16
DPD-3 Combined Chlorine Test Procedure
This procedure is only valid when run as a continuation of the
eXact
®
Strip Micro CL (DPD-1 Free Chlorine) Test Procedure
located on the previous page.
7
Remove one (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.
REMOVE STRIP
9
PRESS READ AGAIN
Press
READ
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 CL6 Menu. After testing is completed, rinse cell immediately. Record
the Total Chlorine as the highest value the meter displayed.
8
Dip the
eXact
®
Strip Micro CL (DPD-3)
into the
CELL
and immediately press
READ
. This
starts the
20 SECOND
countdown timer. During this time move the strip in a gentle back
and forth motion (approx. 2 strokes/sec).
Remove and discard the strip when “1” on the
display disappears
. The cursor will move across the display while the meter prepares to
measure the sample. This result is automatically stored in CL6 Menu (NOTE: The Iodide added
with DPD-3 will, in the presence of Combined Chlorine or Chloramines, convert into Iodine).
DIP STRIP AND PRESS “READ”
*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 two minutes and then make your measurement. NOTE: From testing in our lab,
water samples above 70°F (20°C), generally, reach a stabilized reading quicker then 2 minutes.
eXact
®
Strip Micro CL (DPD-1/DPD-3/DPD-4) Interferences (Part Nos 486637/486638/486670)
Interfering Substance
Acidity
Alkalinity
Bromine & Bromamines, Br
2
Chlorine Dioxide, ClO
2
Copper, Cu
+2
Iodine, I
2
Manganese, oxidized (Mn
+4
, Mn
+7
)
or Chromium, oxidized (Cr
+6
)
Monochloramines (NH
2
Cl)
(applies to DPD-1 only)
Ozone, O
3
Peroxides
pH
Interfering Levels & Treatments
If sample has strong acidity, test may not develop full color.
Neutralize to pH 6.0 to 7.0 with 0.5 N Sodium hydroxide.
If sample has alkalinity above 200mg/L CaCO
3
test may not develop
full color. Neutralize to pH 6.0 to 7.0 with 0.5 N Sulfuric acid.
Color similar to free chlorine reaction at all levels.
Color similar to free chlorine reaction at all levels.
Color development is reduced above 10 ppm (mg/L).
Color similar to free chlorine reaction at all levels.
See AWWA procedure 4500-CL F, 1(d) for removal of interferences.
Monochloramine interferences are known to occur in free chlorine
DPD methods. This interference is dependent on temperature and
monochloramine concentration.
Color similar to free chlorine reaction at all levels.
Interference is possible.
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
(0.5 N Sulfuric acid) or base (0.5N Sodium hydroxide).
CL
CL6
CL6: Chlorine and Iodine react with N,N-diethyl-p-phenylenediamine as it is released from the strip to
form a magenta color, directly proportional to the Chlorine concentration. (Ozone, Bromine, and
Permanganate also form the color)
