Thermo Fisher Scientific Ion Selective Electrodes Sodium - Manual (Page 15)

Instruction Manual Sodium Electrode
13
TROUBLESHOOTING HINTS
Symptom Possible Causes Next Step
Out of Range Reading defective meter check meter with shorting strap
(see meter instruction manual)
defective electrode check electrode operation
electrodes not plugged in
properly unplug electrodes and reset
reference electrode not filled replenish reference filling solution
electrodes not in solution put electrodes in solution
air bubble on redipping
electrode remove bubble by membrane
"Incorrect Answer" (but
calibration curve is
good) incorrect scaling of semi-log
paper plot millivolts on the linear axis. On
the log axis, be sure concentration
numbers within each decade are
increasing with increasing
concentration
incorrect sign be sure to note sign of millivolt
number correctly
incorrect standards prepare fresh standards
wrong units used apply correct conversion factor:
1.0X10-
3
M = 23.0 ppm as Na
+1
sample pH too acidic adjust pH with ISA
Drift (reading changing
in one direction) samples and standards at
different temperature allow solutions to come to room
temperature before measurement
incorrect reference filling
solution use recommended filling solution
electrode exposed to
interference soak overnight in electrode storage
solution
pH too acidic adjust pH with ISA
ISA not used use recommended ISA
Low Slope or No Slope standards contaminated or
incorrectly made prepare fresh standards
standard used as ISA use ISA
pH too acidic adjust pH with ISA
electrode exposed to
interference soak overnight in electrode storage
solution
air bubble on membrane remove bubble by redipping probe
Noisy or Unstable
Readings (reading
changing randomly) defective meter check meter with shorting strap
ISA not used use recommended ISA
meter or stirrer not grounded ground meter or stirrer
defective electrode replace electrode
electrode exposed to
interference soak overnight in electrode storage
solution