1. PREPARED BY:
PAREKH HEJAL B.
M.PHARM SEMESTER-1(2011-12)
PHARMACEUTICAL FORMULATION,
DEVELOPMENT & BIOPHARMACEUTICS
1

2. CRYSTALLINITY
2

3. LIST OF CONTENTS
INTRODUCTION
CLASSIFICATION OF SOLIDS
AMORPHOUS
POLYMORPHS
SOLVATES
CLATHRATES
COMPARISON OF CRYSTALLINE AND AMORPHOUS FORMS
CRYSTAL STRUCTURE AND MORPHOLOGY
MODIFICATION OF CRYSTAL HABIT AND ITS
CHARACTERIZATION
CRYSTALLIZATION
ANALYTICAL METHOD FOR CHARACTERIZATION
IMPORTANCE IN PREFORMULATION STUDIES
LATEST TECHNIQUE DEVELOPMENTS
3

4. INTRODUCTION
A crystal is a solid in which the constituent
atoms, molecules, or ions are packed in a regularly
ordered, repeating pattern extending in all three
spatial dimensions.
The study of the crystalline form as a part of
preformulation study is termed as crystallinity
study.
4

5. CLASSIFICATION OF CHEMICAL COMPOUND
Solids
Amorphous
Crystalline
(Non-crystalline)
Single entity Molecular adducts
Non-stoichiometric Stoichiometric
Polymorphs
Inclusion compounds compounds
Cage
Enantiotropic Monotropic Channel Layer Hydrates Solvates
(Clathrate)
5

6. AMORPHOUS COMPOUND
They have atoms or molecules randomly placed as in a
liquid. They are typically prepared by:
 Lyophilization E.g. Fluprednisolone in tert-butanol.
 Rapid quenching of chloramphenicol palmitate solution in
hydrophilic solvent.
 Rapid quenching of melted chloramphenicol palmitate in the
refrigerator to -10˚
 Precipitation is also used to prepare the amorphous prompt
insulin zinc suspension.
6

7. EFFECT ON INSULIN
NO TYPE OF INSULIN FORM OF ONSET DURATION OF
. INSULIN OF ACTION
ACTION
1 Prompt insulin- Amorphous Fast Short
zinc suspension
(semilente)
2 Extended crystalline Slow Long
insulin-zinc
suspension
(ultralente)
3 Insulin-zinc 30% Fast Intermediate
suspension amorphous+
(lente) 70%
crystalline 7

8. Amorphous forms are of :-
 Higher thermodynamic energy
 Greater solubility and dissolution rate.
But due to high energy they are unstable and
revert back to a stable form.
E.g. Amorphous novibiocin suspension.
Agents like
 methylcellulose,
 polyvinylpyrollidone, and
 several alginic acid derivatives such as sodium alginate and
propylene glycol alginate are used to prevent such condition.
8

9. POLYMORPHS
Many drug substances can exist in more than one
crystalline form with different space-lattice arrangements.
This phenomenon is known as polymorphism and the
different crystalline forms as polymorphs.
 Drugs like barbiturates have polymorphic forms.
 Also steroid hormones have 42 and sulphonamides have 30
polymorphic forms.
9

10. SOLVATES (PSEUDOPOLYMORPHISM)
Solvates are molecular complexes that have incorporated the
crystallizing solvent molecule in their specific lattice position
and in fixed stoichiometry.
Estradiol forms highest number of solvates with all 30
solvents.
Other examples are
erythromycin, chloramphenicol, ampicillin, sulphanilamide
etc.
Solvates can be distinguished from polymorphs by observing
bubbles of gas in silicon oil upon heating.
10

11. CLATHRATES
A clathrate is a single-phased solid with two distinct
components: the host and the guest.
The guest is retained in the closed cavities provided by the
crystalline structure of the host.
Thus it is a non-stoichiometric molecular adduct.
The major classes of clathrates are hydroquinone
clathrates, water clathrates, phenol clathrates etc.
11

12. PHARMACEUTICAL APPLICATIONS
OF CLATHRATES:-
PURIFICATION-
SEPARATION OF RARE GASES-
SEPARATION OF OPTICAL ISOMERS-
STORAGE OF INERT GASES-
MODE OF ACTION OF ANAESTHETICS-
[ JPS-1975, 64, 1264.]
12

