EUTECH INSTRUMENTS WATERPROOF C401 COLORIMETER Instrukcja Obsługi Pobierz pdf (Strona 15)

Measurement: Chlorine, Free & Total C401/301/201/102/101

2.4.3 Interferences

Acidity:

Greater than 250ppm CaCO3 may cause interference. To remove this

interference, neutralise a separate sample to pH6-7 using 1N Sodium

Hydroxide. Record the volume used and add the same volume of 1N

Sodium Hydroxide to the sample before carrying out the above test

procedure. Use a multiplication factor to correct for the dilution of the

sample.

Alkalinity:

Greater than 250ppm CaCO3 may cause interference. To remove this

interference, neutralise a separate sample to pH6-7 using 1N Sulphuric

Acid. Note the volumes used and add the same volume of 1N Sulphuric

Acid to the sample before carrying out the above test procedure. Use a

multiplication factor to correct for the dilution of the sample.

Hardness:

No effect at less than 2000ppm CaCO3.

Monochloramine:

Monochloramine will cause a gradual increase in the Free Chlorine result

over time. Take the test result within 1 minute of adding the reagent

sachet to avoid these errors.

Oxidants, including Bromine, Chlorine Dioxide, Iodine and Ozone:

These will interfere with the test method at all levels. It is recommended

that an alternative test method is used if these species are present.

Oxidised Manganese or Oxidised Chromium:

All levels will cause interference. To remove this interference:

1. Test a 10ml sample as described in the above procedure.

2. Adjust the pH of a separate 10ml sample to pH6-7 using 1N Sodium

Hydroxide or 1N Sulphuric Acid.

3. Add 1 drop of 20% Potassium Iodide Solution; swirl to mix and then

wait 60 seconds.

4. Add 3 drop of 5g/l Sodium Arsenite Solution and swirl to mix.

5. Use this as the sample in the above test procedure and make a note

of the result. Use a multiplication factor to correct for the dilution of

the sample.

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EUTECH INSTRUMENTS WATERPROOF C401 COLORIMETER Instrukcja Obsługi Strona 15