1. Design and Calibration of a Dissolution Test Equipment Training Workshop on Dissolution, Pharmaceutical Product Interchangeability and Biopharmaceutical Classification System. Kyiv, Ukraine, June
Dr. Sandra Klein, Institute of Pharmaceutical Technology,
Johann Wolfgang Goethe University Frankfurt

2. Dosage forms to be tested
immediate release dosage forms
powders, granules / beads, tablets, capsules
controlled release dosage forms
transdermal systems
implants

3. Official Dissolution Monographs
United States Pharmacopeia
USP XXX (30)
European Pharmacopoeia
Ph. Eur. 5th Edition, Supplement 5.3
British Pharmacopoeia
BP 2007
Japanese Pharmacopoeia
JP XIV (14)

4. Official dissolution apparatus
USP 30 classification
Rotating Basket (Ph.Eur./BP/JP)
Paddle (Ph.Eur./BP/JP)
Reciprocating Cylinder (Ph.Eur.)
Flow Through Cell (Ph.Eur./BP/JP)
Paddle Over Disk (Ph.Eur.)
Rotating Cylinder (Ph.Eur.)
Reciprocating Holder

5. Which type of dissolution apparatus ?
Depends on intention
Quality control
examining batch homogeneity
examining batch to batch conformity
examining stability
Research & Development
examining drug release behavior of preformulations
in vitro simulation of the gastrointestinal passage
IVIVC

6. Apparatus 1 - Basket Useful for Standard volume capsules beads
delayed release / enteric coated dosage forms
floating dosage forms
surfactants in media
Standard volume
900/1000 ml
1, 2, 4 liter vessels

7. Apparatus 1 - Basket Advantages
breadth of experience (more than 200 monographs)
full pH change during the test
can be easily automated which is important for routine investigations

8. Apparatus 1 - Basket Disadvantages
disintegration-dissolution interaction
hydrodynamic „dead zone“ under the basket degassing is particularly important
limited volume  sink conditions for poorly soluble drugs ?

9. Apparatus 1 - Basket

10. Apparatus 2 - Paddle Useful for Standard volume
tablets
capsules
beads
delayed release / enteric coated dosage forms
Standard volume
900/1000 ml
Method of first choice !!!

11. Apparatus 2 - Paddle Advantages easy to use robust
can be easily adapted to apparatus 5
long experience
pH change possible
can be easily automated which is important for routine investigations

12. Apparatus 2 - Paddle Disadvantages pH/media change is often difficult
limited volume  sink conditions for poorly soluble drugs ?
hydrodynamics are complex, they vary with site of the dosage form in the vessel (sticking,floating) and therefore may significantly affect drug dissolution
„coning“
sinkers for floating dosage forms

13. Sinker types JP/ USP / Ph. Eur. 5.3 Sinker
„a small loose piece of nonreactive material such as
not more than a few turns of wire helix may be attached
to dosage units that would otherwise float …“
„…. other validated sinker devices may be used“

14. Coning

15. Apparatus 2 - Paddle

16. Apparatus 3 – Reciprocating cylinder
Useful for
tablets
beads
controlled release formulations
Standard volume
ml per station

17. Apparatus 3 – Reciprocating cylinder
Advantages
easy to change the pH
pH-profiles
hydrodynamics can be directly influenced by varying the dip rate
Disadvantages
small volume (max. 250 ml)
little experience
limited data

18. Apparatus 3 – Reciprocating cylinder

19. Apparatus 4 – Flow-Through Cell
Useful for
low solubility drugs
microparticulates
implants
suppositories
controlled release formulations
Variations
open system
closed system

20. Cell types
Tablets 12 mm Tablets 22,6 mm Powders / Granules Implants Suppositories / Soft gelatine capsules

21. Apparatus 4 – Flow-Through Cell
Advantages
easy to change media pH
pH-profile possible
sink conditions
different modes a) open system b) closed system
Disadvantages
Deaeration necessary
high volumes of media
labor intensive

22. Apparatus 4 – Flow-Through Cell

23. Apparatus 5 – Paddle over disk
Useful for
transdermal patches
Standard volume
900 ml

24. Apparatus 5 – Paddle over disk
Advantages
standard equipment (paddle) can be used, only add a stainless steel disk assembly
Disadvantages
disk assembly restricts patch size

25. Apparatus 6 – Rotating cylinder USP apparatus 7 – Reciprocating holder
most probably will be removed from the USP !!!

26. Summary Immediate release dosage forms:
 apparatus 1 or 2 (preferably 2)
Controlled release dosage forms:
 apparatus 1 or 2 using different media for QC  apparatus 3 or 4 for R&D purposes
Beside the selection of an adequate dissolution apparatus, adequate test conditions are crucial for all purposes !

