Pharmaceutical Analysis Lecture 2: Chromatographic Theory

The capacity factor (k) measures how long an analyte stays within the column. It compares the retention volume or time of the analyte to the void volume or time.

The selectivity (α) indicates how well the column separates two analytes, based on the ratio of their retention volumes or times.

Number of theoretical plates (n) represents the efficiency of a chromatographic column. It indicates how well the column separates compounds based on their interactions with the stationary phase.

The void volume (Vo) is the volume of the mobile phase outside of the stationary phase in a chromatographic column. It's the volume traversed by a non-retained solute.

The retention time (tr) is how long it takes an analyte to pass through the column. It's the time between injection and detection of the analyte peak.

A graph that shows the separation of components in a mixture based on their retention times and peak areas. Each peak represents a different compound, and the area under the peak is proportional to the concentration of the compound.

The time it takes for a compound to travel through the chromatography column and reach the detector.

The area under the peak in a chromatogram, which is proportional to the amount of analyte in the sample.

A theory that describes the separation process in chromatography by dividing the column into theoretical plates, where equilibrium occurs between the mobile phase and the stationary phase.

A theory based on the kinetics of the separation process, taking into account the rates of mass transfer between the mobile and stationary phases.

A mathematical equation that relates the efficiency of a chromatographic separation to the width of the peaks and the flow rate of the mobile phase. It can be used to optimize the separation process.

A measure of how well two compounds are separated in a chromatography experiment.

The ability of a chromatographic system to separate different components in a mixture.

A measure of column efficiency, calculated as the number of theoretical plates (Neff) or the height equivalent of a theoretical plate (HETP or H).

The length of column required for a single partition step to occur, calculated by dividing the column length (L) by the number of effective plates (Neff).

The spreading of a chromatographic peak, resulting in a wider peak shape.

A model that explains the factors contributing to band broadening in chromatography, accounting for the time required for analyte equilibration in the mobile and stationary phases.

An equation that describes the relationship between HETP (H) and the linear velocity of the mobile phase (u), considering various factors causing band broadening.

One of the terms in the Van Deemter equation, related to the random paths taken by molecules through the packed stationary phase, leading to band broadening.

A term in the Van Deemter equation, accounting for the diffusion of analyte molecules along the column length in the mobile phase, which contributes to peak broadening.

A term in the Van Deemter equation, representing the resistance to the transfer of analyte molecules from the mobile to the stationary phase, contributing to band broadening.

A term in the Van Deemter equation, representing the resistance to the transfer of analyte molecules from the mobile phase to the stationary phase, caused by the diameter and shape of the stationary phase particles.

The effectiveness of a column in separating components, affected by factors like diffusion coefficient of the analyte and the size and uniformity of the stationary phase particles.

A measure of column efficiency in chromatography. It represents the height of a theoretical plate, which is a hypothetical section of the column where separation occurs.

A plot that shows the relationship between plate height (H) and the linear velocity of the mobile phase (u). It helps to understand the factors affecting column efficiency and optimize separation.

The term in the Van Deemter equation that represents the contribution of eddy diffusion to band broadening. Eddy diffusion occurs due to the different path lengths that molecules take through the packed column.

The term in the Van Deemter equation that represents the contribution of longitudinal diffusion to band broadening. Longitudinal diffusion occurs when molecules diffuse in the direction of flow, spreading out the band.

The term in the Van Deemter equation that represents the contribution of mass transfer to band broadening. Mass transfer describes the time it takes for molecules to equilibrate between the mobile and stationary phases.

A measure of how well two components are separated in a chromatogram. A higher resolution indicates better separation between the peaks.

A factor that influences the separation of components in chromatography. It describes the difference in retention times of two components relative to their average retention time.

The time a component spends in the stationary phase relative to the time it spends in the mobile phase. A higher retention factor indicates greater interaction with the stationary phase.

A type of gas chromatography (GC) where the stationary phase is coated onto the inside of a long, narrow capillary tube. Open tubular columns offer high separation efficiency and fast analysis times due to their low resistance to flow.

The use of smaller particles in the stationary phase, which leads to:

• Higher efficiency: Smaller particles allow for more frequent interactions between analyte molecules and the stationary phase, resulting in better separation.

• Faster analysis: Less resistance to flow, leading to faster analysis times.