CISA = Chloride
Ionic Strength Adjustor
Orion 941709, 1 M HNO3 and 0.1 M NaBrO3
Removal of Various Interferences with CISA
CISA is an oxidizing agent which will oxidize up to a 100-fold excess
of CN-1 over Cl-1, 100 ppm NH3, 100 ppm Br-1 I-1 or 500 ppm S-2.
Chloride measurement interferences may be removed by using CISA.
To prepare CISA, add approximately 800 ml of distilled water to a 1
liter volumetric flask. Add 15.1 grams of NaBrO3 to the flask and swirl
to dissolve the solid. Slowly add 75 ml of concentrated nitric acid (70%
w/w or l5.9N), mix, and dilute to the mark with distilled water.
To use CISA, mix equal amounts of CISA and sample. Allow solutions
to stand for ten minutes before measuring. Since chloride will be
oxidized upon prolonged standing, all standards or samples mixed with
CISA should be discarded after measuring. Prepare a fresh mixture of
CISA and standard for each calibration. After adding CISA, follow the
procedures for direct measurement.