Taylor K-8000, User Manual, Page: 71 / 100

3-45 TTi
®
Colorimeter User’s Manual
Part 3 Colorimeter Operation
USER-DEVELOPED TESTS
A total of 8 user-developed tests can be programmed and transferred to the instrument using the TTi
®
Colorimeter Series PC App. When transferred to the instrument, user-developed tests are stored in the ALL
TESTS menu and can be added to the FAVORITES test menu or incorporated into a Series Test. Navigation
and available options are the same as preprogrammed tests.
PROGRAM AND TRANSFER A USER-DEVELOPED TEST
Four actions are required to program and transfer a user-developed test to the Colorimeter.
• prepare a calibration curve
A calibration curve is prepared by measuring the absorbance of reacted standards (e.g., standards containing
the substance to be measured plus test reagents) at various known concentrations. These absorbance vs.
concentration data pairs (up to 12 data pairs for each test) are then entered into a table in the PC App and a
graph of the calibration curve is automatically generated. The calibration curve can be linear or nonlinear with
either a positive or negative slope. If the calibration curve is linear, only two data pairs are required (the lowest
and highest concentration standard) to obtain accurate results throughout the range of the test. If the calibra-
tion curve is nonlinear, more data pairs may be needed in the area of nonlinearity to obtain accurate results
throughout the range of the test.
When preparing a calibration curve, do not exceed 2.5 absorbance (ABS) units. For positive-sloped calibration
curves, this will be the highest concentration standard. For negative-sloped calibration curves, this will be the
lowest concentration standard. If the absorbance reading exceeds 2.5 ABS, try using the shorter sample cell
viewdepth (15 mm). A sample dilution technique using a multiplication factor may also be incorporated into
the test procedure for tests with a positive-sloped calibration curve. If the sample cannot be diluted or the ABS
readings using the 15 mm sample cell still exceed 2.5 ABS, then the useable range of the test will need to be
decreased for positive-sloped calibration curves. Negative-sloped calibration curves will require a modification
to the test procedure that uses a lower indicator concentration, which may result in a decreased range for the test.
Prepare at least five or six standards from the lowest (usually 0 concentration) to the highest concentration in
increments that cover the anticipated range of the test. For instance, if the anticipated range is 0–10 ppm, then
prepare standards at 0, 2, 4, 6, 8, and 10 ppm.
Procedure
1. Turn on the Colorimeter.
2. Select a test menu (ALL TESTS, RECENT TESTS, or FAVORITES) containing Absorbance using

.
3. Select Absorbance using

; then press ENTER .
4. Select the best wavelength for the test using

; then press ENTER .
5. Rinse and fill a 25 mm sample cell to the 10 mL mark with deionized water; then cap.
6. Insert the sample cell into the sample cell compartment. Align marks.
7. Select ZERO using

; then press ENTER . Zero will be displayed.
8. Remove the sample cell from the sample cell compartment.
9. Rinse and fill a 25 mm sample cell to the 10 mL mark with the lowest concentration standard (usually
0 concentration).
10. Follow your test procedure for reagent addition, etc.; then cap and swirl to mix thoroughly.
11. Insert the sample cell into the sample cell compartment. Align marks.
12. Select READ using

; then press ENTER . Result will be displayed.
13. Record the ABS and concentration data pairs.
14. Repeat steps 9–13 for each concentration standard.