Method development for HILIC assays

In this review, method development for hydrophilic interaction LC (HILIC) is highlighted. HILIC is a chromatographic technique that uses aqueous‐organic solvent mobile phases with a high organic‐solvent fraction, and a hydrophilic stationary phase. It is mainly applied for the separation of polar and hydrophilic compounds. Method development, in general, can be done uni‐ or multivariately. In the univariate approach, the factors that are expected to potentially affect the separation of the compounds will be examined sequentially and one‐at‐a‐time. All HILIC methods found in the literature were developed in this way. For these methods, the analytes, the considered factors, the selected responses, and the finally chosen experimental conditions are discussed in this review. Where examined, the method validation and the comparison with other analytical assay methods is also described. For the multivariate method‐development approach, which is based on the use of experimental designs, only a possible strategy is presented, because of the lack of relevant publications in the literature.