Layer-by-layer self-assembly of polyelectrolyte multilayers on silica spheres as reversed-phase/hydrophilic interaction mixed-mode stationary phases for high performance liquid chromatography

•A series of PEMs coated silical gels are prepared via layer-by-layer self-assembly approach.•The developed stationary phases possess both RPLC and HILIC retention mechanisms.•The chromatographic performance can be tuned with the chemical structure and bilayer numbers of PEMs.•The stationary phases could be used for separation of both polar and nonpolar compounds.

In this study, a series of stationary phases, comprising silica spheres and polyelectrolyte multilayers (PEMs) as the core and surface coating, respectively, were prepared via a layer-by-layer self-assembly approach for use in high-performance liquid chromatography. PEMs coatings were formed by the alternate deposition of positively charged poly(allylamine hydrochloride) and negatively charged poly(ethylene-alt-maleate) anions which were synthesized by esterification between poly(ethylene-alt-maleic anhydride) and n-alkyl alcohols (CnH2n+1OH, n = 4, 8, 10, 12). The chromatographic performance and retention mechanism of the new stationary phases were evaluated in simultaneous reversed-phase/hydrophilic interaction mixed-mode chromatography using different solute probes, such as alkyl benzene, p-hydroxybenzoic acid and its esters, anilines, phenols, and pyrimidines. The separation performance of the new stationary phases was optimized by tuning the n-alkyl chain length of poly(ethylene-alt-maleate) and bilayer numbers of PEMs. These results indicated that the new stationary phases demonstrate promise for the simultaneous separation of complex hydrophobic and hydrophilic samples with high selectivity.