Hach DR/850, Procedures Manual, Page: 327 / 460

327
Accuracy Check
The results of this procedure may be compared with the results of
a dissolved oxygen meter (Cat. No. 51815-01).
Method Performance
Precision
In a single laboratory, using a standard solution of 8.0 mg/L O
2
determined by the Winkler method and two representative lots of
reagent with the instrument, a single operator obtained a standard
deviation of
±0.41 mg/L O
2
.
Estimated Detection Limit
The estimated detection limit for program 70 is 0.10 mg/L O
2
. For
more information on the estimated detection limit, see Section 1 .
Interferences
Summary of Method
The High Range Dissolved Oxygen AccuVac Ampul contains
reagent vacuum sealed in a 12-mL ampul. When the AccuVac
ampul is broken open in a sample containing dissolved oxygen, a
yellow color forms, which turns purple as the oxygen reacts with
the reagent. The color developed is proportional to the
concentration of dissolved oxygen.
Interfering Substance Interference Levels and Treatments
Cr
3+
Greater than 10 mg/L
Cu
2+
Greater than 10 mg/L
Fe
2+
Greater than 10 mg/L
Mg
2+
Magnesium is commonly present in seawater and causes a
negative interference. If the sample contains more than
50% seawater, the oxygen concentration obtained by this
method will be 25% less than the true oxygen
concentration. If the sample contains less than 50%
seawater, the interference will be less than 5%.
Mn
2+
Greater than 10 mg/L
Ni
2+
Greater than 10 mg/L
NO
2
-
Greater than 10 mg/L
OXYGEN, DISSOLVED, High Range,
continued