NOVA BIOMEDICAL Stat Profile PRIME, Instructions For Use Manual

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B-2
Prime CCS Instructions for Use Manual
C
x
E
=
E
x
- E
std =
S log
____
Equation 4
C
std
By holding C
std
in Equation 4 constant, E is dependent on
only 1 variable, C
x
, the concentration of the ion of interest
in the sample. Equation 5 can be rearranged to isolate this
variable:
C
x
= (C
std
) 10
(E/S)
Equation 5
The analyzer’s microcomputer uses Equation 5 to calculate
the concentration of sodium, potassium, calcium, and
chloride ions in the sample.
B.1.2 pH Sensor
Definition of pH
The pH of an unknown sample is calculated using the
following equation:
E
std C
– E
x
pH E
std C
- E
x
= pH
std C
+ ––––––––– Equation 6
Slope
E
std C
– E
x
where Slope =
——————————
Equation 7
pH
std C
– pH
std D
Principle of pH Measurement
pH is measured using a hydrogen ion selective membrane.
One side of the membrane is in contact with a solution of
constant pH. The other side is in contact with a solution
of unknown pH. A change in potential develops which is
proportional to the pH difference of these solutions.
This change in potential is measured against a reference
electrode of constant potential. The magnitude of the
potential difference is a measure, then of the pH of the
unknown solution.