution absorbs mostly green light.
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14 COD3 Plus Colorimeter 11.07
REAGENT BLANK
Some tests will provide greater accuracy if a reagent blank is determined to
compensate for any color or turbidity resulting from the reagents themselves. A
reagent blank is performed by running the test procedure on demineralized or
deionized water. Use sample water to SCAN BLANK. Insert the reacted reagent
blank in the colorimeter chamber and select SCAN SAMPLE. Note result of
reagent blank. Perform the tests on the sample water as described. Subtract
results of reagent blank from all subsequent test results. NOTE: Some tests
require a reagent blank to be used to SCAN BLANK.
COLORIMETER TUBES AND CHAMBER
Colorimeter tubes and colorimeter chambers which have been scratched through
excessive use should be discarded and replaced with new ones. Dirty tubes
should be cleaned on both the inside and outside. Fingerprints on the exterior
of the tubes can cause excessive light scattering and result in errors. Handle the
tubes carefully, making sure the bottom half of the tube is not handled.
LaMotte Company makes every effort to provide high quality colorimeter tubes.
However, wall thicknesses and diameter of tubes may still vary slightly. This may
lead to slight variations in results (e.g. if a tube is turned while in the sample
chamber, the reading will likely change slightly). To eliminate this error put the
tubes into the sample chamber with the same orientation every time.
The tubes that are included with the colorimeter have an index mark to facilitate
this. If possible, use the same tube to SCAN BLANK and SCAN SAMPLE.
METER CARE
The optical system of the COD3 Plus must be kept clean and dry for optimal
performance. Dry the colorimeter tubes before placing them in the chamber to
avoid introducing moisture. For best results store the instrument in a area that is
dry and free from aggressive chemical vapors.
SELECTING AN APPROPRIATE WAVELENGTH
The most appropriate wavelength to use when creating a calibration curve
is usually the one which gives the greatest change from the lowest reacted
standard concentration to the highest reacted standard concentration. However,
the absorbance of the highest reacted standard concentration should never
be greater than 2.0 absorbance units. Scan the lowest and highest reacted
standards at different wavelengths using the absorbance mode to nd the
wavelength which gives the greatest change in absorbance without exceeding 2.0
absorbance units. Use this wavelength to create a calibration curve.
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COD3 Plus Colorimeter 11.14 15
Below is a list of suggested wavelengths for the color of the reacted samples. Use
these as a starting point.
Sample Color Wavelength Range
Yellow 428
Pink 525
Red 568
Green and Blue 635
NOTE: Available wavelengths in the COD3 Plus are 428 nm and 635 nm.
CALIBRATION
As with all pre-calibrated meters, it is highly recommended, even if not required
by regulations, that the user periodically verify the performance of the meter
by running standards with a predetermined concentration. Results outside of
specication are an indication that the meter needs to be adjusted. This can be
done following the user calibration described on page 32. If the user calibration
fails to properly adjust the meter then the meter should be returned to LaMotte
Company for recalibration. (See page 68).
CALIBRATION CURVES
The COD3 Plus Colorimeter contains tests for the LaMotte reagent systems. The
rst step in using a non-LaMotte reagent system with your COD3 Plus Colorimeter
is to create a calibration curve for the reagent system. To create a calibration
curve, prepare standard solutions of the test factor and use the reagent system to
test the standard solutions with the COD3 Plus Colorimeter. Select a wavelength
for the test as described above.
Plot the results (in ABS or %Transmittance) versus concentration to create
a calibration curve. The calibration curve may then be used to identify the
concentration of an unknown sample by testing the unknown, reading
Absorbance or %T, and nding the corresponding concentration from the curve.
The linear range of the reagent system can be determined and this information
can be used to input a User Test into the COD3 Plus Colorimeter (see Edit User
Tests, page 39).
PROCEDURE
Prepare 5 or 6 standard solutions of the factor being tested. The concentration of
these standards should be evenly distributed throughout the range of the reagent
system, and should include a 0 ppm standard (distilled water). For instance,
the solutions could measure 0, 10%, 30%, 50%, 70%, and 90% of the system’s
maximum range.
1. Turn on the COD3 Plus Colorimeter. Select the appropriate wavelength from
the absorbance mode. Be sure to select the appropriate wavelength for the
color produced by the reagent system.
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16 COD3 Plus Colorimeter 11.07
2. Use the unreacted 0 ppm standard to standardize the colorimeter by using it
to scan blank.
3. Following the individual reagent system instructions, react each standard
solution beginning with 0 ppm. Continue with standards in increasing
concentration. Record the reading and the standard solution concentration
on a chart. Readings can be recorded as percent transmittance (%T) or
absorbance (A).
4. Plot results on graph paper or computer using any available plotting program.
If results are as %T versus concentration, semilog graph paper must be
used. Plot the standard solution concentrations on the horizontal, linear axis,
and the %T on the vertical, logarithmic axis. If results are as absorbance
versus standard solution concentration, simple linear graph paper can be
used. Plot the standard solution concentration on the horizontal axis, and the
absorbance on the vertical axis.
5. After plotting the results, draw a line, or curve, of best t through the
plotted points. The best t may not connect the points. There should be
approximately an equal number of points above the curve as below the curve.
Some reagent systems will produce a straight line, while others produce a
curve. Many computer spreadsheet programs can produce the curve of best
t by regression analysis of the standard solution data.
NOTE: Only reagent systems which produce a straight line can be used for a
User Test.
A sample of each type of graph appears below:
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COD3 Plus Colorimeter 11.14 17
PREPARING DILUTE STANDARD SOLUTIONS
Standard solutions should be prepared to create a calibration curve. Standard
solutions can be prepared by diluting a known concentrated standard by
specied amounts. A chart or computer spreadsheet can be created to determine
the proper dilutions. Use volumetric asks and volumetric pipets for all dilutions.
1. In Column A – Record the maximum concentration of test as determined by
the range and path length.
2. In Column B – Record the percent of the maximum concentration the
standard solution will be.
3. In Column C – Calculate the nal concentration of the diluted standard
solutions by multiplying the maximum concentration (In Column A) by the %
of maximum concentration divided by 100. (C = A x
B
/
100
).
4. In Column D – Record the nal volume of the diluted sample (i.e. volume of
volumetric ask).
5. In Column E – Record the concentration of the original standard.
6. In Column F – Calculate the milliliters of original standard required (F = (C x
D
/E)).
A sample chart appears below:
A B C =
A x B/
100
D E F =
C x D/E
Maximum
concentration
of test
% of Maximum
concentration
Final
concentration
of Diluted
Standard
Volume of
Standard
Concentration
of Original
Standard
mL of
Original
Standard
Required
10.0 ppm 90 9.0 ppm 100 mL 1000 ppm 0.90 mL
10.0 ppm 70 7.0 ppm 100 mL 1000 ppm 0.70 mL
10.0 ppm 50 5.0 ppm 100 mL 1000 ppm 0.50 mL
10.0 ppm 30 3.0 ppm 100 mL 1000 ppm 0.30 mL
10.0 ppm 10 1.0 ppm 100 mL 1000 ppm 0.10 mL
10.0 ppm 0 0 ppm 100 mL 1000 ppm 0 mL
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STANDARD ADDITIONS
A common method to check the accuracy and precision of a test is by standard
additions. In this method a sample is tested to determine the concentration of
the test substance. A second sample is then “spiked” by the addition of a known
quantity of the test substance. The second sample is then tested. The determined
concentration of the spiked sample should equal the concentration of the first plus
the amount added with the spike. The procedure can be repeated with larger and
larger “spikes.” If the determined concentrations do not equal the concentration of
the sample plus that added with the “spike”, then an interference may exist.
For example, a 10.0 mL water sample was determined to contain 0.3 ppm iron.
To a second 10.0 mL sample, 0.1 mL of 50 ppm iron standard was added. The
concentration of iron due to the “spike” was (0.10 mL x 50 ppm)/10.0 mL = 0.50
ppm. The concentration of iron determined in the spiked sample should be 0.3 +
0.5 = 0.8 ppm iron. (Note: any error due to the increased volume from the “spike” is
negligible).
LaMotte offers a line of calibration standards which can be used to generate
calibration curves and perform standard additions.
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COD3 Plus Colorimeter 11.14 19
SAMPLE DILUTION TECHNIQUES & VOLUMETRIC
MEASUREMENTS
If a test result using the COD3 Plus Colorimeter gives an over range message
then the the sample must be diluted. The test should be repeated on the diluted
sample to obtain a reading which is in the concentration range for the test. (Note:
This is not true for colorimetric determination of pH.)
Example:
Measure 5 mL of the water sample into a graduated cylinder. Add
demineralized water until the cylinder is lled to the 10 mL line. The
sample has been diluted by one-half, and the dilution factor is therefore
2. Perform the test procedure, then multiply the resulting concentration
by 2 to obtain the test result.
The following table gives quick reference guidelines on dilutions of various
proportions. All dilutions are based on a 10 mL volume, so several dilutions will
require small volumes of the water sample. Graduated pipets should be used for
all dilutions.
