Stability – Turbiscan – Multiple Light Scattering (MLS)

 Stability and shelf-life are key parameters in formulation studies. TURBISCAN is the first patented technology to analyse destabilization mechanisms in concentrated media. Creaming, sedimentation, agglomeration, aggregation and coalescence are detected at a very early stage without dilution nor stress. Stability kinetics and index are provided for an efficient sample analysis.

Instruments

Measurement principle

Multiple light scattering (MLS) consists of sending photons (NIR light source, 880nm) into the sample. These photons, after being scattered many times by the particles (or droplets) in the dispersion emerge from the sample and are detected by the 2 detectors of the TURBISCAN™ reading head:

• Transmission (T) for non-opaque samples (0° from light source)
• Backscattering (BS) for opaque samples (135° from the light source)

Backscattering is directly related to the photon transport mean free path. Thus Backscattering intensity depends on particle size and concentration.

Stability – Turbiscan – Multiple Light Scattering (MLS)

 

The combination of Backscattering and Transmission sensors with a vertical scanner enables to detect physical heterogeneities (size increase or local concentration change) over the whole sample height with a vertical resolution up to 20µm. Thus, nascent destabilization phenomenon can be detected in any sample locations up to 200 times faster than visual tests.

Backscattering or Transmission profiles (i.e. signal over sample height) are recorded at different time intervals to report kinetic stability. Stability kinetics are calculated over the whole sample height for a global stability assessment or on specific zone (bottom / middle / top) depending on the stability criteria. TURBISCAN Stability Index (TSI) is calculated for easy and accurate stability reporting. Patented sample positioning enables to guaranty an optimal repeatability and reproducibility.

Benefits and key features

Migration Analysis

Local variation of light intensity corresponds to phases formation.

• Phase thickness kinetics
• Sedimentation rate
• Creaming rate
• Particles migration speed
• Hydrodynamic diameter

Size variation Analysis

Global variation of light intensity corresponds to size increase.

• Size kinetics
• Mean diameter
• Agglomeration rate
• Coalescence rate
• Dispersibility ratio

Turbiscan Stability Index (TSI)

Based directly on the raw data, this unique number takes all destabilisation into account, providing you with a powerful tool to rank & compare all your formulas in just one-click. It is a key parameter for easy classification of samples regarding to their stability. Determining shelf-life of your products has never been easier!

No Mechanical Stress

When it comes to shelf-life, and real-life evolution of the end-products, it makes no sense to apply a mechanical stress to a sample. Our measurements are always performed at rest, without any external stress. That way, you can be sure that the results you get are representative of what will happen in real life, only detected way earlier!

Main Advantages

• No Sample preparation
• 200x faster than conventional tests
• Quantification of stability
• No Sample dilution
• Wide range of concentration (10^-4 – 95%)
• Wide range of size (10 nm – 1,000 µm)

References and norms

/1/ DIN ISO 18748
/2/ Partikelwelt 18; p. 16-19; “Vorhersage der Langzeitstabilität von polymerstabilisierten O/W-Emulsionen mittels statischer Mehrfachlichtstreuung” (only available in German)
/3/ Particle World 20; p. 16-17; “Fast determination of stability and packing in inkjet inks – Examination of different pigments”