27. Qualification of Dissolution Systems

28. Calibration Why ? How ? When ?
to confirm suitability of the equipment and proper operation of the apparatus
How ?
mechanical calibration (verification of physical parameters)
chemical calibration („Apparatus Suitability Test“ – USP)
When ?
before using new test equipment
after relocation or major maintenance
at regular intervals („every 6 months“)

29. Factors that may affect reliability of the test
Proper alignment/geometry of dissolution apparatus
dimensions of vessels, paddles, baskets, cylinders
height, centering and wobble
Proper conditions during dissolution test
temperature
agitation speed
degassing
sampling (sampling zone, timing, filtration, dilution)
vibration
Proper validation of analytical method
specified in USP Chapter <1225>

30. Mechanical calibration
Verification of physical parameters specified in the pharmacopoeia: USP apparatus 1 and 2

31. Mechanical calibration - Parameters
Height – Vertical Position of the Paddle or Basket
the vertical position of paddle or basket affects the hydrodynamics condition in the vessel
each paddle or basket should be individually adjusted to the compendial distance
in the pharmacopoeia, a distance of cm is specified
different kinds of height gauges can be used to align or check* this parameter *

32. Mechanical calibration - Parameters
Rotational Speed – Stirring Rate
input variable that affects the hydrodynamics
changes in the rotational speed result in a changing liquid-solid interface between the solvent and the dosage form
the rotational speed can be checked by using a digital tachometer*
the compendia specify a rotational speed tolerance of + 4 % *

33. Mechanical calibration - Parameters
Shaft Wobble – Eccentricity of Stirring Device
assumed to alter the pattern of fluid movement in both paddle and basket apparatus and therefore may influence the dissolution rate
can be measured with a micrometer*
measured is the sum of distance between both sides (180°) of the axis of rotation *

34. Mechanical calibration - Parameters
Centering (Vessel / Shaft)
the axis of the rotating shaft must coincide at all points with the axis of the vessel to within + 1 mm
“the shaft has to positioned so that is axis is not more than 2^mm at any point from the vertical axis of the vessel and rotates smoothly without significant wobble” *

35. Mechanical calibration
Measurement tools
all mechanical tools used for calibration should be certified to assure their reliability
the results of mechanical calibration have to be documented

36. Apparatus suitability test (USP)
if all parts ( apparatus, geometry, test conditions, analytical method) are within compliance – why perform an apparatus suitability test?
the apparatus suitability is to check for parameters that can not be conveniently measured (vibration, vessel cleanliness, medium degassing ...) and also to provide an overall check of the system

37. Apparatus suitability test (USP)
first established in 1978
routine test in most pharmaceutical laboratories
calibration at regular intervals (every 6 months)
standard calibrator substances according USP chapter <711>
only the method(s) to be used have to be calibrated !
if six units are tested – all have to pass

38. Apparatus suitability test (USP)
Standard calibrators according to USP chapter <711>
Apparatus I, II and V:
disintegrating type
USP Prednisone Tablets
nondisintegrating type
USP Salicylic acid Tablets
Apparatus III:
USP Chlorpheniramine Maleate Extended-Release Tablets

39. Information supplied with calibrators

40. Apparatus suitability test (USP)
USP Prednisone Tablets RS – current lot P0E203
(10 mg nominal prednisone content per tablet)
disintegrating type
paddle and basket, 50 rpm
500 ml deaerated water, 37°C
quantity of prednisone released after 30 minutes is determined
specified ranges Lot P0E203: Apparatus 1: % Apparatus 2: %

41. Apparatus suitability test (USP)
USP Salicylic acid Tablets RS – current lot Q0D200
(300 mg nominal salicylic acid content per tablet)
nondisintegrating type
paddle and basket, 100 rpm
900 ml deaerated phosphate buffer, 37°C
quantity of salicylic acid, released after 30 minutes is determined
specified ranges Lot Q0D200: Apparatus 1: % Apparatus 2: %

42. Apparatus suitability test (USP)
Controversies regarding the current test
the variability in the intrinsic performance of the USP calibrator tablets is so great that it exceeds the variability in intrinsic performance of modern test dissolution assemblies
this variability becomes obvious in both vessel-to-vessel variability and inter-laboratory variability of results for a given lot of calibrators

43. Troubleshooting Calibrator Tablets:
always check the incoming tablets !
right lot of calibrators ?
are the tablets broken, fused or severely chipped ?
particularly salicylic acid tablets are often subject to sublimation ( dust on the tablets and the inner surface of the container)
use correct storage conditions !
take the tablets out of the original container immediately before test !

