STUDY OF DIFFERENT EVALUATION PARAMETER IN SELECTION …

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627

Sharma et al. World Journal of Pharmaceutical Research

STUDY OF DIFFERENT EVALUATION PARAMETER IN SELECTION

OF POLYMERS USED FOR FILM COATING

Dr. Mrs. P. H. Sharma1 *,

Dr.Mrs. J. G.Avari2

Department of Pharmaceutics, Padmashree Dr. D.Y. Patil College of Pharmacy, Akurdi,

Pune, Maharashtra. India

Department of Pharmaceutics, University Department of Pharmaceutical Sciences,

Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, Maharashtra. India

ABSTRACT

The application of coating to the surface of pharmaceutical dosage

form especially tablets has been practised for over 150 years. Film

coating are an integral part of the dosage form development process.

Film coating systems are concentrated blend of polymers, plasticizers,

pigments, opacifiers, glident etc. Polymer constitutes a major

component of the film coating system. The objective of the present

study is to evaluate the different parameters of polymer for its selection

for the purpose of film coating of tablet, with respect to their

physicochemical properties to prevent the cracking of film on storage.

The cellulose acetate and cellulose acetate Phthalate were used for film

coating and evaluated for physicochemical parameters such as colour,

softening point, acid value, glass transition temperature, moisture

absorption study, IR study and Thermo gravimetric analysis. The film of cellulose and

cellulose acetate Phthalate were prepared by mercury substrate technique and evaluated for

different parameter such as thickness, moisture absorption study, Water vapour transmission

study. Due to the great increase in the number of polymeric materials developed in recent

years, an examination of these polymer and their properties for application in pharmaceutical

coating is required .Hence the present study gives the detail information regarding the

evaluation parameters of polymer with to respect to its physicochemical properties and the

effect of plasticizer on film forming properties of polymers, which helps and give a complete

guideline for the selection of polymers for film coating of tablet.

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Article Received on

29 October 2014,

Revised on 21 Nov 2014,

Accepted on 03 Dec 2014

*Correspondence for

Author

Dr. P. H. Sharma

Department of

Pharmaceutics,

Padmashree Dr. D.Y.

Patil College of

Pharmacy, Akurdi, Pune,

Maharashtra. India


628


Keywords- polymers, plasticizers, softening point, acid value, glass transition temperature.

INTRODUCTION

Film coating of solid dosage forms is a high sophisticated process, first described in 1930.1Its

obvious advantages resulted in a soon replacement of the traditional sugar coating by the

emerging technology, thus the first film-coated tablet became commercially available in 1954.

The technology advanced with the introduction of the semi-synthetic cellulose derivatives

and the synthetic acrylic polymers in the early 1950s. [2, 3]

Film coatings are applied for several reasons [1, 4, 5]

- Taste masking and moisture- / light protecting coatings

- Improved product appearance

- Improved mechanical resistance of the coated product (e.g. reduced friability)

- Modified drug release (e.g. gastric resistant or extended release coatings)

The properties and performance of the final coat is strongly affected by the polymer

properties and the formulation parameters. The coating formulation may contain other major

components beside the polymer such as the solvent, plasticizers or pigments.1,6

Various

coating material are available in the market, but polymeric film are widely used in

pharmaceutical research and development. Polymers are used to coat various dosage forms.

When selecting a polymer for film coating, it is necessary to define these materials in terms

of chemical structure, molecular weight and physicochemical property. The objective of the

present study is to evaluate the different parameters of polymer for its selection for the

purpose of film coating of tablet, with respect to their physicochemical properties and effect

of plasticizer on film forming properties of polymers to prevent defects of film coating on

storage.

MATERIAL AND METHOD

Cellulose acetate, Cellulose acetate Phthalate, Mercury were purchase from Research

Lab.Fine Chem Industries Mumbai .All other reagents used were of A.R.grade.

Physicochemical characterization of cellulose acetate and cellulose acetate phthalate

1. Colour[7]

Colour comparision of material was carried out usually against white background.

2. Acid Value[8]

Acid value was determined by Indian pharmacopoeia test method.


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3. Softening point[9]

Herculus drop softening method was used to determine softening point.

