Oxygen, Dissolved
Oxygen, Dissolved
Page 2 of 4
OxygenDis_AccuVac_UHigh_UHR_Eng_Ody.fm
Interferences
Sample Collection, Preservation, and Storage
The main consideration in sampling with the High Range Dissolved Oxygen
AccuVac Ampul is to prevent the sample from becoming contaminated with
atmospheric oxygen between breaking open the ampule and reading the
absorbance. This is accomplished by capping the ampule with an ampule cap.
If the ampule is securely capped, the ampule should be safe from contamination
for several hours. The absorbance will decrease by approximately 3% during the
first hour and will not change significantly afterwards.
Sampling and sample handling are important considerations in obtaining
meaningful results. The dissolved oxygen content of the water being tested may
change with depth, turbulence, temperature, sludge deposits, light, microbial
action, mixing, travel time, and other factors. A single dissolved oxygen test
rarely reflects the accurate over-all condition of a body of water. Several samples
taken at different times, locations, and depths are recommended for most
reliable results. Samples must be tested immediately upon collection although
only a small error results if the absorbance reading is taken several hours later.
9. Place the blank into
the cell holder.
10. Touch Zero.
The display will show:
0.0 mg/L O
2
11. Place the AccuVac
Ampul into the cell
holder.
12. Touch Read.
Results will appear in
mg/L O
2
.
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 interferes. If the sample contains more than
50% seawater, the oxygen concentration observed will be 25% lower 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
10 mL
Zero
Read
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