Calibrating the SIET
Calibration of the SIET
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Model of a Diffusional Point Source and the Noninvasive Scanning
Ionselective Electrode Technique, SIET
Predicted and observed µVolt difference curves for diffusion of protons
(left) and potassium (right) from a point source:
Predictive equation for dV, the µV difference at a point in space,
r µ from a point source:
eff = efficiency of the measure
S K dr r = distance to point source
dV = eff  / (Cb + K/r) , where: dr = oscillation distance
z r^{2} K = slope of [ion] curve
Cb = background [ion]
S = Nernst coeficient
z = unit charge on the ion
This calibration curve allows one to estimate the efficiency, eff, of
the electrode which can be used to turn any µV difference measured with
a similar electrode into an observed flux of that ion in the space arround
a cell or tissue.
Ion flux, J, emanating from a distant (µm) point source:
Observed and predicted values for 2 LIXs proton (left) and
potassium (right).
Predictive equation for ionic flux, J_{o}:
D = diffusion coeficient for the ion (cm^{2} sec^{1})
J_{o} =  D dC/dr , where dC = concentration differential
dr = oscillation differential
Ion 
D_{o} 
i 
Nernst slope 
LIX 
t_{90} 
Hz 
eff% 
K^{+}
 19.6
 +1
 58
 K IB
 <1s.
 0.3
 70%

H^{+}
 93.7
 +1
 58
 H IIA
 ~0.6s
 0.3
 80%

Ca^{++}
 7.9
 +2
 29
 Ca IIA
 <5s
 0.3
 50%

Mg^{++}
 7.1
 +2
 29
 Mg IV
 <30s
 0.25
 30%

Cl^{}
 20.3
 1
 58

D is expressed as 10^{6}D/cm^{2} sec^{1}.
Nernst Slope, S, is expressed in mV.
If you have questions about calibrating the various vibrating probes
or the University of Massachusetts
Vibrating Probe Facility,
email its PI, Joe Kunkel
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UMass VPF
Page maintained by Joe Kunkel,
joe@bio.umass.edu. Copyright(c) 1995, 1996, 1997.
Created: 95/10/28 Updated:
97/06/22