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OZONE,
continued
9.
Place the AccuVac
ampul containing the
blank into the cell
holder. Tightly cover
the ampul with the
instrument cap.
Note: Standardization for
this procedure is
intentionally reversed.
Sampling
Stability of Indigo Reagent
Method Performance
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L ozone will
be displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Section 1).
The chief consideration when collecting a sample is to prevent the
escape of ozone from the sample. The sample should be collected
gently and analyzed immediately. Warming the sample or
disturbing the sample by stirring or shaking will result in ozone
loss. After collecting the sample, do not transfer it from one
container to another unless absolutely necessary.
Indigo is light-sensitive. Therefore, the AccuVac Ampuls should
be kept in the dark at all times.
However, the indigo solution decomposes slowly under room light
after filling with sample. The blank ampul can be used for multiple
measurements during the same day.
Precision
In a single laboratory, using standard solutions of 0.15, 0.28 and
0.96 mg/L ozone for the low, mid and high range, respectively,
and two representative lots of reagent with the instrument, a single
operator obtained a standard deviation of ±0.01, ±0.02 and ±0.02
mg/L O
for the low, mid and high range tests, respectively. For
3
more information on Hach's precision statement, see Section 1.
334
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