4.4 Calibration: PFP7/C
When using the PFP7/C, a calibration curve is not required as the display is calibrated in
direct
concentration units. Therefore only one top standard is required to enable this calibration to
be
performed
.
Installation and set-up procedures should be carried out as for the standard Model
PFP7.
NOTE: The Model PFP7/C allows direct readout of Na and K
concentration
in
serum samples. Na levels in urine samples may also be
read
directly from
the display.
Samples of both serum and urine should be diluted 1 in 100 or 1
in
200 to obtain optimum results from the flame
photometer.
To calibrate the unit for clinical use the following steps should be carried
out:
1. Aspirate deionised water and set the display to read
zero.
2. Select the appropriate element (Na or K) on the filter select control and the position
of
the decimal point using the d.p.
switch.
3. Aspirate the required standard, e.g. 140mmol/l Na, 5.0mmol/l K which has been
pre-
diluted at least 1 in 100 and set the display reading accordingly using the fine
and
coarse sensitivity
controls.
4. Adjust the fuel valve in a clockwise direction until a peak reading is obtained. Re-set
the
display reading accordingly for the standard being
aspirated.
NOTE: There is a time delay between adjusting the flow of fuel and
seeing
the
effect of the adjustment. A pause of a few seconds is
therefore
necessary
between making every fine
adjustment.
The optimum flame conditions are different for Na and K
and
retuning is necessary when switching between
elements.
5. Re-check the zero setting and adjust if
necessary.
6. Aspirate the pre-diluted sample and note the
reading.
7. Calibration needs to be checked periodically by aspirating the blank and
standard
solutions. Initially this check should be carried out after every 10 samples.
Experience
and increased confidence in the PFP7/C will enable you to best judge the frequency
of
this
check.
4.5
Shutdown
1. Aspirate deionised water for at least ten
minutes.
2. If the shutdown is short term i.e. the instrument is to be used again the same day/shift,
it
is
adequate to remove electrical power from the unit by depressing the power
switch.
This
will safely extinguish the
flame.
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