Micropipette calibration

• 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.
  

 Calibration Process:

• 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
10-100 ml	20-200ml	100-1000 ml
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	10 ml	25 ml	50 ml	100 ml
Weight 1
Weight 2
Weight 3
Weight 4
Weight 5
Weight 6
Weight 7
Weight 8
Weight 9
Weight 10
Mean
Mean Volume
Standard Deviation (SD)
Coefficient of variation (CV) or Related Standard Deviation (RSD)
Accuracy (A)

• 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.