Laboratory Techniques: Centrifugation and Chromatography

Vocabulary-style flashcards covering the definitions, principles, and components of centrifugation, ultracentrifugation, and chromatography as presented in the lecture notes.

Centrifuge

A core laboratory instrument used to separate components of complex mixtures quickly and efficiently based on differences in density, size, and shape.

Centrifugation

A process involving the spinning of samples at very high speeds to generate centrifugal force, which accelerates sedimentation to achieve separation within minutes.

Pellet

The compact mass of sedimented particles found at the bottom of a tube after centrifugation.

Supernatant

The liquid layer above the pellet containing dissolved or lighter substances.

Principle of Centrifuge

Based on the application of centrifugal force that acts outward on particles when they are rotated around a central axis; each particle experiences a force proportional to its mass, radius, and rotational speed.

Relative Centrifugal Force (RCF)

A standardized way to describe the strength of centrifugation calculated as $RCF = \frac{r \omega^2}{g}$, where $r$ is radius, $\omega$ is angular velocity, and $g$ is acceleration due to gravity.

RPM

Revolutions Per Minute; a measure of how fast the centrifuge rotor spins.

Rotor

A component of the centrifuge that holds the sample tubes and rotates at high speed.

Spindle

A part that connects the rotor to the motor, transforms rotational energy, and ensures smooth and stable spinning.

Control Panel

A component providing precise control over temperature, time, speed, and acceleration/deceleration rates.

Ultracentrifugation

A powerful laboratory technique used to separate extremely small particles like nucleic acids, proteins, cell organelles, and viruses by spinning samples at speeds up to $1,50,000\,rpm$.

Sedimentation coefficient ($s$)

A value described by the Svedberg equation, where $s = \frac{V_s}{a \times g \times r}$. $V_s$ is sedimentation velocity, $a$ is angular velocity, $g$ is acceleration due to gravity, and $r$ is radius.

Differential Centrifugation

The simplest form of centrifugation used to separate particles based on their sedimentation rate, collecting pellets after each high-speed run for sequential isolation.

Density-Gradient Centrifugation

A method that uses a pre-formed density gradient medium (such as sucrose or $CsCl$) to improve separation.

Rate-Zonal (Size) separation

A type of density-gradient centrifugation where samples are layered on top of a gradient and particles separate based on their size and shape as they move through it.

Isopycnic (density) separation

A process where particles move through a gradient until they reach a position where their density matches the surrounding medium, creating distinct bands.

Chromatography

A separation method where an analyte is combined with a mobile phase (liquid or gas) and allowed to move through a stationary phase, separating components based on their interaction with each phase.

Mobile Phase

A pure solvent like water or gas that carries the components of a mixture over the stationary phase.

Stationary Phase

An immobile phase (solid or liquid film) that interacts differently with sample components, helping to separate them.

Retention time

The specific time at which a sample component elutes from the stationary phase.

Chromatogram

A record of the signals from a detector, plotted to show the separation of components.

Planar chromatography

A form of chromatography where the stationary phase is a solid particle or thin liquid film coated on an inert substance like glass or plastic (e.g., TLC or Paper chromatography), moving via capillary action.