The slide has detailed description about dissolution theories and dissolution test apparatus used in pharma industry.

1. DISSOLUTION TEST
APPARATUS
Guided by :-
Prof. Dr. H. S.Mahajan
H.O.D. Pharmaceutics
Prepared by :-
Nilesh K. Bornare
M.Pharm 1st year
R.C.PATEL INSTITUTE OF PHARMACEUTICAL EDUCATION AND RESEARCH,
SHIRPUR.
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2. CONTENTS
• INTRODUCTION:
• NEED FOR DISSOLUTION TESTING
• THEORIES OF DISSOLUTION
• TYPES OF DISSOLUTION TEST APPARATUS
• CONCLUSION
• REFERENCES
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3. INTRODUCTION
Dissolution is the physicochemical process by which a solid substance enters the
solvent phase to yield a solution.
Dissolution rate : the amount of solid substance that goes into solution per
unit time under standard condition of temp, pH,& solvent composition and
constant solid surface area.
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4. NEED FOR DISSOLUTION
TESTING
Batch to batch drug release uniformity .
Development and optimization of dosage forms .
Ensures quality, safety, efficacy and stability of the product .
Evaluation of IVIVC correlation / bioavailability.
To support waiver for bioequivalence requirement.
For assessing pre and post approval changes in manufacturing process or
formulation .
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5. THEORIES OF DRUG DISSOLUTION
Three type of dissolution model are proposed depending on the relative
significance and the means by which the transport is effected . these models which
can be used to describe the dissolution rate mechanism .
The three models are:
1.Diffusion layer model / film theory.
2.Danckwert’s model / penetration or surface renewal theory .
3.Interfacial barrier model /double barrier or limited solvation theory.
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6. 1.DIFFUSION LAYER MODEL / FILM THEORY:
The process of dissolution of solid particle in a liquid, in the absence of reactive or chemical
forces consist of two steps :
Solution of the solid to form a thin film or layer at the solid / liquid interface called stagnant film
or diffusion layer.(Rapid step)
Diffusion of the soluble solute from the stagnant layer to the bulk of the solution. (Slower step
&RDS)
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7.  The rate of dissolution when the process is diffusion controlled and involves no chemical reaction was given by noyes and
whitney equation
Dc/d t = k (cs - cb)
Where,
Dc/ dt = dissolution rate of the drug .
K = dissolution rate constant .
(cs –cb) =conc gradient for diffusion of drug.
 Nernst and brunner ( fick’s first law diffusion ) modified the noyes and whitney equation
I.E. Dc/d t = dakw/o ( cs –cb)/vh
Where,
D = diffusion coefficient (diffusivity) of drug .
A= surface area of dissolving solid .
kw/o = water/oil partition coefficient.
V = volume of dissolution medium.
H = thickness of the stagnant layer.
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8. 2.DANCKWERT’S MODEL (PENETRATION OR SURFACE
RENEWAL THEORY )
 Danckwert’s Did Not Approve Of The Existence Of A Stagnant Layer And Suggested That Turbulence In
The Dissolution Medium Exists At The Solid/Liquid Interface.
 Danckwert’s Model Is Expressed By Equation :
Vdc/D T=d M/D T=a( Cs-Cb). √(Γ.D)
Where,
M=mass Of Solid Dissolved.
Γ=rate Of Surface Renewal .
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9. 3. INTERFACIAL BARRIER MODEL (DOUBLE
BARRIER OR LIMITED SOLVATION THEORY)
 According to the interfacial barrier model ,an intermediate conc can exist at the interface as a result of
solvation mechanism and is a function of solubility rather than diffusion. When dissolution of a crystal ,each
face of the crystal will have a different interfacial barrier.
G = Ki (Cs –Cb)
Where,
G = dissolution rate per unit area.
Ki= effective interfacial transport constant.
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10. USPAPPARATUS (COMPENDIAL METHOD)
1.ROTATING BASKET APPARATUS
2.ROTATING PADDLE APPARATUS
3.RECIPROCATING CYLINDER APPARATUS
4.FLOW THROUGH CELL APPARATUS
5.PADDLE OVER DISC APPARATUS
6.CYLINDER APPARATUS
7.RECIPROCATING HOLDER APPARATUS
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13. 1. ROTATING BASKET APPARATUS:
 Design :
 Vessel : -made of borosilicate glass
 semi hemispherical bottom
 capacity 1000ml.
 Shaft :-made of ss 316
 Rotates smoothly without significance wobble(100).
 Speed regulator .
 Water bath: maintained at 37 ±0.5 ℃
 Use :tablet, capsule, chewable tablet ,delayed release formulations.
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14.  Advantages:
• Full pH change during the test .
• can be easily automated which is imp for routine investigation .
Disadvantages:
• Basket screen is clogged with gummy particle .
• degassing is particularly important .
• mess gets corroded by HCL solution .
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15. 2.ROTATING PADDLE APPARATUS:
 Design:
 Vessel:-same as basket apparatus.
 Shaft :-the blade passes through the shaft so that the bottom of the blade
fuses with bottom of the shaft.
 Stirring elements:-made of tefflon (for laboratory purpose)and ss316.
 Water bath: maintained at 37 ±0.5℃.
 Sinkers: platinum wire used to prevent tablet/capsule from floting.
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16.  Use: tablet, orally disintegration tab, chewable tab, controlled release products, suspension.
 Advantages:
• Easy to use
• Robust
• pH change possible
• can be easily automated which is imp for routine investigation.
 Disadvantages:
• Sinkers for floating dosage form
• Hydrodynamic are complex ,they vary with site of the dosage form in the vessel(sticking, floting)and
therefore may significantly affect drug dissolution .
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17. 3.RECIPROCATING CYLINDER
 Design:
 Vessel:-set of cylindrical flat bottom glass vessels
• Set of reciprocating cylinders
• Stainless steel fitting(316) and screen made of non-sorbing or
nonreactive materials.
 Agitation type: reciprocating 5 -35 rpm
 Volume of dissolution medium: 200-250ml
 Water bath:maintained at 37±0.5℃
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18. Uses: tablets, controlled release bead(pellet) type
formulations.
Advantages:-easy to change the pH
- Hydrodynamic can be directly influenced by varying the
dip rate.
Disadvantage:-small volume (max .250ml)
- Little experience
- Limited data 18

