Generally, only semi-quantitative information can be obtained from classical gel
electrophoresis; visual comparisons can be made with standards run on the
same gel. Scanning densitometry, as used in TLC(Topic D3) provides more
reliable data, but variations in gel thickness, band spreading and reactions with
reagents and staining dyes all contribute to considerable variability in the
measurements.
For CEand CEC, the methods used for quantitative chromatography (Topic
D2) are suitable, and alternative calibration procedures are described in Topic
A5. Peak areasare more reliable than peak heights, as they are directly propor-
tional to the quantity of a solute injected when working within the linear range
of the detector.Quantitative
analysis
188 Section D – Separation techniques