Molybdenum, Molybdate
Molybdenum, Molybdate
Page 4 of 6
Molybdenum_AVPP_High_MAA_Eng_Ody.fm
Interferences
Sample Collection, Storage and Preservation
Collect samples in clean plastic or glass bottles. Adjust the pH to 2 or less with
nitric acid (about 2 mL/L). Preserved samples can be stored up to 6 months at
room temperature. Adjust the pH to 7 with 5.0 N Sodium Hydroxide before
analysis. Correct the test result for volume additions.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify the chemical form.
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. Open a bottle of Molybdenum Standard Solution, 1000-mg/L Mo
6+
.
9. Place the prepared
sample into the cell
holder.
10. Touch Read.
Results will appear in
mg/L Mo
6+
.
Interfering Substance Interference Levels and Treatments
Aluminum Greater than 50 mg/L
Chromium Greater than 1000 mg/L
Copper
Samples containing 10 mg/L copper or more will exhibit an increasing positive interference upon
standing. Read these samples as soon as possible after the five minute reaction period is complete.
Iron Greater than 50 mg/L
Nickel Greater than 50 mg/L
Nitrite
Interference from up to 2000 mg/L as NO
2
–
can be eliminated by adding one Sulfamic Acid Powder
Pillow (Cat. No. 1055-99) to the sample.
Highly buffered samples
or extreme sample pH
May exceed the buffering capacity of the reagents and require sample pretreatment; see Section
3.3 Interferences on page 41.
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