Dilution Procedures; Preparation Of Turbidity-Free Water - LaMotte TC-3000 Manual

Dilution Procedures

If a sample is encountered that is more than 4000 NTU, a careful dilution with 0 NTU
or very low turbidity water will bring the sample into an acceptable range. However,
there is no guarantee that halving the concentration will exactly halve the NTU value.
Particulates often react in an unpredictable manner when diluted.

Preparation of Turbidity-Free Water

A 0 NTU Standard (Code 1480) is included with the meter. An accessory package
(Code 4185) is available for preparing turbidity-free water for blanking the meter and
dilution of high turbidity samples.
The preparation of turbidity-free water requires careful technique. Introduction of
foreign matter will affect the turbidity reading. A filtering device with a special
membrane filter is used to prepare low turbidity water. The filter, filter holder and
syringe must be conditioned by forcing at least two syringes full of deionized water
through the filtering apparatus to remove foreign matter. The first and second rinses
should be discarded. Low turbidity water as prepared below may be stored in the dark
at room temperature in a clean glass bottle with a screw cap and used as required.
The storage container should be rinsed thoroughly with filtered deionized water before
filling. The water should be periodically inspected for foreign matter in bright light.
PROCEDURE
1. Remove the plunger from the syringe (0943). Attach the
filter to the bottom of the syringe.
2. Pour approximately 50 mL of deionized water into the
barrel of the syringe. Insert the plunger. Exert pressure
on the plunger to slowly force the water through the
filter. Collect water in the clean storage container. Rinse
walls of the container then discard this rinse water.
CALIBRATION & ANALYSIS • TURBIDITY 41