Introduction; Applications - Radiometer Analytical ISE25Pb Mode D'emploi

ISE25Pb
Lead Ion-selective Electrode

Introduction

The ISE25Pb electrode is a solid state, ion selective electrode with
a polycristalline sensing element. The electrode is characterised
by near theoretical sensitivity, fast response, a high degree of
selectivity for lead ions against a background of other ions, low
redox sensitivity, low maintenance level, and sturdy structural
properties.

Applications

The electrode is primarily intended for measurement of the activity
of lead ions, either by direct measurement or as an indicator
electrode in lead titrations. However, sulphate can also be
determined by titration with lead perchlorate.
In dilute solutions the concentration of free lead ions equals the
activity and can be measured directly at a suitable ionic strength,
and after proper calibration. The discrepancy between activity and
concentration is considerable only in solutions of rather high
concentration, where the conversion factor and the activity
coefficient are only not known accurately. Thus, as regards
-1 2+
concentrated lead solutions, for example, 10 M Pb , it is
advisable to dilute the samples, for example 100 times, before
measurement and determine the true concentration by multiplying
by 100 afterwards.
Another problem arises if the sample contains a fairly high back-
ground concentration of ions other than the lead, it is recommen-
ded to add a certain quantity of an indifferent salt e.g. KNO , to
3
both standards and samples so that the total ionic strength is
almost entirely governed by the salt addition.
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