4. Differential scanning Colorimetric (DSC)

The thermograms were recorded using Perkin Elmer DSC model -7. The instrument

calibrated with indium and zinc prior to analyzing the samples under nitrogen. Sample (1-

2mg) was accurately weighed and sealed hermetically in flat bottom open aluminum cells at a

scanning rate of 5˚C/min conducted over a temperature range of 30- 250˚C. The samples

were heated in sealed aluminum pans under nitrogen flows (50 ml/min).

5. Loss on Drying[10]

Weigh about accurately 1 g of the sample into porcelain dish .The sample was dried in oven

at 100° c to150°c till gets constant weight of sample after drying for 3 hours.

6. Molecular Weight[11]

The molecular weight determined by Viscometry using Ostwald viscometer. The polymer

solution was filled in bulb (A) of Ostwald viscometer through tube L to slightly above the

mark G. The tube was placed vertically in water bath maintained at 20°c. The solution was

sucked to point about 5mm above the mark E. Pressure was released and time taken for the

bottom of the measure to fall from the top edge to mark C to the top edge of mark F was

noted using stop watch .The procedure repeated for six such readings. The average molecular

weight was calculated using Mark-Houwink formula

[ η ] = K (MB)a

Where

[ η ] --- Intrinsic viscosity

K and a - constants depending on the polymer, solvent and temperature

M - Molecular weight

7. Solubility [12]

For determination of the solubility 1 g of material was placed in different screw capped test

tube. The 10 ml of organic solvent and different pH solution were added to each test tube

respectively. All the tubes than placed in mechanical shaker which was operated for 24 hrs at

a speed of 50 rpm and maintained at 100°c. The increase in weight relative to the solvent

blank was used to determine the solubility of material in organic solvent and pH solution.


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8. Moisture absorption study

Glass desiccators were maintained at controlled relative humidity conditions brought about

by use of different saturated salt solution with an excess amount of salts such as potassium

acetate, potassium carbonate, sodium chloride and potassium nitrate. [13]

Saturated salt solution % Relative humidity

Potassium acetate 23

Potassium carbonate 43

Sodium chloride 75

Potassium nitrate 93

After equilibrating the desiccators with appropriate concentration of saturated salt solution

for three days, accurately weighed previously dried coating material placed in Petri dish were

kept in the desiccators undisturbed for 14 days. The difference in weight gives the amount of

moisture observed at various relative humidities.

9. Infra- red Spectroscopy study

FT-IR-Spectra were recorded by FT-IR spectrophotometer (Shimadzu Corporation, Japan,

8101A) using KBr disc method. Each sample was gently triturated with KBr powder in a

weight ratio of 1: 100 and pressed using a hydrostatic press at a pressure of 10 tons for 5 min.

The disc was placed in the sample holder and scanned from 4600 to 400 cm-1

at a resolution

of 1 cm-1

at zero time.

10. Thermo gravimetric analysis (TGA)

TGA-studies were carried out using a Perkin Elmer thermal analysis system under nitrogen

atmosphere. The heating rate was 10 °C/min in the temperature range from ambient up to

600 °C. The thermal stability of the samples was evaluated in terms of decomposition

temperature. As the temperature increases the weight loss for the sample occurs.

Free film preparation and evaluation of cellulose acetate and cellulose phthalate film

1. Film formation

Free film prepared by mercury substrate technique. [14]

A (1.5%, 2.5%, 3.5%, 4.5%) solution

of ethylcellulose was prepared in ethanol. The prepared solution was stirred for 30 min. Then

the polymer solution was poured in Petri dish containing mercury and the solvent was

allowed to evaporate in an oven at 60 ˚c to 70˚c.This method produces film with the control

constant thickness which can be controlled by varying the strength or volume of polymer

solution poured.


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2. Selection of plasticizer

The selection of a plasticizer depends on selected physical properties of the plasticizer e.g.

hygroscopicity (which may affect moisture uptake by the film and its effectiveness as a

moisture barrier) and water solubility. Plasticizer solubility is often important in

pharmaceutical applications especially when higher plasticizer concentration is required. A

soluble plasticizer needed for a soluble coating and an insoluble plasticizer required

producing an enteric or slow release coating.Depending, upon water solubility of plasticizer,

in the presence study the selected plasticizer was dibutyl phthalate was selected from

insoluble category. The plasticizer used in concentration of 5% of polymer weight.

