Hach DR2400 Manual page 753

Accuracy Check
Sulfite_Other_Eng_Ody.fm
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch . Touch
Options
additions procedure will appear.
3. Touch to accept the default values for standard concentration, sample
OK
volume, and spike volumes. Touch
are accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Prepare three sample spikes. Fill three Mixing Cylinders (Cat. No. 20886-40)
with 25 mL of sample. Use a pipet to add 1.0 mL, 2.0 mL, and 3.0 mL
of 15-mg/L Sulfite Standard Solution, respectively, to each sample and mix
thoroughly.
5. Transfer 10 mL of each sample spike to a clean sample cell and analyze each
sample spike as described in the procedure above, starting with the 1.0 mL
sample spike. Accept each standard additions reading by touching
Each addition should reflect approximately 100% recovery.
6. After completing the sequence, touch
the standard additions data points, accounting for matrix interferences. Touch
, then select
View: Fit
the sample spikes and the "Ideal Line" of 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Standard Solutions
Prepare a 3.00-mg/L Sulfite standard solution as follows:
1. Using Class A glassware, pipet 20 mL of 15-mg/L Sulfite Standard Solution
into a 100-mL volumetric flask. Dilute to the mark with deionized water.
Prepare this solution daily. Perform the Colorimetric Sulfite procedure as
described above.
2. To adjust the calibration curve using the reading obtained with the 3.0-mg/L
standard solution, touch
.
Standard Adjust
3. Touch . Press
On OK
concentration is used, touch the number in the
actual concentration. Touch
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
. A summary of the standard
Standard Additions
to change these values. After values
Edit
Graph
and touch
Ideal Line OK
on the current program menu. Touch
Options
to accept the displayed concentration. If an alternate
.
OK
Sulfite
Read
to view the best-fit line through
to view the relationship between
field and enter the
Adjust to
Page 3 of 4
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Sulfite