WPI APOLLO 4000, Инструкция по эксплуатации

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APOLLO 4000
NITRIC OXIDE DETECTION
WORLD PRECISION INSTRUMENTS C-7
Calibration of NO sensor by decomposition
of SNAP
This method can be used to calibrated all NO sensors (see Ref. 1: Zhang,
et al.,
“Novel Calibration Method for Nitric Oxide Microsensors by Stoichiometrical
Generation of Nitric Oxide from SNAP”
Electroanalysis, 2000,
12 : 6).
S-nitroso-N-acetyl –D,L-penicillamine ( SNAP ) is a stable NO containing compound
that can be used for quantitative generation of NO in solution. SNAP decomposes
to NO and a disulfide by product when dissolved in water. However, the rate of
decomposition of the SNAP is very slow. The kinetics controlling the decomposition
of SNAP depends on several parameters including, pH, presence of catalyst,
temperature and light.
In the procedure described here, SNAP is used in combination with a catalyst,
cuprous chloride, to generate known amounts NO in solution, which can then be
used to accurately calibrate various NO-sensors. The protocol does not investigate
all parameters involved in SNAP decomposition neither is it intended to propose a
model by which SNAP is decomposed.
Two methods are described here for the calibration of NO sensors based on
decomposition of SNAP. The first method relies on the use of Cu(I) as a catalyst for
the 100% conversion of SNAP into NO. This method is extremely accurate but
technically more demanding than the second method, which relies on the use of
Cu(II) for the partial but quantifiable conversion of SNAP to NO.
Method 1: Calibration by decomposition of a S-
nitrosothiol compound using Cu(I) as a catalyst
This method of calibration results in the 100% conversion of SNAP to NO. The
amount of NO produced, therefore, is based on the final concentration of SNAP.
CAUTION: The described calibration procedure requires the use of cuprous (I)
chloride, CuCl, where Cu (I) is the active catalyst for the conversion of SNAP to
NO. The calibration curve assumes only the presence of Cu (I) and hence a 100%
conversion efficiency of SNAP to NO (see “A novel method to calibrate nitric oxide
microsensors by stoichiometrical generation of nitric oxide from SNAP”, X. Zhang,
L. Cardosa, M. Broderick, H. Fein, I. R. Davis,
Electroanalysis, 2000, 12(6),425-