X84; Sample Dilution Techniques - LaMotte DC1500-CL Manual

new ones.
Tubes should always be washed on the inside and outside with mild detergent
prior to use to remove dirt or fingerprints. The tubes should be allowed to air-
dry in an inverted position to prevent dust from entering the tubes. Dry tubes
should be stored with the caps on to prevent contamination.
After a tube has been filled and capped, it should be held by the cap and the
outside surface should be wiped with a clean, lint-free absorbent cloth until it
is dry and smudge-free. Handling the tube only by the cap will avoid problems
from fingerprints. Always set the clean tube aside on a clean surface that will
not contaminate the tube. It is imperative that the tubes and light chamber be
clean and dry. The outside of the tubes should be dried with a clean, lint-free
cloth or disposable wipe before they are placed in the meter chamber.
Tubes should be emptied and cleaned as soon as possible after reading a
sample to prevent deposition of particulates on the inside of the tubes.
Variability in the geometry of the glassware and technique is the predominate
cause of variability in results. Slight variations in wall thickness and the
diameter of the tubes may lead to slight variations in the test results. To
eliminate this error the tubes should be placed in the chamber with the same
orientation each time.
Chambers which have been scratched through excessive use should be
discarded and replaced with a new one.

„ 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
10 mL
5 mL
2.5 mL
1 mL
0.5 mL
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.
lobalScientificSupply
Deionized Water to Bring
Final Volume to 10 mL
0 mL
5 mL
7.5 mL
9 mL
9.5 mL
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