11
HCA1 Micro CL (DPD-1, -4) Strip Interferences
Interfering Substance
Interference Level and treatment
Acidity
If sample has acidity above 150mg/L CaCO
3
test may not develop full color. Neutralize to
pH 6.0 to 7.0 with 0.5N sodium hydroxide.
Alkalinity
If sample has alkalinity above 200mg/L CaCO3
test may not develop full color. Neutralize to
pH 6.0 to 7.0 with 0.5N sulfuric acid.
Bromine & Bromamines, Br2
Color similar to free chlorine reaction at all
levels.
Chlorine Dioxide, ClO2
Color similar to free chlorine reaction at all
levels.
Copper, Cu+2
Color development is reduced above 10 ppm
(mg/L).
Iodine, I2
Color similar to free chlorine reaction at all
levels.
Manganese, oxidized (Mn+4, Mn+7)
or Chromium, oxidized (Cr+6)
See AWWA procedure 4500-CL F, 1(d) for
removal of interferences.
Monochloramine (NH2Cl)
(applies to DPD-1 only)
Monochloramine interferences are known to
occur in free chlorine
DPD methods. This interference is dependent
on temperature and
Monochloramine concentration.
Ozone, O3
Color similar to free chlorine reaction at all
levels.
Peroxides
Interference is possible.
pH
Typical pH samples of potable water with a
pH of 6.0 to 9.0 are OK. If outside this range
adjust to pH 6.0 to 7.0 using acid (0.5N
Sulfuric acid) or base (0.5N Sodium
hydroxide).
HCA1 Chlorine Plus Tips for Best Accuracy
1.
Become familiar with the meter and the different tests by reading the
instructions carefully.
2.
The Free Chlorine and Total Chlorine reagents are compliant for meeting
USEPA (4500-Cl G); ISO 7393/2; and German DIN 38408 G4-2 requirements.
3.
Observe the dip time (as required for the test) for accurate results.
4.
Test immediately after filling the CELL when testing for oxidizers.
5.
Be sure the CELL is filled to capacity (4ml).
6.
Rinse the CELL with clean water immediately after completing the test. (DPD
will stain the CELL wall if allowed to remain in the CELL)
7.
Just before testing, rinse the sample CELL with the sample water several times
to get a representative sample. Store the meter and all test materials out of
direct sunlight and away from chemical storage areas.