Preferred Label : interfering substance;
Detailed label : interfering substance in electroanalytical chemistry;
IUPAC acronym : PVC;
IUPAC definition : Any substance, other than the ion being measured, whose presence in the sample solution
affects the measured emf of a cell. Interfering substances fall into two classes:
'electrode/electrochemical' interferences and 'chemical' interferences. Examples of
the first class include: ol li Those substances which give a similar response to
the ion being measured and whose presence generally results in an apparent increase
in the activity (or concentration) of the ion to be determined (e.g. Na sup class
plus /sup for the Ca sup 2 /sup electrode). /li li Electrolytes present at
a high concentration that give rise to appreciable liquid junction potential differences
or results in a significant activity coefficient decrease, or incipient Donnan exclusion
failure. The second class of substances that should be recognized as chemical interferences
includes: /li li Species that interact with the ion being measured so as to decrease
its activity or apparent concentration. The electrode continues to report the true
activity (e.g. CN sup class minus /sup present in the measurement of Ag sup class
plus /sup ), but a considerable gap will occur between the activity and concentration
of the ions even in very dilute solutions. Under these circumstances the determination
of ionic concentration may be problematic. /li li Substances interacting with
the membrane itself, blocking the surface or changing its chemical composition [i.e.
organic solvents for the liquid or poly(vinyl chloride) (PVC) membrane electrodes]
are grouped as interferences or electrode poisons. /li /ol ;
Origin ID : I03093;
Automatic exact mappings (from CISMeF team)
See also
Any substance, other than the ion being measured, whose presence in the sample solution
affects the measured emf of a cell. Interfering substances fall into two classes:
'electrode/electrochemical' interferences and 'chemical' interferences. Examples of
the first class include: ol li Those substances which give a similar response to
the ion being measured and whose presence generally results in an apparent increase
in the activity (or concentration) of the ion to be determined (e.g. Na sup class
plus /sup for the Ca sup 2 /sup electrode). /li li Electrolytes present at
a high concentration that give rise to appreciable liquid junction potential differences
or results in a significant activity coefficient decrease, or incipient Donnan exclusion
failure. The second class of substances that should be recognized as chemical interferences
includes: /li li Species that interact with the ion being measured so as to decrease
its activity or apparent concentration. The electrode continues to report the true
activity (e.g. CN sup class minus /sup present in the measurement of Ag sup class
plus /sup ), but a considerable gap will occur between the activity and concentration
of the ions even in very dilute solutions. Under these circumstances the determination
of ionic concentration may be problematic. /li li Substances interacting with
the membrane itself, blocking the surface or changing its chemical composition [i.e.
organic solvents for the liquid or poly(vinyl chloride) (PVC) membrane electrodes]
are grouped as interferences or electrode poisons. /li /ol