Sulfate
Sulfate
Sulfate_UniCell_Turb_Eng_Ody.fm Page 3 of 4
Sample Collection, Storage, and Preservation
Analyze samples within 3 hours after collection for best results. Samples may be
stored up to 28 days at 4 °C (39 °F). Warm samples to room temperature before
analysis.
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.
4. Prepare three sample spikes. Fill three mixing cylinders with 25 mL of
sample. Use a pipet to add 0.2 mL, 0.4 mL, and 0.6 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 0.2 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 500-mg/L sulfate standard solution as follows:
1. Using Class A glassware, pipet 20 mL of Sulfate Standard Solution,
2500-mg/L, into a 100-mL volumetric flask. Dilute to the mark with
deionized water. Prepare this solution daily. Perform the SulfaVer procedure
as described above.
2. To adjust the calibration curve using the reading obtained with the
500-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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