Figure 4.3.2: Typical calibration curve measuring ppm.
Customers working in medical environments are quite likely to be using the S.I. unit of mmol/l to report their
results. The relationship between mmol/l and ppm is defined below:
This relationship means that Na and K samples in the normal clinical range of 136-145mmol/l Na and 3.5-
5.0mmol/l K should be pre-diluted 1 in 100 or 1 in 200 to get optimum results from the flame photometer.
Aspirate a blank solution and set the readout to 000 using the blank
control.
Aspirate the highest standard solution and set the readout to an appropriate
reading
using the
fine and coarse sensitivity controls. Re-check the blank setting and adjust
if necessary.
Aspirate the remaining standard solutions (if used) to construct the calibration curve
and
note the
results.
When the blank and standards are set, unknown samples can be aspirated and
the
results
noted directly from the instrument readout.
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 will enable you to best judge the frequency
of
this
check.
The decimal point (d.p.) switch can be set to illuminate the decimal point in
any
significant
position. This should be chosen to give sufficient resolution for the
test required.
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