YSI 9300 Photometer - Manual (Page 35)

PHOTOMETER TEST INSTRUCTIONS
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Bromine and bromine-release compounds are used for the disinfection of
swimming pool water, and in many other water treatment systems. Accurate
measurement of the bromine residual is an essential aspect of control of these
processes.
The bromine level can be expressed in terms of the free bromine, combined
bromine or total bromine residuals. However free and combined bromine are
both considered powerful disinfectants and it is not normally necessary to
differentiate between these two forms. For the majority of applications therefore
the measurement of the total residual is sufficient.
The YSI DPD bromine method provides a simple means of measuring bromine
residuals over the range 0 - 10.0 mg/l. A supplementary procedure can be used
to differentiate between free and combined bromine if desired.
Method
The YSI bromine test uses the DPD method now internationally recognised as
the standard method of testing for disinfectant residuals. In the DPD method
the reagents are provided in tablet form for maximum convenience and
simplicity of use.
Bromine reacts with diethyl-p-phenylene diamine (DPD) in buffered solution to
produce a pink coloration. The intensity of the color is proportional to the total
bromine concentration and is measured using a YSI Photometer.
For the separate determination of free and combined bromine, a supplementary
procedure using sodium nitrite is used. The nitrite destroys the free bromine in
the sample and the color produced in the DPD test then corresponds to the
combined bromine only. The free bromine content is thus obtained by difference
between the total bromine and combined bromine results.
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
0 – 10.0 mg/l
PHOT.5.AUTO