Method and apparatus for analyzing a sample of sub-micron particles

1. A method of analysing a sample comprising a polydisperse population of sub-micron particles, said sample comprising a plurality of small particles, and a plurality of large nanoparticle tracking analysis (NTA)-detectable particles, the method comprising: determining first information about the size and number of the NTA-detectable particles in the sample by NTA; determining second information about average particle size of all the particles in the sample by dynamic light scattering (“DLS data”); using the first information to produce third information comprising the predicted effect of the NTA-detectable particles on the results obtained by dynamic light scattering; and using the third information to compensate for the predicted effect of the NTA-detectable particles on the DLS data to produce fourth information representing corrected information on average particle size.

2. The method according to claim 1 , wherein the first and second information are obtained simultaneously from the same sample.

3. The method according to claim 1 , wherein the sample comprises a suspension or other dispersion of solid particles in liquid.

4. The method according to claim 1 , wherein the sample is illuminated by a focused beam of radiation.

5. The method according to claim 1 , wherein the first information further includes information on particle brightness/spectral characteristics.

6. The method according to claim 1 , wherein the second information also further includes information on particle size distribution.

7. The method according to claim 1 , wherein the first information and the second information are obtained using respective detector systems.

8. The method according to claim 1 , wherein the first information is used to generate a theoretical correlation curve or function for one or more of the detected particle sizes.

9. The method according to claim 8 , wherein the correlation function is size-weighted, with larger particles being given greater weighting.

10. The method according to claim 8 , wherein correlation functions for different particle sizes are summed.

11. The method according to claim 1 , wherein the first information includes information on the relative amount of light scattered by each detected particle.

12. The method according to claim 1 , wherein the sample comprises proteins.

13. The method according to claim 1 , wherein the sample comprises particles which are fluorescent.

14. The method according to claim 1 , wherein the first or second information is obtained whilst the particles are subjected to a user-applied external electric or magnetic field.

15. An apparatus adapted and configured for performing the method of claim 1 , the apparatus comprising:

a light source producing a focused beam of radiation to illuminate the sample;

a first detector system for obtaining the first information using nanoparticle tracking analysis (NTA);

a second detector system for obtaining the second information using dynamic light scattering; and

data processing means programmed to determine the third information from the first information.

16. The apparatus according to claim 15 , wherein the data processing means is further programmed to adjust the second information, using the third information, to produce the fourth information.

17. The apparatus according to claim 15 , wherein the first and second detector systems are spatially common and temporally common.

18. The apparatus according to claim 15 , wherein the first and second detector systems are spatially common but temporally different.

19. The apparatus according to claim 15 , wherein the first and second detector systems are spatially different but temporally common.

20. The apparatus according to claim 15 , wherein there are one or more components which are common to the first and second detector systems.