Topics - Peak Tailing
Peak symmetry depends primarily on the shape of the absorption isotherm for the distribution of the solute between the two phases. If the adsorption isotherm is linear over the concentration range concerned, the peak tends to be symmetrical. In fact, due to the heat of solution being evolved
at the front of the peak and being absorbed
at the back of the peak, the front of the peak is always at a slightly higher temperature than the back of the peak so there is usually some slight
peak asymmetry (but no tailing). However, if the adsorption isotherm is not linear, then the peak will be asymmetrical and if this nonlinearity arises from adsorption (e.g. active sites on the surface of the support) then this will result in peak tailing
. Adsorption as opposed to partition will always result in asymmetric peaks (usually with tailing) unless the surface is very carefully prepared or deactivated. Peak tailing is most likely to occur (and be a problem) in gas chromatography but can be reduced by acid washing the support, drying, and treating with hexamethyldisilazane before coating with the stationary phase.