Pipetting

Adjustment

Adjustment means altering the pipette settings so that the dispensed volume is within the specifications, dispensing the desired volume.

Aspirate

To draw liquid up into the pipette tip

Blow-out

To empty the tip completely

Calibration check

Checking the difference between the dispensed volume and the selected volume

Dispense

To deliver the sample

Ejector

The tip ejector releases the pipette tip.

Plunger

Plunger is depressed and raised to create partial vacuum and draw or dispense liquid.

Precise

Precision refers to the repeatability of the pipettings. It is expressed as standard deviation (s).

Calibration

Determining the difference between the dispensed volume and the selected volume.

P20, P200, P1000

The classes of pipettes. The numbers refer to the maximum volume (in microliters) that can be pipetted by that instrument.

Shaft

Attachment point for a disposable tip.

Spectrophotometer

The spectrophotometer is an instrument which measures the amount of light of a specificed wavelength which passes through a medium. According to Beer's law, the amount of light absorbed by a medium is proportional to the concentration of the absorbing material or solute present.

Optical density (OD)

Optical density is a measure of the amount of light that can travel through a medium. For example, increased optical density relates directly to increased concentration.

Minimum volume

Minimum volume = 10% of the max volume of pipette (microliters, uL).

Ex: P200 minimum volume = (10%)(200) = 20uL

Maximum volume

Maximum volume = number listed on the pipette (microliters, uL).

Ex: P200 maximum volume = 200uL

Pipette tip

The tip is where the liquid is drawn up. The color of the pipette plunger (blue or yellow) corresponds to the tip size to use (blue or yellow box). NEVER use your pipette without a tip.

Eppendorf tube

Tapered plastic vessel with cap, holds 1-2mL. Usually calibrates on the side

Accurate

Free from error or defect; consistent with a standard, rule, or model; precise; exact.

Dilution

A reduction of concentration by dilution the original substance with diluent in a certain ration. A 1:10 dilution is 1 part of the original and 9 parts diluent.

Serial Dilution

Dilution of a substance several times by the same amount each time. Each new dilution serves as the 'stock' for the next dilution. The original sample is only used for the first dilution.