BI-MwA – Molecular Weight Analyzer

The BI-MwA has the highest performance/price ratio of any light scattering detector used for molecular weight determination. Eliminate SEC/GPC column calibration and improve data quality. Rapidly reduce uncertainty with no assumptions required and true extrapolation to zero angle.

Inject your sample into the low-volume, 7-angle flow cell. The sample is illuminated by a temperature-stabilized, precision power-controlled diode laser. The ultra-stable, high-sensitivity, low-noise CCD detector automatically collects the scattered light. Then, the software extrapolates the data to zero angle for the absolute molecular weight determination.

Determine the molecular weight distribution (flow mode) or determine the average molecular weight (batch mode). Macromolecular samples often have a range of molecular weights. In some cases, this distribution is quite narrow, and in other cases, it is very broad and/or multimodal. Variations in the distribution can indicate the presence of impurities or aggregation. However, for other applications, the average molecular weight is sufficient to characterize your sample. Sometimes the distribution is of interest, and sometimes the overall average is sufficient. Either way, the BI-MwA is the right tool for the job.

When the distribution of molecular weights in your sample is important, consider the BI-MwA as a chromatography detector for your SEC/GPC system. In this way, you can readily determine the true molecular weight distribution. Many average values unavailable from a batch mode measurement can be calculated from these distributions. Better yet, the molecular weight distribution is determined while the problems of column calibration are avoided.

Size exclusion chromatography (SEC), also known as gel permeation chromatography (GPC), uses columns to separate polymer samples. In the standard method, columns are calibrated to obtain a relationship between molecular weight and elution volume. However, the column-sample interaction depends on not just the size (molecular weight) but also the chemistry of the sample. Therefore, an accurate column calibration requires standards over a range of molecular weights with the same chemistry and structure (e.g., branching) as the sample. With a few exceptions, such standards are difficult or impossible to obtain, especially for new or unique materials.