16
• Do not let the reacted sample stand too long after reagent is
added, or accuracy will be lost.
• It is possible to take multiple readings in a row, but it is
recommended to take a new zero reading for each sample and to
use the same vial for zeroing and measurement where possible
(for most precise results follow carefully the measurement
procedures).
• All the reaction times reported in this manual are referred to 20°C
(68°F). As a general rule of thumb, they should be doubled at
10°C (50°F) and halved at 30°C (86°F).
DIGESTION
• Some analytical methods do require digestion of the sample. Use
for digestion of the vials only the
Hanna C9800 block heater
.
Use of the optional
HI 740217
safety shield
is strongly
recommended. For correct use of the reactor follow the Reactor
Instruction Manual. At the end of the digestion period, the vials
are still hot: allow the vials to cool to room temperature in the
optional
HI 740216 test tube cooling rack
.
REAGENT BLANK CORRECTION
• The measurement procedure of some parameters requires a “reagent
blank correction”. The blank and the sample are prepared exactly
in the same way, with the only difference that for the blank
deionized water is used instead of sample.
A blank vial may be used more than once: stability and storing
conditions are described for each parameter in the related chapter.
INTERFERENCES
• In the parameter related measurement sections we have reported
the most common interferences that may be present in an average
wastewater matrix. It may be that for a particular treatment
process other compounds do interfere with the method of analysis.
65
• Replace the cap tightly and mix by
inverting the vial a couple of times.
This is the blank.
• Mark the vial with a pencil on the
white band to place an orientation
sign. Use this sign to insert the test
vial always in the same position into
the holder.
•
Place the vial into the holder and
push it completely down.
•
Press ZERO and “SIP” will blink on the display.
•
Wait for a few seconds and the
display will show “-0.0-”. Now the
meter is zeroed and ready for
measurement.
•
Remove the vial.
•
Remove the cap and add the content
of one packet of HI 93758-0
Phosphorus Reagent.
•
Replace the cap tightly and shake
gently to mix for about 2 minutes
until all the powder is completely
dissolved. This is the reacted sample.
•
Place the vial into the holder and
push it completely down. Ensure that
the vial orientation respect to the
holder is the same as the blank.
Phosphorus, Total