Total Oxidants
Total Oxidants
50081_TotalOxidants.fm Page 125
Safety
Good safety habits and laboratory techniques should be used throughout the procedure.
Consult the Material Safety Data Sheet (MSDS) for information specific to the reagents
used in this procedure.
Summary of Method
This method gives results as “total oxidants”, which includes total chlorine (Cl
2
),
chlorine dioxide (ClO
2
), and chlorite (ClO
2
–
). The first titration yields total chlorine
(includes any chloramines and free chlorine) plus a portion of the chlorine dioxide. The
second titration (pH 2) yields chlorite plus a smaller portion of chlorine dioxide not
titrated at pH 4.
The AutoCAT stores all titration results and calculates the results for total oxidants. The
total oxidant value represents the sum of chlorite plus chlorine dioxide. Since chlorine
dioxide has a short residence time in most drinking water, the total oxidant result mainly
consists of the chlorite ion. This method can therefore be employed as an acceptable
surrogate operational control for monitoring chlorite, which must be less than 1 mg/L.
This method is not acceptable for regulatory testing.
Required Reagents
Description Qty. required per test Unit Cat. No.
Acetate Buffer Solution, pH 4, with dropper .............................................. 1 mL................. 100 mL ...............14909-32
Phenylarsine Oxide (PAO) Titrant, 0.00564 N............................................varies................ 1000 mL ...............1999-53
Hydrochloric Acid Standard Solution, 2.5 N ..............................................4 mL................. 100 mL .................1418-32
Potassium Iodide ......................................................................................... 1.0 g ................. 100 g....................167-26H
Required Apparatus
Beaker, Glass, 250-mL ................................................................................1 ....................... each......................500-46H
Magnetic Stir Bar, Teflon
®*
coated.............................................................1 ....................... each.....................50085-00
Measuring spoon, 1.0 g ............................................................................... 1 ....................... each.........................510-10
Pipet, Volumetric, Class A, 100-mL............................................................1 ....................... each.....................14515-42
Optional Reagents
Dilution water, organic-free ........................................................................ varies................ 500 mL ...............26415-49
Optional Apparatus
Mini-printer, thermal, w/cable............................................................................................... each.....................A70P021
Cylinder, Graduated, 250 mL ......................................................................1 ....................... each.........................508-46
*Teflon is a Registered Trademark of EI DuPont Company.
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