Thermo Fisher Scientific C101 Colorimeter - Manual (Page 35)

Measurement: Bromine
C104 Colorimeter
31
Bromine Measuring Hints & Tips
2.8.1 Sample Collection
Bromine determination must take place as soon as possible after the
sample is taken or else low results may be obtained.
Plastic containers should not be used to collect the sample because these
may have a high chlorine demand which will lead to low reading results. It
is advisable to wash the container with sample water before the sample is
collected.
Avoid agitating the sample excessively as this may also lead to low
results.
2.8.2 Sample Measurement
If the pink color forms and then rapidly fades, this is an indication that the
bromine concentration may be very high. If this is the case, dilute the
sample with de-ionized water and retest. Multiply the result by the dilution
factor used.
Example: if the sample was diluted 2:1 with de-ionized water (i.e. 1 part
sample water to 1 part de-ionized water), the result is multiplied by 2 to
give the true concentration of the original sample.
Note: Results obtained by this method will not be as accurate as stated in
this manual because some chlorine will be lost in the dilution process.
After use, the vial should be cleaned thoroughly to avoid contaminating the
next sample. Do not use household cleaners as these may have a
chlorine demand which will lead to low results on subsequent tests.
After testing Bromine give extra attention to cleaning the vial as any
residual reagent will affect any subsequent tests.
2.8.3 Interferences
Acidity:
Greater than 250ppm CaCO
3
may cause interference. To remove this
interference, neutralise a separate sample to pH6-7 using 1N Sodium
Hydroxide. Record the volume used and add the same volume of 1N
Sodium Hydroxide to the sample before carrying out the above test
procedure. Use a multiplication factor to correct for the dilution of the
sample.
Alkalinity:
Greater than 250ppm CaCO
3
may cause interference. To remove this