13. COMPARISON OF THE MECHANICAL PROPERTIES
OF THE COMPACTS OF THE CRYSTALLINE AND
AMORPHOUS FORMS OF A DRUG SUBSTANCE
CRYSTALLINE FORM AMORPHOUS FORM
More ductile (low Least ductile (high
indentation hardness indentation hardness
value) value)
Form compacts with Form compacts with lowest
highest tensile tensile strength
strength
Compacts have low Compacts have high
brittleness value brittleness value
Require higher Require lower compression
compression stress stress
13

14. COMPARISON OF SOLUBILITY OF
CRYSTAL, SOLVATE AND HYDRATE:
Amorphous form more soluble than a corresponding
crystalline form.
The dissolution rates of hydrates are less than corresponding
anhydrous crystalline form. E.g.
gluthethimide, theophylline, caffeine, succinyl
sulphathiazole, phenobarbitol.
The dissolution rates for organic solvates are higher than
corresponding pure crystalline form. E.g. 1,4-dioxane solvate
of nifedipine shows better solubility than dehydrate form.
So organic solvates should be preferred in place of pure
crystals which solves both problems, solubility and
stability, but only if ICH guidelines about limits of organic
residues permit. 14

15. Crystals are of two types:-
Irregularly shaped crystals known as anhedral or
allotriomorphic.
Definite shaped crystals bound by plane faces known as
euhedral or idiomorphic.
Any crystal is characterized by its internal structure and
habit. Habit is the description of the outer appearance of a
crystal whereas the internal structure is the molecular
arrangement within the solid.
15

16. CRYSTAL SYSTEM
(INTERNAL STRUCTURE)
The most symmetric system is cubic system.
Other six systems, in order of decreasing symmetry, are
hexagonal, tetragonal, rhombohedral (also known as
trigonal), orthorhombic, monoclinic and triclinic.
Thus there are fourteen types of unit cell called as the
Bravais lattices.
We can identify the various planes of crystal using the
system of Miller indices.
16

17. STRUCTURE OF CRYSTALS
17

18. CRYSTAL HABIT
There are five types of crystal habit widely recognized:
Platy: plates
Tabular: moderate expansion of two parallel faces
Prismatic: columns
Acicular: needle-like
Bladed: flat acicular
These occur in all the seven systems.
18

19. Crystal habit:
can be quantitatively expressed in terms of Aspect ratio (AR).
AR defined as the ratio of length to width and values of AR
approaching 1 (spherical or cube shape) are considered to be
pharmaceutically good.
It is preferable to keep the AR values below 5 so as to avoid
problems with flow.
AR in polar solvents was as high as 9.4 in comparison with 5-
6 in non-polar solvents.
[JPP-2007, 59, 29-39.]
19

20. METHODS OF MODIFICATIONS OF CRYSTAL HABIT
Excessive super saturation. E.g. transform a prism or
isodiametric crystals to needle shape.
Cooling rate and agitation. E.g. naphthalene gives thin plates
if rapidly cooled whereas slow evaporation yields prisms.
The crystallizing solvent. E.g. resorcinol produces needles
from benzene and squat prisms from butyl acetate.
Addition of co-solvents or solutes. E.g. sodium chloride is
cubic but urea produces octahedral habit.
Crystal habit can also be modified by adding
impurities or „poisons‟; for example, sulphonic acid dyes alter
the crystal habit of ammonium, sodium and potassium
nitrates.
20

21. CHARACTERIZATION OF HABITS
The angle between two crystals faces can be described
in two ways:
 Included or edge angle between two faces,
 Interfacial or polar angle, the angle between the normals to
the faces of the crystal.
Interfacial angle is of importance in crystallography.
They are measured by instruments known as goniometers.
21

22. CRYSTALLIZATION
 Crystallization is a chemical solid-liquid separation
technique, in which mass transfer of a solute from the
liquid solution to a pure solid crystalline phase occurs.
The crystallization process consists of two major
events:
 Nucleation
Homogenous
Heterogeneous
 Crystal growth
22

23. Super saturation is the driving force of the
crystallization
This can be achieved by various methods, with
1) solution cooling,
2) addition of a second solvent to reduce the solubility of the
solute (technique known as anti-solvent or drown-out)
3) chemical reaction
4) change in pH being the most common methods used in
industrial practice.
Other methods, such as solvent evaporation, can also be
used.
23

