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Prepare formazin standards
For the best accuracy and long-term data comparability, use formazin
stock solution from Hach to make formazin standards.
Note: As an alternative, a 4000-NTU formazin stock solution that is prepared by
the user may be used to make formazin standards. Refer to
formazin stock solution
on page 46.
Prepare formazin standards immediately before calibration in an
environment that is at the same ambient temperature as the instrument.
Discard after use.
Refer to
Table 6
for the procedures to make the recommended
calibration standards.
Table 6 Formazin standard preparation
Standard
Step 1
20 NTU
Add 100 mL of dilution
water to a clean 200-
mL Class A volumetric
flask. Refer to
Prepare
dilution water
on page 24.
200 NTU
Add 50 mL of dilution
water to a clean 100-
mL class A volumetric
flask.
8
A class A volumetric pipet may be used in place of a TenSette Pipet.
Making 4000-NTU
Step 2
Step 3
®
With a TenSette
Dilute to the mark
Pipet, add 1.00 mL
with dilution water.
of well-mixed 4000-
Stopper and mix.
NTU formazin stock
solution to the 200-
mL flask.
8
With a TenSette
Dilute to the mark
Pipet, add 5.00 mL
with dilution water.
of well-mixed 4000-
Stopper and mix.
NTU formazin stock
solution to the 100-
mL flask.
Table 6 Formazin standard preparation (continued)
Standard
Step 1
1000 NTU Add 50 mL of dilution
water to a clean 100-
mL class A volumetric
flask.
4000 NTU Rinse a clean sample
cell two times with well-
mixed 4000-NTU
formazin stock solution.
Put about 30 mL of
4000-NTU formazin
stock solution in the
sample cell. No dilution
is necessary.
7500 NTU The 7500-NTU
formazin standard is
provided in an ampule
and is ready for use.
Refer to
Accessories
on page 56. Do not
open the ampule or
use the contents as
dilution stock. The
7500-NTU formazin
standard is stable for
up to one year.
Calibration notes
• Make sure that the instrument is in the same ambient conditions as
where it is used.
• Make sure that the standards are at the same ambient temperature as
the instrument before use.
Step 2
Step 3
8
With a TenSette
Dilute to the mark
Pipet, add 25.00 mL
with dilution water.
of well-mixed 4000-
Stopper and mix.
NTU formazin stock
solution to the 100-
mL flask.
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English 43
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