elutropic series - a relative ranking of HPLC solvents ranging from non-polar to very polar properties. Polarity effects are due, in part, to dielectric constant, dipole moment and hydrophobic-hydrophillic properties.
endcapping - an adsorbent is said to be endcapped when a small silylating agent (e.g. trimethylchlorosilane) is used to bond residual silanol groups on a packing surface. Most often used with reversed-phase packings. May cut down on undesirable adsorption of basic or ionic compounds.
See also endcapping.
endfitting - the fitting at the end of the column that connects it to the injector or detector. Most HPLC endfittings contain a frit to hold the packing and have a low dead volume for minimum band spreading. Usually made of stainless steel.
See column hardware.
excess adsorption - the amount of analyte concentrated on the surface expressed as the surface excess over the amount which would be on the surface in the absence of adsorption forces.