Charge‐ and Size‐Based Separations of Polyelectrolytes by Heart‐Cutting Two‐Dimensional Capillary Electrophoresis

Abstract

Summary: This work reports the separation of polyelectrolytes according to their charge density and their molecular mass by two‐dimensional capillary electrophoresis (2D‐CE). The two dimensions of the separation are performed in the same capillary using a heart‐cutting approach. The first dimension of the separation is performed in free‐solution CE (i.e. in the absence of sieving matrix) and allows separating the polyelectrolytes according to their charge density. A selected fraction stemming from the first dimension is next submitted to a second separation medium that is introduced in the capillary by electro‐osmotic flow. The second dimension of the separation is performed in the presence of an entangled polymer solution and allows the size‐based separation of the polyelectrolytes. The interest of heart‐cutting 2D‐CE in comparison with one‐dimensional separations is clearly demonstrated using a model mixture containing ten synthetic polyelectrolytes. Good repeatability on migration times (RSD from 0.12% to 0.33%, calculated on 5 successive runs) and relative peak areas (RSD from 0.74% to 3.6%) was obtained using this new methodology.

Separation and Characterization of Highly Charged Polyelectrolytes Using Free-Solution Capillary Electrophoresis

“…Indeed, for ξ > 1, counterion condensation occurs and the effective charge density (as well as the effective electrophoretic mobility) should theoretically no longer depend on f . This behavior was roughly observed by Hoagland et al [10] for acrylic acid/acrylamide copolymers, and by Gao et al [11] and Cottet et al [12] for random copolymers (PAMAMPS) of 2-acrylamido-2-methylpropanesulfonate (AMPS) and acrylamide (AM). However, all groups experimentally found a weak dependence of the electrophoretic mobility with f , even above the 0.37 critical value ( ξ > 1).…”

“…The average molecular masses of the PAMAMPS were evaluated using size-exclusion chromatography coupled with multi-angle laser light scattering (SEC–MALLS), and ranged between 3 × 10 5 and 10 6 g/mol [21]. For such high molar masses, the PE electrophoretic mobility is independent of the molar mass (free-draining behavior [8,12,22]). For more details on the synthesis and characterization of the PAMAMPS used in this work, the reader can refer to Reference [21].…”

Generalized polymer effective charge measurement by capillary isotachophoresis

“…Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and statistical copolymer poly(acrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid), f (chemical charge density) = 10% (PAMAMPS 10%) were prepared in laboratory as described in supplementary information (SI) and [33][34][35]. The polymers were re-lyophylised prior to sample preparation in order to limit moisture content in the solid product.…”

Multidimensional capillary electrophoresis

“…To achieve this, Cottet's group proposed to perform the second dimension in counter‐EOF mode . The potential of interface‐free heart‐cutting 2D‐CE was then investigated for the separation of sample containing ten polyelectrolytes of different charge densities and different molecular masses .…”