Hach DR/850 - Page 130

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each of two beakers.
c) Use a TenSette Pipet to add 0.2 mL of the standard to one
of the beakers (this is the spiked sample). Swirl to mix.
d) Fill a DPD Total Chlorine AccuVac completely from each
beaker.
e) Analyze the spiked and unspiked sample as described
in
the procedure.
f) Calculate the concentration of mg/L chlorine added to the
sample:
g) The spiked sample result should reflect the analyzed
sample result + the calculated mg/L Cl
2
added (step f).
h) If this increase does not occur, see Standard Additions in
Section 1 for more information.
Method Performance
Precision
In a single laboratory, using a standard solution of 1.00 mg/L
chlorine and two lots of reagents with the instrument, a single
operator obtained standard deviations of ±0.01 mg/L chlorine.
In a single laboratory, using a standard solution of 1.00 mg/L
chlorine and two representative lots of AccuVac Ampuls with the
instrument, a single operator obtained a standard deviation of
±0.01 mg/L chlorine.
Estimated Detection Limit (EDL)
The estimated detection limit for programs 9 and 11 is 0.02 mg/L
Cl
2
. For more information on derivation and use of Hach’s
estimated detection limit, see Section 1.
mg/L chlorine added
0.2 (vol. standard added) Label value (mg/L Chlorine)×
25.2 (sample + standard volume)
--------------------------------------------------------------------------------------------------------------------------=
CHLORINE, TOTAL, continued