CALIBRATION OF SINGLE CRYSTAL ANTIMONY pH CATHETERS
Before to perform the calibration, the catheter must be free of any residues
from previous usage.
The recommended procedures for calibrating the Single Crystal Antimony pH
catheter are
a) the calibration buffers must be at same temperature (23ºC)
b) Insert the sensor and the reference electrode together in the buffer pH
7.
c) the catheter must be in the buffer pH 7 until the reading became stable
d) After the calibration in pH 7, remove the buffer pH 7 from the catheter
with absorbent paper
before to introduce the catheter in the buffer pH 1.
e) insert the sensor and the reference electrode together in the buffer pH 1
f) the catheter must be in the buffer pH 1 until the reading became
stable
g) After the calibration in pH 1, remove the buffer pH 1 from the catheter
with absorbent paper
before to introduce the catheter in patient
h) Introduce in the software the temperature correction factors (some
manufacturers have default
values for different types of pH catheters)
Influences from buffers, gel, reference electrode, measurement temperature,
etc, all play various roles, but such influences can be included in one
single temperature correction factor.
The factors are:
Temperature dependence of
a) the Single Crystal Antimony sensor
b) the reference electrode
c) the calibration buffers
Voltage offsets due to
a) chloride ion differences between the buffer and the gel used with the
reference electrode
b) junction potential between the gel and the skin
The temperature correction factors for the REUSABLE pH CATHETERS are:
+ 0.2pH for pH1
+ 0,3pH for pH4
+ 0.3pH for pH7
The temperature correction factors for the SINGLE-USE pH CATHETERS are:
+ 0.3pH for pH1
+ 0,4pH for pH4
+ 0.5pH for pH7
The temperature correction factors are only valid if the recommended buffers
and gel are used and the calibration procedures are followed.
The buffers must be free of phosphates.
For the calibration of catheters with external reference, the buffers must
have the same Chlorine ion activity.
The recommended buffers are made by Reagecon.
The recommended gel is made by General Electric (Hellige gel cat number 217
083 06)