24. IMPORTANCE OF CRYSTALLINITY IN
PREFORMULATION STUDIES
EFFECT ON SOLUBILITY & BIOAVAILABILITY
Antibiotic novobiocin is inactive in crystalline form while
amorphous form has 10 times more solubility and hence more
bioavailable.
24

25. CHEMICAL STABILITY
 At instances crystalline form are more stable than
amorphous form.
 e.g. crystalline forms of penicillin G as potassium or sodium
salt are more stable.
SUSPENSION SYRINGEABILITY
 A suspension of plate shaped crystals may be injected
through a needle with a greater ease than one with needle
shaped crystals of same dimensions.
25

26. EFFECT ON GRANULATION
 Sulphathiazole can exist in different crystalline forms . Form
III has water adsorption of 0.046 mg/m2 & form I has water
adsorption of 0.031 mg/m2 so form III shows better wetting
and so easy granulation.
 Use of amorphous form of calcium pentothenate in multi-
vitamin tablets prepared by wet granulation process, is not
desirable because polymorphic transformation makes the
granulation mass sticky, making further granulation
virtually impossible.
26

27. HARDNESS OF TABLET
 Sulphamerazine is available in two different crystalline
forms SMZ-I & SMZ-II. SMZ-I forms harder tablets than
SMZ-II at same compression pressure and so it shows
delayed release.
27

28. POLYMORPHIC TRANSFORMATION
 Many drugs undergo polymorphic transformation during
various processes. E.g. during grinding drugs like
digoxin, estradiol, spironolactone, phenylbutazone undergo
transformation.
 By granulation of theophylline with water converts into
monohydrate from anhydrous form.
 Similarly by drying and compression also drugs undergo
change in their form.
28

29. LATEST TECHNIQUE DEVELOPMENTS IN
CRYSTALLIZATION
SPHERICAL CRYSTALLIZATION-
 It has been developed by Yoshiaki and co-workers.
 It is a solvent exchange crystallization method in which
crystal agglomeration is purposefully induced through the
addition of third solvent termed as “Bridging liquid” which
act as granulating agent.
29

30. It is a novel technique .
to improve compressibility,
good flow ability and
bioavailability of pharmaceuticals.
Moreover tablets formed have greater mechanical strength and lower
friability.
Various drugs have been successfully undergone this process to acquire
improved micromeritic properties and thus have shown increased
dissolution rate like
salicylic acid,
mefenemic acid,
aminophylline,
tolbutamide.
[Pharmaceutical Research-1994, 11(4)] 30

31. METHODS OF SPHERICAL CRYSTALLIZATION
 SIMPLE SPHERICAL CRYSTALLIZATION
E.g. spherical crystallization of salicylic acid from ethanol by
addition of water, using chloroform as bridging unit.
 QUASI-EMULSION-SOLVENT-DIFFUSION METHOD
E.g. antirheumatic drug bucillamine was crystallized as
spheres by this method using HPMC. Also controlled
release microspheres of ibuprofen with acrylic polymers
was accomplished by this method.
 AMMONIA DIFFUSION METHOD
Useful for amphoteric drugs like enoxacin.
 NEUTRALIZATION METHOD
Tolbutamide dissolved in sodium hydroxide and HPEC
aqueous solution was crystallized using this method.
31

32. SUPER CRITICAL FLUID CRYSTALLIZATION
 It is a novel technique used for selective production of
polymorphs and pseudo polymorphs from aqueous solution.
CHIRAL DRUGS
 Resolution of chiral drugs and drug intermediate is done by
preferential crystallization.
32

33. POLYMORPHISM
LIST OF CONTENTS :
 Definition
 Need to study polymorphism
 Types
 Transition temperature
 How to differentiate them
 Pseudo polymorphism
 How to differentiate pseudo polymorphs from true polymorphs?
 Methods to identify polymorphism
 Parameters to be cared by preformulator
 Properties
 Stability of metastable polymorph
 Factor affecting polymorphism
 Effect of polymorphism on bioavailability
33

