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PN3621 Multi-Angle Light Scattering Detector

The PN3621 Multi-Angle Light Scattering Detector has been developed for coupling Postnova Field-Flow Fractionation separation system. The unique PN3621 detector meets the highest requirements in terms of sensitivity, precision and flexibility, backed by many advanced features:

Maximum Number of Angles
The Postnova PN3621 MALS detector system incorporates 21 full working angles for use along with aqueous and organic solvents, resulting in highest precision in molecular weights and particle size determination. With 21 angles, best results are achieved through improved data fits especially for high molar mass polymers, particles and protein aggregates.

Unique Low Angle Range
Offering a complete set of stable working low angles at 70, 120, 200 and 280 onwards which are crucial for correct molar mass and size determination, the PN3631 MALS is ideal for analysing branched polymers, high molar mass macromolecules, protein aggregates and particles.

Vertical Flow Cell
Because of their size and fragile nature, protein aggregates and other macromolecules  need a gentle treatment to avoid potentially shear forces, chain degradation, conformational changes and deterioration or complete loss of bioactivity which can be induced by turbulent light scattering flow cells.  Also aggregation, adsorption and sedimentation phenomena can cause problems inside a light scattering cell, especially when constructed with internal flow obstacles, edges and dead volumes. The new Postnova PN3621 avoids all this and offers a vertical flow cell where the sample easily can pass through without any alteration.

The PN3621 MALS employs the latest opto-electronic and laser designs, including digital signal processing for each of the 21 angles.  The electronics is based on a true 24 bit resolution AD system and offers a broad dynamic signal range. For maximum flexibility it is possible to read-in up to 3 external analogue signals. The design is compact with a small footprint allowing the system to placed on laboratory workbench efficiently.

Broad Application Range

  • Biotechnology: Alginates, Carrageenans, Hyaluronic Acids, Cell Organelles, Exosomes
  • Biopharmaceuticals: Peptides, Proteins, Antibodies, Virus Aggregates and Conjugates
  • Food and Agro Science:  Starches, Pectins, Polysaccharides, Proteins, Casein Micelles
  • Polymers:   Rubbers, Latex Dispersions, Polyolefins, Polyelectrolytes
  • Environmental Research: Humic-Fulvic Colloids, Iron Oxides, Clays, Silica Particles
  • Nanotechnology: TiO2, CNT, C60, Latex, ZnO Nanoparticles and Silica Nanoparticles

Absolute Molecular Weight Determination with Static Light Scattering (MALS)

A MALS detector can be used to measure the absolute molecular weight of a polymer, biopolymer, protein or antibody sample. Here, the correlation between MALS-signal intensity and molecular weight is given by the Rayleigh light scattering equation:
MALS-Signal = KMALS x Conc x (dn/dc)2 x Mw
Mw is the weight average molecular weight, dn/dc is the refractive index increment and KMALS is the calibration constant.  Instead of measuring several standards with narrow molecular weight distributions, the MALS detector can be calibrated with a single standard of known molecular weight, concentration and dn/dc value to determine the calibration constant. The absolute molecular weight of a sample can then be calculated directly from the MALS-signal while the RI detector measures the concentration of the sample at each point of the elution volume.

The MALS detector shows large peaks for protein aggregates (dimer and trimer) thereby revealing superior sensitivity compared to both concentration detectors (RI and UV) conventionally used in HPLC. This is particularly useful for the detection of small amounts of high molar mass protein aggregates, which otherwise would not be accessible.  Moreover, MALS detection enables the determination of the absolute  molar mass of protein monomer, dimer and trimer thus delivering valuable additional information that cannot be assessed using UV-only detection with conventional calibration which is prone to many errors.

Separation of BSA monomer, dimer, trimer and higher aggregates using
HPLC-MALS-RI (green line: MALS-signal; red line: RI-signal; magenta: UV-signal

Corresponding molar mass (red line) of BSA monomer, dimer and trimer
obtained from MALS data (green line: concentration detector signal)

Molar mass for BSA monomer, dimer and trimer obtained
from HPLC-UV-MALS-RI measurement