Particle Size Analysis with Differential Centrifugal Sedimentation. Marc Steinmetz Sales & Support Manager CPS Instruments Europe

Transcription

1 Particle Size Analysis with Differential Centrifugal Sedimentation Marc Steinmetz Sales & Support Manager CPS Instruments Europe

2 What is important to you from a particle sizing technique? Many people talk about High Resolution in relation to particle size techniques. But what does that really mean?

3 Ultra High Resolution Capabilities? Detect, measure & resolve peaks which differ in size by as little as 2% by differential sedimentation. Eg. mixture of polystyrene calibration standards

4 Sedimentation Particles that are different in density from the fluid in which they are suspended sediment at rates that depend on the following factors: Gravitational field strength Difference in density Fluid viscosity Particle size Particle shape Particles settle at constant speed where the forces are in equilibrium Viscous Drag Up Net Weight G-force Down

5 Types of Sedimentation Integral Sedimentation Differential Sedimentation

6 Why use a density gradient? Density Gradients Allows stable sedimentation without streaming effects. Provides separated peaks for each narrow band of particle sizes rather than broad overlapping peaks. Can be composed of nearly any combination of soluble materials: A B Water based gradients are often based on differing sucrose concentrations and could include salts, buffers, and different phs etc. to maintain compatibility with the sample. Gradients based on organic liquids are used for samples that dissolve in water or that are received as a dispersion in organic liquid.

7 Density Gradients Very easily constructed. Eg. using only two sucrose solutions; low density (8% w/w) & high density (24% w/w) Using an Automatic Gradient Builder. Or Simply making a series of manual injections of gradually decreasing density fluids (9 quick and easy injections) No Need for Great Accuracy in Creating Gradient!

8 Front View of the Disc

9 Front View of the Disc

10 Front View of the Disc

11 Front View of the Disc

12 Front View of the Disc

13 Front View of the Disc

14 Cross Section of the Disc

15 Cross Section of the Disc

16 Cross Section of the Disc

17 Cross Section of the Disc

18 Cross Section of the Disc

19 Cross Section of the Disc Light source 405nm

20 Running Samples

21 Separated Bands Down to ~2% Difference in Particle Size

22 Calibration Raw data is simply time vs absorption; Therefore, running a calibration standard simply CONVERTS ANALYSIS TIME TO PARTICLE SIZE A calibration standard has a known particle size and particle density and is NIST traceable. Calibration standard is run before the sample and optionally in between samples during a run. e.g. every 1 to 10 samples. Calibration before each analysis gives the highest accuracy and repeatability.

23 Application (1): Characterise Coating of Nano-particles Ability to measure/monitor coating thickness, eg. polymer coating of Gold or Silver nano-particles being developed for targeted drug delivery. Gold Citrate + Polymer coating Gold citrate core = 13.2nm Gold core + polymer coating = 10.8nm Gold core density = 19.3g/ml Coating material density = 1.20g/ml Shell thickness = 3.5nm

24 Application (2): Challenge testing of filters Eg 0.4 micron filter with a latex Multistandard Largest peak removed filter cut point Individual peak suppression pore size distribution

25 Application (2): Challenge testing of filters Eg Determination of pore size distribution in a 0.4mm filter Mode 0.35µm Max (B.Pt) 0.52µm

26 Application (3): Resolve Aggregates & Agglomerates Detect, measure and quantify multiple particle peaks Eg. aggregation of adenovirus particles for purification and process monitoring. Adenovirus

27 Application (4): High Sensitivity Detect & measure extremely small and subtle changes in size distributions e.g. Polystyrene bead production for use in diagnostic testing. Polystyrene beads

28 Application (4): High Sensitivity Detect and measure small additional peaks that could be critical to certain processes such as inkjet printing.

29 Results that are Comparable to SEM / Microscopy Analysis? Silica

30 Accurate, Reliable & Reproducible Results? Traceability & Calibration to NIST particle size standards PVC Mixture

31 Ultra High Resolution CPS Disc Centrifuge Higher resolution Quiet Operation Improved Solvent Resistant Disc Added Operational Flexibility

32 Feature & Benefit Summary of Technique of Differential Sedimentation Particle size analysis from 2 nm to 80 µm Ultra High Resolution (~2% peak resolution) Accurate, reliable and reproducible measurements High sensitivity Dynamic range extension with speed ramping Measurement of low-density particles Easy to use technique

33 Same Sample Different Results! Which method shows the real distribution? Which technique is really high resolution? What resolution do you need?

34 Questions? But I ll do my best!