WPI APOLLO 4000, Instruction Manual

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APOLLO 4000
NITRIC OXIDE DETECTION
WORLD PRECISION INSTRUMENTS C-9
in dark and in absence of trace metal ions proceeds very slowly due to the
presence of chelating reagent, EDTA). The standard SNAP solution can then be
used for many calibrations of NO probes throughout the day. However, since SNAP
will slowly decompose even if stored correctly as described, it is recommended
that a fresh standard stock solution of SNAP is prepared at the beginning of
everyday. This will ensure an accurate calibration of the NO sensor.
The concentration of SNAP (and hence NO produced) in the stock solution is
calculated as follows:
[C] = [A•W/(M•V)]1000
Where C is the concentration of SNAP in micromolars, A is the purity of SNAP, W is
weight of SNAP in milligrams and V is the volume of the solution in liters. If SNAP
purity is 98.5%, hence in the above example the concentration of SNAP is:
[C] = [98.5% x 5.6 / (220.3 x 0.25)] x 1000 = 100.1
µ
M
Note: The purity of SNAP used is extremely important to ensure an accurate
calibration. We recommend the use of high grade SNAP with minimal purity of 98%
or better. SNAP can be purchased from WPI in various amounts.
Calibration Procedure
Within a nitrogen or argon environment, place 10.0 mL of solution #1 (CuCl) in a
20 mL vial (supplied in the calibration kit). Drop a small stirring bar into the
solution, and place the vial on the top of a magnetic stirring plate. Immerse a NO
probe into this solution, and while stirring, allow the background current to decay
and stabilize for 3-5 min. As soon as the background current becomes stable start
recording the data on the APOLLO4000 .
Next inject 3 aliquots containing 5
µ
L, 10
µ
L and 20
µ
L sequentially of the SNAP
stock solution (solution #2) into the vial containing cuprous chloride solution.
Depending on the required calibration range ( i.e., the final amount of NO
produced) desired, the volumes of SNAP stock solution could be increased to
produce a greater concentration of NO. It is recommended that calibration range
be kept close to the anticipated experimental concentration of NO.
Immediately following the first addition of SNAP into Solution#1 the current (pA) output
from the ISO-NO will be seen to increase rapidly. Within a few seconds the response