YSI 9300 Photometer - Manual (Page 139)

Important Note
Chlorine dioxide is
extremely volatile and can be lost from solution very easily.
Extreme care must be taken when extracting and dispensing samples to minimise
any loss from solution to ensure accurate measurement. When pouring the
sample into a test tube, it is recommended that this is done by holding the tube
at a slight angle and pouring slowly and gently down the side of the tube to
minimise any splashing and turbulence which may cause loss of chlorine dioxide
vapour.
Test Procedure - Chlorine Dioxide
1 Rinse a clean test tube with sample leaving a few drops in the tube.
2 Add one Chlordiox Buffer tablet and one Chlordiox LR tablet, crush and mix
both together in the small volume of sample left in the tube to produce an
even mixture of well crushed material.
3 Rinse and fill another clean test tube with sample to the 10 ml mark and
slowly pour this into the tube containing the crushed tablets.
4 Mix the tube contents with a crushing rod to ensure complete dissolution of
the tablet material.
5 Stand for one minute to allow the chlorine dioxide to react with the indicator.
6 Select Phot 74 on photometer.
7 Take photometer reading in usual manner (see photometer instructions). This
result represents the chlorine dioxide residual in terms of mg/l ClO
2
.
Note - to obtain the chlorine dioxide residual as mg/l Cl
2
divide the result by 1.9.
Interferences
Studies of the effect of expected levels of common species which may be present
in chlorine dioxide containing waters were undertaken to determine if these
would detrimentally affect the results of the test. These included other chlorine
compounds and oxidising agents, metal ions, hardness, alkalinity, nitrate,
phosphate and sulphate. No interference effect was observed.
Temperature Effect
The method is calibrated for use at 15 – 25°C - lower temperatures will cause a
slightly high bias to results. For accurate results, equilibrate a full glass bottle of
sample, with no headspace, to room temperature for analysis.
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