19
Combined Chlorine
test procedure
REMOVE STRIP
Remove 1
eXact
®
Strip Micro CL (DPD–3)
, Part No. 486638
from the bottle before beginning the test. Set the strip in a dry,
convenient place and recap the bottle immediately.
8
This procedure is only valid when ran as a continuation of the eXact
®
Strip Micro
CL (DPD–1 Free Chlorine). Test procedure located on the previous page.
NOTE:
Standard Method (4500–Cl G, procedure for total chlorine) requires the reading to be made after 2 minutes
from the time the KI is added. For compliance testing, you must time the 2 minutes and then make your measurement.
6
DIP STRIP & PRESS READ
Dip the
eXact
®
strip micro (DPD–3)
into the
CELL
, and
immediately press
. This will start a
20 second
countdown
timer. During this time, move the strip in a gentle back and
forth motion (approx. 2 strokes per second).
Remove and
discard the strip after
‘
1
’
on the display disappears.
*
The
cursor will move across the display while the meter prepares
to measure the sample. Record the value displayed and this
value is automatically stored in the
CL MENU
, the result will
be saved in the app’s ‘
RESULTS
’.
(
NOTE: The Iodide added with DPD–3 will, in the presence of
Combined Chlorine or Chloramines, convert into Iodine).
9
PRESS READ AGAIN
Press
again and the meter will count down and display the next reading. If
this reading matches the previous result, then record this as the Total Chlorine
result. This value is automatically stored in the
CL MENU
. After testing is
completed, rinse
CELL
immediately. Record the highest value the meter
displayed as your Total Chlorine result. After testing, rinse cell immediately and
clean with brush.
10
*
For best accuracy, when testing outdoors in sunlight, place cap over cell cover
Interfering Substance
Interfering Levels and Treatments
Acidity
If sample has acidity above 150mg/L CaCO3 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 and Bromamines, Br
2
Color similar to free chlorine reaction at all levels.
Chlorine Dioxide, ClO
2
Color similar to free chlorine reaction at all levels.
Copper, Cu
2+
Color development is reduced above 10 ppm (mg/L).
Iodine, I
2
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.
Monochloramines (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, O
3
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).