44. Troubleshooting Standard / Standard solution: USP Standard used ?
drying procedure conducted ?
standard solution prepared on day of test ?
standard solution filtered in the same manner as sample ?
amount of alcohol used in the standard < 5% ?

45. Troubleshooting Vibration
vibration produces unwanted variation in dissolution data and mostly results in an increased dissolution rate
internal vibration may be caused e.g. from frayed drive belts
external vibration may be caused by e.g. magnetic stirrers, centrifuges, vacuum pumps, old fridges, nearby construction, ...
inability to properly measure vibration levels at various points within an apparatus is the main reason why calibrator tablets were originally developed
Vibration is a variable that can seriously distort the data from any dissolution system. Therefore the system must be free of vibration that significantly interferes with the test.
Vibration may be caused internal for example from frayed drive belts or the circulation of the water bath but rather by external sources like magnetic stirrers, centrifuges, nearby construction and so on.
The inability to properly measure vibration levels at various points within an apparatus was the main reason why calibrator tablets were originally developed.

46. Troubleshooting Vibration effects – case example:
Effect of vibration levels of the dissolution apparatus on the dissolution rate of enteric coated granules of Cefalexin. The vertical dotted line indicates 0.05 m/s2.
Kaniwa N. et al. (1998) Int J Pharm, 175,
„Low vibration“: < 0.05 m/s2
„High vibration“: > 0.05 m/s2
A possible effect of high vibration levels on the dissolution rate was also shown in a collaborative study of Kaniwa et al. (1998).
In order to develop a dissolution standard for evaluating vibration levels for dissolution apparatus, a series of tests, examining enteric coated granules of cefalexin was performed at seven independent laboratories.
The vibration of the dissolution apparatus during the test was measured with a vibration meter and the resulting values were plotted against the corresponding release rates of cefalexin. The enteric coated granules worked very well in detection of high vibration levels (especially in the basket apparatus). There seems to be a critical value between so called low and high vibration apparatus at about 0.05 m/s2. Dissolution apparatus that belong to the high vibration category according this classification do not seem to provide accurate and reproducible results!
Based on the results of this study, in the event of dissolution results that show unexpectedly high release rates, troubleshooting concerning vibration is crucially important.

47. Troubleshooting Vibration: dissolution equipment placed planar ?
drive chain or belt free of tension and/or dirt ?
torn parts replaced ?
correctly functioning gear plates ?
individual spindles are not surging ?
bench/table stable ?
no sources of vibration nearby ?

48. Troubleshooting Dissolution medium: correctly degassed ?
correct amount used (900/500 ml) ?
correct amount dosed (weight/volume) ?
dosing procedure gentle (resaturation/spillage) ?
buffer correct (pH units, buffer salts, molarity) ?
correct temperature during test (32°C / 37°C + 0.5°C)?
evaporation during test negligible ?

49. Troubleshooting Importance of degassing:
insufficient degassing may result in decreased dissolution rates of several drugs
e.g. prednisone tablets but also a range of poorly soluble drugs are very sensitive to the amount of dissolved gases in the dissolution medium
the degassing procedure should therefore be efficient and reproducible for every test
I really want to point out the importance of degassing, because ….

50. Troubleshooting Deaeration method USP
heat the dissolution medium to about 41°C
vacuum filter through a 0.45-µm-porosity membrane into a flask, stirring with a magnetic stirrer
continue to draw a vacuum and stir for an additional 5 min
gently transfer the medium directly into the vessel
rotating the apparatus 2 shafts to speed equilibration to 37°C is discouraged!!!
use medium promptly after equilibration
An adequate dearation method is decribed in the USP:
First, a suitable volume of medium is heated to 41°C. With the aid of vacuum it is filtered through a 0.45 µm porosity membrane into a filtering flask equipped with a stirring device. The flask is sealed and while stirring for an additional 5 minutes, the vacuum is been continued. Then the medium is gently transferred directly into the vessel and promptly used after equilibration to a temperature of 37°C.

