Dissolution is the physicochemical process by which a solid substance enters the solvent phase to yield a solution.

1. DISSOLUTION TESTING
APPARATUS
Bushra S.
1

2. Dissolution is the physicochemical
process by which a solid
substance enters the solvent
phase to yield a solution.
2

3. Need of Dissolution testing
devices
• Solid drugs absorbed only from the solution .
• In vitro test – estimate amount of drug
released per unit time.
• In vitro disintegration test not sufficient .
• In vitro dissolution test most reliable
predictors of in vivo performance.
• Dissolution - rate limiting factor.
3

4. Common conditions
• Simulated gastric and intestinal fluids – 37 deg
Celsius
• Fixed speed agitator
• Screen for separation of disintegrated
particles from the bulk
4

5. I.P. USP B.P. E.P.
Type 1
Paddle
apparatus Basket apparatus Basket apparatus Paddle apparatus
Type 2
Basket
apparatus Paddle apparatus Paddle apparatus Basket apparatus
Type 3
Reciprocating
cylinder
Flow through cell
apparatus
Flow through cell
apparatus
Type 4
Flow through cell
apparatus
Type 5 Paddle over disk
Type 6 cylinder
Type 7
Reciprocating
holder
5
Classification of dissolution apparatus in different
pharmacopeias:

6. USP APP. DESCRIPTOIN ROT. SPEED DOSAGE FORM
Type 1 Basket apparatus 50-120rpm Conventional tablets,
chewable tablets, CR
Type 2 Paddle apparatus 25-50rpm orally Disintegrating
tablets, chewable
tablets, CR,
suspensions
Type 3 Reciprocating cylinder 6-35rpm CR, chewable tablets
Type 4 Flow through cell
apparatus
N/A ER , poorly soluble API,
powder, granules,
microparticles,
implants
Type 5 Paddle over disk 25-50rpm Transdermal
Type 6 cylinder N/A Transdermal
Type 7 Reciprocating holder 30rpm CR(non
disintegrating oral and
Transdermal ) 6
USP APPARATUS

7. APPARATUS FOR CONTROLLED RELEASE
AND SUSPENSIONS
• APPARATUS I II AND III are for controlled release.
• APPARATUS II is for suspensions.
• There is also a Controlled Release Rotating Bottle Apparatus for controlled
release products.
7

8. Apparatus 1- Basket apparatus
The assembly consists of the following :
• A covered vessel
• Transparent material
• A motor
• A metallic drive shaft,
• A cylindrical basket,
• The water bath permits the holding of temp inside vessel at 37±0.5 ̊C
• The vessel is a cylindrical with hemispherical bottom .
8

9.  The shaft is positioned so that its
axis is not more than 2mm at any
point from the vertical axis of the
vessel and rotates smoothly and
with out significant wobble.
 Use 40mm mesh cloth.
 A basket having a gold coating
0.0001 inch thick may be used.
• The dosage unit is place in a dry
basket at the beginning of each
test.
• The distance between the inside
bottom of the vessel and the
basket is maintained at 25± 2m.
9
Drug product:
• Solids (mostly floating)
•Monodisperse (tablets)
•Polydisperse (encapsulated
beads)
Disadvantage:
• Formulation may clog to 40
mesh screen

10. Apparatus 2- Paddle apparatus
• The assembly from apparatus 1.
• Except paddle formed from a blade.
• a shaft is used as the stirring element
• The vertical center line of the blade is
flush with the bottom of the shaft.
• The distance of 25±2 mm between the
blade and the inside bottom of the
vessel.
10

11. 11

12. 12
•The paddle, blade and shaft may be
coated with a suitably inert coating.
•The dosage unit is allowed to sink
to the bottom of the vessel before
rotation of the blade.
•A small, loose piece of nonreactive
material such as wire helix may be
attached to dosage units in order to
prevent floating.
Standard volume: 900/1000 ml
 Advantages:
1. Easy to use and robust
2. pH change possible
3. Can be easily adapted to
apparatus
 Disadvantages
• Floating dosage forms require
sinker
• Positioning of tablet

