[1S] UNIT 3: Pipetting
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➢ glass or plastic tubes ➢ open at both ends ➢ transfer specific amounts of liquid from one container to another. ➢ usually used for volumes between .01 and 10 milliliters.
Pipettes
TYPE 1: ACCORDING TO DESIGN Water is used for calibration. Allow liquid to flow by gravity, don’t blow. For non-viscous liquids
To deliver
TYPE 1: ACCORDING TO DESIGN Hg is used for calibration. Exact volume is delivered by repeated filling and emptying with the diluents. For viscous liquids
To contain
TYPE 2: ACCORDING TO DRAINAGE CHARACTERISTIC • similar to TD pipet • Last drop is blown out to get the exact volume • An etched or frosted ring indicate calibration
To blow out pipet
TYPE 2: ACCORDING TO DRAINAGE CHARACTERISTIC contents are allowed to drain by gravity
Self draining
TYPE 3: MEASURING / GRADUATED PIPETS has calibration marks to the tip and is generally a blow-out pipet
Serologic
• capable of dispensing different volumes • Uniform graduation along its length • Deliver fractional quantity of liquid • Used for reagent measurements
Measuring or Graduated pipets
TYPE 3: MEASURING / GRADUATED PIPETS does not have graduations to the tip, self draining
Mohr
TYPE 3: MEASURING / GRADUATED PIPETS may either be a serological or mohr. Calibrated either TC or TD. With total holding volume of less than 1 ml.
Micropipet
Printed on the neck of the pipette are the specifications that indicate:
• maximum volume of liquid that can be transferred • size of the divisions on the pipette • temperature at which calibrations were made • if the pipette is a “to deliver”(TD) or “to contain”(TC) pipette.
designed to dispense one volume
Transfer Pipets
TYPE 3.B: TRANSFER PIPETS • has a cylindrical bulb located midway between the mouth and the tip. • calibrated TD a fixed volume of liquid • allowed to drain only
Volumetric
TYPE 3.B: TRANSFER PIPETS • used for accurate measurement & other non-viscous fluids • has the greatest accuracy & precision • deliver a single specific volume of liquid, usually between 1 and 10 ml.
Volumetric
TYPE 3.B: TRANSFER PIPETS • For accurate measurements • Deliver one volume only
Volumetric
SPECIFICATIONS ON A VOLUMETRIC PIPETTE T/F: 1. When emptying a volumetric pipette, the liquid is not allowed to drain out. It is forced out.
F; When emptying a volumetric pipette, the liquid is allowed to drain out. It is NOT forced out.
SPECIFICATIONS ON A VOLUMETRIC PIPETTE T/F: 2. After it is emptied, the small amount of liquid which remains in the tip should not be blown out.
T
SPECIFICATIONS ON A VOLUMETRIC PIPETTE T/F: Volumetric pipettes are NOT blow-out pipettes
T
TYPE 3.B: TRANSFER PIPETS • bulb is located closer to the delivery tip • with an etched ring/blow-out pipet • used to measure viscous fluid
Ostwald-Folin Pipet
TYPE 3.B: TRANSFER PIPETS have no calibration marks and are used to transfer solutions or biologic fluids without consideration of a specific volume.
Pasteur pipet
TYPE 3.B: TRANSFER PIPETS most routinely used. Advantages: safety, stability, ease of use, increased precision, saves time, less cleaning is required.
Automatic pipets
AUTOMATIC PIPETS • associated with 1 volume • ranges from 1ul to 1000 ml
• fixed • variable
AUTOMATIC PIPETS has a pipetting capability of less than 1 ml
Micropipet
AUTOMATIC PIPETS dispenses greater than 1 ml
Automatic macropipet
GENERAL TYPES OF AUTOMATIC PIPETS relies on a piston for suction creation to draw the sample into a disposable tip that must be changed after each use.
Air Displacement