polymorphism (copy) 4

how does polymorphism occur

when the molecules are arranged in two or more different ways

how else can polymorphism occur (3)

• when they are packed differently in the crystal lattice

• differences in the orientation and conformation

• different melting points, solubility, shapes

how can you prepare different polymorphs

by manipulating the conditions of crystallisation

What conditions are manipulated in crystallisation?

solvent

temp

pressure

cooling rate

stirring rate

How do you change the polymorphic form?

milling

drying

compression

time

Pharmaceutical and biopharmaceutical properties which are affected :

–Density

–Melting point

–Hygroscopicity

–Electrical and optical properties

–Reactivity

–Dissolution velocity

–Apparent Solubility

what is bioavaliabilty

the rate and extent to which a substance is absorbed and circulated around the body

why can polymorphs have different bioavaliability

depending on their solubility and dissolution rates

some polymorphs are lower in energy than others , what does this cause

higher energy polymorphs to change to lower form

what can polymorphs be characterised by

x ray diffraction

• infrared spectroscopy

• microscopy

• thermal analysis

what is a solvate

crystals that trap solvent molecules

what is a hydrate

trapped solvent that is water

what can polymorphs be characterised using (3)

• differencial scanning calorimetry (DSI)

• thermal grarimetric analysis (TGA)

• Hot stage microscopy

what does differential scanning calorimetry do (DSC)

detect melting points if they exist

what does thermal gravimetric analysis do (TGA)

analyses the constant heating rate

what does hot stage microscopy do

• detect different melting points and see transitions

• can also detect the loss of solvents

• distinguishes between solvates, hydrates and polymorphs

how do we know if hot stage microscopy has successfully detected the loss of solvent

the formation of bubbles