(a) In an isocratic elution, the solvent composition is held constant throughout the elution.
(b) In a gradient elution, two or more solvents are used and the composition of the mobile phase is changed continuously or in steps as the separation proceeds.
(c) In a stop-flow injection, the flow of solvent is stopped, a fitting at the head of the column is removed, and the sample is injected directly onto the head of the column. The fitting is then replaced and pumping is resumed.
(d) A reversed-phase packing is a nonpolar packing that is used in partition chromatography with a relatively polar mobile phase.
(e) In a normal-phase packing, the stationary phase is polar and the mobile phase is relatively nonpolar.
(f) In ion-pair chromatography a large organic counter-ion is added to the mobile phase as an ion-pairing reagent. Separation is achieved either through partitioning of the neutral ion-pair or as a result of electrostatic interactions between the ions in solution and
charges on the stationary phase resulting from adsorption of the organic counter-ion. 2
(a) In an isocratic elution, the solvent composition is held constant throughout the elution.(b) In a gradient elution, two or more solvents are used and the composition of the mobile phase is changed continuously or in steps as the separation proceeds.(c) In a stop-flow injection, the flow of solvent is stopped, a fitting at the head of the column is removed, and the sample is injected directly onto the head of the column. The fitting is then replaced and pumping is resumed.(d) A reversed-phase packing is a nonpolar packing that is used in partition chromatography with a relatively polar mobile phase.(e) In a normal-phase packing, the stationary phase is polar and the mobile phase is relatively nonpolar.(f) In ion-pair chromatography a large organic counter-ion is added to the mobile phase as an ion-pairing reagent. Separation is achieved either through partitioning of the neutral ion-pair or as a result of electrostatic interactions between the ions in solution andcharges on the stationary phase resulting from adsorption of the organic counter-ion. 2
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