NOVA BIOMEDICAL Stat Profile PRIME, Инструкция по эксплуатации

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B-1
Appendix B
Appendix B
B Principles of Measurement
This section explains the Principles of Measurement for the
Stat Profile Prime CCS Analyzer.
B.1 Measured Values
Measuring Technology: Ten Planar Sensor Technology (Na,
K, Cl, iCa, pH, P CO
2
, P O
2
, Glucose, Lactate, Hematocrit)
in a MicroSensor Card
B.1.1 Sodium, Potassium, Chloride, and Ionized Calcium
Calculating Sample Concentration
Equation 1 links the voltage of the cell (E
m
) to the activity
of the ion. Activity is related to concentration (C) through
the activity coefficient in the relation a = f * C. The activity
coefficient is a function of ionic strength. Thus, Equation 1
can be rewritten in terms of concentration as follows:
E
cell
= E
o
+ S log a
o
- E
r
- E
j
Equation 1
E
cell
= E
o
+ S (log(f * C)
o
) - E
r
- E
j
Equation 2
Similarly, Equation 2 is rewritten:
(fC)
x
E = E
x
- E
std
= S log
_________
Equation 3
(fC)
std
The total ionic strength of whole blood is relatively constant
over the physiological range.
1
As a result, the activity
coefficients of sodium, potassium, calcium, and chloride
can be assumed to be constant. The internal standards
are formulated to reflect the same ionic strength as that
of whole blood. Therefore, a given ion’s activity coefficient
can be assumed to be equal in the standard and sample.
The activity coefficient terms in Equation 3 cancel out with
these results: