The migration characteristics of small polar molecules are evaluated on etched, chemically modified capillaries with four different moieties (C5, C18, diol and cholesterol) bonded onto a silica hydride surface. The effects of pH on migration are used to determine the possible contributions of eletrophoretic mobility, electroosmotic flow (EOF) and analyte/bonded phase interactions. The EOF on etched capillaries is more complicated than on ordinary fused capillaries because it changes from anodic to cathodic as the pH is raised. A mixture of neurotransmitters and related compounds is used to further evaluate the effects of the bonded moiety on the separation properties of this particular electrophoretic format.
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