Managing sample introduction problems in hydrophilic interaction liquid chromatography

Sample injection can cause serious problems in hydrophilic interaction liquid chromatography (HILIC) when the injection solvent has higher elution strength than the mobile phase (mp). It can lead to asym-metric peak shapes and poor efficiency. The problem can occur when the mp contains a high proportion of organic e.g. 95% acetonitrile (a weak solvent) whereas the injection solvent contains a higher propor-tion of water (a strong solvent) that is necessary to dissolve polar samples. We investigated different strategies to overcome this problem. A simple method is pre-column dilution where the injector is pro-grammed to deliver a plug of weak solvent (e.g. pure acetonitrile) along with the sample dissolved in a solvent with higher water content than the mp. Another option is to use alternative organic solvents to acetonitrile in the injection solvent, e.g. isopropanol, acetone or tetrahydrofuran, that may give enhanced sample solubility. The role of the volume of injection solvents was investigated as well as the possible ef-fects of mass overload on the results. The use of small sample volumes is always recommended to reduce mismatch effects.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

Sample injection in HILIC can cause issues when the injection solvent has higher elution strength than the mobile phase, resulting in asymmetric peak shapes and poor efficiency. Strategies to overcome this problem include pre-column dilution with a weak solvent and using alternative organic solvents in the injection solvent. Controlling the volume of injection solvents and using small sample volumes is recommended to reduce mismatch effects.