Polar-embedded alkyl chain

Use of alkylamide phases, in which alkyl chains are attached to the silica surface via an alkylamide group, reduces interactions with free silanols, by an internal masking mechanism. Residual silanols interact by hydrogen bonding with the embedded amide groups and thus become less active toward analytes. The embedded polar amide groups lessen the hydrophobicity of these phases compared to that of C18 bonded phases prepared from the same silica. Improved peak shapes of ionizable compounds were reported and this stationary phase was successfully used under IPC conditions to analyze streptomycin and its dihydrostreptomycin derivative in food... 

The strong polar character, which is characteristic of these phases, results from short alkyl chains, polar groups on the surface, or embedded polar groups in the alkyl chains. 

Zorbax Bonus is more hydrophobic than Nucleosil Nautilus, and this in turn is more hydrophobic than Prontosil ACE. The most polar embedded phase with a long alkyl chain is Symmetry Shield, with carbamate as the embedded polar group. 

The most polar embedded phases of all are such phases with even shorter alkyl chains, e.g. HyPURITY ADVANCE and SynergiPOLAR RP. 

Polar groups directly on the surface, as in the case of Spherisorb ODSl, Platinum EPS, and Supelcosil ABZ PLUS, and perhaps in combination with short alkyl chains as in the case of SynergjPOLAR RP, impart the strongest polar character, which is not possible by the introduction of a polar group into the alkyl chain (embedded phases). 

Strong polar surface SynergiPOLAR RP Short alkyl chain, embedded polar group, polar terminal phenyl group, hydrophilic endcapping... 

The dipolarity/polarizability parameter s closes the list of the interaction parameters from Eq. (5). Again, the data show a negative sign, indicating more pronounced dipole or induced-dipole activity in the eluent than in the stationary phase. Principally, phases with higher carbon load show weaker dipolar interactions and thus more strongly negative s parameters. As expected, the polar embedded phases and the cyano phase exhibit smaller values. The difference between Symmetry Shield Cjg and Cg reflects the differences in the steric effects of the alkyl chains. 

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