Hach DR2400 - Page 319

Iodine
Iodine
Iodine_AVPP_Other_DPD_Eng_Ody.fm Page 3 of 4
Interferences
5. Touch the timer icon.
Touch
OK.
A three-minute reaction
period will begin. Perform
steps 6-7 during the
reaction period.
6. Wipe the blank and
place it into the cell
holder.
7. Touch Zero.
The display will show:
0.00 mg/L I
2
8. Within three minutes
after the timer beeps,
wipe the prepared
sample and place it into
the cell holder.
Touch
Read.
Results will appear in
mg/L I
2
.
Interfering Substance Interference Levels and Treatments
Acidity
Greater than 150 mg/L CaCO
3
. May not develop full color or color may fade instantly. Neutralize
to pH 6–7 with 1 N Sodium Hydroxide (Cat. No. 1045-32). Determine amount to be added on
separate sample aliquot, then add the same amount to the sample being tested. Correct for
volume addition (See Section 3.1.3 Correcting for Volume Additions on page 29).
Alkalinity
Greater than 250 mg/L CaCO
3
. May not develop full color or color may fade instantly. Neutralize
to pH 6–7 with 1 N Sulfuric Acid (Cat. No. 1270-32). Determine amount to be added on separate
sample aliquot, then add the same amount to the sample being tested. Correct for volume
addition (See Section 3.1.3 Correcting for Volume Additions on page 29).
Bromine Interferes at all levels
Chlorine and chloramines Causes a positive interference at all levels
Chlorine Dioxide Interferes at all levels
Chloramines, organic May interfere
Hardness No effect at less than 1000 mg/L as CaCO
3
Manganese, Oxidized (Mn
4+
,
Mn
7+
) or
Chromium, Oxidized (Cr
6+
)
1. Adjust sample pH to 6–7.
2. Add 3 drops Potassium Iodide (30-g/L) (Cat. No. 343-32) to a 25-mL sample.
3. Mix and wait 1 minute.
4. Add 3 drops Sodium Arsenite* (5-g/L) (Cat. No. 1047-32) and mix.
5. Analyze 10 mL of the treated sample as described in the procedure.
6. Subtract the result from this test from the original analysis to obtain the correct iodine
concentration.
* Samples treated with sodium arsenite for manganese or chromium interferences will be hazardous wastes as regulated by the
Federal RCRA for arsenic (D004). See Section 4 for more information on proper disposal of these materials.
Ozone Interferes at all levels
Peroxides May interfere
Extreme sample pH or highly
buffered samples
Adjust to pH 6 –7. See Section 3.3 Interferences on page 41.
10 mL
Zero