Sulfite
Sulfite
Sulfite_Other_Eng_Ody.fm Page 3 of 4
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
3. Touch
OK to accept the default values for standard concentration, sample
volume, and spike volumes. Touch
Edit to change these values. After values
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
Read.
Each addition should reflect approximately 100% recovery.
6. After completing the sequence, touch
Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
View: Fit, then select Ideal Line and touch OK to view the relationship between
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
Options on the current program menu. Touch
Standard Adjust.
3. Touch
On. Press OK to accept the displayed concentration. If an alternate
concentration is used, touch the number in the
Adjust to field and enter the
actual concentration. Touch
OK.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
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