WPI APOLLO 4000, Instruction Manual

Page: 38 / 74

APOLLO 4000
NITRIC OXIDE DETECTION
WORLD PRECISION INSTRUMENTS C-14
is subsequently oxidized immediately before it is detected by the NO sensor.
Example for creating a calibration curve and related computations
1. SNAP weight = 6.4 mg.
2. SNAP was dissolved in 250 mL solution #1 to obtain the standard stock solution.
3. 20
µ
L, 40
µ
L, and 80
µ
L of SNAP stock were added sequentially into 10 mL of
solution # 2.
4. The current was continuously recorded during the course of the calibration.
5. A standard calibration curve was constructed according to the recorded date.
[SNAP] [NO] = 0.6 X [SNAP] Output Current
232.4 nM 139.4 nM 230 pA
462.0 nM 277.2 nM 488 pA
916.8 nM 550.1 nM 1001 pA
Y = -32.038 + 1.88X
The data from calibration curve indicates that this procedure allows an excellent
linear calibration of NO probes (R 2 = 1). The accuracy of calibration is
approxi/- 10% from mean. The source of error arises most probably from
gravimetric measurement of the standard reagent, SNAP. In addition, purity of
SNAP as well as partial oxidation of generated NO in the calibration solution could
contribute to this error. Such a deviation may not be so important when NO is
quantified in biological systems because most often the ability to measure changes
in the basal concentration of NO is more significant than measurement of the
absolute level of NO.