Hach APA 6000 Operation Manual page 18

Section 5
Repeat Steps 2–4 for
second standard.
5.
Repeat Steps 2–4,
using the APA Standard 2
(low range) 1.0 mg/L
in Step 2 and 3 in place of
the Zero Standard. Label
as "1 ppm standard".
Repeat Steps 7 and 8.
9.
Repeat Steps 7–8,
using the 1-ppm standard.
Page 18
Bench Method Procedure
440 nm
6.
Using a 1-cm sample
cell and a Hach DR/4000*
Spectrophotometer,
zero at 440 nm with
deionized water.
*
High concentration samples
and standards will have an
absorbance >1.5. Use a DR/4000
for accurate measurements at
these conditions.
10.
The blank is the
absorbance value of the
0-ppm standard. The slope
is the difference between
the absorbance values of
the 1-ppm standard and
the 0-ppm standard.
7.
Within 10 minutes of
adding reagents, transfer
3 mL of the 0 ppm
standard into a 1-cm cell.
Measure the absorbance
at 440 nm.
Note: For best accuracy,
rinse the cell three times
with the standard before
measurement.
8.
Record the value.
6202918bench.fm