13.  TIME:
• If single time specification is
given, the test may be
concluded in a shorter
period .
• If two or more times are
specified, specimen are to be
withdrawn only at the stated
times within a tolerance of
±2 %
 PROCEDURES
• Place the stated volume of the dissolution
medium in the vessel.
• Equilibrate the dissolution medium to
37±o.5 ̊c
• Place 1 tablet or 1 capsule in the apparatus.
• Operate the apparatus
• Within the time interval, withdraw a
specimen from zone midway between the
surface of the dissolution medium and the
top of the rotating basket or blade, not less
than 1cm from vessel wall.
• Replace the aliquots withdrawn for analysis
with equal volume of dissolution medium at
37 ̊c.
13

14. Limitations of USP Apparatus 1and 2:
1. USP 2 (and USP1) Apparatus has plenty of HYDRODYNAMICS.
2. Complicated 3-dimensional flow generated by the paddle.
3. Significant impact of convective transport –Conditions used (50 – 100
rpm) highly exaggerates flow in the GI.
4. Use of solvents and surfactants non-native to GI.
14

15. • The assembly consists of:
a set of cylindrical, flat-
bottomed glass vessels; a set of
glass reciprocating cylindrical;
stainless steel fitting;
screen; a motor and drive.
• The vessel is immersed in water
bath holding temp at 37± 0.5 ̊
15
Apparatus 3- Reciprocating cylinder

16.  PROCEDURE:
• Place the stated volume of the
dissolution medium in each vessel .
• Equilibrate the dissolution medium to
37 + 0.5°
• Place 1 dosage-form unit in each of
the six reciprocating cylinders.
• Operate the apparatus
• During the upward and downward
stroke, the reciprocating cylinder
moves through a total distance of 9.9
to 10.1 cm
• Within the time interval specified
withdraw a portion of the solution
under test from a zone midway
between the surface of the dissolution
medium and the bottom of each
vessel.
• Perform The analysis as directed in
the individual monograph. 16
Useful for: Tablets, Beads,
controlled release formulations
Standard volume: 200-250
ml/station
Advantages:
1. Easy to change the pH-profiles
2. Hydrodynamics can be directly
influenced by varying the dip
rate.
 Disadvantages:
1. small volume (max. 250 ml)
2. Limited data

17. Controlled Release Rotating
Bottle Apparatus

18. Apparatus for
suppositories
18

19. • The assembly consists of a reservior and a pump for the
dissolution medium; a flow-through cell; a water bath.
• The pump forces the dissolution medium upwards through the
flow-through cell.
• The pump has a delivery range between 240 and 960 mL per
hour, with standard flow rates of 4, 8, and 16 mL per minutes.
• The cell is immersed in a water bath and the temperature is
maintained at 37 + 0.5°
• The apparatus uses a clamp mechanism and two O-rings for
the fixation of the cell assembly.
Apparatus 4- Flow through cell
19

20. .
• .
20

21.  PROCEDURE:
• Place the glass beads into the cell specified in
the monograph.
• Place 1 dosage form unit on top of the beads.
• Assemble the filter head and fix the parts
together by means of a suitable clamping
device.
• Introduce by the pump the dissolution medium
warmed to 37 + 0.5° through the bottom of the
cell.
• Collect the eluate by fractions at each of the
times stated.
• Perform the analysis as directed in the
individual monograph.
21

22.  Useful for:
• Low solubility drugs,
• Micro particulates,
• Implants,
• Suppositories
 Advantages:
1. Easy to change media pH
2. PH-profile possible
3. Sink conditions
 Disadvantages:
1. Deaeration necessary
2. High volumes of media
3. Labor intensive
22
Tablets 12 mm Tablets 22,6 mm Powders /Granules
Implants Suppositories/soft
gelatin capsule