34. Ability of any compound or element to crystallize as more than one
distinct crystal species with different Internal lattice.
Example:- Carbon --- cubic: diamond
---Hexagonal: graphite
 The term polymorphism was coined by AGUIAR ETAL in 1967
34

35. NEED TO STUDY POLYMORPHISM
 Show the same properties in the liquid or gaseous state but
they behave differently in the solid state.
 Polymorphism is remarkably common particularly within
certain structural groups. For e.g.
class % of polymorphs
Barbiturates 63
Steroids 67
Sulfonamides 40
35

36.  The effect of polymorphism on bioavailability is
the most important consequence for drug
substances if the bioavailability is mediated via
dissolution.
 Examples:-
chloramphenicol palmitate.
noviobiocine
griseofulvine
Carbamazepine
aspirin
ampicillin
 The polymorphism of the excipients may also play
an important role in bioavailability.
 Polymorphic behavior of drugs and excipients is
an important part of the preformulation work.
36

37. TYPES
 PHASE TRANSITION: process of transformation of one
polymorph into another, which may also occur on storage or
during processing is called phase transition.
 ENANTIOTROPHS :-phase transition is reversible that means
metastable↔stable . E.g.sulfur
 MONOTROPHS:-phase transition occurs only in one direction
that means metastable→stable.eg. glyceryl stearate.
37

38. TRANSITION TEMPERATURE
 “Temperature at which both stable and metastable forms
exist in equilibrium with each other.”
 In case of monotropy higher melting form is always
thermodynamically stable form.
 In case of enantiotropy lower melting form is
thermodynamically stable at the temperature below the
transition temperature and higher melting form is stable at
the temperature above the transition temperature
38

39. HOW TO DIFFERENTIATE THEM
• Differentiated by vapor pressure versus temperature curve and solubility
versus temperature curve.
 Here form I is stable at temperature T1 and if it exist in form I&II, the
phenomena is called enantiotrophism. In case of enantiotrophism
transition temperature of both the forms are same.
 A different situation exists if compound exists as form III. Such
phenomena is referred as monotrophism. Here transition temperature of
both the forms are different since form III is relatively unstable than
form I.
39

40. PSEUDOPOLYMORPHISM
 The term pseudo means false.
 Phenomenon in which solvent molecules get incorporated
into crystal lattice of solid are known as solvates. These
solvates exist in different crystal form called pseudo
polymorphs and the phenomenon is called as pseudo
polymorphism.
 Also known as hydrates when water is solvent.
 E.g. when the potent synthetic estrogen ‘ethynylestradiol’
is crystallized from the solvents
acetonitrile, methanol, chloroform and saturated with
water; four different crystalline solvates are formed.
40

41. HOW TO DIFFERENTIATE PSEUDOPOLYMORPHS
FROM TRUE POLYMORPHS?
 Melting behavior in silicon oil using HOT STAGE
MICROSCOPY.
 Pseudo polymorphs--- evolve gas (steam or solvent
vapors) causing bubbling of the oil.
 True polymorphs--- merely melts, forming second
globular phase.
41

42. METHODS TO IDENTIFY
POLYMORPHISM
 Optical crystallography
 Hot stage microscopy
 X-ray diffraction method
 NMR technique
 FTIR
 Dilatometry
 Microcalorimetry
 Thermal methods
A)DSC [differential scanning calorimetry]
B)DTA [differential thermal analysis]
C)TGA [thermal gravimetric analysis]
Measures heat loss or gain from physical or chemical changes occurring in
sample which is recorded as a function of temperature.
 Melting point determination
42

43. PROPERTIES
 show the same properties in liquid or gaseous state but they behave
differently in solid state.
 differ from each other with respect to physical properties like
Melting and sublimation temperature
Vapour pressure
Solubility and dissolution rate
Stability
Optical and electrical properties
Crystal habit
Hygroscopicity
Heat capacity
Solid –state reactions
Conductivity
Compression characteristics etc..
43

44. 1)stability characteristics:-If a compound exist
polymorphism, one of the form will be more stable
(physically) than the other form.
 Depending upon relative stability there are two forms of
polymorphs:
 a) stable form having lowest energy state, highest melting
point and least aqueous solubility.
 b)Metastable form having higher energy state, lower
melting point and higher aqueous solubility.
44

