Chromatography terminology

### A

_{s}> 1.0 and fronting when A

_{s}< 1.0. Gaussian peaks are defined as A

_{s}= 1.0.

### B

### C

*chroma*, color, and

*graphein*, to write.

### D

### E

High efficiency means that the band broadening is low, and that you’ll obtain sharp peaks. It’s often given as the number of theoretical plates (N) or as theoretical plates per meter (N/m) to an independent measure of column length in the experiment. Efficiency plays a central role in qualifying and monitoring packed bed performance. The ideal high column efficiency gives low band and peak broadening, and indicates how well packed the column is before starting purification.

Column efficiency is typically defined using two parameters:

- Peak broadening over the column is described by an equivalent number of theoretical plates.
- Peak symmetry is described by a peak asymmetry factor, A
_{s}.

Each Cytiva resin protocol describes the procedure to determine column efficiency. You can also find it in our application note, Column efficiency testing.

### F

### G

### H

### I

### L

### M

### P

A measure of chromatography peak broadening and column efficiency. Also referred to as the number of theoretical plates. Scientists use the plate number of a column to measure column efficiency. The more plates a packed column has, the higher the column efficiency.

The plate number is calculated from N = 5.545 × (V_{R}/W_{h})^{2} assuming a Gaussian peak, where:

- V
_{R}= retention (elution) volume - W
_{h}= peak width at half peak-height.

V_{R} and W_{h} must have the same unit (e.g., mL). You can substitute V_{R} with retention time, t_{R}, but then the unit of W_{h} must be time.