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7. Change the actual volume with the scroll key and accept with OK.
8. Save? is displayed. Accept with Yes.
The adjustment has been changed.
Formulas for calculating results
Conversion of mass to volume
V = (w + e) × Z
where: V = volume (µL); w = weight (mg); e = evaporation loss (mg); Z = conversion factor for mg/µL
conversion
Evaporation loss can be significant with low volumes. To determine mass loss, dispense water to the
weighing vessel, note the reading and start a stopwatch. See how much the reading decreases
during 30 seconds (e.g. 6 mg = 0.2 mg/s).
Compare this to the pipetting time from tareing to reading. Typically pipetting time might be
10 seconds and the mass loss is 2 mg (10 s x 0.2 mg/s) in this example. If an evaporation trap or lid
on the vessel is used the correction of evaporation is usually unnecessary.
The factor Z is for converting the weight of the water to volume at test temperature and pressure. A
typical value is 1.0032 μl/mg at 22 °C (71.5 °F) and 95 kPa.
Accuracy (systematic error)
Accuracy is the difference between the dispensed volume and the selected volume of a pipette.
A = V – V
0
where: A = accuracy; V = mean volume; V
Accuracy can be expressed as a relative value:
A% = 100% × A / V
0
Precision (random error)
Precision refers to the repeatability of the pipettings. It is expressed as standard deviation (s) or
coefficient of variation (cv).
where:; S = standards deviation;
Standard deviation can be expressed as a relative value (cv).
cv = 100% × S /
Maintenance
Multiple hazards. Only qualified personnel must conduct the tasks described in this section of the
document.
14 English
= nominal volume
0
= mean volume; n = number of measurements
C A U T I O N
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