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Resolution - Is the ability of a chromatographic column to separate peaks.  It is usually expressed in terms of the separation between two adjacent peaks.  The following equations are generally used in the determination of the resolution values between two peaks.  A value of 1 is considered to be the minimum resolution value for a significant separation to occur.  Values of 1.7 or larger are generally desirable.

Selectivity - Is a thermodynamic factor measured by the relative retention of two substances by the stationary phase in a chromatographic column and their partition against a constant mobile phase composition.

Capacity - Is a chromatographic parameter that measures the degree of retention of a compound by the stationary phase in a chromatography column.

Theoretical Plates - Is a measurement of efficiency for a chromatographic column.  First described by "Martin & Synge" it relates chromatographic separation to the theory of distillation, hence the term (N) is used to measure a column efficiency in terms of "plates".  The following two equations are normally used to calculate (N).

Height Equivalent to a Theoretical Plate - Is another way of expressing column efficiency taking the length of the column in consideration. The HETP value is calculated by dividing the length of the chromatographic column by the total numbers of plates (N-as calculated above). HETP = L / N

Asymmetry - Is a chromatographic factor that describes the shape of a chromatographic peak.  It describes the degree of tailing  (As > 1) or fronting  (As < 1).  Generally a fronting peak suggests voids or channels in the chromatographic bed, while tailing suggests non-specific interactions between the sample and the stationary phase.  An asymmetry value between 1 and 1.2 is desirable.