Size of Sample
Deionized Water to
Bring Volume to 10 mL Multiplication Factor
10 mL 0 mL 1
5 mL 5 mL 2
2.5 mL 7.5 mL 4
1 mL 9 mL 10
0.5 mL 9.5 mL 20
If the above glassware is not available, dilutions can be made with the colorimeter
tube. Fill the tube to the 10 mL line with the sample then transfer it to another
container. Add 10 mL volumes of demineralized water to the container and
mix. Transfer back 10 mL of the diluted sample to the tube and follow the
test procedure. Continue diluting and testing until a reading, which is in the
concentration range for the test, is obtained. Be sure to multiply the concentration
found by the dilution factor (the number of total 10 mL volumes used).
Example:
10 mL of sample is diluted with three 10 mL volumes of demineralized
water; the dilution factor is four.
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20 COD3 Plus Colorimeter 11.07
INTERFERENCES
LaMotte reagent systems are designed to minimize most common interferences.
Each individual test instruction discusses interferences unique to that test. Be
aware of possible interferences in the water being tested.
The reagent systems also contain buffers to adjust the water sample to the ideal
pH for the reaction. It is possible that the buffer capacity of the water sample may
exceed the buffer capacity of the reagent system and the ideal pH will not be
obtained. If this is suspected, measure the pH of a reacted distilled water reagent
blank using a pH meter. This is the ideal pH for the test. Measure the pH of a
reacted water sample using the pH meter. If the pH is signicantly different from
the ideal value, the pH of the sample should be adjusted before testing.
Interferences due to high concentration of the substance being tested, can be
overcome by sample dilution (see page 19)
STRAY LIGHT INTERFERENCE
When scanning samples in 16 mm tubes, such as COD, the sample chamber lid
can not be closed. The COD adapter minimizes stray light. To further reduce stray
light interference, do not scan sample in direct sunlight.
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COD3 Plus Colorimeter 11.14 21
OPERATION OF THE
COD3 PLUS COLORIMETER
OVERVIEW
The COD3 Plus is a portable, microprocessor controlled, direct reading
colorimeter. It has a graphical liquid crystal display and 6 button keypad. These
allow the user to select options from the menu driven software, to directly read
test results or to review stored results of previous tests in the data logger. The
menus can be displayed in seven different languages.
The test library consists of 29 LaMotte tests and 25 “User Tests”. The LaMotte
tests are precalibrated for LaMotte reagent systems.The colorimeter displays the
result of these tests directly in units of concentration. The 25 “User Tests” may be
used to enter additional calibrations. All of these tests may be arranged in any of
3 sequences. These sequences can be modied a limitless number of times to
meet changing testing needs.
The optics feature 2 different colored LEDs. Each LED has a corresponding
silicon photoiode with an integrated interference lter. The interference lters
select a narrow band of light from the corresponding LED for the colorimetric
measurements. The microporcessor automatically selects the correct LED/
photodiode combination for the test.
A USB wall adapter, USB computer connection or lithium battery powers the
COD3 Plus.
A USB port on the back of the meter allows an interface of the meter with a
Windows-based computer for real-time data acquisition and data storage using
a PC. The COD3 Plus may be interfaced with any Windows-based computer by
using the LaMotte SMARTLink3 Program.
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22 COD3 Plus Colorimeter 11.07
COMPONENTS
Figure 1 shows a diagram of the COD3 Plus Colorimeter and its components.
COD3 Plus
COLORIMETER
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COD3 Plus Colorimeter 11.14 23
GENERAL OPERATING PROCEDURES
The operation of the COD3 Plus Colorimeter is controlled by a microprocessor.
The microprocessor is programmed with menu driven software. A menu is a list
of choices. This allows a selection of various tasks for the colorimeter to perform,
such as, scan blank, scan sample, and edit test sequences. The keypad is
used to make menu selections which are viewed in the display. There are three
selections accessible from the Main Menu: Testing Menu, Editing Menu and Run
PC Link.
THE KEYPAD
The keypad has 6 buttons which are used to perform specic tasks.
This button will scroll up through a list of menu selections.
ENTER
The button is used to select choices in a menu viewed in
the display.
This button controls the backlight on the display.
This button will scroll down through a list of menu
selections.
EXIT
This button exits to the previous menu.
This button turns the meter on or off.
EX I T
ENTER
SAMPLE HOLDERS
The sample chamber is designed for 25 mm round
tubes. An adapter to hold 16 mm COD tubes and 1
cm square UDV cuvettes is included.
