- Micropipette requires to calibration, this process is known as pipette calibration.
- Pipette calibration mainly two types
1.
Gravimetric method
2.
Colorimetric method
1.
Gravimetric Method.
- Gravimetric method based upon water gravity.
- Under a constant temperature and atmospheric pressure and relative humidity, the density of distilled water is constant.
- When determining the volume of water, the accuracy of measurements is effected by ambient temperature, atmospheric pressure and relative humidity.
- These factors are usually combined to
give the Z factor, used in calculation of volume of water.
- Calibrate the micropipette in a vibration free room at a constant temperature of distilled water between 20 to 250C.
- Use analytical balance with a readability of 0.1 mg.
- First determine the density factor of water and set the desired volume.
- Take a clean, dry glass beaker or vial (based upon water evaporation). Keep it on the weighing pan of analytical balance and tare the volume.
- Adjust the pipette volume using adjustment setting knob.
- Carefully fit the tip.
- Flush (rinse ) the tip with distilled water at least 3 times.
- Aspirate the distilled water and tare the volume .
- Repeat the at least ten times and record the results( the weight display of balance should be adjusted to zero every time).
All the ranges of micropipettes shall be calibrated as
per the table.
Pipette range
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10-100 ml
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20-200ml
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100-1000 ml
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10 ml
|
20 ml
|
100 ml
|
25 ml
|
50 ml
|
250 ml
|
50 ml
|
100 ml
|
500 ml
|
100 ml
|
200 ml
|
1000 ml
|
Micropipette ID No :
Micropipette Range : 10-100 ml
Analytical balance ID No:
Mean Volume ( ml or ml ) = Mean Weight ( mg or mg ) x Z
Z value : conversion factor, which is conversion of
density
Set Volume
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10 ml
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25 ml
|
50 ml
|
100 ml
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Weight 1
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Weight 2
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Weight 3
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Weight 4
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Weight 5
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Weight 6
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Weight 7
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Weight 8
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Weight 9
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Weight 10
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Mean
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Mean Volume
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Standard Deviation (SD)
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Coefficient of variation (CV) or Related
Standard Deviation (RSD)
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Accuracy (A)
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- Calculate the average ( Mean )
- Calculate the standard deviation (S.D.)
- Calculate the imprecision or Coefficient of viaration ( C.V. ) or RSD
- Calculate the accuracy
Acceptance Criteria:
- Accuracy value must be 99-101 % and C.V. value must be less than 1 %.
2.
Colorimetric
method :
- The more expensive method for micropipette calibration.
- Colormetric method in colored water is used & dispensed.
- The spectrophotometer is used for measuring the color and weight can be derived on the basis of those readings.
- Based on result of either of the method, Micro pipette should be recalibrated with tool provided with each pipette by manufacturer to ensure readings are within tolerance range as recommended in ISO-8655 standards.