3. Thickness

The Digital Verniar Caliber instrument was used to measure the thickness at a different point

throughout the film and recorded as the mean of five measurements.

4. Difusion study

The diffusion of drug studied using Keshary-Chein diffusion cell. [15,16]

The polymer film was

sandwiched between two compartments namely donor and receptor. 20 ml of phosphate

buffer (pH 6.8) was used as receptor fluid. 5ml of drug solution (10µg/ml) was poured into

the donor compartment. The receptor fluid was agitated using a magnetic stirrer and the

temperature was, maintained at 37±1˚C. Samples (2ml) were withdrawn periodically from the

receptor compartment over a period of 1 hr, the amount of drug diffuse at various interval

was determined. After suitable dilution, absorbance was noted using double beam

spectrophotometer at 258 nm. After each sampling, equal volume of drug free buffer solution

was added to the receptor compartment to ensure constant volume of receptor fluid.


Glass desiccators were maintained at controlled relative humidity conditions brought about

by use of different saturated salt solution with an excess amount of salts such as potassium

acetate, potassium carbonate, sodium chloride and potassium nitrate After equilibrating the

desiccators with appropriate concentration of saturated salt solution for three days, accurately

weighed previously dried films placed in Petri dish were kept in the desiccators undisturbed

for 14 days. The difference in weight gives the amount of moisture observed at various

relative humidities.


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6. Water vapour transmission rate study [17,18]

The prepared films were cut to a suitable size. Thickness of the dry films were determined at

five different places with Digital Verniar Caliber instrument and were mounted on assembled

transmission cell (vials).These vials containing a saturated salt solution with excessive

quantity of sodium chloride, to provide the relative humidity (RH) condition of 75% and the

charged vials were weighed and placed in pre equilibrated desiccators maintained at 0% RH,

containing fused calcium chloride.

The vials were reweighed in the same manner at 24 h interval for 72 h.

The RH inside the chambers was measured by hygrometer. It was ensured that it was

maintained at 0% RH. The amount of water transmitted through the film was given by the

loss of weight of the vials. The rate of water vapor transmission was calculated using the

following Utsumi's 19

WVT equation:

Where

W = Gm of water transmitted per 24 hours

L = film thickness in cm

S =Surface area in sq. cm

Q = water vapor transmission in g .cm thickness /cm2 areas 24 hours.

Since Utsumi's equation take the thickness of the film sample into consideration.

7. Mechanical Properties

The dried films were cut into size of 2 mm width x 130 mm length. The thickness of the dry

film was determined at five different places by micrometer screw gauge. To determine

mechanical properties of dry film, a tensile test was performed on Instron (Model - 4467,

Instron crop, Carton, MA) instrument based on ASTM standard test principle. The gauge

length was kept at 500 mm and crosshead speed was 1.0000 mm / min and the test was

performed at 50% RH at room temperature. The mechanical properties viz tensile strength,

percentage elongation and modulus of elasticity were automatically computed by the

instrument.Each experiment was repeated at least three times.


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8. Surface morphology

The surface morphology of each polymeric film was determined by scanning electron

microscopy.

RESULT AND DISCUSSION

Physicochemical characterization of cellulose acetate and cellulose acetate phthalate

Table 1: Physicochemical characteristic of cellulose acetate and cellulose acetate

phthalate

Figure 1 Differential Scanning Calorimetry of Cellulose acetate.

Acid value of polymer indicates the resistivity of polymer for acid and thus acts as a acid

resistance material, it was found that the CAP (Cellulose acetate phthalate) contain free acidic

group and may act as acid resistant material therefore may be used as enteric coating material

whereas cellulose acetate acts as a rate controlling membrane.

The softening point of cellulose acetate and cellulose acetate phthalate is somewhat towards

higher side due to which the free films prepared from these polymers were brittle .However

brittleness of the free films can considerably reduced by the addition of Plasticizers.

