Separation of polar compounds on polar stationary phases with partly aqueous eluents is by no means a new separation mode in LC. The first HPLC applications were published more than 30 years ago, and were for a long time mostly confined to carbohydrate analysis. In the early 1990s new phases started to emerge, and the practice was given a name, hydrophilic interaction chromatography (HILIC). Although the use of this separation mode has been relatively limited, we have seen a sudden increase in popularity over the last few years, promoted by the need to analyze polar compounds in increasingly complex mixtures. Another reason for the increase in popularity is the widespread use of MS coupled to LC. The partly aqueous eluents high in ACN with a limited need of adding salt is almost ideal for ESI. The applications now encompass most categories of polar compounds, charged as well as uncharged, although HILIC is particularly well suited for solutes lacking charge where coulombic interactions cannot be used to mediate retention. The review attempts to summarize the ongoing discussion on the separation mechanism and gives an overview of the stationary phases used and the applications addressed with this separation mode in LC.

Hydrophilic interaction chromatography.

Validation of bioanalytical LC-MS/MS assays: evaluation of matrix effects.

Matrix-dependent signal suppression or enhancement represents a major drawback in quantitative analysis with liquid chromatography coupled to atmospheric pressure ionization mass spectrometry (LC-API-MS). Because matrix effects (ME) might exert a detrimental impact on important method parameters (limit of detection, limit of quantification, linearity, accuracy, and precision), they have to be tested and evaluated during validation procedure. This review gives a detailed description on when these phenomena might be expected, and how they can be evaluated. The major sources of ME are discussed and illustrated with examples from bioanalytical, pharmaceutical, environmental, and food analysis. Because there is no universal solution for ME, the main strategies to overcome these phenomena are described in detail. Special emphasis is devoted to the sample-preparation procedures as well as to the recent improvements on chromatographic and mass spectrometric conditions. An overview of the main calibration techniques to compensate for ME is also presented. All these solutions can be used alone or in combination to retrieve the performance of the LC-MS for a particular matrix-analyte combination.

An overview of matrix effects in liquid chromatography-mass spectrometry.

Separation efficiencies in hydrophilic interaction chromatography.

Overcoming matrix effects using the dilution approach in multiresidue methods for fruits and vegetables.

https://www.waters.com/webassets/cms/library/docs/720002135en.pdf

Systematic and comprehensive strategy for reducing matrix effects in LC/MS/MS analyses

Hydrophilic interaction chromatography (HILIC) is a useful technique for the retention of polar analytes that offers a difference in selectivity compared to traditional reversed-phase chromatography. This paper examines the use of a silica column for HILIC, including mechanistic studies of analyte retention on silica in aqueous-organic mobile phases. The authors compare a silica column and C18 column to demonstrate the increased sensitivity of using HILIC with electrospray ionization mass spectrometry (ESI-MS). They also report a quantitative LC-MS method for the analysis of acetylcholine, choline, and choline-trimethyl-d 9 , and describe a simplified solid-phase extraction (SPE) procedure that allows the direct injection of extracted organic fractions from SPE devices onto a silica column.

Diane M. Wagrowski-Diehl

Papers

Systematic and comprehensive strategy for reducing matrix effects in LC/MS/MS analyses

Hydrophilic Interaction Chromatography Using Silica Columns for the Retention of Polar Analytes and Enhanced ESI-MS Sensitivity

Chapter 6 - Method development in reversed-phase chromatography