Hanna Instruments HI 4008 - Manual (Page 14)

14
the free ions from the measurement pool.
Cu
2+ + EDTA <—>Cu-EDTA
The EDTA reacts with the cupric ion forming a complex. The
EDTA also can react with a host of other metals. Working at
a pH between 4 and 6 optimizes the pH of the Cu-EDTA
complex, and also discourages complexing with other ions
that form stable complexes at high pH. Consult a
comprehensive Analytical Chemistry Treatise for techniques
concerning your particular interferent. The end point is
assumed to be at the inflection of the mV versus titrant
volume curve. Measurements may be automated by use of
the Hanna Titrator HI 901 or titrated manually.
Notes:
•
Use of the an acetic acid buffer may increase the end
point break. Prepare buffer by diluting glacial acetic
acid (17.4 M) to 1M and adjust to pH 4 with KOH.
Add 1part buffer to 10 parts sample.
•
Addition of ISA is suggested (2 mL/100 mL sample).
•
The EDTA titrant should be 10X more concentrated
than the expected Cupric concentration.
•
Competing metals will need to be identified and
removed or masked.
Plot generated on Hanna HI 901 Titrator during Plot generated on Hanna HI 901 Titrator during Plot generated on Hanna HI 901 Titrator during Plot generated on Hanna HI 901 Titrator during Plot generated on Hanna HI 901 Titrator during
automated Cupric ion titration using HI 4108 as
automated Cupric ion titration using HI 4108 as automated Cupric ion titration using HI 4108 as automated Cupric ion titration using HI 4108 as automated Cupric ion titration using HI 4108 as
indicator electrode.
indicator electrode. indicator electrode. indicator electrode. indicator electrode.