Hoefer Single Channel Variable Pipette - Manual (Page 5)

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6. CALIBRATION
Each Hoefer pipette has been factory calibrated and certified according to ISO 8655/Din
12650. A calibration certificate is included with each pipette.
6.1 Confirming Calibration
Note: A scale with the ability to be set to 2 digits beyond the decimal point is
needed for pipette calibration. The room temperature should be 20 to 25ºC
without drafts.
1. Set the desired pipette volume. Hoefer recommends three different set
volumes: maximum volume, 50% of the maximum volume and 10%
of the maximum volume.
2. Firmly place the tip on the shaft of the pipette.
3. Pre-rinse the pipette tip with distilled water 5 times.
4. Carefully aspirate the liquid ensuring that the pipette is vertical.
5. Pipette the distilled water into a tarred container and record the weight
in milligrams. Repeat at least 5 times recording each result.
6. To calculate the volume dispensed, divide each measured weight by
the density of distilled water (1.0032).
7. Calculate accuracy:
a. Calculate the mean volume dispensed
n
X
X
∑
=
) (
Where:
X = the calculated volume for each measurement
= the number of measurements n
b. Use the mean volume to determine accuracy
Accuracy % = 100 *
) (
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛ −
volume set
volume set X
8. Calculate precision:
a. Calculate Standard Deviation of volume dispensed
S =
1
2 )^ (
−
−
∑
n
X Xi
Where:
Xi = individual volume
X = mean volume
n = number of measurements
b. Use the Standard Deviation and mean volume to determine
precision
Precision % =
⎟
⎠
⎞
⎜
⎝
⎛
X
S
*100