STUDY OF DIFFERENT EVALUATION PARAMETER IN SELECTION …
Transcript of STUDY OF DIFFERENT EVALUATION PARAMETER IN SELECTION …
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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
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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.
5. 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 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
02 2.4 Insoluble Insoluble
03 3.2 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.
8. Moisture absorption study
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.
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