Thermo Fisher Scientific Ion Selective Electrodes Nitrate - Manual (Page 17)

Instruction Manual Nitrate Ion Electrode
15
Low Slope or standards contaminated prepare fresh standards
No Slope or incorrectly made
ISA not used use recommended ISA
standard used as ISA use ISA
electrode exposed soak electrode in
to interferences nitrate standard
defective electrode check electrode operation
air bubble on
remove bubble by
membrane re-dipping probe
"Incorrect Answer" incorrect scaling
plot millivolts on the linear axis. On the
(but calibration of semi-log paper log axis be sure concentration numbers
curve is good) 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:
10
-3
M = 62.0 ppm as
NO
3
= 14.0 ppm as N
sample carryover rinse electrodes thoroughly between
samples