Sr. No Test Cellulose Acetate Cellulose Acetate Phthalate

1. Colour White White

2. Acid Value 20.4 66.19

3. Softening point 196-198 °C 140-145°C

4. Tg 82.95°C 69.91°C

5. Loss on drying 0.052 % w/w 0.090 % w/w

6. Molecular weight 28000 5000


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Loss on drying of cellulose acetate and cellulose acetate phthalate was found to be

0.052%w/w and 0.09%w/w which were as per the specification.

The molecular weight of cellulose acetate and cellulose acetate phthalate was found to be

28,000 and 50,000 which was as per the specification.

Figure 2 Differential Scanning Calorimetry of Cellulose acetate phthalate.

The Figure 1 and 2 were obtained by Differential scanning calorimetry of the cellulose

acetate and cellulose acetate phthalate and Tg of these polymer found to be 82.95°c and

69.95°c which is relatively high which attributes the brittle nature of polymer. However Tg

can be reduced by the addition of plasticizer.

7. Solubility study

Table-2 Solubility of cellulose acetate and cellulose acetate phthalate in organic solvent

Sr.No solvent Solubility

cellulose acetate cellulose acetate phthalate

01 Acetone Soluble Soluble

02 Diethyl ether Insoluble Insoluble

03 Chloroform Insoluble Insoluble

04 Dichloro methane Insoluble Insoluble

05 Isoprppyl alcohol Insoluble Insoluble

06 Benzene Insoluble Insoluble

07 Methanol Insoluble Insoluble


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From table-2 it can be observed that cellulose acetate and cellulose acetate phthalate are

soluble in only acetone and insoluble in other organic solvent .It means cellulose acetate and

cellulose acetate phthalate has limited solubility in organic solvent and water.

Table-3 Solubility study of and cellulose acetate and cellulose acetate phthalate in

different pH solutions.

Sr.No Ph solution Solubility

cellulose acetate cellulose acetate phthalate

01 1.7 Insoluble Insoluble



04 6.8 Slightly soluble Soluble

05 8.0 Insoluble Soluble

From table-3 it is observed that solubility of cellulose acetate phthalate increases gradually

with increase in PH

of the solution upto 6.8 This indicates that solubility of cellulose acetate

phthalate has comparatively more in alkaline PH

than in acidic PH.

This property may render

the polymer for enteric coating. But solubility does not increase gradually with increase in PH

in case of cellulose acetate and therefore it has potential as rate controlling membrane.


Table-4 Moisture absorption study of cellulose acetate and cellulose acetate phthalate

Sample Percent moisture absorption at percent relative humidity

23% 43% 75% 93%

cellulose acetate 0.11 0.33 0.36 1.19

cellulose acetate phthalate 0.164 0.412 1.28 2.93

From table-4 It can be observed that moisture absorption capacity of cellulose acetate

phthalate is higher than cellulose acetate. Similarly the moisture absorption capacity of

cellulose acetate and cellulose acetate phthalate increases with increase in humidity. Moisture

will exert a significant effect on the properties of polymeric films. The presence of moisture

reduces the glass transitition temperature.

08 Carbon tetrachloride Insoluble Insoluble

09 Iso butyl alcohol Insoluble Insoluble

10 Distill water Insoluble Insoluble


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9. Infrared Spectroscopy Study

Figure -3 Infra red spectra of Cellulose acetate

Figure 4 Infra red spectra of Cellulose acetate phthalate

The figure 3 and 4 were obtained by Infrared Spectroscopy of Cellulose acetate and cellulose

acetate phthalate from which functional group present were interpreted In IR spectrum of

Cellulose acetate OH peak is almost suppressed but ester carbonyl band with a strong


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intensity is seen at 1755 cm-1

. This represents the acetylate of cellulose whereas OH group

are converted into acetate group through ester linkage.

10. Thermogravimetric Analysis

Figure 5.Thermogravimetric graph of cellulose acetate

Figure 6. Thermogravimetric graph of cellulose acetate phthalate

The fig 5 & 6 were obtained by thermo gravimetric analysis from which thermal stability of

polymer has been interpreted.


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Free film preparation and evaluation of cellulose acetate and cellulose phthalate film

1. Thickness

Table 5- Thickness of cellulose acetate and cellulose acetate phthalate.

