Hach DR/850 Procedures Manual page 103

CHLORINE, FREE, Ultra-high Range, continued
Accuracy Check
•
A common error in testing for chlorine is failure to obtain a
representative sample. If sampling from a tap, let the water
flow for at least five minutes to ensure a representative
sample. Let the sample container overflow with sample
several times. Cap the container so there is no air above the
sample.
•
If sampling with a sample cell, rinse the cell several times
with the sample, then carefully fill to the 5-mL mark. Proceed
with the chlorine test immediately.
1. Fill three mixing cylinders (Cat. No. 20886-38) with 5-mL
of sample.
2. Snap the neck of a HR Chlorine Ampule Standard, 50–
75 mg/L Cl . Using the TenSette
2
and 0.3 mL of standard, respectively, to each cylinder and
mix thoroughly.
3. Analyze each standard addition sample as described in the
procedure. Record each result.
4. Calculate the concentration of mg/L chlorine added to each
sample.
volume of standard added
mg/L chlorine added = ------------------------------------------------------------------------------------------------------------------------------------------------------ -
The spiked sample results should reflect the analyzed sample
result plus the calculated mg/L Cl
increases do not occur, see Standard Additions in Section 1 of a
DR/800 Procedure Manual for more information.
103
®
Pipet, add 0.1 mL, 0.2 mL,
×
label value of Cl
sample volume + volume of standard added
added to each sample. If these
2
standard ampule
2