Important Definitions Which is used during HPLC/GC Analysis

Definitions Related to HPLC/GC Instrument:

Important Definitions Which is used during HPLC/GC Analysis:


DEFINITIONS:

Column: 

A tube which contains the stationary phase. The stationary phase deferentially interacts with the samples constituent compounds as they are carried along in the mobile phase.

HPLC Column (Image taken from Waters.com)

Tailing Factor / Asymmetry:

The factor describing the shape of a chromatographic peak. The symmetry factor is the ratio between the peak apex and the back side of the chromatographic curve to the distance peak apex and the front side of the chromatographic curve.

Tailing Factor (This image is property of Separation science)

Capacity Factor: 

Capacity factor k is a mass distribution ratio often used to describe the migration rate of an analyte in a column.

image taken from LC  resources

Column Efficiency:

The column efficiency is a measure of the band spreading of a peak. The smaller the band spread, the higher the number of column efficiency, which indicates the good column and system performance. Column efficiency is also called as theoretical plate count.

Retention Time:

It is the time between injection and the appearance of the peak maximum.

Relative Retention Time:

It is a measure of the difference of affinities of two compounds for the stationary phase; it is used in quality control, for reproducibility and method validation calculations.

Normal Phase Chromatography: 

Chromatography on Silica gel, Aluminium oxide and polar chemically bound Silica Gel with non-polar organic solvents as eluents i.e. stationary phase is polar than mobile phase.

Reverse Phase Chromatography:

Chromatography on lipophilic stationary phase i.e. mobile phase is 

significantly more polar than the stationary phase.

Baseline: 

The portion of the chromatogram recording the detector response 

when only the mobile phase emerges from column.

Resolution:

Resolution is a measure of the separation between two peaks. This resolution helps to evaluate the separation capacity of column.

System Suitability:

System suitability is series of tests performed to check the 

system performance during the analysis i.e. from the start to end.

Blank :

The solvent in which sample or standard solution is prepared.

Isocratic Run :

The mobile phase composition remains same throughout the run.

Gradient Run :

The composition of the mobile phase is varied over the run time.

Late Elution :

The peaks that comes off the column after the normal run time 

is called late eluting peak.

Carry Over :

Elution of the same compound / analyte in the subsequent injection

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