Method Performance - Hach POCKET COLORIMETER II Instruction Manual

Chlorine, Free and Total, LR,
Interfering Substance Interference Levels and Treatments
Manganese, Oxidized
4+ 7+
(Mn , Mn ) or Chromium,
6+
Oxidized (Cr )
Monochloramine, LR
method
Ozone

Method Performance

Estimated Detection Limit (EDL) = 0.02 mg/L
Typical precision (95% confindence interval) = 1.00 ± 0.05 mg/L
continued
1. Adjust sample pH to 6–7.
2. Add 3 drops Potassium Iodide (30-g/L) (Cat. No. 343-32) to a
10-mL sample.
3. Mix and wait one 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 chlorine concentration.
Causes a gradual drift to higher readings. When read within
1 minute after reagent addition, 3 mg/L monochloramine causes
less than a 0.1 mg/L increase in the reading.
Interferes at all levels.
1—30