YSI 9300 Photometer - Manual (Page 114)

PHOTOMETER TEST INSTRUCTIONS
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The use of organophosphonate compounds as inhibitors in cooling systems has
become widespread in recent years. It is essential to monitor the active
organophosphonate content of the cooling water to ensure the treatment is fully
effective.
The YSI OP test provides a reliable means of monitoring organo-phosphonate
levels over the range 0 - 20 mg/l PO
4
. The test has been developed for use with
commercially available organophosphonate products such as those based on
amino trimethyl phosphonic acid and hydroxyethane diphosphonic acid.
Method
In the YSI OP test, organophosphonates are first converted to orthophosphate
by a catalysed cold oxidation process. Excess oxidising agent is removed from
the sample by precipitation and filtration. The orthophosphate formed in the
reaction is then determined using the 'molybdenum blue' method. The reagents
for the procedure are provided in tablet form and the test is simply carried out
by adding the appropriate tablets in sequence to a diluted sample of the water.
The intensity of the blue coloration formed in the test is proportional to the
organophosphonate concentration and is determined using a YSI Photometer.
A separate correction procedure is applied to those samples known or suspected
to contain orthophosphate. This compensates for the orthophosphate originally
present in the sample so that a true value for organophosphonate concentration
can be obtained.
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
0 – 20 mg/l PO
4
PHOT.44.AUTO