HOW DO I CLEAN MY FLUORIDE ISE ?
Q My Fluoride ISE has stopped measuring at very low levels (below 0.1ppm). It used to be very sensitive but no longer what can I do?
A The sensitive membrane will have been contaminated or coated with something. Easy solution is to clean the membrane area completely with some Methanol on a cotton wool bud. Wipe completely rinse with water. This will get it back to its former condition.
This procedure will improve the electrode slope and enable the ISE to sense at low levels if this part of the range has been lost.
To calculate slope measure the mV values of a 100 and a 1000ppm standard. The difference should be -59.16 mV at 25 degrees if it is perfect. Below 80% of that value is normally means electrode replacement is required.
