A
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ICE
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51
PIPETMAN® M
|
USER’S GUIDE
APPENDICES
Appendix A – Example of a Performance Check
Below is an example of how to evaluate the performance of PIPETMAN P10M at 1 µL.
1.
Determine the mean value e
of the evaporation loss e
i
that
occurs during your pipetting
cycles. Proceed as described in
on
page 53 to determine
e
i
.
2. Change the pipette tip and perform
the first weighing.
Then, keep a
regular cycle and perform the ten
following measurements.
3. Calculate the mean weight
w
r
= 0.957 mg
w
1
= 0.968 mg
w
6
= 0.966 mg
w
7
= 0.955 mg
w
2
= 0.960 mg
w
8
= 0.972 mg
w
3
= 0.984 mg
w
4
= 0.942 mg
w
5
= 0.969 mg
w
9
= 0.958 mg
w
r
rinsing measurement which is
disregarded for the calculation
w
10
= 0.967 mg
W =
_
W =
(0.968+0.960+0.984+0.942
+ 0.969+0.966+0.955+0.972
+ 0.958+0.967) / 10
_
W
=
0.964 mg
_
n
number of weighings
W
i
weighing results
W
i
1
n
n
i=1
4. Calculate the mean volume.
For a temperature of 21.5°C and an air
pressure of 1013 hPa, the Z factor is
equal to 1.0032 µL/mg (see table 3 in
on page 52).
5. Evaluate accuracy
6. Evaluate precision (repeatability)
Standard Deviation
(SD
W
)
V = ( W+e ) x Z
V
=
(0.964+0.018) x 1.0032
_
V
=
0.985 µL
_
E = V - V
0
V
0
true value set on the instrument
E
= 0.985 - 1 = - 0.015 µL
E% = (V - V
0
) x 100 / V
0
E%
= (-0.015 x 100) / 1 =
- 1.50 %
Systematic
error (
E
):
Relative error
(
E%
):
(W
i
- W)
n - 1
SD
w
=
2
n
i=1
n
i=1
SD
w
2
=
( W
i
- W )
2
1
n - 1
1
9
SD
w
2
=
SD
w
=
0.011 mg
(0.968-0.964)
2
+ (0.960-0.964)
2
+ (0.984-0.964)
2
+
(0.942-0.964)
2
+ (0.969-0.964)
2
+ (0.966-0.964)
2
+
(0.955-0.964)
2
+ (0.972-0.964)
2
+ (0.958-0.964)
2
+
(0.967-0.964)
2
SD
v
=
SD
w
x Z
SD
v
=
0.011 x 1.0032 =
0.011 µL
Random error (
SDv
):
