A New SEC Column to Be Used with MALS

With the recent increase of polymer research, there has been a growing need for polymer analysis. The best way to determine the size and estimated molecular weight of polymers and biopolymers is achieved using size exclusion chromatography (SEC). Within SEC, the most commonly used detectors are differential detectors immediately followed by light scattering detectors. When coupling a light scattering detector with a refractometer, a very powerful mode of advanced detection for SEC analysis is the result. Specifically, multiangle light scattering (MALS) allows for the collection of useful information including the molecular weight, average number molecular weight, and distribution of the polymer.

Shodex introduces the LB-806M column with a durable polymer based packing material for aqueous SEC analysis. This column has also been shown to be suitable for light scattering due to the controlled column bleed. Shodex LB-806M is appropriate for polymer and biopolymer analysis, has demonstrated the determination of molecular weight for sodium alginate.

The molecular weight of sodium alginate, a common biopolymer extracted from algea, was determined by OHpak LB-806M, a column for aqueous SEC. The LB-800 series are compatible with MALS detectors. By minimizing the baseline noise level, LB-800 series enables the MALS detector to detect a wider range of molecular weight compounds which are difficult to be detected by conventional columns.

Experimental Conditions

The analysis of sodium alginate was accomplished with Shodex LB-806M (8.0 mm ID × 300 mm, 13 µm), a polymer-based column for aqueous SEC analysis. Column temperature was 30 °C and flow rate was 1.0 mL/min. Eluent conditions were 0.1 M NaNO₃ aq. Injection volume of 5 µL of dissolved sodium alginate was used for the experiment. The HPLC system was coupled with Shodex RI MALS detector.

Results

The sodium alginate sample was analyzed successfully by SEC and RI MALS detection with LB-806M (Figure 1). From this one run Mw, Mn, and Mw/Mn were all determined. The average molecular weight (Mw) was found to be 166,200. The number average molecular weight (Mn) was found to be 58,790. With these two values determined from the data, the polydispersity index (Mw/Mn) was calculated to be 2.83.

Figure 1: The analysis of sodium alginate using LB-806M.

Conclusions

Shodex LB-806M, a size exclusion chromatography (SEC) chromatography column is suitable for polymer and biopolymer analysis, has demonstrated the determination of molecular weight, number average molecular weight, and polydispersity index.

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