# VERY OFTEN PIPETTE USERS ARE NOT CERTAIN WHETHER THEIR PIPETTES SHOULD BE CALIBRATED AT 2 OR 3 VOLUMES? ISO 8655-6; 2002 7.1.1. Test volume In the case.

## Presentation on theme: "VERY OFTEN PIPETTE USERS ARE NOT CERTAIN WHETHER THEIR PIPETTES SHOULD BE CALIBRATED AT 2 OR 3 VOLUMES? ISO 8655-6; 2002 7.1.1. Test volume In the case."— Presentation transcript:

VERY OFTEN PIPETTE USERS ARE NOT CERTAIN WHETHER THEIR PIPETTES SHOULD BE CALIBRATED AT 2 OR 3 VOLUMES? ISO 8655-6; 2002 7.1.1. Test volume In the case of variable-volume apparatus, at least THREE volumes shall be tested: - the nominal volume - approximately 50% of the nominal volume - the lower limit of the useful volume range or 10% of the nominal volume (whichever is the greater) Measurements of further volumes is optional AS 2162.2-1998 5.4.5. Adjustable volume POVA Replicate tests should be carried out at TWO settings within the range, e.g. of 20 percent and 100 percent maximum deliverable volume for each adjustment of volume within the range of the instrument. AT PIPETTE CLINIC WE FOLLOW AUSTRALIAN STANDARD AS 2162.2-1998 10% OR 20% OF NOMINAL VOLUME DEPENDING ON MANUFACTURER SPECIFICATION AND NOMINAL VOLUME

We believe that there are many disadvantages of calibrating variable volume pipettes at three points ( Volumes ): First and foremost they send confusing and very often incorrect information about the pipette's linearity That is SET volumes versus DELIVERED volumes We believe that there are many disadvantages of calibrating variable volume pipettes at three points ( Volumes ): First and foremost they send confusing and very often incorrect information about the pipette's linearity That is SET volumes versus DELIVERED volumes 100 µL500 µL1000 µL101.75497.55998.683.001.000.60 Two Point vs Three Point Pipette Calibration With these three points, pipette's linearity can be described with three different lines ( Black, Blue and Pink line ) which can contradict obtained results and/or pipette's performance. If the pipette's linear response is described by low and middle point ( Black Line ) or middle and high point ( Blue Line ), very often by extrapolating these lines, one can find that the pipettes have actually failed manufacturers specification for inaccuracy. If, on the other hand, the pipette's linear response is described by low and high point ( Pink Line ) then the actual measurements at middle point become pointless. 96.7 µL Extrapolated Volume ( µL ) … … … … … … … … … … … … … … 500.4 µL Calibration Data 1.75-0.49-0.13 Status Imprecision CV ( % ) Specification ( <% ) Specification ( +% ) Inaccuracy ( % ) Mean Volume ( uL ) 10 Measurement / Volume 9 8 7 6 5 4 3 2 1 101.99 102.12 102.01 102.12 101.41 102.09 102.05 101.59 101.37 100.74 497.80 497.70 496.90 497.20 498.30 497.10 498.00 497.30 498.00 497.20 999.40 998.60 999.00 997.90 999.74 998.67 999.34 997.80 998.50 997.80 PASS 0.450.090.07 0.600.20 PASS 500 µL100 µL1000 µL DELIVERED VOLUME ( µL ) SET VOLUME – Pipette’s counter Manufacturer Specification BB Linearity 100-500 µLY = 0.9895x + 2.7987Linearity 500-1000 µLY = 1.0023x – 3.5750Linearity 100-1000 µLY = 0.9966x + 2.0906992.3 µLFAIL96.7 µLFAIL500.4 µLPASS 992.3 µL Extrapolated Volume ( µL ) … … … … … … The SET volumes lie on the straight line Other disadvantages of calibrating variable volume pipettes at three volumes are, but not limited to: Three volume calibrations require more time to complete and therefore they are more expensive. As three volume calibrations take more time to complete they are more likely to be affected by changes in the environmental conditions ( Especially in the case of multi-channel pipettes ). With three volume calibration, apart from those three measured volumes, it is impossible for the user to determine what would be the delivered volume of a pipette for any given volume set on the counter. It is evident that calibrations done at two points ( Low and High ) eliminate all of these problems, provide more ACCURATE RESULTS and save significant TIME and MONEY 495 µL 505 µL 103 µL 97 µL 1006 µL 994 µL

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