The influence of charged groups in gel permeation chromatography of polyelec‐trolytes

Abstract

When polyelectrolytes (lignosulfonates) with a broad molecular weight distribution are eluted from Sephadex gels with water, the fractionation is affected by steric exclusion, polyelectrolyte expansion, ion exclusion, and ion inclusion effects. The ion inclusion effect is due to interaction of charged sites in the macro‐ions which are more or less excluded from the gel with charged sites in more permeable macro‐ions. The ion inclusion effect depends on the cation of the lignosulfonates in such a way that the elution of lignosulfonates with a univalent cation is affected to a greater extent than the elution of lignosulfonates with a divalent cation. This is due to the existence of a higher density of free charges in the lignosulfonates with a univalent cation owing to a lesser tendency to form ion pairs. By choosing suitable eluents, it is possible to alter the retention volumes of lignosulfonates of different sizes and thus optimize the resolution.

Galactoglucomannan Recovery with Hydrophilic and Hydrophobic Membranes: Process Performance and Cost Estimations

“…Previous reports have shown that lignosulfonates were ion excluded when water was used as an eluent during SEC measurements [26]. This resulted in the early elution of the solutes and high MW determinations.…”

The absolute molecular weight distribution of hydroxypropylated lignins

“…In addition, proper calibration of the VPO is critical for accurate data acquisition and the application of ultracentrifugation to lignins is fraught with difficulties.7,10 With the relatively recent advent of gel permeation chromatography (GPC), most investigators have turned to this instrument for lignin characterization due to its ease of use and short analysis time. 3,4,[6][7][8][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] However, the GPC molecular weights and hence molecular weight distributions typically obtained thus far have only been relative quantities since the calibration method commonly used was based on the molecular weights of polystyrene standards, which are structurally and topologically very different from lignins. In an attempt to obtain absolute numbers while bypassing the use of calibration standards with substantially different chemical structures, Kolpak et al have resorted to a dual detection system for GPC that utilized both a differential refractive index (DRI) detector and a lowangle laser light scattering (LALLS) detector.3 However, the use of GPC/LALLS to study lignins has complex problems associated with it that make its application to lignin analysis difficult.…”

Lignin. 18. Associative effects among organosolv lignin components

“…Figure10. Effect of betaine on the molecular weight distributions of Organosolv lignins (Sephadex G75/0.10 M aqueous NaOH containing 0.10 M betaine, monitored at 280 nm): (A) red alder lignins formed with liquor:substrate ratios of (1) 8:1 (v/w) and (2) 20:1 (v/w); (B) wheat straw lignins formed with liquor:substrate ratios of (1) 20:1 (v/w) and (2) 65:1 (v/w).…”