Sulfate
Sulfate
Sulfate_UniCell_Other_Turb_Eng_Ody.fm Page 3 of 4
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.
4. Prepare three sample spikes. Fill three mixing cylinders with 25 mL of
sample. Use a pipet to add 0.1 mL, 0.2 mL, and 0.3 mL of 2500-mg/L SO
4
2–
standard, respectively, to each sample and mix thoroughly.
5. Transfer 5 mL of each sample spike to a sample vial and analyze each sample
spike as described in the procedure above, starting with the 0.1 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
1. To check accuracy, use a 100-mg/L sulfate standard solution listed in
Optional Reagents. Perform the Sulfate procedure as described above.
2. To adjust the calibration curve using the reading obtained with the
100-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.
Method Performance
Precision
Standard: 70 mg/L SO
4
2–
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
Sulfate ions in the sample react with barium chloride in aqueous solution and
form a precipitate of barium sulfate. The resulting turbidity is measured
photometrically.
Program 95% Confidence Limits of Distribution
811 63–77 mg/L SO
4
2
–
Program Portion of Curve ∆Abs ∆Concentration
811 Entire range 0.010 5 mg/L SO
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2–
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