Cyanide
Cyanide
Cyanide_UniCell_Other_PPZ_Eng_Ody.fm Page 3 of 4
Accuracy Check
Standard Additions Method (Sample Spike)
Caution: cyanides and their solutions, and the hydrogen cyanide liberated by
acids, are very poisonous. Both the solutions and the gas can be absorbed
through the skin.
1. Prepare a 100-mg/L CN
–
stock solution weekly by dissolving 0.2503 grams,
or an equivalent amount of pure potassium cyanide, in deionized water and
diluting to 1000 mL.
2. Immediately before use, prepare a 10.00-mg/L cyanide working solution by
diluting 10.00 mL of the 100-mg/L stock solution to 100 mL using deionized
water.
3. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
4. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
5. 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.
6. Measure 100 mL of sample into three graduated cylinders.
7. Pipet 0.5 mL, 1.0 mL, and 1.5 mL of 10-mg/L CN
–
, respectively, into the three
cylinders and mix thoroughly.
8. Analyze as described in the procedure. Accept each standard additions
reading by touching
Read. Each addition should reflect approximately 100%
recovery.
9. 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 Solution Method
1. Analyze a 0.30-mg/L CN
–
Standard Solution using the procedure described
above.
2. To adjust the calibration curve using the reading obtained with the
0.200-mg/L standard solution, touch
Options on the current program menu.
Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration (the value
depends on the selected chemical form). If an alternate concentration is used,
touch the number in the box to enter the actual concentration, then touch
OK.
Touch
Adjust.
Perform the cyanide procedure as described above. See Section 3.2.4 Adjusting the
Standard Curve on page 40 for more information.
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