Electro-Chemical Devices (ECD) T80 - Manual (Page 58)

8.3.4 P H E LECTRODE C ARTRIDGE C LEANING
Remove the sensor from the process and carefully wash the wetted end of the electrode cartridge in a mild
solution of detergent and water or with methyl alcohol. If the electrode response is not improved, soak the
electrode in 0.1 Molar HCl for 5 minutes. Remove and rinse the electrode with tap water and soak in 0.1 Molar
NaOH for 5 minutes.
Remove the electrode from the NaOH solution, rinse the electrode and soak in a 4 pH buffer solution for 10
minutes. This should improve the response of the electrode. If not, replace the electrode.
If the electrode must be left out of the process for an extended period of time, store it in a solution of water
saturated with KCl or a 4.0 pH buffer solution. ECD does not recommend the storage of electrodes in distilled or
deionized water.
8.3.5 ORP E
LECTRODE
C
ARTRIDGE
C
LEANING
Cleaning the platinum surface to remove coating can be done using an abrasive cleaner like 600-800 grit wet/dry
sand paper or chemical reagents specific for the type of coating. Abrasive cleaning is the most common method
of cleaning and is usually sufficient to restore the platinum surface; however, some processes can form a hard
coating requiring chemical cleaning with a strong acid solution. Acid solutions greater than 10% are not
recommended.
8.3.6
P
I
ON
E
LECTRODE
C
ARTRIDGE
C
LEANING
Ion selective electrodes require periodic service. Weekly checks should be performed to assure the accuracy of
the measurement.
The ion selective crystal that senses the ion concentration can become sluggish in response due to coating or
reactions with the process solution. Periodic cleaning or polishing will minimize drift and maintain the sensors
response.
CLEANING
The solid state crystal based electrodes, bromide, chloride, copper, cyanide, fluoride, silver, sulfide are fairly
robust and can be cleaned with alcohols, detergents or dilute acids to remove coatings caused by greases, oils or
films. A soft tooth brush or paper towel should be used to remove stubborn coatings. Do not clean with a wire
brush. Metal carryover from the brush will compromise the measurement. Cleaning should be followed by
polishing before calibrating the sensor.
The PVC membrane sensors, Ca++, K+, NH4+, NO3- are fragile membranes and should be cleaned using a soft
artist style paint brush while rinsing with a stream of water. Dilute dish washing detergents can be used to
remove oily films Solvents or strong acid/alkaline solution will irreparably harm the electrode.
Calibration may be necessary after cleaning.
POLISHING
Abrasive polishing is only recommended for the solid state crystal style Combination Electrodes. ECD supplies
two styles of abrasive cleaning kits, a package of light blue colored polishing strips or a small vial of 0.3 micron
alumina powder with Q-tips with the fluoride electrodes.
The sensing surface of solid state electrodes can wear over time, which causes drift, poor reproducibility and
loss of response in low level samples. The electrode can be restored by polishing the sensing surface with a
polishing kit. The polishing kit can also be used if the sensing surface has been etched or chemically poisoned.
Page 57 Model T80