Since the 1990s Postnova has been a leading innovator and developer of special advanced online Light Scattering solutions for coupling with chromatographic separation systems via tha Multi angle light scattering phenomenon.
|Static Light Scattering:||This light scattering techniques is also called Classical Light Scattering|
Light scattering has become one of the most important techniques for the characterization of macromolecules and nanoparticles in solution. Depending on the analytes, different light scattering techniques can or have to be used. When compared to many other characterization methods, the light scattering techniques show a high precision, have a fast response time and are noninvasive. Once the light scattering technique is set-up properly, absolute measurements of molar mass and particles size can be performed without the use of standards. Beside Laser Diffraction, the most commonly used light scattering techniques are Static Light Scattering (SLS) and Dynamic Light Scattering (DLS):
Light scattering can be done in Batch Mode and or in Flow Mode. Batch Mode analysis is easy to perform, but in case of crude complex sample mixtures with a broad and or multi-modal distribution, this approach has significant limitations, as it is difficult to calculate the correct molar mass and particle size distribution with light scattering only. A solution to overcome this limitation is the combination of a separation technique, such as Field-Flow Fractionation or Chromatography, with online light scattering detection (Flow Mode). Field-Flow Fractionation and Size Exclusion Chromatography provide high resolution fractions of the polymers/particles under investigation. After the separation, the eluting monodisperse sample fractions can be ideally sized online by light scattering. Thus the combination of a separation technique and a light scattering detection technique provides a very powerful characterization tool, which exceeds the performance of the single separation or the single detection technology when used alone. An additionally advantage is that sample fractions can be recovered for further subsequent analysis with other techniques after leaving the detector.
The scientific attractiveness of light scattering is based on the unique combination of high sensitivity, high resolution, easy handling and fast analysis times. Other techniques, which can be seen more as complementary than competing, are Analytical Ultracentrifugation, Mass Spectroscopy and membrane Osmometry. Analytical Ultracentrifugation for example shows high resolution, but is much more expensive and complicated and has longer run times. Mass Spectroscopy has become very famous in the last decade, but this technique also requires a big investment and does not reach the same upper molar mass range as light scattering does.
Since the 1990s Postnova has been a leading innovator and developer of special advanced online Light Scattering solutions for coupling with chromatographic separation systems. The first model was the PD2000 - Static Light Scattering detector for coupling with Asymmetric Flow FFF. Later on the models PN3020 SLS and PN3070 MALS have been launched. Based on over two decades of practical experience, Postnova has collected a unique competence in the area of Laser Light Scattering and has developed the unique PN3621 MALS - Multi-Angle Light Scattering detector series. The model PN3621 MALS is a completely new type of high performance MALS detector system with a unique range of specifications.Maximum Angle Number
The Postnova PN3621 MALS detector system employs full 21 angles and has the broadest angular range of any commercial light scattering instrument available today. These 21 angles are crucial to fulfil the high requirements set for accuracy for measuring complex particular samples, ensuring the highest precision in molecular weight and particle size determination. With 21 angles the PN3621 can achieve the highest quality data fit for the most scientifically meaningful results in your laboratory, especially for high molar mass polymers and large particles.Unique Low Angle Range
The precision of molar mass and particles size determination is not only dependent on the number of angles but also on the number of low angles which are available for calculation. Especially the angles between 0° and 35° are the most important angles for correct and precise molar mass and size determination. Typically in the past, Static Light Scattering has been often limited in use as low angles have not been available or, when available, just do not work properly. The lack of low angles can be tolerated when investigating smaller species, such as proteins or macromolecules, where there is no angular intensity dependence. But for larger and more complex samples, such as branched polymers, high molar mass macromolecules, large protein aggregates and nanoparticles, the existence of high quality low angles are critical for precision and accuracy. The new Postnova PN3621 MALS overcomes these limitations and offers a complete set of stable working low angles, starting from 7°, 12°, 20° and 28° onwards.Clean Vertical Flow Cell
MALS is typically being used to measure larger sample species, such as protein aggregates, high molar mass macromolecules and particles. Because of their size and fragile nature these samples have to be treated in a gentle way to avoid any alteration. Potentially shear forces, chain degradation, conformational changes and deterioration or complete loss of bioactivity can be induced by highly turbulent light scattering cells. Also aggregation, adsorption and sedimentation phenomena can cause trouble inside light scattering cells, especially when they have edges, dead volumes or right angle flow path changes inside. The new Postnova PN3621 avoids all these limitations and offers a vertical flow cell where the sample can pass through easily without any obstacles in its way. The flow cell has no right angel entry and outlets which could induce shear forces or cause particles to settle and adsorb.Advanced Electro Optics
The PN3621 MALS employs the latest opto-electronic 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 PN3621 has the smallest footprint available in the market, saving rare lab space and allowing a flexible use at different locations and also seamlessly fits into the line of other Postnova products such as the PN3150 Refractive Index detector.