WPI APOLLO 4000, Instruction Manual

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APOLLO 4000
NITRIC OXIDE DETECTION
WORLD PRECISION INSTRUMENTS C-12
slowly decline because generated NO is quickly oxidized to nitrite and nitrate
which will not be detected by the probe.
Note: You can change the volume of injected aliquots according to the
concentration of SNAP stock solution. Decrease the volume of aliquot if the
electrode is very sensitive or increase the volume of aliquot if the electrode is less
sensitive.
Because NO sensors can be calibrated in a linear fashion, the magnitude of every
signal should almost double as the volume of SNAP solution added is doubled in
the course of the calibration. Use the recorded data to construct a calibration
curve. The calibration curve can be simply constructed by plotting the signal
output ( e.g., in pA) vs. the concentration of SNAP added at that time. Note that
every addition of SNAP solution corresponds to a particular NO concentration. This
will be discussed below. After the sensitivity of the NO probe is established, the
APOLLO4000 software can be programmed to display data in either concentration
mode ( i.e., nM, mM) or redox current (i.e., pA, nA).
The standard SNAP solution can be used for the calibration of NO probes
throughout the day. Store the solution in the dark and refrigerate when not in use.
Prepare a fresh stock solution of SNAP in the beginning of every day to ensure
minimal decomposition of SNAP in the stock solution. Concentration of SNAP
decreases to 5-10% of its nominal value after approximately 4-5 hours.
NOTE: Remember that most NO probes are sensitive to changes in temperature.
It is therefore recommended that the calibration of your sensor is performed at
experimental temperature.