Analysis apparatus and method

1. A method of determining dissolution characteristics of a tablet, the method comprising:

irradiating a tablet with radiation having at least one frequency in the range from 40 GHz to 100 THz;

detecting radiation which has been transmitted through or reflected by the tablet;

determining an indication of the density of a coating layer of the tablet from the detected radiation; and

determining information about the dissolution characteristics of the tablet from the indication of the density.

2. A method according to claim 1 , wherein the indication of the density is the thickness of the tablet coating.

3. A method according to claim 2 , wherein the information about the dissolution characteristics is determined by using a negative correlation between the coating thickness or time of flight of radiation through the coating and the time which dissolution takes.

4. A method according to claim 1 , wherein the indication of the density is the time of flight of the radiation through the tablet coating.

5. A method according to claim 1 , further comprising measuring the weight of the tablet coating.

6. A method according to claim 1 , wherein the indication of the density is the refractive index of the tablet coating.

7. A method according to claim 6 , wherein the refractive index is determined from the maximum signal strength of the radiation reflected by the tablet.

8. A method according to claim 1 , wherein the indication of the density is the size of the signal reflected from the interface between the coating and the core of the tablet.

9. A method according to claim 1 , wherein the indication of the density is the size of the signal reflected from the external surface of the tablet.

10. A method according to claim 1 , wherein the indication of the density is the size of the signal reflected from the interface between the coating and the core divided by the size of the signal reflected from the external surface of the tablet.

11. A method according to claim 1 , wherein the information about the dissolution characteristics is determined by using a positive correlation between the density and the time which dissolution takes.

12. A method according to claim 1 , wherein the dissolution characteristics are defined by dissolution parameters selected from: the mean dissolution time; the dissolution rate constant and the dissolution at specified times.

13. A method according to claim 1 , further comprising measuring the indication of the density for a plurality of points on said tablet.

14. A method according to claim 13 , wherein the indication of the density is measured on the two main opposing surfaces of the tablet and the central band.

15. A method according to claim 1 , wherein the indication of the density is measured on the central band.

16. A method according to claim 1 , wherein the tablet is a sustained release tablet.

17. A method of determining dissolution characteristics of a tablet, the method comprising:

irradiating a tablet with radiation having at least one frequency in the range from 40 GHz to 100 THz; detecting radiation which has been reflected by the tablet; determining an indication of the density of a coating layer of the tablet from a maximum signal strength of the radiation reflected by the tablet; and determining information about the dissolution characteristics of the tablet from the indication of the density wherein a measurement of the dissolution characteristics is obtainable from the maximum signal strength reflected from a single point on the tablet coating.

18. A method according to claim 17 , wherein the information about the dissolution characteristics is determined by using a positive correlation between at least one dissolution parameter and the maximum signal strength.

19. A method according to claim 18 , wherein the dissolution parameter is selected from: the mean dissolution time; the dissolution rate constant and the dissolution at specified times.

20. A method of determining if a tablet is of sufficient quality, said method comprising:

irradiating a tablet with pulsed radiation having at least one frequency in the range from 40 GHz to 100 THz;

detecting radiation which has been transmitted through or reflected by the tablet;

determining an indication of the density of a coating layer of the tablet from the detected radiation; and

determining if said tablet is of sufficient quality by comparing the density of the tablet with a pre-determined reference value and rejecting said tablet the density of the coating layer is lower than said reference value.

21. A method according to claim 20 , wherein determining a parameter indicative of an indication of the density of the tablet coating comprises determining the weight of the coating and dividing it by the amplitude of the reflected THz signal.

22. An apparatus for performing dissolution analysis on a tablet, comprising:

a source for irradiating a tablet with radiation having at least one frequency in the range from 40 GHz to 100 THz;

a detector for detecting radiation which has been transmitted through or reflected by the tablet;

a processor for determining an indication of the density of a coating layer of the tablet from the detected radiation; and

a processor for determining information about the dissolution characteristics of the tablet from said indication of the density.

23. An apparatus according to claim 22 , wherein said source is a source of pulsed radiation.

24. An apparatus according to claim 22 , wherein the processor for determining a parameter indicative of the density of a coating layer of the tablet comprised means for determining the time of flight of radiation through said coating layer.

25. An apparatus according to claim 22 , wherein the processor for determining an indication of the density of the coating layer of the tablet comprises means for determining the strength of the reflected radiation signal.