Manual

Reagents and Equipment
YSI Oxidising OP Tablets
YSI OP-A Tablets
YSI OP-B Tablets
YSI OP-AX Tablets
YSI 9300 or 9500 Photometer
YSI Test Tube, 20 ml plastic (PT 526)
Round Test Tubes, 10 ml glass (PT 595)
A filtration is required during the course of this procedure. The use of YSI
Filtration Kit (PT 600) is recommended for this purpose. Alternatively, standard
laboratory equipment with Whatman GF/B or equivalent papers may be used.
Correction Procedure
The photometer is programmed for both Organophosphonate and correction
calibrations, and will automatically calculate the corrected organophosphonate
concentration. Use program Phot 44 Organophosphonate, then select the ‘Follow On’
option on screen to continue test for program Phot 45 Correction Factor.
Sample Preparation and Dilution
1 Filter sample if necessary to obtain a clear solution.
2 Prepare x5 dilution of the sample using the YSI dilution tube.
This diluted sample is used for both the organophosphonate and correction
procedures. he test calibrations take this dilution into account - it is not necessary
to apply a dilution factor in the result calculation.
Test Procedure - Organophosphonate
1 Fill the plastic test tube with diluted sample to the 20 ml mark.
2 Add one Oxidising-OP tablet. Replace screw cap and shake tube until tablet
dissolves.
3 Allow the tube to stand for five minutes.
4 Add one OP-A tablet. Replace screw cap and shake tube until tablet dissolves.
5 Allow the tube to stand for two minutes.
6 Filter a portion of the solution into a round glass test tube filling to the 10 ml
mark.
7 Add one OP-B tablet, crush tablet and mix to dissolve.
8 Stand for five minutes to allow full color development.
9 Select Phot 44 on photometer.
10 Take photometer reading in the usual manner (see photometer instructions).
The test may be terminated at this stage if the original sample is known not to
contain orthophosphate.