Sample Polymer concentration Thickness (cm)

cellulose acetate

0.5

01

1.5

02

0.03

0.05

0.06

0.08

cellulose acetate phthalate

01

02

03

04

0.02

0.04

0.06

0.08

From Table -5 The thickness of film strongly affected the drug permeability rate with

increase in film thickness. Thus the permeation rate decreases.

2. Diffusion Study

Table 6- Diffusion study of cellulose acetate and cellulose acetate phthalate.

Polymer Polymer concentration

(%) Thickness (cm) Time

%

release

Cellulose acetate

0.5 0.03

15

30

45

60

43.64

63.68

73.42

88.16

01 0.05

15

30

45

60

33.21

40.43

47.19

52.92

1.5 0.06

15

30

45

60

18.09

21.53

29.66

41.00

02 0.08

15

30

45

60

12.37

25.54

30.92

34.24

Cellulose acetate phthalate

01 0.02

15

30

45

60

45.58

51.54

66.43

71.01

02 0.04

15

30

45

60

43.64

45.58

54.98

61.05

03 0.06

15

30

45

42.38

45.58

47.30


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60 51.54

04 0.08

15

30

45

60

43.52

45.93

48.10

50.97

Table-6 shows the diffusion of drug through cellulose acetate film is less as compared to

cellulose acetate phthalate. The permeability of cellulose acetate phthalate is relatively high

as compared to cellulose acetate film the increase in polymer concentration increase thickness

which decreases the diffusion of drug from film.

3. Moisture absorption study of cellulose acetate and cellulose acetate phthalate film

Table-7 Moisture absorption study of cellulose acetate and Cellulose Acetate phthalate

Table-7 shows that water soluble plasticizer absorb more moisture than water insoluble

plasticizer because water soluble plasticizer has affinity for hydrophilic group. The presence

of moisture has plasticizing effect on film.

4. Water vapour Transmission rate study

Table-8 Water vapour Transmission rate study of Cellulose acetate and cellulose

acetate phthalate film.

Sr.

no Polymer Area (cm

2) Thickness (cm)

WVTR X 10-4

(gm-cm/cm2)

24 h 48 h 72 h

01 Cellulose acetate 1.24 0.08 11.97 14.0 16.9

02 Cellulose acetate

phthalate 1.24 0.08 12.08 37.72 48.09

From Table-8 The WVTR studies of cellulose acetate and cellulose acetate phthalate film

indicates that the material may possible be used as a good film former. They also would offer

good protection to water sensitive drugs. In pharmaceutical coating this film can provide

adequate protection from atmospheric moisture.

Polymer Polymer

concentration

% Moisture absorption at percent relative humidity

23% 43% 75% 93% Avrage

Cellulose Acetate

0.5 1.36 2.28 2.30 3.89 2.60

1.0 0.68 1.34 2.98 3.14 2.17

1.5 1.29 2.57 3.62 4.01 2.87

2.0 0.35 1.65 3.07 3.57 2.16

Cellulose Acetate phthalate

0.5 1.31 2.34 2.65 6.24 3.13

1.0 1.84 2.48 2.57 2.98 2.46

1.5 0.43 1.36 1.38 1.39 1.14

2.0 1.16 1.18 1.36 1.96 1.40


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5.Mechanical Properties

Table-9 Mechanical Properties of free film of cellulose acetate and cellulose acetate

phthalate

Polymer Polymer

concentration

Thickness Tensile

strength

(M.Pa.)

%

elongation

Modulus of

Elasticity

(M.Pa.)

Tensile

strength/

Modulus of

Elasticity

Cellulose

acetate

0.5

1.0

1.5

2.0

0.03

0.05

0.06

0.08

-

12.352

12.243

7.229

-

2.225

3.574

4.100

-

11034.48

5212.431

0

-

0.011

0.0023

-

Cellulose

acetate

phthlate

1.0

2.0

3.0

4.0

0.02

0.04

0.06

0.08

-

22.292

29.137

30.018

-

4.114

3.298

4.349

-

5849.91

992.65

863.02

-

0.0038

0.0293

0.0347

Table- 9 shows that castor oil has high ratio of tensile strength to modulus of elasticity and

expected that it produce the least coating defects. The water insoluble plasticizer due to their

hydrophobic nature are compatible with water insoluble and show high value of tensile

strength to modulus of elasticity ratio than water soluble plasticizer. Hence the extent of

interaction between the plasticizer and the polymer and has an important influence on ratio of

tensile strength to modulus of elasticity of film produce. Therefore water insoluble

plasticizers are suitable plasticizer.


