Hach-Lange 2100 AN Laboratory Turbidimeter User Manual - Manual (Page 43)

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
Making 4000-NTU
formazin stock solution on page 44.
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 Step 2 Step 3
20 NTU Add 100 mL of dilution
water to a clean 200-
mL Class A volumetric
flask. Refer to
Prepare
dilution water
on page 23.
With a TenSette ®
Pipet, add 1.00 mL
of well-mixed 4000-
NTU formazin stock
solution to the 200-
mL flask.
Dilute to the mark
with dilution water.
Stopper and mix.
200 NTU Add 50 mL of dilution
water to a clean 100-
mL class A volumetric
flask. With a TenSette 1
Pipet, add 5.00 mL
of well-mixed 4000-
NTU formazin stock
solution to the 100-
mL flask.
Dilute to the mark
with dilution water.
Stopper and mix.
Table 6 Formazin standard preparation (continued)
Standard Step 1 Step 2 Step 3
1000 NTU Add 50 mL of dilution
water to a clean 100-
mL class A volumetric
flask.
With a TenSette 1
Pipet, add 25.00 mL
of well-mixed 4000-
NTU formazin stock
solution to the 100-
mL flask.
Dilute to the mark
with dilution water.
Stopper and mix.
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 54. Do not
open the ampule or
use the contents as
dilution stock. The
7500-NTU formazin
standard is stable for
up to one year.
— —
1 A class A volumetric pipet may be used in place of a TenSette Pipet.
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.
• Use only the provided silicone oil. This silicone oil has the same
refractive index as the vial glass and masks minor glass differences
and scratches.
English 41