23. Apparatus For Transdermal And Topical
Dosage Forms
• APPARATUS V VI AND VII are used for transdermal products.
• APPARATUS V AND VI are used for topical dosage forms.
23

24. • The paddle and vessel assembly from
apparatus 2 with the addition of
stainless steel disk assembly.
• The temperature is maintained at 32
+ 0.5°C
• A distance of 25 + 2 mm between the
paddle blade and the surface the disk
assembly is maintained during the
test.
• The disk assembly is designed to
minimize any dead volume between
the disk assembly and the bottom of
the vessel.
Apparatus 5- Paddle over disk
24

25.  PROCEDURE:
• Place the stated volume of dissolution
medium in the vessel assemble the apparatus
without the disk assembly and equilibrate the
medium to 32 + 0.5°C
• Apply the transdermal system disk assembly.
• The system may be attached to the disk by a
suitable adhesive.
• Place the disk assembly flat at the bottom of
the vessel with the release surface facing up
and parallel to of the paddle blade and surface
of the dissolution medium.
• Operate the apparatus
• At each sampling time interval, withdraw a
sample from a zone midway between the
surface of the dissolution medium and the top
of the blade, not less than 1 cm from the
vessel wall.
• Perform the analysis on each sampled aliquot
as directed in the monograph.
 Standard volume: 900 ml
 Disadvantages:
• Disk assembly restricts the
patch size.
25

26. • The vessel assembly from
apparatus 1 except to replace the
basket and shaft with a stainless
steel cylinder stirring element and
to maintain the temperature at 32
+ 0.05°C
• The dosage unit is placed on the
cylinder at the beginning of each
test.
• The distance between the inside
bottom of the vessel and the
cylinder is maintained at 25 + 2
mm during the test.
26
Apparatus-6 Cylinder

27. 27
 PROCEDURES:
• Place the stated volume of the dissolution medium in the vessel.
• Equilibrate the dissolution medium to 32 + 0.5°C
• Prepare the test system prior to test as follows.
• Remove the protective liner from the system and place the adhesive side on a
piece of cuprophan.
• Cuprophan covered side down, on a clean surface, and apply a suitable adhesive to
the exposed cuprophan borders.
• Dry for 1 minutes.
• Press the cuprophan covering to remove trapped air bubbles.
• Place the cylinder in the apparatus and immediately rotate at the rate specified
• Within the time interval specified, withdraw a quantity of dissolution medium for
analysis from a zone midway between the surface of the dissolution medium and
the top of the rotating cylinder, not less than 1 cm from the vessel wall.
• Perform the analysis as directed in the individual monograph.

28. • The assembly consists of a set
of volumetrically calibrated or
tared solution containers.
• A motor and drive assembly to
reciprocate the system
vertically
• A set of suitable sample
holders.
• The solution containers are
partially immersed in a suitable
water bath, inside the
temperature of the containers at
32 + 0.5°C
USP Apparatus 7 – Reciprocating
Holder
28

29. Franz diffusion cell
• It is a simple, reproducible test for measuring the drug release
from creams,ointments and gel.
• The cell comprises of 2 parts:
• (a) sample holder containing 250 mg or 450 mg of sample.
• (b) reservoir of the diffusion cell.
29

30. Non compendial method Franz diffusion
cell : topical dosage form

31. References
1. Banakar V. U. and et. al. , pharmaceutical dissolution testing, markcel deken, pg
4,16,57,136-137
2. Remington, the science and practice of pharmacy, mack pub. Co. , 19th edition pg
594,601,602
3. Brahmankar D.M. , Jaiswal S. , biopharmaceutics and pharmacokinetics a
treatise, vallab prakashan, 2nd edition, pg 29-34
4. www.dissolutiontech.com
5. U.S. Pharmacopia,2008
31