45. CONTINUED…
2)Relative solubility of polymorphs:-In order to assess the relative increase in
solubility of polymorphs with respect to another, a simple solubility ratio can
be defined:-
 solubility ratio =solubility of metastable form
solubility of stable form
 Examples:-
Aspirin-1.2
Carbamazepine-1.2
Indomethacine-1.4
Tetracycline-1.6
 From above example, we can say that solubility ratio is higher than one just
because of relative higher solubility of metastable form, which leads to increase in
apparent solubility.
45

46. 3)Dissolution behavior of the polymorphs:-
 The absorption rate and bioavailability of drug
administered orally is controlled by many factors among
which dissolution rate is one of the most important.
 Therefore physicochemical state such as polymorphism or
amorphism of drugs affect bioavailability of
pharmaceutical preparation.
 Amorphous>metastable> stable
46

47. FACTOR AFFECTING
POLYMORPHISM
(A)Temperature and humidity:-
 Storage conditions affect physicochemical reactions which are
accelerated at higher temperature.(Arrhenius theory).
 Humidity act as catalyst on the solid surface. Therefore both
are the important factors for the prefomulator scientist to
consider.
 E.g. 1. chlortetracycline hydrochloride has two different
polymorphs forms: α and ß. Alpha form is stable up to 82% RH
while beta form is hygroscopic.
2.polymorphic transformation of phenylbutazone and
cocoa butter occur after heating.
47

48. (B)Photostability:-
 Generally light sensitive drugs are protected from the
photolytic degradation by packing them suitably in light
resistant container. However the bulk powder of the stable
crystalline forms resists photochemical degradation and do
not require light resistant system. But still there are fewer
reports:
 For e.g. five different polymorphic form of 21-tert-butyl
acetate out of which form 1 and 4 are unstable under U.V.
light while form 2 ,3 and 5 were stable.
(C) Effect of solvent:-
 Solvent can bring dramatic change in growth mechanism
and morphology. Growth kinetic of crystal growing from
solution was determined by two important factors:
 Degree of molecular roughness
 Nature of absorption of the solvent from surface.
48

49. (D)Effect of grinding:-
 Grinding process reduce particle size ,so increasing
specific surface area and that’s why direct effect on
dissolution rate and bioavaibility of the preparation.
During grinding process solid state polymorphic
transformation in to non-crystalline or metastable
form is caused by mechanical action..
 E.g. prasterone sulfate dehydrate
Here dehydrate form was more stable than
anhydride form. with increasing grinding time, water
content compound become unstable because grinding
weakened bonding crystals and water molecules
participating in hydrolysis process of the drug.
49

50. (F)Effect of surfactant:-
 Surfactant affect solution mediated transformation of
the drug which depends on molecular and
supramolecular structure of the drug.
 eg.carbamazepine has two different polymorphic
forms :-anhydrous and dehydrate. Here dehydrate
form has higher dissolution rate.
 In SLS increase growth of dehydrate form while in case
of poloxamer , polysorbate 80 decrease growth of
dehydrate form.
50

51. EFFECT OF POLYMORPHISM ON BIOAVAILABILITY
 If the absorption of active ingredient in drug through
G.I.T. is dissolution rate dependent then
polymorphism is an important preformulation tool.
 Here successful utilization of polymorph having
significant greater thermodynamic activity
(solubility)may provide good therapeutic blood level
from otherwise inactive drugs
 E.g. novobiocin, identified in two different forms:
crystalline and amorphous. In tablet or capsule
formulation novobiocin is used as sodium salt which is
active orally but unstable chemically while insoluble
form is stable chemically and orally inactive
(unabsorbable).
51

52. VARIOUS CHARACTERIZATION TECHNIQUES
USED IN PREFORMULATION
LIST OF CONTENTS :
 Differential thermal analysis (DTA)
 Differential scanning calorimetry (DSC)
 X-ray diffraction
 Fourier transform infrared spectrophotometry (FTIR)
 Other thermal techniques
 Innovation in thermal analysis
52

53. Differential Thermal analysis (DTA)
PRINCIPLE:
A Technique in which the temperature difference between a
substance & a reference material is measured as a function of
temperature, while the substance & reference are subjected to a
controlled temperature programmed.
 The Difference in temperature is called as Differential temp(∆T)
is plotted against temp. or a function of time.
53

