Glycine-based polymeric surfactants with varied polar head group: II. Chemical selectivity in micellar electrokinetic chromatography using linear solvation energy relationships

Abstract

A series of four acyl and four alkenoxy glycinates (i.e., mono-, di-, tri-, and tetraderivatives of polysodium N-undecenoyl glycinate (poly-SUGs) as well as polysodium N-undecenoxy carbonyl glycinates (poly-SUCGs)) were compared for simultaneous separation of nonhydrogen bonding (NHB), hydrogen-bond acceptor (HBA), and hydrogen-bond donor (HBD) solutes. An increase in the number of glycine units in the polar head group of polymeric surfactant decreases both the retention and the migration window of all solutes with some changes in separation selectivity. The poly(sodium N-undecenoxy carbonyl-glycinate) (poly-SUCG1) with one glycine unit was the least polar surfactant and has the lowest phase ratio, but this monoglycinate surfactant provided the best simultaneous separation of 10-NHBs and 8-HBAs. On the other hand, 9-HBDs were well separated using any of the six mono-, di-, and triglycinate surfactants compared to the two tetraglycinates. Linear solvation energy relationships (LSERs) and separation of the geometrical isomers studies were also performed to further envisage the selectivity differences. From LSER studies, the phase ratio and hydrogen-bond-donating strength of the poly-SUG series of surfactant were found to increase with an increase in the size of the head group, but no clear trends were observed for poly-SUCG surfactants. The cohesiveness for all poly-SUG and poly-SUCG was positive, but the values were generally lower (with exception of the poly(sodium N-undecenoyl glycyl-glycyl-glycinate)) at a higher number of glycine units. Finally, the poly(sodium N-undecenoyl glycinate) and poly-SUCG1 were found to be the two best polymeric surfactants as they provided relatively higher shape selectivity for separation of two of the three sets of geometrical isomers.

Recent progress in the use of ionic polymers as pseudostationary phases for EKC

“…1B) and undecenoyl glycinate (SUG n , Fig. 1C) surfactants and polymers with one, two, three, or four glycine units as the head group were reported [28,29]. The CMC of the surfactants were observed to decrease by approximately a factor of two with the addition of each glycine unit, while the aggregation numbers increased.…”

“…The polymers did, in some cases, show significant differences in selectivity toward geometrical isomers of phenylimidazole, nitrotoluene, or methoxyphenethylamine. LSER studies of the series showed few significant differences or trends among the PSPs, although the materials do appear to become more compact and cohesive as the number of glycinate units increases [28].…”

Electrokinetic chromatography with polymeric pseudostationary phases

“…Some significant selectivity differences were observed for certain geometrical isomers as well as for nonhydrogen bonding solutes. LSER studies indicated that the materials appear to become more resistant to the formation of a solvation cavity as the number of glycinate units is increased [55].…”

“…2A) and undecenoyl glycinate (Fig. 2B) surfactant monomers and polymers with one to four glycine units at the head group were studied with regard to solvation character and performance [55,56]. The CMCs of the monomers decreased by a factor of approximately 2 with the addition of each glycine unit, while the aggregation numbers increased.…”

Monoclonal Behavior of Molecularly Imprinted Polymer Nanoparticles in Capillary Electrochromatography

“…26,27 Structurally, polymeric surfactants are very similar to conventional micelles, but form spherical aggregates, which are covalently linked via the hydrophobic tails, while the polar head groups remain on the outside of the aggregate. 28,29 Several studies have shown the influence on chemical selectivity in MEKC [30][31][32] is dependent on the polar head group and the hydrocarbon chain length. Therefore, it would be favorable to incorporate such polymeric surfactant monomers in the MIP-NP process.…”