19. 4.FLOW THROUGH CELL
Design:
 Reservoir:- for dissolution medium
Pump:
• forces dissolution medium through cell
• Holding a sample
• Flow rate 10-100ml/min
• Laminar flow is maintained
• peristaltic/centrifugal pumps are not recommended
Water bath:- maintained at 37±0.5℃
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20. Uses: low solubility drugs, powders and granules, microparticles, implants .
 advantages:
• Easy to change media pH
• PH profile possible
• sink condition maintained
• different mode i.e. open system and closed system.
Disadvantages:
• De-aeration necessary
• high volume of media
• Labor intensive
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21. 5.PADDLE OVER DISK
 Design:
 Vessel, shaft : same as apparatus 2 .
 stirring elements:-rotating speed 25-50rpm
 Sample holder:
• -Disk assembly that hold a product in such a way that release surface is
parallel with paddle
• -Paddle is directly attached over disk assembly
• -Samples are drawn between surface of the medium and top of the
paddle blade.
 Volume: 900ml
 Temperature:32℃
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22. Uses: transdermal formulations ,ointments , emulsion.
Advantages:
• Easy to handle
• sink condition are maintained
• membrane effect is minimum i.e. drug is placed on the disc at the bottom.
Disadvantages:
• Disk assembly restrict the patch size
• 17 mesh is standard .
• accommodates patches up to 90mm. 22

23. 6.ROTATING CYLINDER
 Design:
 Vessel : in place of basket, cylinder is used.
 Shaft: ss 316
 Sample:
Mounted to cuprophan(inner porous cellulosic material) an
entire system adhere to cylinder
Dosage unit is placed in cylinder and release from side out.
 Water bath: maintained at 32±0.5℃
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24. Uses: transdermal formulations
Advantages:
-Equipment (apparatus 1) available with the manufactures can be used with
modification as apparatus 6.
Disadvantages:
- Large volume of medium is required
- Drug gets diluted and causes difficulties in analysis
- Difficult to clean the cylinder
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25. 7.RECIPROCATING HOLDER
 Design:
 Vessel:
- Flat bottomed cylindrical vessel
- volume of dissolution medium
 Sample:- placed on disk shaped holders
 Agitation:- reciprocation
• Reciprocating frequency 30cycles/min
 Water bath: maintain at 32℃
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26. SAMPLE HOLDERS FOR DISSOLUTION TESTING
OF DIFFERENT DOSGAE FORMS
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27. Uses: controlled release formulations ,non disintegration and transdermal
formulations.
Advantages:
-Convenient method for selecting the volume of the medium
-Sink conditions can be maintained
-More sensitivity
Disadvantages: investment is high because the design is totally different from
standard equipment already available in industry.
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28. CONCLUSION
• Dissolution research started to develop in 1897 when Noyes and Whitney derived
their equation in the course of their dissolution studies on benzoic acid and lead
chloride.
• The goal of dissolution testing is to assure the pharmaceutical quality of the
product (manufacturing of product, release property and biopharmaceutical
characteristics e.g. Rate and extent of absorption ).
• Dissolution testing is a routine work for pharmaceutical quality control for oral
solid dosage forms like tablets, capsules and transdermal drug delivery systems.
• The science of dissolution testing is developing every day.
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29. REFERENCES
 G.S. Banker And C.T. Rhodes “ Modern Pharmaceutics Revised And Extended
4th Edition, Page No 53-101.
 Lachman And Liberman The Theory And Practice Of “Industrial Pharmacy 4th
Edition, Page No 182-213.
 D.M. Brahmankar And S.B. Jaiswal “Biopharmaceutics And Pharmacokinetics
–A Treatise” 3rd Edition, Page No 328-345
 C.V.S. Subrahmanyam “Biopharmaceutics And Pharmacokinetics -Concept And
Applications , 3rd Edition, Page No 152-165.
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