Position the COD/UDV Adapter (Code 1724) so
that the notches in the adapter t around the posts
on the chamber. Turn the adapter counterclockwise
until the arrows are at the top and bottom of the
chamber and the adapter is locked into place. Turn
the adapter clockwise to unlock the adapter and
remove it from the chamber.
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24 COD3 Plus Colorimeter 11.07
THE DISPLAY & THE MENUS
The display allows menu selections to be viewed and selected. These selections
instruct the COD3 Plus to perform specic tasks. The menus are viewed in the
display using two general formats that are followed from one menu to the next.
Each menu is a list of choices or selections.
The display has a header line at the top and a footer line at the bottom. The
header displays the title of the current menu. The footer line displays the time
and the date, the data logger status and the battery status. The menu selection
window is in the middle of the display between the header and the footer.
The menu selection window displays information in two general formats. In the
rst format only menu selections are displayed. Up to 4 lines of menu selections
may be displayed. If more selections are available they can be viewed by
pressing the arrow buttons to scroll the other menu selections into
the menu selection window. Think of the menu selections as a vertical list in the
display that moves up or down each time an arrow button is pressed.
Some menus in the COD3 Plus are looping menus. The top and bottom menu
choices are connected in a loop. Scrolling down past the bottom of the menu will
lead to the top of the menu. Scrolling up past the top of the menu will lead to the
bottom of the menu.
Header Menu Title
Main Window Selection First Choice
Second Choice
Third Choice
Another
Footer
12:00:00 001/500
And Another
And So On
A light bar will indicate the menu choice. As the menu is scrolled through, the
light bar will highlight different menu choices. Pressing the
ENTER
button will
select the menu choice that is indicated by the light bar.
In the second format the menu choice window takes advantage of the graphical
capabilities of the display. Large format graphic information, such as test results
or error messages or the LaMotte logo is displayed. The top two lines of the
display are used to display information in a large, easy to read format. The menus
work in the same way as previously described but two lines of the menu are
visible at the bottom of the display.
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COD3 Plus Colorimeter 11.14 25
Header Menu Title
Message or Result Window
Result or
Message
Another
Main Window Selection And Another
Footer
12:00:00 001/500
And So On
Last Choice
As described previously, the
EXIT
button allows an exit or escape from the
current menu and a return to the previous menu. This allows a rapid exit from an
inner menu to the main menu by repeatedly pushing the
EXIT
button. Pushing
at any time will turn the COD3 Plus off.
The display may show the following messages:
Battery Status
More choices are available and can be viewed by
scrolling up and/or down through the display.
Header Identies the current menu and information on units
and reagent systems if applicable.
Footer In the data logging mode the number of the data point
is displayed and the total number of data points in the
memory will be shown. The footer also shows current
time and battery status
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LOOPING MENUS
Long menus, such as All Tests, incorporate a looping feature which allows the
user to quickly reach the last choice in the menu from the rst choice. In a looping
menu the last choices in the menu are above the rst choice and scrolling upward
moves through the menu in reverse order. Scrolling downward moves through the
menu from rst choice to last but the menu starts over following the last choice.
So all menu choices can be reached by scrolling in either direction. The diagrams
below demonstrate a looping menu.
AND SO ON AND SO ON AND SO ON
: : : : : : : : :
: : : : : : : : :
THIRD TO LAST LAST CHOICE LAST CHOICE
SECOND TO LAST AND SO ON AND SO ON
LAST CHOICE : : : : : :
TESTING MENU TESTING MENU TESTING MENU
FIRST CHOICE : : : : : :
SECOND CHOICE THIRD TO LAST THIRD TO LAST
THIRD CHOICE SECOND TO LAST SECOND TO LAST
ANOTHER LAST CHOICE LAST CHOICE
12:00:00 001/500 12:00:00 001/500 12:00:00 001/500
AND ANOTHER FIRST CHOICE FIRST CHOICE
AND SO ON SECOND CHOICE SECOND CHOICE
: : : THIRD CHOICE THIRD CHOICE
: : : ANOTHER ANOTHER
LAST CHOICE AND ANOTHER AND ANOTHER
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COD3 Plus Colorimeter 11.14 27
TESTING
TESTING MENU
The Testing Menu is used to run all LaMotte pre-programmed tests, User Tests
and Absorbance tests at one of two wavelengths. Testing from any of three
sequences can also be done.
1. Press and briey hold
to turn the meter on. The
LaMotte logo screen will
appear for about 3 seconds
and the Main Menu will
appear.
Main Menu
Testing Menu
Editing Menu
Run PC Link
12:00:00 001/500
2. Press
ENTER
to select Testing
Menu.
