SOP on Calibration of Pipette, Graduated
SOP on Calibration of Pipette, Graduated
1.0 Purpose: This SOP describes a procedure for the measurement of capacity of graduated pipette.
2.0 Scope: This SOP is applicable to all graduated pipettes of different nominal capacity.
3.0 Responsibility: It is the responsibility of Quality Assurance Manager to ensure that the procedure is followed.
4.0 Materials and Equipment Used:
4.01 A weighing balance that is calibrated with traceable weights and regularly maintained.
4.02 A calibrated thermometer.
4.03 A weighing vessel.
4.04 Distilled water.
4.05 Acetone.
4.06 4% Acetic acid solution
4.07 Worksheets or forms to record the raw data.
5.0 Procedure: The determination of capacity of pipettes is based on weighing water and calculating mass and volume based on the density at the appropriate temperature.
5.01 Clean the pipette with soap solution and water to remove any adhering dirt or grease. Rinse the pipette with acetic acid solution and then wash with water till free from all acid.
5.02 Dry the pipette by rinsing with acetone.
5.03 Weigh a cleaned and dried weighing vessel (W1).
5.04 Fill the pipette with distilled water at ambient temperature sufficiently above the zero mark.
5.05 Then hold the pipette in a vertical position, and adjust the falling meniscus at any graduation line shall be performed as follows –
(a) Set the meniscus so that the plane of the top edge of the graduation line is horizontally tangential to the lowest point of the meniscus, the line of sight being in the same plane.
(b) Remove any drop adhering to the jet of the pipette by bringing the surface of a glass vessel into contact with the tip of the jet.
5.06 Deliver the water thus measured into cleaned tared vessel slightly inclined so that the tip of the jet is in contact with the inside of the vessel, but without movement of the one against the other throughout the delivery and waiting periods.
5.07 Stop the delivery of distilled water when the meniscus reaches a few ml above the graduation line up to which accuracy is to be determined. Make the final setting of meniscus by controlling the delivery and gradually stopping it when the meniscus touches the graduation line.
5.08 After the setting of meniscus at a particular graduation line is done, add any drop, adhering to the jet, to the delivered volume by bringing the inside of the receiving vessel into contact with the jet.
5.09 Again weigh the vessel containing distilled water (W2).
5.10 Note the temperature of water and calculate the volume of water delivered by the pipette at the reference temperature of 270C.
6.0 Calculation: Calculate the volume of water delivered by pipette using the following formula –
V= W2 – W1 / D
Where:
V = Volume of the pipette, Cm3 (ml )
W1 = Weight of empty weighing vessel.
W2 = Weight of empty weighing vessel & distilled water.
D = Density of water at 270C (i.e. 0.9965 g /cc)
7.0 Reporting: Record all the observations in the worksheets or forms. Calculate the correct volume of water delivered by the pipette and, the amount by which this differs from the indicated volume, is the volumetric error.