51. Troubleshooting Alternative deaeration methods
the USP states that „other validated deaeration techniques for removal of dissolved gases may be used“
other techniques include:
heating
sonication
vacuum
helium sparging (expensive)

52. Troubleshooting Sampling
take each sample at the correct time point  sampling time points (+ 2%)
use a single glass syringe for each vessel
sample from the right location within the vessel  between media surface and top of the paddle blade  n.l.t. 10 mm from vessel wall

53. Troubleshooting Sampling
always use a suitable filter  check filter adsorption
check the clearity of the filtered sample
filter the sample immediately after sampling
for automated sampling also check the tubings

54. Troubleshooting Physical conditions of the apparatus
vessels scrupulously clean ?
vessel surface smooth and curvature appropriate ?
Apparatus 1
the conditions of the baskets, particularly of their clips is critical
check all baskets for corrosion and blocked meshes before using them
align the air holes to prevent air cushions emerging during the test

55. (Semi) Automation Advantages high throughput of samples
minimizes analyst-to-analyst variability in sampling and filtration
reduces the average costs per analysis
very promising for QC purposes

56. Media preparation automated mixing of water and concentrate
preheating of medium
deaeration (vacuum and stirring)
media can be dispensed directly into the vessel
In this slide you can see a media preparation system that offers you a time- and effort- saving way of mixing, preheating, deaerating and dipensing of your medium.
The test medium can be mixed from concentrate (buffer or acid) and water, preheated to a defined temperature, deaerated under vacuum over a particular time and then be directly dipensed into the vessel.
Altogether this procedure should result in a reproducible degassing process.

57. Offline system
Here you can see an Offline system for apparatus 1 and 2. This system consists of a dissolution bath, coupled with a sampling unit. Samples can be taken at predetermined time points. If necessary they can be diluted immediately and after that collected in test tubes for UV-analysis or in HPLC vials respectively.

58. Online system
If you have a high throughput of samples that do not require dilution before UV analysis, a so-called Online system will make sense. This system consists of a dissolution bath that is directly coupled with an UV-spectrophotometer. Using this setup, it is possible to record multiple-point (real time) dissolution curves using a flow through-cuvette-system (closed system).

59. On- / Offline system
A combination of On- and Offline System combines two major advantages of single On- and Offline System by offering the possibility of an online-UV-measurement of automatically diluted samples.
The system also can be run in single offline or online mode like described before.

60. HPLC - online system
A further possibility for online-detection is represented by an HPLC – online system that combines the dissolution bath with a complete HPLC system. This system would be helpful in case of a high throughput in samples that cannot be measured by simple UV-analysis. For example this will be the case as you have excipients that would interfere with perturb UV-analysis or as you use biorelevant media like e.g. FaSSIF or FeSSIF as test media.

61. Automation
always validate automated methods, including analytical and sampling methods
validation should be performed using manual analysis, withdrawing samples at the same times and comparing to the automated results:
not highly variable dissolution results: two concurrent runs
highly variable dissolution results: simultaneous sampling
pay attention to automated dilution and filtering processes
What do you have to consider when thinking about (semi-) automation?
Automated methods always have to be validated. The validation should include analytical and sampling methods. Validation should be performed using manual analysis, withdrawing samples at the same times and comparing to automated results.
If the dissolution results are not highly variable, it is possible to compare two concurrent runs. If they are highly variable, simultaneous sampling has to take place.
Special attention should be paid to automated dilution and filtering processes!

62. Suggested reading
FIP Guidelines for dissolution testing of solid oral products. Dissolution Technologies 4:5-14 (1997).   
SM Diebold, JB Dressman. Dissolved oxygen as a measure for de- and re-aeration of aqueous media for dissolution testing. Dissolution Technologies 5: (1998).
S Qureshi. Calibration – the USP dissolution apparatus suitability test. Drug Inf. J. 30, (1996).
N Kaniwa et al. Collaborative study on the development of a standard for evaluation of vibration levels for dissolution apparatus. Int. J. Pharm. 175: (1998).
VA Gray, CK, Brown, JB Dressman, LJ Leeson. A new general information chapter on dissolution. Pharmacopoeial Forum 27 (6) [Nov.-Dec. 2001]
W Brown. General information <1092> The dissolution procedure: development and validation Pharmacopoeial Forum 30 (1) [Jan.-Feb. 2004]
Of general interest:
Dissolution Technologies:
With this slide, I want to end my talk.
You can see some references for more information regarding calibration of dissolution systems.
It is also worth to have a view at the homepage of „Dissolution technologies“. This journal is published quarterly and contains a lot of useful informations for all areas of dissolution testing.

63. Johann Wolfgang Goethe University
Dr. Sandra Klein
Johann Wolfgang Goethe University
Institute of Pharmaceutical Technology
9 Max von Laue Street
Frankfurt, 60438, Germany
With this slide, I want to end my talk.
You can see some references for more information regarding calibration of dissolution systems.
It is also worth to have a view at the homepage of „Dissolution technologies“. This journal is published quarterly and contains a lot of useful informations for all areas of dissolution testing.