Testing Menu
All Tests Menu
Sequence 1
Sequence 2
Sequence 3
12:00:00 001/500
3. Press or to scroll
to desired option. All Tests
contains all of the available
pre-programmed tests. The
three sequences have user
selected tests. Absorbance
has %T/ABS tests.
Testing Menu
All Tests Menu
Sequence 1
Sequence 2
Sequence 3
12:00:00 001/500
4. Press
ENTER
to select the
option.
All Tests
001 Alkalinity UDV
002 Aluminum
003 Ammonia-N LRF
004 Ammonia-N LRS
12:00:00 001/500
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TEST SEQUENCES
Sequence 1, Sequence 2, And Sequence 3 are alterable sequences. They may
be edited using the Editing Menu. Any of the LaMotte pre-programmed tests or
User Tests may be placed in these sequences in whatever testing order that is
preferred. Some examples of typical sequences are given below.
NOTE: Test in the examples may not be included in the COD3 Plus.
Sequence 1 Sequence 2 Sequence 3
015 Chlorine F UDV 002 Aluminum 003 Ammonia-N LRF
079 Phosphate HR 035 Cyanuric Acid 032 Cu UDV
009 Benzotriazole 053 Iron Phenanthro 064 Nitrate-N LR
076 pH UDV 055 Manganese LR 067 Nitrite-N LR
12:00:00 001/500
12:00:00 001/500 12:00:00 001/500
061 Molybdenum HR 064 Nitrate-N LR 074 pH PR
086 Silica HR 067 Nitrite-N LR 078 Phosphate LR
045 Hydrazine 077 Phenol 085 Silica LR
032 Cu UDV 078 Phosphate LR
051 Iron Bipyridyl 090 Sulde LR
These alterable sequences allow a series of tests to be setup that are run
frequently. The order of the individual tests in the sequence is determined by the
user. After running a test, press
ENTER
to select the next test in the sequence.
Continue this pattern until the entire sequence has been completed.
All Tests is a xed sequence containing the LaMotte pre-programmed tests, User
Tests, and Absorbance tests.
Modication of the alterable sequences is accomplished through the Editing
Menu. This menu is explained in greater detail in Editing Menu (p. 39).
Pressing
EXIT
while in a sequence menu will escape back to the Testing Menu.
Pressing the at any time will turn the colorimeter off.
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COD3 Plus Colorimeter 11.14 29
GENERAL TESTING PROCEDURES
The following are some step by step examples of how to run tests from the
Testing Menu. These test procedures are designed to be used with LaMotte
SMART Reagent Systems.
LaMotte Company continuously updates the list of pre-programmed tests as the
calibrations become available. Pre-programmed calibrations can be added to
the COD3 Plus Colorimeter in the eld. A Windows-based computer running a
Windows Operating System is required.
Call LaMotte Technical Services at 1-800-344-3100 (410-778-3100 outside the
USA) or email at tech@lamotte.com for a current list of available calibrations and
downloading instructions.
TESTING WITH LaMOTTE PRE-PROGRAMMED TESTS
NOTE: Test in the examples may not be included in the COD3 Plus.
1. Press and briey hold
to turn the meter on. The
LaMotte logo screen will
appear for about 3 seconds
and the Main Menu will
appear.
Main Menu
Testing Menu
Editing Menu
Run PC Link
12:00:00 001/500
2. Press
ENTER
to select Testing
Menu.
Testing Menu
All Test Menu
Sequence 1
Sequence 2
Sequence 3
12:00:00 001/500
3. Press
ENTER
to select All Tests
Menu.
All Tests
001 Alkalinity UDV
002 Aluminum
003 Ammonia-N LRF
004 Ammonia-N LRS
12:00:00 001/500
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30 COD3 Plus Colorimeter 11.07
4. Press or to scroll
to the desired test.
All Tests
001 Alkalinity UDV
002 Aluminum
003 Ammonia-N LRF
004 Ammonia-N LRS
12:00:00 001/500
5. Press
ENTER
to select the test.
002 Aluminum
Scan Bank
Scan Sample
12:00:00 001/500
6. Insert the blank into the
chamber. Close the lid.Press
ENTER
to scan the blank. The
screen wil display Blank
Done for about 1 second and
then return to the Test Menu.
002 Aluminum
Scan Blank
Scan Sample
12:00:00 001/500
7. Insert the reacted sample
into the chamber. Close
the lid. Press
ENTER
to scan
the sample. The screen will
display READING for about 1
second. The result will appear
on the screen.
002 Aluminum
1.00 ppm
Scan Blank
Scan Sample
12:00:00 001/500
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