54. Endothermic Peak:
An endothermic peak, is a peak where the
temperature of the sample falls
below that of the reference
material, i.e., ∆T is negative.
Exothermic peak:
An exothermic peak, is a peak where the
temperature of the sample rises above that
of the reference material, i.e. ∆T is positive.
54

55. APPLICATIONS :
 DTA is particularly useful in preformulation studies
including purity, polymorphism, solvation, degredation &
excipient compatability.
 It measures physical or chemical changes of drug
molecules.
55

56. Differential scanning calorimetry (DSC)
PRINCIPLE:
 It is a technique in which the energy necessary to establish a
zero temp. difference between the sample & reference
material is measured as a function of temp.
 DSC Is widely used to measure glass transition temp &
characterization of polymer.
 Glass Transition temp(Tg): Temp at which an amorphous
polymer or an amorphous part of crystalline polymer goes
from hard ,brittle state to soft, Rubbery state.
56

57. Types of reaction
ENDOTHERMIC EXOTHERMIC
Physical reaction Chemical reaction
e.g vaporisation
e.g vaporisation Oxidation,
Oxidation,
Sublimation,
Sublimation, catalytic reaction,
catalytic reaction,
absorption
absorption polymerization
polymerization
57

58. INSTRUMENT OF DSC
58

59. Ideal DSC curve:
59

60. APPLICATIONS :
 DSC is best method for detection of impurity.
 DSC is also used in drug excipient compatability study.
e.g. DSC of sparfloxacin
• DSC is used in study of polymer.
60

61. 61

62. GENERAL PRINCIPLE & APPLICATION OF FT IR SPECTRUM & X-RAY
DIFFERACTION METHOD.
FT IR:
 New technique in preformulation.
 Generally used in combination with other
technique.
62

63. ADVANTAGE:
- Simple
- Sensitive
- Accurate
- Speedy
DISADVANTAGE:
1) Generally not used alone.
2) Gives peak at same wave number,
e.g so not differentiate polymorph.
63

64. B)X-RAY POWDER DIFFERACTION
 Why only x-ray are used?
Because x-rays have wavelengths of about the same magnitude as
the distance between the atoms or molecules of crystal.
PRINCIPLE: x-ray are Diffracted & order of this diffraction is measured
in form of graph.
 Diffraction occur as a result of the interaction of radiation with electron
of atom.
64

65. Application 0f x-ray diffraction
1)For structure determination:
2)Identification Of Impurity:
3)Characterization of polymorphism:
4) Characterize spray dried &
crystalline material.
5)For particle size analysis.
65

66. OTHER THERMAL TECHNIQUES :
1) Thermo photometry:
2) Thermo luminescence:
3) Thermo microscopy:
4) Micro thermal analysis:
5) Differential mechanical analysis:
6) Emanation thermal analysis:
7) Thermo particulate analysis:
66

67. INNOVATION IN THERMAL ANALYSIS
1) MULTIELEMENTAL SCANNING THERMAL
ANALYSIS(MESTA)
2) MICROTHERMAL ANALYSIS
3) MODULATED DSC
4) ROBOTIC SYSTEM
5) FAST SCAN DSC
6) DYNAMIC MECHANICAL ANALYSIS
67

68. GTU QUESTIONS
 Define polymorphism and pseudo-polymorphism.
Enlist the methods to identify polymorphism.
Comment on dissolution behavior and stability of
polymorphs.
 What is polymorphism? What is its significance in
dissolution and patenting? Name the methods to identify
polymorphs.
68

69. REFERENCES
 Pharm. Dosage forms and drug delivery system , ANSEL, 100,151.
 Pharm. Dosage forms, LACHMANN and LIBERMANN, 1, 26-30.
 Modern pharmaceutics, BANKER,MARSHALL DEKKER INC.
 Pharm Encyclopedia, 3, 399.
 Pharm Encyclopedia, 12, 320-321.
 Advanced pharmaceutical solids, CARSTENSEN, 110, 6.
 Physical pharmacy, ALFRED MARTIN.
 Industrial pharmacy, LACHMANN and LIBERMANN.
 Physico-chemical principles of pharmacy, A.T.FLORENCE &
D.ATTWOOD, 8-10.
69

70. 70