Quadra 4 Operator Manual
Tomtec
202
Section XI - Some Properties of Liquids That Affect
Pipetting Accuracy
1.0 The relationship between liquid and gaseous
states of a solvent have an effect on pipetting
VOLATILITY: The property of changing readily from a solid or liquid to a vapor.
VAPOR PRESURE: The pressure exerted by a vapor; often understood to mean
saturated vapor pressure.
PARTIAL PRESSURE: The pressure that one component of a mixture of gases
would exert if it were alone in a container.
2.0 Additional properties of liquids that might have
an effect on pipetting
DENSITY: The density of a liquid will significantly impact the ability of an air
displacement pipetting mechanism to aspirate the liquid into the pipette tip.
COMPRESSION: Different liquids and gases have different compression coefficients
that can effect pipetting, especially when the flow is partially obstructed.
VISCOSITY: This contributes to the resistance-to-flow of a liquid.
SURFACE TENSION: Is an effect within the surface layer of a liquid that causes the
layer to behave as an elastic sheet.
WETTING: Refers to the contact between a fluid and a surface, when the two are brought
into association. When a liquid has a high surface tension (strong internal bond), it will form
a droplet, whereas a liquid with low surface tension will spread out over a greater area
(bonding to the surface). On the other habd, if the surface has a high surface energy (or
surface tension), a drop will spread, or wet, the surface. If the surface has a low surface
energy, a droplet will form. This phenomena is the result of the minimization of interfacial
energy. If the surface is high energy, it will want to be covered with a liquid because this
interface will lower its energy, and so on.
NOTE: All of the above properties are affected by temperature.
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