eutech-instruments cyanide epoxy User Manual

Cyanide Electrode 

 

Instruction Manual

 

 

12

 
Cyanide levels from 5X10

-6

M to 1X10

-2

M cyanide can be measured with the cyanide electrodes.  

However, since cyanide ion attacks the electrode membrane, measurements above 1X10

-3

M should 

be done only intermittently. 
 
The electrodes respond to cyanide in the sample as well as to ions dissolved from the membrane at 
low levels. The electrode membrane shows a very slight water solubility. The detection limit of the 
electrode is determined by this factor. The low-level procedure is recommended if measurements 
are to be made in the non-linear region below 8X10

-6

M. 

 
Plastic lab-ware must be used and the beakers must be covered with Parafilm for low level cyanide 
determinations or cyanide will be lost. Allow a longer stabilization time before taking the meter 
reading for best results. 
 

 
A cyanide electrode can be used over the pH range 11 to 13. It is necessary to adjust the sample pH 
to above 11 using the recommended ISA to convert all cyanic acid species in solution to cyanide. 
 

 
A cyanide ion electrode will last six months in normal laboratory use. On-line measurements might 
shorten operational lifetime to several months. In time, the response time will increase and the 
calibration slope will decrease to the point calibration is difficult and electrode replacement is 
required. 
 

 
The cyanide electrode may be stored for short periods of time in 1.0x10

-4

M cyanide solution with 

ISA added. For longer storage (longer than two weeks), rinse and dry the sensing pellet and cover 
the membrane tip with any protective cap shipped with the electrode. The reference portion of the 
combination electrode (or the outer chamber of the reference electrode) should be drained of filling 
solution, if refillable, and the rubber insert placed over the filling hole. 
 
 
ELECTRODE THEORY