15
(b)
shake the vial
: move the vial up and down. The movement
may be gentle or vigorous.
This mixing method is indicated like “shake gently” or “shake
vigorously”, with the icons:
• To obtain most reproducible readings, insert the test vial always in
the same way into the holder: place an orientation sign by marking
the vial with a pencil on the white band. As reference you can use
the alignment indicator on the top of the casing.
Pay attention to push the vial completely down in the holder.
• Whenever the vial is placed into the
measurement cell, it must be dry
outside, and completely free of
fingerprints, oil or dirt. Wipe it
thoroughly with
HI 731318
or a
lint-free cloth prior to insertion.
shake gently
shake vigorously
66
• Press TIMER and the display will show the countdown prior to the
measurement. Alternatively, wait for 3 minutes and press READ
DIRECT. In both cases "SIP" will blink during measurement.
• The instrument directly displays concentration in
mg/L of phosphate
(PO
4
3-
) on the Liquid Crystal Display.
The method detects free (orthophosphate), condensed inorganic
forms (meta-, pyro- and other polyphosphates) and organic forms
of phosphates present in the sample.
• To convert the reading to mg/L of P
2
O
5
, multiply by a factor of
0.748.
• To convert the reading to mg/L of phosphorus (P) concentration,
multiply by a factor of 0.326.
Note
: for accurate measurements
1) wash glassware only with phosphate-free detergents
2) clean all glassware with 1 : 1 hydrochloric acid solution and rinse with
deionized water.
INTERFERENCES
Interference may be caused by:
Arsenate: at any level
Silica:
above 50 mg/L
Sulfide:
above 90 mg/L.
Turbidity: turbidity and suspended matter in large amounts may
cause interference because the strongly acidic reaction
conditions may dissolve suspended matter or cause
desorption of phosphates from particles. Before
measurement, turbidity or suspended matter should be
removed by treatment with active carbon and by prior
filtration.
Phosphorus, Total