Hach DR/850 Procedures Manual page 199

IRON, TOTAL,
Method Performance
Interferences
continued
Precision
In a single laboratory, using a standard solution of 2.00 mg/L Fe
and two representative lots of powder pillow reagents with the
instrument, a single operator obtained a standard deviation of
±0.017 mg/L.
In a single laboratory, using a standard solution of 2.00 mg/L Fe
and two representative lots of AccuVac ampuls with the
instrument, a single operator obtained a standard deviation of
±0.009 mg/L Fe.
Estimated Detection Limit (EDL)
The EDL for program 33 is 0.03 mg/L Fe. For more information
on derivation and use of Hach's estimated detection limit, see
Section 1.
Interfering Substances and Suggested Treatments
Interfering Substance
2+
Calcium, Ca
-
Chloride, Cl
2+
Copper, Cu
High Iron Levels
Iron Oxide
Magnesium
Molybdate, Molybdenum
2-
High Sulfide Levels, S
Interference Level and Treatment
No effect at less than 10,000 mg/L as CaCO
No effect at less than 185,000 mg/L.
No effect. Masking agent is contained in FerroVer Iron
Reagent.
Inhibits color development. Dilute sample and retest to
verify results.
Requires mild, vigorous or Digesdahl digestion (see Sec-
tion 2). After digestion, adjust sample to pH 3-5 with
sodium hydroxide, then analyze.
No effect at 100,000 mg/L as CaCO
No effect at 25 mg/L as Mo.
1. Treat in fume hood or well-ventilated area. Add
5 mL HCl to 100 mL sample in a 250-mL Erlenmeyer
flask. Boil 20 minutes.
2. Cool. Adjust pH to 3-5 with NaOH. Re-adjust volume
to 100 mL with deionized water.
3. Analyze.
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