LaMotte TC-3000 Tri-Meter - Manual (Page 9)

expected to give the same result because the absorbance spectrum of natural water is
usually not identical to the absorbance spectrum of chloroplatinate/cobalt standards.
The reading that the meter displays is a correlation between the color of the sample
water and the color standards at a fixed wavelength. The correlation, and reading, will
change as the wavelength changes The TC-3000 takes advantage of this fact by
selecting a wavelength that gives much greater sensitivity when measuring the color of
most natural waters, than single wavelength meters that use much higher wavelengths.
Taking Color Water Samples
Samples should ideally be collected in glass containers. Perform the analysis soon after
sampling since the color may change with time. For true color determinations, remove
turbidity by filtration or centrifugation.
SAMPLE DILUTION TECHNIQUES
If a test result is out of the range of the meter, it must be diluted. The test should then
be repeated on the diluted sample. The following table gives quick reference
guidelines for dilutions of various proportions.
Amount of Sample Deionized Water to Bring
Final 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
All dilutions are based on a final volume of 10 mL so several dilutions will require
small volumes of the water sample. Graduated pipets should be used for all dilutions.
If volumetric glassware is not available, dilutions can be made with the colorimeter
tube. Fill the tube to the 10 mL line with the sample and then transfer it to another
container. Add 10 mL volumes of deionized water to the container and mix. Transfer
10 mL of the diluted sample to the colorimeter tube and follow the test procedure.
Repeat the dilution and testing procedures until the result falls within the range of the
calibration. Multiply the test result by the dilution factor. For example, if 10 mL of the
sample water is diluted with three 10 mL volumes of deionized water, the dilution
factor is four. The test result of the diluted sample should be multiplied by four.
SAMPLE DILUTION TECHNIQUES 9