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6. Scanning Electron Microscopy

Surface topographical analysis of selected polymeric film was carried out by Scanning

Electron Microscopy and results are shown in figure 7.

CONCLUSION

From the above study it was concluded that the evaluation parameter such as softening point,

and Tg of polymers gives the idea about brittleness of polymer film. The moisture absorption

study shows the moisture absorption capacity of film to protect moisture sensitive drug. Thus

the parameters are useful in selection of polymer. The only physicochemical characterization

of polymer was done which is not sufficient for selection of polymer. So that some more

evaluation parameter should be used for selection of polymer for film coating especially

related to film forming properties and other evaluation parameter such as effect of plasticizer.

The future work will be based on above mentioned parameters.

REFERENCE

1. Cole G, Hogan J, Aulton M. Film-coating materials and their properties in

Pharmaceutical Coating Technology.6th ed. London: Taylor & Francis Books; 1995.

2. Lehman K, Mcginity J W.Aqueous polymeric coatings for Pharmaceutical dosage forms.

2 nd ed.New York: Marcel Dekker; 1989.

3. Van SG, Rhodes C T. The sustained release coating of solid dosage forms: a historical

review. Drug Dev. Ind. Pharm. 1995; 21: 93–118.

4. Schmid S, Muller C C, Schmidt PC. Interactions during aqueous film coating of

ibuprofen with Aquacoat ECD. Int. J. Pharm. 2000; 197: 35-39.

5. Reiland T L, Seitz J A, Yeager J L, Brusenback R A. Aqueous film coating vaporization

efficiency. Drug Dev Ind Pharm. 1983; 9: 945–958

6. Porter SC, Bruno C, Lieberman, HA., Lachman, L. & Schwartz, J. Pharmaceutical dosage

forms: Tablets. 2nd ed. New York: Marcel Dekker; 1990.

7. Ramani CC, Puranick PK.Study of maleoabietic acid as matrix forming material. Int. J.

Pharm. Adv, 1996; 1: 344-345.

8. Government of India, Ministry of Health and Family welfare. Appendix – 3.26 :A-

50. New Delhi: Controller of Publications; 1996. Indian Pharmacopoeia.

9. Ramani CC, Puranick PK. Study of diabietic acid as matrix forming material. Int. J.

Pharm. Adv, 1996; 1:137-138.


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10. Government of India, Ministry of Health and Family welfare. Appendix – 8.7:A-89. New

Delhi: Controller of Publications; 1996. Indian Pharmacopoeia.

11. Government of India, Ministry of Health and Family welfare. Appendix – 8.14 :A-

97. New Delhi: Controller of Publications; 1996. Indian Pharmacopoeia.

12. Ministry of Health and Family Welfare, Pharmacopoeia of India. Vol 2. New Delhi:

Ministry of Health and Family Welfare, Govt of India; 1985. A-142

13. Costa P, LoboMS. Modelling and comparison of dissolution profiles. European J of

Pharm Sci 2001; 13:123-133.

14. Patel M, Patel JM, Lemberger AP. Water vapour permeation of selected cellulose ester

films. J. Pharm. Sci.1964; 53:286–290.

15. Banker G, Film coating theory and practice. J. Pharm. Sci 1966; 55:81-82.

16. CrankJ, ParkG .Diffusion in Polymers. New York: Academic Press; 1968. p1-37.

17. HiguchiT, Aguiar A. A study of permeability to water vapor of fats, waxes, and other

enteric coating materials J Amer Pharm Assoc Sci, 1959; 48:578.

18. Utsumi I, Takahashi T, Suigmoto N. Water vapour transmission properties of polymeric

materials. J. Pharm. Sci, 1961; 50: 592-594.

19. Utsumi I, Takahashi T, Sugimoto N. Water vapour transmission properties of polymeric

materials. J. Pharm. Sci, 1961; 50: 592–597.

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